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The Warrior Zero Body Weight Challenge

The Warrior zero body weight challenge was created by Helder Gomes, he is a service-connected disabled veteran. He has been a victim of body slowing down and energy stripped off, he has used the techniques and now is sharing with you to assist you as well. He has also experienced the working of other programs and has testified that they were actually doing more harm than good, so if you are thinking of other programs, don't. Filled with a decade of research information, the product has been used widely by various clients and has proven to work, it can, therefore, be trusted and used. It is an operational fitness program that will get you the lean muscles and body shape you have hoped for, without signing up for expensive membership programs at the gym or using fancy types equipment. This fitness operator shows the men over forty years how to keep active and eliminate weakness. This will also teach you how to build combat-ready conditioning at any age. This secret training method is used by the most dangerous men there exists. In the program; you will find thirteen weeks of precision fitness system operator programming that is strategically designed to help you eliminate, weakness and build a stable body. And each week you are guaranteed a result that will leave you in shock! How to get through the defined exercise performance from start to finish. Continue reading...

The Warrior Zero Body Weight Challenge Summary

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My The Warrior Zero Body Weight Challenge Review

Highly Recommended

The writer presents a well detailed summery of the major headings. As a professional in this field, I must say that the points shared in this manual are precise.

As a whole, this ebook contains everything you need to know about this subject. I would recommend it as a guide for beginners as well as experts and everyone in between.

Particle Fitness and Collective Fitness

To simplify the treatment of fitness at two levels, we ignore the distinction between realized and expected fitness. The notion of particle fitness is then straightforward. A particle's fitness is the number of offspring particles it leaves, over some appropriate number of particle 16 Note that 'allelic fitness' as the term is used here means the fitness of an allele within a diploid genotype. This is not the same as the 'marginal allelic fitness' of standard population genetics textbooks, which is the fitness of an allele-type averaged across all genotypes. See Chapter 5, Section 5.3 and Kerr and Godfrey-Smith (2002) for further discussion of this point.

The adaptive landscape A D fitness map

In any giving species, there are a huge number of different possible genotypes, and we can't possibly know the fitness of each different genotype we just know that each genotype has a fitness. In order to think about all that information, scientists use the adaptive landscape. The adaptive landscape is a three-dimensional imaginary structure that gives us a way of talking and thinking about how differences in genotype affect fitness. Figure 6-1 is an example of a fitness landscape. The letter A represents a mutation that's beneficial (moving the species up the hill to greater fitness) the letter B represents a mutation that decreases a species' fitness. This landscape is like a 3-D relief map that you can set down on your coffee table. A relief map indicates, through the height of the bumps, the altitude of any region such a map of the U.S. would show the Rockies and the Sierra Nevadas, the Midwestern plains, the small mountains of Appalachia, and so on. The adaptive landscape has the...

How fitness fits in with natural selection

The process of evolution by natural selection is driven by differences in fitness, or how successful an organism is at getting its genes (or characters) into the next generation. In short, fitness is all about how well an organism reproduces. Characters (or genes) that increase an individual's fitness are more likely to be passed to the next generation than genes that don't. This process is how the frequency of genes changes through time. In the evolutionary process, fitness has nothing to do with how buff you are. It's purely a measure of the differential reproductive success among different individuals, which is a fancy way of saying that it refers to how successful an individual is at producing offspring. If one individual produces twice as many offspring as the next individual, all other things being equal, it's twice as fit.

Step Testing whether viral sex leads to increased fitness

With his low-fitness viruses, Chao collaborated with Thutrang Tran and Crystal Matthews in designing experiments to test whether viral sex leads to an increase in fitness. The scientists grew different pairs of the debilitated viruses together with their host bacteria, and they controlled how much sex was going on by altering the ratio of bacteria to viruses. When they put in far fewer bacteria than viruses, they ensured that multiple viruses would be infecting the same host bacterium. As they increased the likelihood of producing viral progeny that had genetic material from two parent viruses, they found that they were more likely to find progeny with increased fitness.

Life History And Fitness

Life history is the progress of an individual throughout his or her life. An individual is first born, then grows into an adult or fails to survive to adulthood. If the individual survives to adulthood, then the individual perhaps mates and reproduces at specific ages and finally dies at some age. In Chapter 11, we defined the fitness components of viability, mating success, and fertility fecundity. To examine life history and its evolutionary implications, we must first make each of these fitness components an explicit function of age. We start with the fitness component of viability. Viability can be measured in an age-specific fashion by the age-specific survivorship, lx, the probability of an individual surviving to age x. Ideally, age should be measured from fertilization in order to cover the diploid individual's entire life history, but in practice a time point well after conception is used in many species. For mammals, and humans in particular, the initial time point is...

Fitness Of The Cosmos For Life

This highly interdisciplinary book highlights many of the ways in which chemistry plays a crucial role in making life an evolutionary possibility in the universe. Cosmologists and particle physicists have often explored how the observed laws and constants of nature lie within a narrow range that allows complexity and life to evolve and adapt. Here, these anthropic considerations are diversified in a host of new ways to identify the most sensitive features of biochemistry and astrobi-ology. Celebrating the classic 1913 work of Lawrence J. Henderson, The Fitness of the Environment, this book looks at the delicate balance between chemistry and the ambient conditions in the universe that permit complex chemical networks and structures to exist. It will appeal to scientists, academics, and others working in a range of disciplines.

Michod On Fitness Decoupling And The Emergence Of Individuality

Consider again the model life cycle depicted in Figure 8.2. This model presumes that the transition has proceeded far enough so that the multicelled organisms can possess fitnesses in the MLS2 sense, that is, a process of reproduction at the organismic level takes place. An organism's fitness is its number of offspring propagules this number may be influenced by various factors. One important factor, Michod argues, is the frequency of cooperating (C) cells in the adult. The higher this frequency, the greater the functionality of the adult organism, so the more propagules it will produce. Therefore, Michod and Roze (1999) suggest the following expression for the fitness of the ith organism Is expression (8.1) satisfactory Clearly, this depends on whether frequency of C cells in the adult is the only factor that affects an organism's propagule production. Michod and Roze argue that another factor may be adult size, that is, total number of cells in the adult. Since there is no separate...

Your fitness your relatives fitness inclusive fitness

Inclusive fitness is simply the sum of an individual's fitness plus the additional benefits accrued through increasing the fitness of related individuals. In English You're more fit not only if you reproduce, but also if relatives who share your genes reproduce, too. Here's a simple example of inclusive fitness in action Helping your identical twin sister have a baby that she would not have been able to have without your help is just as good a way to pass on your genes to the next generation as having a baby of your own. Most humans aren't one half of an identical pair, of course. To understand how inclusive fitness works in more common situations, you need to understand a concept called degree of relatedness, which simply means how many of your genes you share with others. So how many offspring do you have to help your siblings make to equal one of your own offspring If you're an identical twin (that is, you and your twin have a degree of relatedness of 1.0 because you have exactly...

Lenski experiment increase in fitness

The smooth curve in the graph of increasing cell size as the generations go by gives support to the idea that the improvement is gradual. But perhaps it is too gradual Wouldn't you expect to see actual steps, as the population 'waits' for the next improving mutation to turn up Not necessarily. It depends on factors such as the number of mutations involved, the magnitude of each mutation's effect, the variation in cell size that is caused by influences other than genes, and how often the bacteria were sampled. And interestingly, if we look at the graph of the increase in fitness, as opposed to cell size, we do see what could at least be interpreted as a more overtly stepped picture (above). You remember, when I introduced the hyperbola, I said it might be possible to find a more complicated mathematical function that would fit the data better. Mathematicians call it a 'model'. You could fit a hyperbolic model to these points, as in the previous graph, but you get an even better fit...

Differential Fitness

Fitness in evolutionary terms is not physical fitness, like muscle tone and health. Fitness is the number of offspring an individual produces which is the equivalent of its reproductive success. Some variations are more advantageous than others. Organisms with advantageous traits will survive and have more offspring who will carry those advantageous traits and pass them on to their offspring. Differential reproduction occurs when individuals with advantageous traits reproduce more than those without the traits. The increased survival and reproductive rates of an individual's offspring contribute to that individual's fitness being greater than another's. This phenomenon occurs because a trait is being selected for or because it is being favored by natural selection.

Some Implications Of Fundamental Equations Of Natural Selection

Natural selection can only operate when there is genetic variation associated with phenotypic variation for fitness in the population. If there were no genetic variation influencing the phenotype of fitness, fitness could not possibly be heritable and therefore equation 11.22 implies no evolution due to natural selection. Likewise, without genetic variation associated with phenotypic variation of fitness, there can be no nonzero average excesses of fitness, and therefore equation 11.5 also implies no evolution by natural selection. 2. The only fitness effects that influence the response to natural selection are those transmissible through a gamete. Equation 11.5 shows that there is no response to selection unless the average excess for fitness is not zero, and equation 11.22 shows that there is no response to selection unless the additive genetic variance for fitness is not zero. The additive genetic variance can only be nonzero if the average effects are nonzero, and the average...

You cant get there from here Constraints and tradeoffs

Constraints are problems that natural selection can't seem to solve. As a result of how an organism is put together, some types of variation just aren't expected to appear. All vertebrates, for example, have (at most) four limbs. Think about it You never see mice with six legs. And based on human understanding of mammalian development, it's pretty unlikely that Pegasus, with his four legs and two wings, would ever evolve. Being a mammal and having six limbs is just not a variant you ever see. So even if having a few extra limbs conferred a fitness advantage, natural selection can't get there because there is no heritable variation for extra limbs. Trade-offs, the balance between fitness benefits and fitness costs, represent another key concept in evolutionary biology. You can think of trade-offs as being the jack of all trades, master of none phenomenon. Consider all the different kinds of birds in nature. Why isn't there a superbird with the talons of an eagle, the webbed feet of a...

The Self Referential Model

Our study of the formation of the genetic code (Guimaraes et al., 2007, and earlier references therein) allowed the proposition of a procedure for obtaining synthesis of proteins that is considered plausible and consistent with the present day knowledge on cellular processes, and can dispose of the requirement for an early mRNA to be translated. It is called self-referential to the tRNAs and based on a simple type of symmetry produced by the dimerization of tRNAs through the complementary anti-codons (Grosjean et al., 1986 Grosjean and Houssier 1990). We will start with a presentation of the model and then give an account of its consistency with the main attributes that have been found adequate and necessary to fit the evolutionary paradigm, e. g. of going from simple to complex arrangements and of providing a driving force or a phenotype with fitness value that can be selected for.

Finegrained Heterogeneity

An individual often experiences environmental heterogeneity within its own lifetime. Because an individual can only be at one place at any given time, an individual experiences both spatial and temporal heterogeneity within its own lifetime as a temporal sequence. Hence, for purposes of microevolutionary modeling, no distinction is necessary between fine-grained spatial and temporal heterogeneity. In many situations, fine-grained heterogeneity needs no special consideration as it can be folded into the constant-fitness models given in Chapter 11. To see this, consider two extreme situations the case in which every individual in the population experiences the same temporal sequence of fine-grained heterogeneity and the case in which every individual experiences an independent sample of temporal sequences of environments within its lifetime. The first case would apply to the situation in which an organism has one generation per year but in which seasonal variation influences the...

Further models of natural selection

Chapter 6 established a series of general predictions about the action of natural selection when fitness is equivalent to genotype-specific viability determined by a single locus with two alleles. The conditions required for the basic diallelic locus model of natural selection are quite restrictive and are probably not met often in biological populations. The goal of this chapter is to extend our understanding of the model of natural selection to increasingly complex and general genetic situations. In a sense then, this chapter explores the process of natural selection under assumptions that might better approximate conditions found in some natural populations. In the first section, we will retain the viability natural selection model and its assumptions but modify the numbers of alleles at a locus and the number of loci. The goal is to examine the outcomes of viability selection when fitness is determined by either a single locus with three alleles or two loci...

The NFL Theorems Still with No Mathematics

The mountainous landscape we discussed is a particular case of what is generally called a fitness landscape, and the heights of the peaks in our example is a particular case of a fitness function. Imagine two algorithms conducting a search on a given fitness landscape. They move from point to point over the search space (choosing the search points either at random or in a certain order). After having performed, say, m measurements, an algorithm produces what Wolpert and Macready call a sample a table wherein the m measured values of the fitness function are listed in temporal order. Generally speaking, two arbitrarily chosen algorithms will not yield identical samples. The probability of algorithm ai producing a specific table that is m rows long is different from the probability of algorithm a2 producing the same table after the same number of iterations. Enter the first NFL theorem if the results of the two algorithms' searches are compared not for a specific fitness landscape but...

The Evolution of Altruistic Social Systems

As I explain throughout this book, evolution by natural selection means that nature selects or favors heritable traits (or characteristics) that increase an organism's fitness how successful it is at getting its genes into future generations. Yet some organisms actually postpone reproduction or forgo it.

The NFL Theorems A Little Mathematics

The first NFL theorem for search pertains to fixed (time-independent) fitness landscapes, while the second is for time-dependent landscapes. Although there is a substantial difference between the two, their principal meaning can be understood by reviewing only the first. Imagine a finite set X called the search space and a fitness function f that assigns a value to each point of X the values of f are within a range denoted Y. Altogether the search points and their fitness values form the fitness landscape. We consider algorithms that explore X one point at a time. At each step, the algorithm decides which point to examine next, depending on the points that have been examined already and their fitness values, but it does not know the fitness of any other points. This decision might even be made at random or partly at random. where aj and a2 are two different algorithms. The summation is performed over all possible fitness functions. Equation (1) means that, in probabilistic terms, the...

Crosslevel Byproducts In

The correlated character scenario shows how a character-fitness covari-ance can be a by-product of direct selection on another character at the same hierarchical level. But what we are really interested in, vis-a-vis the levels of selection, is the idea that a character-fitness covariance might be a by-product of direct selection at a different level. This section and the next examine cross-level by-products in hierarchically organized systems. Intuitively it is easy to see how cross-level by-products in the particles collective direction might arise. For since a collective's character and fitness usually depend on, and are sometimes defined in terms of, the characters and fitnesses of its constituent particles, selection at the particle level might have effects that 'filter up' the hierarchy, generating a spurious character-fitness covariance at the collective level. The challenge is to spell out this intuitive argument in precise terms. Precisely how must character and fitness at...

The Limits of Genic Accounting

It is clear that natural selection, at various levels, does produce gene frequency change. For example, genic selection leads to the spread of genes which boost genic fitness, for example, segregation-distorters organismic selection to the spread of genes which boost organismic fitness and group selection to the spread of genes which boost group fitness, for example, genes for pro-social behaviour. So a gene's-eye perspective on the evolutionary changes produced by these modes of selection is clearly possible. To see the problem, recall the discussion of clonal plants from Chapter 2. We noted that biologists disagree about whether to treat genets or ramets as the bearers of Darwinian fitness, that is, as the focal units. Genet-based theorists argue that clonal production of ramets constitutes growth rather than reproduction ramet-based theorists insist that ramets are genuine evolutionary individuals, with life cycles of their own, despite their asexual origin. If genets are our focal...

The Shifting Balance Hypothesis Its Whats Wright

Sewell Wright (1889-1988) was a key founder of the science of population genetics, and his shifting-balance hypothesis is one of the coolest hypotheses about how evolution might work in certain circumstances. This hypothesis says natural selection and genetic drift can work together to allow populations to reach higher fitness. To help visualize how this might work, you need to get cozy with an especially slippery concept called the adaptive landscape (or fitness landscape). It's slippery even for professional evolutionary biologists, but of course that's part of the fun

Fundamental Theorem Of Natural Selection Unmeasured Genotypes

Equation 11.5 is the fundamental equation describing natural selection for a measured genotype at a single locus. Given that many adaptive traits are polygenic but with the underlying loci being unknown, Fisher (1930) elucidated many properties of natural selection using the theory of the quantitative genetics of unmeasured genotypes (Chapter 9). His central result is summarized in an equation that is the unmeasured genotype analogue of the measured genotype equation 11.5. Fisher called this equation the fundamental theorem of natural selection, which describes how natural selection operates upon the phenotype of fitness when fitness is regarded as a heritable but genetically unmeasured trait. There are many ways of deriving this theorem, and we will present only one of the simplest. Because we assume that no genotypes are being measured, we must focus exclusively upon phenotypes. This means that we can no longer use the primary definition of fitness in population genetics as a...

Is Specified Complexity Smuggled into Evolutionary Algorithms

Dembski suggests a modification of Dawkins's weasel algorithm. In his adjusted procedure, the algorithm will pick a position at random in the sequence. . . . Then randomly alter the character in that position. If the new sequence has a higher fitness function than the old, keep it and discard the old. Otherwise keep the old. Repeat the process (193). I will discuss the fitness function later in this chapter. For now, suffice it to say that the fitness function is the number of letters in the intermediate phrases that coincide with the letters in the same positions in the target phrase. I see no substantial difference between the procedure described on pages 47-48 in Dawkins's book and that suggested by Dembski. In Dembski's view, while Dawkins's algorithm compares consecutive phrases with a target, his own modified algorithm searches for the target solely on the basis of the phase space and the fitness function, hence not smuggling in any obvious teleology (194). But the only...

Abstract Formulations Of Darwinian Principles

In a well-known article, Lewontin (1970) identified three principles that he said 'embody the principle of evolution by natural selection', namely phenotypic variation, differential fitness, and heritability entities possessing these properties he called 'units of selection' (p. 1). Fitness he defined as rate of survival and reproduction, and heritability as parent-offspring correlation. Oddly, Lewontin required that the differences in fitness, rather than the phenotypic differences, should be heritable, that is, the parent offspring correlation should hold with respect to fitness rather than phenotype. This is odd because if selection is to produce cross-generational phenotypic change, it is the phenotypic differences, not the fitness differences, that must be heritable.3 But leaving this oddity aside, Lewontin's formulation seems to capture the essence of the Darwinian process very neatly. In a similar vein, Maynard Smith (1987a) wrote that evolution by natural selection will...

Being the best you can be on your own peak

The adaptive landscape is a way of thinking about the fact that several peaks of high fitness may exist, each peak corresponding to a different genotype. Natural selection will drive a population to the top of whatever peak it's already on, whether or not that peak is the highest one in the adaptive landscape. What natural selection won't do is move the population to an even higher peak if that move means crossing a valley of lower fitness. Why Because natural selection won't backtrack by favoring individuals with lower reproductive success. Individuals with lower fitness arise all the time (remember that most mutations are bad), but they don't increase in frequency as a result of selection.

Til Death Do Us Part The Evolution of Life Span

Evolution via natural selection acts to maximize fitness, and fitness is all about making sure that your genes are around in the future. That being the case, dying just doesn't seem like an especially good idea. After all, death doesn't seem to bode well for the Get your genes to last forever imperative of natural selection. You may think that the simplest way to get your genes into the future is for you to exist into the future. After all, you've got all your genes if you live into the future, your genes live into the future, too. Voil fitness without the rather depressing and (often) messy process of dying. But organisms don't get their genes into the future by living forever, even though they may live for a very long time. All this leaves evolutionary biologists, and not just older ones, puzzling over why things eventually (or not so eventually) die.

Variation thats important to evolution

You can partition variation by whether it's heritable (or not) or has fitness consequences (or not) i Variations that have fitness consequences These variations impact, for better or worse, how well an organism is able to survive and reproduce. 1 Variations that don't have fitness consequences These variations don't impact either positively or negatively an organism's ability to survive and reproduce. 1 If a variation has a fitness consequences but the variation isn't heritable, it won't lead to evolution. For example, people with really cute tattoos may be more likely to pass along their genes, but there's no genetic component to getting a tattoo. Their genes are, on average, no different from anyone else's genes. Remember Without heritable variation, there is no evolution (or evolution books, for that matter). 1 If a variation is heritable but it doesn't cause any fitness differences, then the frequencies of these differences in a population will change only as a result of genetic...

Outlaws And Genetic Conflicts

An outlaw, or SGE, is a gene that enjoys a transmission advantage over other genes in the same organism but does not increase the organism's fitness (Alexander and Borgia 1978 Dawkins 1982 Hurst et al. 1996 Hurst and Werren 2001). Most outlaws in fact reduce organismic fitness this generates selection pressure at all unlinked loci for genes that suppress the outlaw's effects, leading to genetic conflict. Such conflicts are usually called 'intra-genomic', for they involve conflict between the different parts of a single genome. However, Maynard Smith and Szathmary (1995) argue that some SGEs are better thought of as parasites or endo-symbionts, rather than as part of host genome, hence do not generate intra-genomic conflict, but rather conflict between the multiple genomes inhabiting a single organism. Genic selection, as defined above, occurs when there are fitness differences between the genes within an organism. Given this definition, it follows that all outlaws spread by genic...

When selection levels collide

If the gene that increases in frequency has a high fitness cost to the individual, the direction of selection can be different at different levels. Suppose that a gene that reduces the speed at which cheetahs can run is one that, through meiotic drive, has a better than 50 percent chance of ending up in the gamete population. Selection at the level of the individual will act to remove such a costly gene, because cheetahs with this gene will be slower and will produce fewer offspring. Because the fitness of a particular gene can be at odds with the fitness of the individual that carries it, selection at the level of the individual acts to combat the deleterious driver gene. Take, for example, fruit flies. Interestingly, the female fruit flies choose mates that have long eye stalks. The connection The driver gene is associated with a gene for short eye stalk. The female preference for the long eye stalk evolved because the length of the eye stalk correlates to the quality of the mate....

Contextual Analysis Versus The Neighbour Approach

Recall how contextual analysis works. It uses a multiple regression model to assess whether an individual's fitness is affected by individual character, group character, or both where w is individual fitness, z is individual character, and Z is group character, defined for the moment as average individual character. fti and ft are the partial regressions of fitness on individual and group character respectively. Presuming the individual character is transmitted perfectly, this permits the overall change to be written as Though Nunney (1985a) employs a different formalism, his approach is a close relative of contextual analysis, but with one difference. Whereas the contextual approach looks for 'group effects' on individual fitness, Nunney looks for 'neighbourhood effects' on individual fitness. In effect, Nunney is using a variant of the contextual regression model in which the second independent variable is neighbourhood character X, rather than group character Z. An individual's...

The Evolutionary Basis of Social Behavior

Altruism there is no benefit to living in a society. How therefore can social behavior ever have evolved Evolutionary biologists have developed a reasonably good account of how social behavior may have emerged in groups of closely related individuals, in a theory about what is known as inclusive fitness. Another theory, that of reciprocal altruism, explains how behavior could have evolved for helping even unrelated people, or at least those who can be expected to reciprocate the favor at a later time. Why will a bee sacrifice its life in the hive's defense Why should a worker ant embrace sterility and devote her life to raising the queen's offspring The late William Hamilton made a major addition to Darwin's theory in showing how altruism, at least toward one's own kin, makes evolutionary sense. Darwinian fitness, defined as reproductive success, is all about getting as many of one's own genes as possible into the next generation. Hamilton's insight was that the notion of Darwinian...

Selection In Heterogeneous Environments

Premise 3 (Chapter 1) states that phenotypes emerge out of a genotype-by-environment interaction. In Chapter 11 we saw that natural selection arises from this premise when there is genetic variation in the population to produce heritable variation in the phenotype of fitness. There is often variation not only in genotypes but also in environments. We have already seen this before. For example, in Chapter 8, Fisher's basic quantitative genetic model has an environmental deviation that is modeled as a random variable assigned independently to each individual. Thus, there is both genetic and environmental variation in Fisher's model. We have also seen examples of environmental variation that is not random for each individual. For example, we discussed how the environment changed in wet, tropical Africa after the introduction of the Malaysian agricultural complex and how this environmental change altered the phenotype of fitness associated with genetic variation at the human -globin...

One good turn deserves another Reciprocal altruism

An individual can increase its own fitness through reciprocal altruism, the situation in which altruistic acts are repaid. Forgot your lunch No problem. I'll give you half of mine. But at some point in the future, I'll expect you to return the favor. Unlike kin selection (described in the earlier section), in which the good-deed-doer gets an immediate benefit, in reciprocal altruism, the benefit comes at some future time. In addition, reciprocal altruism can occur whether the individuals are genetically related or not.

Selection drift and phylogenetic inertia

Phylogenetic inertia, however, is not incompatible with selection. We have to distinguish between the question of the origin of traits and their presence. When the traits exist by phylogenetic inheritance but decrease in fitness in the new environment and the new species, selection is likely to suppress them or render them vestigial. In the reptilian family, this was probably so in the case of the four legs when it came to the snakes. So origin and presence are two distinct topics. If the inherited traits are still present, one is allowed to postulate no negative selection, but a positive fitness value may promote stabilizing selection to keep them. So selection and inertia are not two competing hypotheses but are sometimes distinct explanans for distinct explananda, and sometimes complementary explanatory resources. In this regard, the idea of a null hypothesis in the question of the maintenance of traits has even been challenged (Reeve and Sherman 2001). As early as the 1930s,...

Not reproducing to help your family Kin selection

Nearly everything about evolution by natural selection involves some sort of cost-benefit analysis. Is the cost of the mutation offset by its benefit Does having an elaborate tail help you more than hurt you Natural selection favors the trait that confers the most benefit from a fitness perspective, meaning that traits that enhance your ability to get your genes into the next generation increase in frequency in subsequent generations. Because the cost (the single offspring that you did not produce who would have shared half of your genes) is less than the benefit (the three nieces or nephews who each share one quarter of your genes), natural selection will favor helping your sibling reproduce. For this reason, genes that are responsible for behaviors that help relatives reproduce can increase in frequency even if they decrease individual fitness as long as they increase inclusive fitness. This type of selective force is called kin selection. The result makes sense from the standpoint...

One girl for every boy

The 50-50 sex ratio makes sense when you think about the grandchild generation in the following way. Each grandchild has exactly one mother and one father. When the sex ratio of the children is exactly 50-50, the two sexes have identical fitness. If the sex ratio of the children changes, the fitness of the two sexes is no longer balanced. Imagine a mutation that changes the sex ratio of the children in favor of the production of females. Now more of the children are female than male. As a consequence, the smaller number of males will average more grandchildren than will the more numerous females. Due to the shortage of males, these males end up producing offspring with multiple females. By producing more children, the male offspring has greater fitness. Because of the bias in the sex ratio, they're in a better position to get their genes into the next generation. If there is a mutation that favors producing more males, it will increase until the sex ratio is again 50-50 and the two...

Where to Go from Here

This book is organized so that you can go wherever you want to find complete information. Want to know about the role natural selection plays in evolution Head to Chapter 5. If you're interested in the link between individual fitness and how certain social systems develop, go to Chapter 11. You can use the table of contents to find broad categories of information or the index to look up more specific things.

Pluralism and Causality

The simplest way of compromising the realism implicit in our framework is to adopt a non-realist view of causation. On such a view, statements of the form 'X causally affects Y' do not report objective facts about the world at all. Anyone holding such a view would deny that it is an objective matter whether a given character causally affects fitness. Similarly, if one held that causation is nothing but correlation, one would deny the reality of the distinction between character-fitness covariance that does and does not reflect direct selection. Given such metaphysical views, the levels-of-selection question can at most be a question about the heuristic utility of one description over another. This argument seems to me unconvincing. To ask about the 'real locus of causation' is to ask about the hierarchical level or levels at which character differences cause fitness differences. So presuming we are realists about questions of the form 'does X causally affect Y ', Kitcher's assertion...

What is Sexual Conflict

As with any relatively new field, there is considerable debate over the definitions, assumptions, and models of sexual conflict (Hosken and Snook 2005 Tregenza et al. 2006). Of course, the notion that male and female reproductive styles do not always coincide perfectly has a long history in evolutionary thinking, beginning with Darwin's (1871) exposition of sexual selection, demonstrated by Bateman's (1948) study of Drosophila reproduction, and elaborated by Williams's (1966) battle of the sexes metaphor. But it was Trivers (1972) who spotlighted the potential for sexual conflict with an ostensibly simple point sex differences in parental investment, originating with anisogamy, but amplified in mammals by gestation, lactation, and postnatal care, will generate different reproductive strategies for the males and females, maximizing quantity vs. quality of offspring, respectively. The implication is that reproductive strategies of the sexes not only diverge, but may comprise elements...

The Trade Off between Survival and Reproduction

From a fitness perspective, the best (that is, most fit) reproductive scenario is one in which the organism begins to reproduce early and often, and all the offspring survive. But that's not the way it happens in nature, mainly because of the trade-offs between survival and reproduction. The resources required for survival are resources that aren't available for reproduction, and the resources necessary for reproduction aren't available for survival. So when All the populations started out exactly the same a bunch of wild fish in tanks. Over five generations, the fish populations responded to the new selective pressure. The results were exactly what the researchers had predicted. When large fish are more likely to be harvested from a population, the advantage of alleles that cause fish to grow large decreases. These alleles are less likely to make it into the next-generation while alleles that result in smaller size now have higher fitness. These changes will cause the fish to be...

Going to extremes Eusociality

For some eusocial species, like ants, bees, and wasps (all Hymenoptera species), kin selection and inclusive fitness explain why a nonreproductive worker class can develop, and it all goes back to a reproductive system that makes individuals more related to their siblings than to their own offspring. For the other organisms, researchers suspect that other forces are at play.

Other eusocial organisms

In trying to understand these other eusocial systems, biologists suspect that eusociality may have been the result of a dynamic between selection at the level of the individual (which favors the fitness of the individual and therefore tends to prevent the formation of such systems) and selection at the level of the group (which favors groups of organisms over individual ones).

Preliminary assumptions concerning the view of selection

The controversies addressed here over the limits and scope of natural selection, although not devoid of empirical content, are largely dependent on the conception that the authors have of the nature of selection. So far, I have left aside the most general alternative regarding this conception, an alternative which provides both a negative view and a positive view of selection. In the former option, selection merely selects, hence it just sorts high-fitness traits against low-fitness ones in the latter option, selection is by itself creative. Mayr (1965b) claims selection is not a purely negative force'' since it gradually improves existing traits. Among biologists, this positive view is widely held Dobzhansky, Simpson, and Gould shared Mayr's view. Neander (1995) challenged this view in a paper expressing the epistemologi-cal substance of Mayr's intuition. Apart from the two questions that I have distinguished (the developmental question'' and the persistence question''), there is the...

Altruism And The Human Colony

Kindness is not necessarily a uniquely human trait, but humans do seem particularly apt to perform selfless acts at their own expense. Natural selection predicts the evolution of cooperative (benefit to all) and selfish (benefit to individual, cost to someone else) traits because both increase the fitness of the individual who carries them. Altruistic (cost to individual, benefit to someone else) and spiteful (cost to everyone) traits decrease the fitness of their carriers and one predicts that natural selection would not favor those behaviors. Thus, altruism is an evolutionary puzzle it is a behavior that seems incompatible with natural selection. Group selection theory predicts that altruistic traits should spread. Genes for altruism would be perpetuated in future generations because altruism is good for the group as a whole. (Genes for altruism do not necessarily directly cause an individual to act selflessly, they could, for example, code for a rewarding, feel-good natural...

Conclusions and Future Directions

Adversaries, such as predators and prey (Dawkins and Krebs 1979). The Red Queen hypothesis, that any gain in fitness by one unit of evolution is balanced by equivalent losses in fitness by others (van Valen 1973), may provide the most appropriate framework for analyzing reproductive strategies as a zero-sum game between opposing males and females (Chapman and Partridge 1996 Rice and Holland 1997). This does not mean, however, that conflict universally characterizes the phenotypic expression of male and female interaction. Affiliation and intersexual cooperation may be one outcome of this coevolutionary conflict, as suggested for chacma baboon friendships. Indeed, the chacma baboon and chimpanzee together highlight the view of universals as process, rather than as pattern. Current evidence suggests that sexually selected infanticide has generated two distinct modes of female counterstrategy in these species promiscuity and association with males. The patterns are different, but the...

Interactions Of Natural Selection Genetic Drift And Gene Flow

Wright (1932) felt that in a population with a large effective size there would be virtually no chance for a peak shift. Hence, the population would evolve toward the nearest local peak, and then selection would maintain the population on that local peak, even if a vastly superior adaptive alternative existed. We have already seen an example of this with the j -Hb locus in human populations living in the malarial regions of Africa most such populations have evolved toward the A S polymorphic peak even though the fixation for the C peak seems to be a far superior adaptive outcome in terms of average fitness (Figure 11.8), percentage of the population protected against malaria, degree of protection against malaria, and eliminating deleterious side effects such as hemolytic anemia from the population. Because selection could keep populations on inferior adaptive peaks, Wright regarded natural selection as a potential impediment to adaptation when it dominated over genetic drift. To...

Different kinds of mutations

In a point mutation, a single nucleotide in the DNA is replaced by some other nucleotide, resulting in a particular three-letter sequence of DNA that's different. Because of the redundancy of the genetic code, point mutations don't always result in a change in the amino acid and, therefore, don't affect the organism's phenotype, making this particular mutation selectively neutral. There is no change in fitness between the original type and the mutant type. Sometimes, though, a point mutation results in a different amino acid being used in the production of a protein. In this type of mutation, the protein may have a different structure and may behave differently. If the organism's phe-notype is changed, this type of mutation may have fitness consequences. Or it may not there are many examples where an amino acid change results in the production of a slightly different protein but one that works exactly as well. Changes of this sort may have fitness consequences, or they may be...

Postcopulatory Sexual Conflict Postzygotic

Infanticide figures prominently in Smuts and Smuts' (1993) original discussion of sexual coercion, but it does not fit easily within Clutton-Brock and Parker's (1995) more general harassment-intimidation dichotomy. It is initially difficult to appreciate that male infanticide might constitute incidental harm to females, since an infant's death seems so directly detrimental to the mother's fitness. But this proposition becomes clearer when we consider that the specific problem that lactating females pose to reproducing males is a straightforward consequence of primate biology a nursing infant is, in the words of Altmann et al. (1978 1029), a perfect contraceptive. The function of sexually selected infanticide, then, is to disrupt this contraceptive system, not to harm the mother (or reduce her fitness) per se. Thus, following the broader theoretical logic of Partridge and Hurst (1998) and Lessells (2005), if, speculatively, males possessed other means of effectively counteracting the...

Understanding gene function

Indicative of negative selection or conservation. Most proteins have been optimized over millions of years of evolution for a given function. Therefore, any given mutation is more likely to decrease fitness and be selected against, reducing the rate of substitution at such sites. In rarer cases, in which adaptation involving modification of protein function is one of several possible causes, mutations increase fitness and are selected for, resulting in Ka Ks 1. This is called positive selection.

Interact box Mullers Ratchet

Selecting the Muller's Ratchet module from the Mutation menu of PopGene.S2 opens a simulation of the fate of new deleterious mutations in a finite population of chromosomes that lack recombination. The simulation starts out with a population of haploid, clonal individuals that have no mutations and then lets mutation, genetic drift, and natural selection act. The fitness of each individual determines its chances of contributing progeny to the next generation. The number of progeny produced by each individual is Poisson-distributed with a mean of one. The effective size of the population, the coefficient of selection against deleterious mutations, and the mutation rate can be set in the simulation. The results are given in terms of the proportion of individuals in the population with a given number of mutations. If the effective population size is small, Muller's Ratchet also leads to accelerated rates of fixation to a single allele within the category of individuals with fewest...

Idea Sex is beneficial because it can eliminate bad mutations

One of the problems faced by asexual organisms is that, after they have a bad mutation, all their descendents will have the same bad mutation. Then, when a second bad mutation occurs in one of these descendents, all its descendents will have two bad mutations, and so on. This suggestion was first made by Hermann Joseph Muller (1890-1967), and the process is referred to as Muller's Ratchet because the increasing number of bad mutations ratchets down the organism's fitness.

Selectionist models of culture and science

Fields of explananda for those theories. It was noticed long ago that one human characteristic, whether unique or just developed to a unique extreme, is culture and the fact is that besides genetic inheritance there is cultural heredity individuals learn, and they can transmit what they have learnt, which appears somehow replicated. So, given that the transmitted items are likely to be slightly modified each time they are reproduced, a selectionist evolutionary account of culture can be worked out. It faces at least two big problems the first one is the relationship between genetic and cultural inheritance. The fact is that an entity may have great ''cultural'' reproductive success while its bearer leaves no offspring. So there is no necessary genetic basis for cultural traits, although if a cultural trait enhances the fitness of its bearer think of any medical device that fights illness then this enhances its own reproductive success. The other problem is the definition of this...

Targets Of Selection Above Level Of Individual

Many phenotypes emerge at the level of interactions between two or more individuals. If these interactions are recurrent across generations, they will have continuity over time and can be targets of selection. Targets emerging from interactions among individuals are not difficult to find. For example, of the three major fitness components outlined in Chapter 11, two in general are more appropriately assigned to an interacting pair of individuals mating success and fertility fecundity. An individual in a dioecious species does not truly have a phenotype of mating success or fertility such phenotypes take on biological reality only in the context of an interaction with another individual. Another common target of selection is intraspecific competition, a phenotype emphasized by Darwin as being important in his theory of natural selection. But competition also takes on biological reality only in the context of interactions among individuals. It is always possible to assign an average...

Evolution Of Senescence

This section, we will see how the fitness measures derived above allow us to address these important questions. Using the life history data in Table 15.1 in equation 15.18, we can calculate the net reproductive rate of bearers of a newly formed Huntington's allele (one that just crossed the threshold repeat number and reached a value of 36 repeats, as discussed in Chapter 13) to be 0.9941 versus the normal net reproductive rate from Table 15.1 of 0.9968. Theneurolog-ical symptoms are relatively mild when they first occur and then get progressively worse, eventually resulting in death. The assumption that all reproduction stops with the onset of symptoms is therefore overly conservative, so the actual difference in net reproductive rates associated with a newly formed Huntington's is even less than that indicated above. Hence, the lethal neurodegeneration of Huntington's disease is essentially neutral with respect to natural selection when an allele reaches the 36 repeat threshold. Of...

Laws and selectionist explanation

The only evolutionary statement that could be a law is, thus, the one enunciating the process of natural selection since it specifies no particular entity. Philosophers debate about the nomothetic status of this principle of natural selection (PNS) (Bock and Von Wahlert 1963 Sober 1984, 1997 Brandon 1996, 1997 Rosenberg 1985,1994,2001). Rosenberg argues that the PNS is the only law of biology and relies on Williams' (1970) axiomatization of the theory, which conceives fitness as an undefined primitive term, e.g., a term which in some definitions, in some contexts, can be given only outside evolutionary theory, in another theory. But, even if by convention we say that it is a law, we still face the question of its differences from the other kinds of law.9 In effect, unlike physical laws, the PNS does not state any natural kind of property such as mass, electric charge, etc. The only property involved in its formulation is fitness, which is a mere supervenient property. So the PNS...

Fundamental Equation Of Natural Selection Measured Genotypes

A complete generation transition, ending up in the next generation at a comparable point to the starting generation. In the models used in Chapter 2 we went from parental genotypes to gametes via Mendelian probabilities, then to offspring genotypes through the mechanisms of uniting gametes (population structure). To include natural selection, we need to expand this model by explicitly modeling the life stages measured by the fitness components. In this chapter, we will assume each of the fitness components can be measured as a constant probability that is assigned as a genotypic value to a particular group of individuals sharing a common genotype.

Interaction Of Natural Selection With Gene Flow

The sign of the component of allele frequency change induced by gene flow in equation 12.13 is determined solely by the initial difference in allele frequencies among the demes, in this case p1 - p2. The sign of the selective component of equation 12.13 is determined solely by the average excess of fitness, which in turn is a function of within-deme allele frequencies, system of mating, and genotypic deviations of fitness in the deme. As a result, there is no biological necessity for the selective and gene flow components to have the same sign. In some cases, selection and gene flow can operate in the same direction, allowing an allele to increase (or decrease) in frequency more rapidly than possible through either selection or gene flow alone in other cases selection and gene flow will be in opposite directions and the evolutionary outcome will depend upon their balance. To illustrate these diverse outcomes, we return to the example of African Americans, a population influenced by...

We Fought The Law And The Law

Farming led to elites, and there was no avoiding their power. Foragers could walk away from trouble, but farms were too valuable (too important to the farmers' fitness) to abandon. So farmers had to submit to authority The old-style, independent-minded personalities that had worked well among egalitarian hunter-gatherers (A Man's a Man for a'That) were obsolete.22 Even when some group had a chance to refound society on a more egalitarian basis, as in the case of the medieval Iceland republic, elites tended to reappear.23 Aggressive, combative people may also have experienced lowered fitness once ruling elites began to appear. With strong states, the personal payoff for aggression may have become smaller, while law and order made combativeness for self-defense less necessary. Sheer crowding must also have disfavored some personality traits that had worked in the past. Intuitively, it seems that a high level of aggressiveness would be less favored when encounters with strangers were...

Duplicating genes A gene is born

When the second copy is nonfunctional These nonfunctional genes are called pseudo-genes. Pseudo-genes look like the original genes, but they're a little, or a lot, broken, and they tend to accumulate more and more mutations over time. The more mutations occur, the harder it is to recognize that these genes are related to existing genes. But since they're already nonfunctional, there's no fitness cost to a few more mutations.

Selection In Agestructured Populations

Up to now we have assumed discrete generations. Under this assumption, all individuals are born at the same time and then reproduce at the same time followed by complete reproductive senescence or death. Such a model approximates reality for some species. For example, many insects and plants have only one generation per year that is synchronized by the seasons, and the discrete-generation model can approximate their evolution. However, as pointed out in Chapter 2, individuals in many species can reproduce at multiple times throughout their life, can mate with individuals of different ages, can survive beyond their age of reproduction, and can coexist with their offspring and other generations. We do not have to look far to find such a species our own falls into this category of overlapping generations. In species with overlapping generations, an important component of population structure is age structure, the distribution of the ages of the individuals found in the population at a...

Physical chemical properties sheer existence

The other aspect that has to be considered in the experimental framework is the fitness approach. According to this approach the performance of developmentally manipulated organisms or naturally occurring mutants is compared with that of normal embryos. This approach is often used to explain evolutionarily conservative characters as constraints caused by selective forces. An example is the investigation of Galis (1999) of the problem of why most mammals exhibit seven cervical vertebrae. Here malformed human and mouse embryos are studied showing that the occurrence of cervical ribs (i.e. a different number of true cervical vertebrae) is associated with a dramatic reduction in health and survival rate and fitness in general (Galis 1999). However, this view faces the problem that all living systems are functionally balanced and that mutations and experiments artificially disturb this functional balance. Accordingly, a reduced fitness may not be surprising and might not explain the...

Coarsegrained Temporal Heterogeneity

Just as a population can move through space via the dispersal of its constituent individuals, a population can also move through time via acts of reproduction to create generation after generation. The environment can change as a population moves through time such that different generations experience different environments, and because fitness is a genotype-by-environment interaction, the fitnesses associated with particular genotypes can also change across the generations. Insight into the evolutionary implications of coarse-grained seasonal selection can be obtained through a simple one-locus, two-allele model (Hoekstra 1975). In most models in population genetics, the basic temporal unit is a point in the life cycle at one generation to the corresponding point in the next generation. However, for a cyclical selection model, Hoekstra chose as his basic unit one complete cycle of the environmental changes, which corresponds to more than one generation in the coarse-grained case. The...

Copy number of plastid genomes

Nomes can avoid evolutionary deterioration. Asexual reproduction is believed to be detrimental because of the accumulation of deleterious mutations over time, a hypothesis known as Muller's ratchet (Muller 1964). Since the vast majority of mutations are deleterious, an asexual genetic system is expected to suffer a continuous decline in fitness. Surprisingly, in spite of their asexual mode of reproduction, plastid genomes even have considerably lower mutation rates than nuclear genomes (Wolfe et al. 1987). A recent study has provided experimental evidence that it is the plastid's high degree of polyploidy which, together with a very active mutation-correcting activity by gene conversion, counteracts the detrimental effects of Muller's ratchet and keeps mutation rates in plastid genomes very low (Khakhlova and Bock 2006). These findings suggest a molecular link between asexual reproduction, high genome copy numbers, and low mutation rates.

Priorities For The Future

Finally, we predict that stress-related studies of giant pandas living in captivity will have application to studying and conserving wild counterparts. A final example is recent work in our laboratory that has addressed the impact of a radiotelemetry collar placed on a giant panda. For years, controversy has swirled in China about radiocollars being problematic for free-living pandas. Without substantive evidence to the contrary, the central government now bans radiocollars on wild giant pandas, which greatly compromises ecological studies of, for example, movement and foraging activities. To begin to generate real, quantifiable data, we immobilised and fitted four giant pandas at the Wolong ex situ facility with standard radiocollars (Durnin et al, 2004). Behaviours and daily urine samples (for glucocorticoid assessments) were measured for two weeks before and two weeks after collar placement. Despite intensive monitoring, we observed no differences between the control (pre-collar)...

Genetic Basic and Ability of Hybridization and Introgression of Spartina Alterniflora

Hybridization and introgression also are the basics of outbreak of invasive species. Hybridization between species or between disparate source populations may serve as a stimulus for the evolution of invasiveness (Ellstrand & Schierenbeck, 2000). After introduced into England, S. alterniflora hybridized with native Spartina maritima and resulted in a sterile hybrid S. x townsendii. Chromosome doubling in this hybrid gave rise to a new fertile allopolyploid species, Spartina anglica (2n 122-124), a vigorous and aggressive perennial plant that has been actively colonising British salt marshes since its formation (Raybould et al., 1991). S. anglica displays wider ecological amplitude than its parents across the successional sequence of salt marsh zones (Thompson, 1991) and rapidly spread along the West-European coast(Baumel et al., 2001). Contrast to native S. foliosa, S. alterniflora had greater mall fitness, and the hybrids appeared vigorous and were recruiting more rapidly than...

Autozygosity or inbreeding coefficient

The process of consanguineous mating or inbreeding is associated with changes in the mean phenotype within a population. These changes arise from two general causes changes in genotype frequencies in a population per se and fitness effects associated with changes in genotype frequencies.

Population Subdivision

Population subdivision with Nm close to 1 was a critical requirement for shifting balance according to Wright. Many species do have subdivided populations. Even humans have an Nm close to 1 (Chapter 6). Our own species is instructive about the potential for shifting balance. Although our overall Nm is close to 1, there is much spatial heterogeneity over our geographical distribution for the amount of local population subdivision. This is often true of other species. For example, the eastern collared lizard (Crotaphytus collaris collaris) shows extreme population subdivision with little to no gene flow among isolated demes in the northeastern Ozarks (a central highland area in North America), gene flow constrained by isolation by distance in the southwestern Ozarks, and less extreme isolation by distance in Texas (Hutchison and Templeton 1999). For many species the necessary degree of subdivision may exist only in a part of the species' range. Therefore, the entire species does not...

Coarsegrained Spatial Heterogeneity

Consider a landscape subdivided into spatial patches or habitats that induce different fitness responses from specific genotypes. We further assume that these genotypes experience only one of these patches in their lifetime (or at least, the selectively relevant portion of their lifetime for the unit of selection of interest). As an example, consider the northern acorn barnacle (Semibalanus balanoides) on the northeastern coast of the United States (Schmidt and Rand 2001). This, as well as many other marine species, has planktonic larval dispersal, resulting in high levels of gene flow and negligible population subdivision at the larval stage. The larvae then settle and enter a completely sessile stage for the remainder of their lives. The intertidal region that they settle in is a mosaic of habitats that greatly differ in environmental parameters that affect barnacle survivorship. A specific individual only experiences the habitat in which it settled, so this is coarse-grained,...

Some Necessary Conditions for Systemic Chemical Self Organization

In addition, Eschenmoser et al. (2000) have shown experimentally that nucleic acids can work by other chemistry than today RNA can be formed with different nucleobases, even with hexoses instead of the pentose ribose, with pyrophosphates it may translate into different amino acids. However, the effectivity (in a Darwinian sense the fitness, as defined by Eigen and Schuster (1971)) of the processes above is generally lower. Thus it is very probable that evolution on the Earth started on a purely chemical stage with different, though similar, building blocks.

An Ecological View of Intracellular Life

In an ecological view of interspecies relationships, interactions between two partners also determine interactions beyond this partnership. Thus, simple coevo-lution is unlikely, because the broad ecological context with its entire range of interacting factors, including food competition and predator-prey interactions, also influence host-parasite symbiont interactions 58 . Intracellular microbes probably also influence each other. In the broader ecological context it can be hypothesized that intracellular symbionts such as Rhizobium or Wolbachia species enhance the fitness of legumes or parasitic nematodes, respectively. Studies on the evolution of virulence have found that the more virulent parasites are, the higher their transmission rates and the less they are controlled by immunity. It has been shown that immune pressure selects for more virulent parasites 59, 60 . These studies, however, never took into account that hosts with higher parasite loads may be an easier prey for...

Environmental Context

In short, humans are comparatively superb endurance athletes, particularly in hot, arid conditions that are conducive to heat-loss from sweating. In fact, humans appear to occupy a rare extreme in the general trade-off between aerobic and anaerobic capabilities (Wilson and James, 2004). Natural selection often favors speed over endurance because of the dynamics of predator-prey interactions slower animals typically have lower fitness. Animals built for speed and power are rarely good at endurance and vice versa, in part because of muscle fiber composition. In most mammals, there is a predominance of Type lib (fast-glycolytic) and Type IIa (fast oxidative) relative to Type I (slow oxidative) muscle fibers. The former fast-twitch fibers can produce several times more force but are anaerobic and fatigue quickly. Slow-twitch fibers have higher aerobic capacity, but produce less force. Most human leg muscles have about 50 of each type (McArdle et al., 1996), but can increase slow-twitch...

Natural Selection versus Developmental Constraints

Brains were historically considered to be shaped by natural selection, unencumbered by developmental constraints. In general, the size and structure of both entire brains and individual brain regions were thought to be optimized. Jerison (1973, p. 8 ), made this idea explicit when he wrote that ''the importance of a function in the life of each species will be reflected by the absolute amount of neural tissue of that function in each species.'' How development produced that fine-tuning was never specified. Presumably, the idea was that genetic mutations could vary the size and structure of individual brain regions freely, leading to steady improvements in fitness until an optimum was reached. Little thought was given to the possibility that brains might be constrained in how they could evolve. However, a few authors proposed that trophic dependencies between interconnected brain regions might cause entire circuits or systems to change size in unison rather than piecemeal (Katz and...

Adaptation As Polygenic Process

One way humans adapted to malaria in wet, tropical Africa was through the A S polymorphism at the j-Hb locus, an adaptation that confers malarial resistance to only about 20 of the population. In general, many loci can contribute to how an individual responds to its environment in determining the phenotype of fitness. As a consequence, adaptation to a new environment is usually a polygenic process, with genetic variation at many loci If a person does not have the A S genotype at the j-Hb locus in a malarial region, the person could still be protected against malaria through the G6PD A- allele. Thus, the Bantu-speaking peoples adapted to malaria as they expanded into wet, tropical Africa with the Malaysian agricultural complex not only by the C and S alleles at the j - Hb locus but also by the A- allele at the G6PD locus. However, as with the S allele, there are fitness tradeoffs associated with the A- and other G6PD-deficient alleles. Although reducing the red blood cell's capacity to...

Why Worry about Species

In the recognition species concept, species are the most inclusive population of individual biparental organisms that share a common fertilization system (McEvey 1993 Paterson 1985). Paterson believed that Mayr overemphasized isolating mechanisms between species. He argued that species arise as incidental consequences of adaptive evolution entailing individual selection, as opposed to species being adaptations, having coadapted gene complexes that isolate them from other species. Isolating mechanisms would have an advantage in the zone of overlap between incipient species but not otherwise. The cohesive species concept (Templeton 1989) also argues for the importance of cohesive properties of species. This latter notion, however, is consistent with Dobzhansky's ideas of an integrated genotype, fashioned by natural selection, whose fitness would be lowered by cross-breeding with other closely related species.

Genetic Background of Language

Actions of different genes do not affect traits (including fitness) independently (epistasis). It is the network of interactions that one should know, and one must not forget that there are networks at different levels, from genetic regulatory networks through protein interaction networks and signal transduction pathways to the immune system or neuronal networks. The question is how the effect of genes percolates upwards. Genes act on expressed molecules (proteins and RNA) that do their job in their context. There is something amazing about the fact that hereditary action on such primitive molecules percolates upwards resulting in heritability of complex cognitive processes, including language.

Sexual Harassment versus Sexual Intimidation

Sexual harassment refers broadly to the fitness costs of mating to females (sensu Daly 1978), particularly costs connected with persistent male courtship, repeated intromission attempts, or the nature of copulation itself. Sexual intimidation refers to situations in which males punish females that refuse to associate with them or that associate with other males and is thus designed to reduce female resistance or promiscuity (Clutton-Brock and Parker 1995, p 1353). When males use sexual intimidation tactics, females learn to modify their behavior to minimize the costs of male aggression. This definition is directly similar to Smuts and Smuts's (1993) original definition of sexual coercion. To illustrate the distinction between sexual harassment and sexual intimidation, consider the following examples

Conflicting hypotheses on the nature of megaevolution

Parasitic Platyhelminthes

One of the reasons that Goldschmidt's ideas were not accepted is that homeotic mutations usually confer a massive loss in fitness another is that the reduction of a pair of wings to halteres (Diptera) or their specialisation for some other purpose (e.g. the evolution of the elytra from the forewing of coleopteran ancestors) can be achieved by a series of small changes. In other words, the invoking of evolution by homeotic mutation in these cases would appear to be both problematic and unnecessary. However, it is possible that the argument of major fitness decrease being necessarily associated with homeotic mutation is context-dependent. For example, the discovery of an apparently healthy adult homeotic centipede in a natural population (Kettle et al. 1999, 2000) contrasts with the Drosophila situation. Also, a role for homeotic mutations in the evolution of angiosperm flowers now seems possible (De Craene 2003).

Selective Scenarios for the Origin of Language

Sexual selection language is a costly ornament that enables females to assess the fitness of a male. According to this theory, language is more elaborate than a pure survival function would require (Miller, 2001). Song hypothesis language evolved rapidly and only recently by a process of cultural evolution. The theory assumes two important sets of pre-adaptations one is the ability to sing the other is better representation abilities (i.e. thinking and mental syntax) (Vaneechoutte and Skoyles, 1998). Status for information language evolved in the context of an 'asymmetric cooperation', where information (that was beneficial to the group) was traded for status (Desalles, 1998). There is an ongoing debate about the honesty of animal communication, centred on the proposition that signals need to be costly to be honest (Zahavi, 1975). Although some models appear to provide support for this statement (Grafen, 1990 Godfray, 1991 Maynard Smith, 1991), there are exceptions. First, cost-free...

Lenski experiment population density

Having discovered what was special about the Ara-3 tribe, Lenski and his colleagues went on to ask an even more interesting question. Was this sudden improvement in ability to draw nourishment all due to a single dramatic mutation, one so rare that only one of the twelve lineages was fortunate enough to undergo it Was it, in other words, just another mutational step, like the ones that seemed to be demonstrated in the small steps of the fitness graph on page 125 This seemed to Lenski unlikely, for an interesting reason. Knowing the average mutation rate of each gene in the genome of these bacteria, he calculated that 30,000 generations was long enough for every gene to have mutated at least once in each of the twelve lines. So it seemed unlikely that it was the rarity of the mutation that singled Ara-3 out. It should have been 'discovered' by several other tribes.

The Two Types of Multi Level Selection

I turn now to an important ambiguity in the concept of multi-level selection, discussed by authors including Arnold and Fristrup (1982), Sober (1984), Mayo and Gilinsky (1987), Damuth and Heisler (l988), Okasha (2001) and others. The ambiguity arises because there are two things that multi-level selection can mean, that is, two ways that the basic Darwinian principles can be extended to a hierarchical setting. The ambiguity has usually been discussed in relation to individual and group selection, but it generalizes to any multi-level scenario, for it stems from the distinction between collective fitness and fitness2. The distinction between MLS1 and MLS2 dovetails with the distinction between collective fitness1 and fitness2. To see this, consider an example ofMLS1 D.S. Wilson's (1975) 'trait-group' model for the evolution of altruism. Organisms are of two types in this model selfish and altruist. They assort in groups for part of their life cycle, during which fitness-affecting...

Sex Its Expensive So Why Bother

I A sexual organism is effectively throwing away half its genes when it reproduces. When an organism reproduces sexually, only half its genes get passed to its offspring the other half come from the other parent. Asexual organisms, on the other hand, pass on all their genes. So from a fitness perspective, it would seem that asexual reproduction is better (read, more fit), hands down. But sexual reproduction hasn't been eliminated, of course, which means that reproducing sexually must have one or more fitness advantages. So what are these advantages Well, the truth is that evolutionary biologists just aren't sure. Many ideas have been suggested, and probably more that we haven't thought of yet will be suggested. The following sections look at the current ideas.

Approaches to Studying Sexual Conflict

A second approach, based on quantitative genetics, defines sexual conflict as negative covariance between the sexes in fitness, particularly over generations (Rice and Chippindale 2001 Shuster and Wade 2003 Pizzari and Snook 2003, 2004). For example, red deer (Cervus elaphus) stags with greater lifetime reproductive success sired less successful daughters and more successful sons than stags with lower lifetime fitness (Foerster et al. 2007). The negative correlation between the fitness of males and females suggests opposing optimal genotypes for males and females, i.e., sexually antagonistic coevolution. Again, this method is impractical for primates because we know relatively little about lifetime reproductive success, particularly for males, and even less about the selection coefficients and heritability of characters related to fitness.

Like father like son The sexysons hypothesis

Beyond looking good as a couple, how does picking a male with a showy tail increase the female's fitness, particularly if the showy tail makes survival more difficult You'd think that if she wants to get her genes into the future, the female would be better off choosing males with less-showy tails so that her offspring have a better chance of survival. As it turns out, that's not quite how it works. Instead, specific cases have been found in which female fitness is reduced when females mate with less-showy males because the mating success of their sons is lower. In other words, having a sexy son can provide a fitness advantage for a female who chooses to mate with an elaborate male. Imagine a mutation that makes a female less likely to choose a male with a big tail. Now consider how that choice may affect her fitness. True, her sons wouldn't be hobbled with enormous tails, but they wouldn't be prime mating material either. If these poor sons can't get mates, they can't pass on their...

The Emergent Character Requirement

This conclusion is bolstered by the analysis of particles collective by-products in Chapter 3. That analysis aimed to make explicit the idea that a character-fitness covariance at the collective level might be a byproduct of particle-level selection. The emergent character requirement can be thought of as a rival way of identifying particles collective byproducts it says that the covariance at the collective level can only not be a by-product if the character in question is emergent. But our analysis implies that this is wrong. In both MLS1 and MLS2, whether a given character-fitness covariance is a cross-level by-product has nothing to do with whether the character is aggregate or emergent these questions are independent in both directions. Knowing whether Z is aggregate or emergent tells us nothing about whether non-zero values of Cov (W, Z) or Cov (Y, Z) are by-products of lower-level selection, nor vice versa. However, this does not close the case on emergent characters...

Parental Investment Theory and Beyond

In mammals, gestation and lactation fall exclusively to females, paternity certainty is never assured, and paternal care is provided facultatively. Therefore male fitness is seen as limited by competition over mates, and female fitness by access to resources that can in some but not all cases, be acquired through males (Emlen and Oring 1977 Wrangham 1980). Thus, the reproductive strategies of each sex, in particular decisions over mating effort and parenting effort, are analyzed as a product of sex differences in parental investment. Trivers' model (in an expanded Third, there is evidence that there are some species in which females are the principal caregivers, but compete more frequently and more intensively with each other than do males. In meerkats (Suricata suricatta, Clutton-Brock et al. 2006) and many other cooperatively breeding vertebrates (Holekamp et al. 1996 Hauber and Lacey 2005), females gain greater reproductive benefits from dominance than do males (e.g., Engh et al....

The Concept Of Clade Selection

This idea may seem plausible, particularly if one endorses the view that all monophyletic groups, not just species, are 'individuals' in the Ghiselin Hull sense. But in fact it faces a critical problem, for the notion of clade fitness turns out to be incoherent. The fitness of a species is normally defined as the number of offspring species it leaves.8 This notion makes sense because species reproduce, 8 Some authors define species fitness slightly differently, as the difference between speciation rate and extinction rate, by analogy with the Malthusian parameter (e.g. Vrba 1984). A similar definition of organismic fitness is used by Michod (1999). The argument below that there is no coherent notion of clade fitness comparable to the notion of species fitness applies whichever definition of species fitness we prefer. It follows that Williams's idea that cladogenesis constitutes 'reproduction for clades' is incorrect. Reproduction means one entity giving rise to another entity of the...

Experimental Approaches For Highthroughput Design Sampling

The procedure used in evaluating structures. Another possibility is to use computation together with directed evolution to design or improve function. Computational modeling may be accurate enough to generate designs that are structurally sound but a few mutations away from the optimum functional fitness. In that case, error-prone PCR and DNA shuffling may help explore additional mutations that computational design has missed.

Preventing bad mutations

A trade-off may occur between speed of DNA replication and accuracy of DNA replication. Although mutations tend to be deleterious, slowing down reproduction is also bad for fitness. Genes responsible for a phenotype that reproduces slowly but accurately would be at a disadvantage against genes that generate a phenotype that reproduces more rapidly and is almost as accurate. Each of the individual descendants of the rapid (but sloppy) organism would be more likely to have a couple of extra deleterious mutations, but many more of them would be around, and the overall reproductive success of less error-prone individuals would be lower.

Kin selection in bees ants and wasps

Bees, wasps, and ants live in highly structured colonies, with each individual performing particular tasks. Each colony, for example, contains a single reproducing female and many non-reproducing females that gather food, feed the young, and defend the nest but don't lay eggs of their own. So how does helping the group help (that is, increase the fitness of) the individuals, especially those that forgo reproduction themselves In these species, non-reproductive females (the workers) increase their own fitness more if they help the queen reproduce than if they reproduce themselves. It's a numbers game. Of all the relationships (parent to offspring, sister to sister, sister to brother), females in these systems share more genes with their sisters than they do with either parent, their brothers, or their own offspring. More sisters mean more fitness. The following sections explain. The upshot of this strange sex-determination mechanism is that females in this reproductive system are three...

Fortyfive Thousand Generations Of Evolution In The

How did the scientists know this They could tell by sampling the lineages as they evolved, and comparing the 'fitness' of each sample against 'fossils' sampled from the original founding population. Remember that 'fossils' are frozen samples of bacteria which, when unfrozen, carry on living and reproducing normally. And how did Lenski and his colleagues make this comparison of 'fitness' How did they compare 'modern' bacteria with their 'fossil' ancestors With great ingenuity. They took a sample of the putatively evolved population and put it in a virgin flask. And they put a same-sized sample of the unfrozen ancestral population in the same flask. Needless to say, these experimentally mixed flasks were from then on entirely removed from contact with the continuing lineages of the twelve tribes in the long-term evolution experiment. This side experiment was done with samples that played no further part in the main experiment. So, we have a new experimental flask containing two...

Gene Transfer in Intracellular Symbionts

Unlike intracellular bacterial parasites, intracellular symbionts have a mutual or commensal relationship with their hosts 6 . Mutualism describes a relationship where both species receive a fitness gain, and commensalism is where one gains but the other is not significantly harmed 86 . However, living together allows symbiotic species to genetically coevolve in a way that can benefit both 87 . Thus, symbiosis is regularly referred to as mutualism 88, 89 .

The Atom of Between Group Alliances

Concurrently, another, distinct process would favor between-group pacification, this one involving the mediation of affines. In-laws are the relatives of one's spouse, or the spouses of one's relatives, depending on one's viewpoint. Cognitively speaking, the recognition of in-laws is similar to kin recognition. It requires no more than the ability to recognize preferential bonds between others - e.g., between one's daughter and the latter's husband. When groups A and B came into contact, ego's father could recognize his daughter's husband (his son-in-law) and, reciprocally, ego's husband could recognize his father-in-law. Importantly, from an evolutionary perspective, relationships between in-laws were bound to be, fundamentally, relationships between potential allies. Brothers-in-law, for instance, share a vested interest in the same female, one as a husband, the other as a brother. Both males derive benefits from the female's well-being, the husband through his own reproductive...

The Averaging Fallacy

The averaging fallacy occurs as follows. A population contains individuals of two types, living in groups. Overall (population-wide) fitness values for each type are calculated, by averaging across all the groups it is then claimed that the type with the higher overall fitness spreads by individual selection. This is fallacious, Sober and Wilson argue, because it ignores the effects of group structure. The type that is fittest overall may actually be less fit within each group, if groups in which the type is common are fitter than groups in which it is rare. If so, then there is a component of both individual and group selection at work, they argue. Sober and Wilson acknowledge that if we merely wish to predict the evolutionary outcome, averaging fitnesses across groups is fine. But if we wish to understand why one type has spread at the expense of the other, averaging is at best useless and at worst misleading. It is useless because it tells us nothing about the level(s) of selection...

Being sneaky Alternative male strategies

In a monogamous species in which males and females enter into long-term reproductive relationships, parents will have an interest in each other's survival because only through the survival of their partners will they be able to produce any offspring. The situation is much different for species with short-lived or no pair bonds. In this case, selection can favor traits of one individual in the pair even if they decrease the partner's fitness. Parents have an interest in providing for the survival of their offspring. From a strictly evolutionary point of view, they don't necessarily have any interest in each other's survival. Why Because from a fitness perspective, it's better for a male if his partner makes only a few offspring, all of which are his, than if she makes very many offspring that aren't his. The female's fitness is increased by adaptations that favor her reproductive output over that of her mate's. The result of the conflicting goals is an evolutionary version of the...

Evolution of Lysozymes in Colobine Monkeys

These differences in the effects of selection on the two types of mutation in the protein coding regions form the basis of inferring the underlying forces on DNA sequence evolution. The rate of synonymous substitutions (dS) is considered to reflect the rate of mutation in that region, while the rate of nonsynonymous substitutions (dN) is shaped by specific types of selection for that region. Therefore, a dN dS ratio smaller than 1 means that nonsynonymous mutations have been fixed more slowly than the mutation rate or the neutral rate. This can be explained by selection to preserve the existing protein sequences, often called, negative or purifying selection. In fact, most protein sequences are assumed to evolve according to this fashion because most of the changes in protein sequences are likely to be deleterious in effect. A dN dS ratio equal to 1 (statistically) suggests that mutations on the sequences are all equal in fitness, regardless of the consequences. This is often referred...

Emergent Relations and the Damuth Heisler Approach

In two papers on multi-level selection, Heisler and Damuth (1987) and Damuth and Heisler (1988) provide an insightful discussion of emergence, and link it to the contextual approach to MLS1. They argue that emergence is relevant to the levels of selection, but not in the way that advocates of the emergent character requirement have thought. The crucial question is not whether a given character is emergent rather than aggregate, but whether the relation between the character and fitness is emergent, Damuth and Heisler argue. The idea of a relation being emergent may sound unusual, but there is no reason why it should not make sense, at least to the extent that emergent characters make sense. For often in metaphysics, a distinction between types of property will be matched by an analogous distinction between types of relation. Damuth and Heisler say that a character-fitness relation is emergent if it 'cannot be accounted for' by a character-fitness relation at a lower hierarchical...

Is Sexual Coercion Beneficial to Females

It is possible that sexual coercion may actually enhance female fitness by providing a behavioral filter for higher quality males as mates or guaranteeing that females' sons will carry sexually antagonistic traits that enable them to achieve higher reproductive success (Eberhard 1996 Cordero and Eberhard 2003). If the net effect on female fitness is therefore positive, then sexual conflict becomes a mechanism of female choice, which Eberhard (2005) contends explains most male mating aggression to resistant females. This hypothesis has not been supported by some mathematical models (Kirkpatrick and Barton 1997), but there is some related evidence for benefits of coercion to females (Valero et al. 2005).

Gametic disequilibrium under both recombination and natural selection

In the Java version of Populus, use the Natural Selection menu to select the Two-Locus Selection simulation. Set pAB pab 0.5 and pAb paB 0.0 as a case where there is maximum gametic disequilibrium initially. Use fitness values of wAaBb 1, all others 0.5 and wAAbb waaBB 1, all others 0.5 to generate strong natural selection (relative fitness values are explained in Chapter 6). Finally, try recombination values of r 0.5 and 0.05. Focus your attention on the D vs. t plot. What do the two different fitness cases do to levels of gametic disequilibrium and how effective is recombination in opposing or accelerating this effect recombination. In such cases, the population reaches a balance where the action of natural selection to increase D and the action of recombination to decrease D cancel each other out. The point where the two processes are exactly equal in magnitude but opposite in their effects is where gametic disequilibrium will be maintained in a population. It is important to...

Evidence for Skeletal Features That Improve ER Performance

Homo Sapiens Body Structure

Put together, there is much evidence that H. erectus but not Australopithecus was capable of ER. However, this inference does not imply that H. erectus was necessarily as good as modern humans or even later archaic Homo at ER. Some modern human features that improve ER performance may have evolved since early H. erectus. In addition, there are some hints that H. habilis may have possessed some ER capabilities, but the evidence is sparse and equivocal (see Bramble and Lieberman, 2004). While it is possible that ER capabilities had evolved by the time of H. habilis, it is premature to be definitive, and there are theoretical reasons to hypothesize that such capabilities, if they existed, were not as developed as in H. erectus. Natural selection tends to take advantage of existing variations in the context of some fitness benefit. Thus, it is unlikely that selection would have favored the evolution of ER-related features if hominins had not already been engaged to some extent in a form...

The Displacement Problem

Dembski (2002a) asserts that the displacement problem is, in fact, the core of his thesis. At a close inspection, however, it becomes clear that the displacement problem is irrelevant to real-life situations. Recall that he defines it as the problem of finding a given target. . . displaced to the new problem of finding the information j capable of locating that target. Our original problem was finding a certain target within phase space. Our new problem is finding a certain j within the information-resource space J (Dembski 2002b, 203). As he explains, the fitness function is of course the additional information that turns the blind search to a constrained search (202). Hence, the information-resource space J is meant by Dembski as a space of (possibly along with other sources of information) all possible fitness functions. According to Dembski, the information-resource space J is in practice . . . much bigger and much less tractable than the original phase space (203). Hence, the...

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