Neanderthals

The first nonhuman hominin fossils known to science were Neanderthals (pronounced Nee-an-der-talls) or Homo neanderthalensis. They were a stocky, muscular, barrel-chested species known from sites in Europe, the Middle East, and Eurasia. The name Neanderthal comes from the location of one of the earliest discoveries of the species, in the Neander Valley, Germany, in 1856. Based on misinterpretations of the anatomy and the desire to elevate humans from our evolutionary cousins, Neanderthals were...

Quadrupedal To Bipedal

Many of the changes that occur along the hominin lineage involve adapting to bipedalism from a quadrupedal ape's body (Figure 3.6). Built for climbing, swinging, and brachiating through the trees, ape bodies feature short, flat trunks, broad hips, long collarbones (clavicles), shoulder blades (scapulas) on the back instead of on the side of the body (like a monkey or a dog), a round head of the humerus which makes for a flexible rotator cuff at the shoulder, semierect posture, long arms, short...

The Human Genus

With the genus Homo we are given the earliest fossil evidence for dispersal outside of Africa (Figure 3.10). As with all lineage beginnings, the identification of the first member of the genus Homo in the fossil record is difficult. There are several specimens from Ethiopia, Kenya, and Tanzania that are worthy candidates. The problem lies in the definition of Homo. The characteristics that warrant inclusion in the exclusive club of the human genus are not generally agreed upon. It is no longer...

Scientific Method

When a paleoanthropologist finds a fossil (Figure 1.2), she applies the scientific method to decipher its place in evolutionary history. Based on prior knowledge gained from other scientists' work and from her own observations, she forms a hypothesis. Then she collects evidence, or data, to test her hypothesis. This is the step where a chemist would perform an experiment, but a paleoanthropologist, instead, collects evidence of evolution's experiment by analyzing other fossils and the bones of...

From Mendel To The Modern Synthesis

Darwin was not able to fully realize his theory of natural selection because at the time no one understood the mechanism of inheritance, the force behind descent with modification. Darwin laid down the foundation for evolution by hypothesizing that traits are passed on to offspring and if a trait is advantageous it will increase in frequency in a population because the offspring with the trait will survive and reproduce better and will pass that trait onto their offspring and so on....

Fossil Apes

At present monkeys far outnumber the apes, but back in the Miocene, the situation was reversed. There are comparatively few monkey fossils in the Miocene. At that time, apes had radiated to fill most niches that monkeys later took over and fill today. The ape diversity decreased through time so that by the Pliocene, monkeys were dominant and there is a rich monkey fossil record from around the Old World to prove it. Possibly, monkeys simply outbred apes. Great ape mothers wait over four years...

Mitochondrial Eve And Ychromosome Adam

Geneticists have traced similarities in our mitochondrial DNA back to a single shared mother of us all and have also determined the hypothetical father of all the males on Earth today by tracing back through their Y-chromosome variation. Most people have only heard of mitochondrial DNA because of the sensation mitochondrial Eve caused in the 1990s. mtDNA is not the same as nuclear DNA, which is found in the nucleus of the cell. MtDNA is located outside of the nucleus in energy-producing...

Multiregional And Out Of Africa Models

Homo erectus was the earliest hominin to disperse outside of Africa. Until then all hominin fossils from about 6 Mya to 2 Mya are restricted to Africa. Almost as soon as H. erectus appeared on the savannahs of East Africa around 1.8 Mya it spread as far north as Dmanisi, Georgia, and as far east as Java, Indonesia. H. erectus endured in parts of Indonesia until as late as 30 Kya. This massive geographic and temporal range of H. erectus is the inspiration for the two major rival theories of...

Worldwide Dispersal

The peopling of the planet should be considered a consequence of dispersal rather than intended migration. It should be imagined as a fluid process with people moving back and forth as opposed to a singular, directional colonization event (Figure 6.2). The cause of the initial hominin dispersal out of Africa is not explicitly told in the fossil or archaeological records. An early hypothesis suggested that the invention of the Acheulean hand ax enabled H. erectus to inhabit new territories. It...

Rewinding And Replaying Evolution

What are we left to think about human existence With all the evidence pointing to our ape-like origins 6 Mya and our shared ancestry with everything down to cockroaches, slime molds, pond scum, tarantulas, pit vipers, foot fungus, and even viruses, the unique evolutionary status of H. sapiens may seem bleak and maybe even disgusting. But even though we have lousy relatives, should we think less of our species If we can forget about the aforementioned negative impacts we have made on the planet...

Humans And Chimpanzees The Narrow Divide

Ever since Emile Zuckerkandl and Morris Goodman independently compared blood proteins of African apes and humans and determined they were indistinguishable, the remarkable molecular similarities between chimpanzees and humans have been obvious. But now with the sequencing and mapping (pinpointing the location of genes on chromosomes) of whole genomes of chimpanzees and humans, it is possible to identify the genes responsible for the expression of the similarities like those blood proteins and...

Bushes And Trees

Until fossils come with tags that describe exactly what species they belonged to, what they ate, who they mated with, and whether or not they could speak, there will always be arguments over their interpretation. The issue is not whether fossil hominins hold clues to our evolution, the issue is how to interpret those clues and come to a logical consensus on how Homo sapiens came to be. The first obstacle in coming to such a consensus is that hominin fossils are rare. Sure, it is hard to visit...

Primates

With clothing, language, automobiles, and mobile phones, it is easy to forget that humans are primates (Figure 2.2). Anatomy and genetics indicate that primates as a group are most closely related to even less-humanlike animals colugos (Dermoptera) which are gliding mammals from Southeast Asia nicknamed flying lemurs and tree shrews (Scandentia) which are tiny shrew-like animals that also live in Southeast Asia. All primates, with a few exceptions, share general trends in behavior, brain size,...

The Science Of Human Origins And Evolution

Whether they study Ice Age cave paintings, chimpanzee DNA, or the bones of the first tiny squirrel-like primates from 60 million years ago, scientists are asking the same questions Where did we come from and how did we get here Although the search for human origins draws upon research from many scientific disciplines, it is mainly kept to the field of anthropology. Broadly defined as the study of humans, anthropology can encompass any scientific pursuit as long as it has a human focus....

Dna Chromosomes Cells And Inheritance

The basic plan for the cell contained in the genome work s so well that each human develops with few defects from a single fertilized egg into a complicated ensemble of trillions of specialized cells that function harmoniously for decades in an ever-changing environment. Individuals, or organisms, are built of organs, which are made of tissues, which are comprised of cells. Humans (and everything but bacteria and Archaea) are made of eukaryotic cells that contain nuclei (sing. nucleus). All...

Ancient Dna And The Neanderthal Genome

When the preservation conditions are right, it is possible to extract DNA from ancient even fossilized animal and plant remains. Cold dry environments or wet anaerobic ones are usually the best for preserving ancient DNA, or aDNA. Because the survival of old molecules of DNA is rare, and because those that survive actually degrade over time, there is a general rule that specimens older than 100,000 years old are not viable candidates for aDNA extraction. (A potential exception maybe...

GLOssARy

A type of stone tool industry characterized by the hand ax from the Pleistocene period in human evolution. Associated with Homo erectus and Archaic Homo sapiens. Named after the site Saint Acheul in France where it Allele. A version, a sort, or a kind of a gene. For example, the gene for human earwax has two alleles, one for dry and one for wet. Altruism. Behaving selflessly, at a cost to oneself but with a benefit to another. Analogy. Similarity among organisms, which is the result...

The Earliest Primates And Fossil Monkeys

The mammalian fossil record is full of fascinating extinct animals, a subset of which is comprised of primate fossils. The earliest primates are Figure 3.4 Global temperature, as measured by ratios of oxygen isotopes in deep sea and ice cores, has undergone a steady average decrease in the last 5 million years marked by huge fluctuations. Figure 3.4 Global temperature, as measured by ratios of oxygen isotopes in deep sea and ice cores, has undergone a steady average decrease in the last 5...

Stone Tools

Stone tools become smaller, more specialized, and more difficult to make through time (Figure 3.15 Table 3.2). The earliest, most primitive, stone tool industry recognized in the archaeological record is the Oldowan industry or the Early Stone Age tradition. It is a culture of simple crude cores and sharp flakes with only a handful of named types in the toolkit like choppers, hammerstones, and scrapers. Flakes held between the thumb and the forefinger can be used like a scalpel to skin Figure...

Vestigial Traits

Small, nonfunctional third nipples are not unusual in humans. These kinds of evolutionary leftovers, like the rare occurrence of a human tail, are what are known as vestigial traits, or atavisms. As the manifestation of an organism's evolutionary history, vestigial traits are stamps in the passport of evolution. Some mammals, like mice and dogs, have multiple mammary glands for feeding litters of young. Humans, like most primates (but there are some exceptional strepsirhines with multiple...

Diet

Paleoanthropologists are concerned with diet evolution because it is so strongly correlated to other variables (like brain size, body size, intelligence, activity levels, geographic range, tooth shape, skull shape, etc.) and, not insignificantly so, because food intake is the primary means of survival. Diet has also changed considerably throughout human evolution. As we have already discussed, tools and teeth lend clues to hominin diet. However, there are several other useful methods for...

Big Brains And Intelligence

The large human brain evolved relatively late in hominin evolution, once Homo erectus arrived on the scene. However, because the human brain is seen as the champion of human evolution, we will consider it first. The irrepressible curiosity surrounding human brain evolution is perpetuated by the very matter that is so puzzling. However, there is nothing inside the human skull that is unique (Figure 5.1). Only the relative sizes of the anatomical regions within the brain and the number of neurons...

Taxonomy And Classification

Categorization is a skill every human uses, even for matters that extend beyond zoological nomenclature. A formal system of classification of organisms, or taxonomy, is essential because it provides a language so that people can collaborate, understand one another's results, and test one another's hypotheses. Not all classification schemes for animals translate across cultures or stand the test of time. For example, the classification of animals in an ancient Chinese encyclopedia includes the...

Australopiths

Members of the genus Australopithecus (which are often referred to as australopithecines or australopiths) are undoubtedly bipedal and some of the species are considered direct ancestors to humans. Like the earliest hominins, australopiths and their descendents Paranthropus are only found in Africa (Figure 3.8). Thanks to the enormous fossil record of australopiths, with thousands of specimens including nearly complete skulls and skeletons, much is known about the genus. Australopiths all share...

Climate Change And Paleoenvironment

Hominin evolution took place during a time of great global climate change. Drilled-out deep sea and glacier cores hold historical records of the Earth's climate. Each layer of ice that formed, and each layer of sea floor that was deposited, contains a snapshot of the climatic conditions during its creation. Those conditions are told by the amount of certain chemical compounds in the layers. Times of cooling (glacials) or warming (interglacials) are indicated by ratios of oxygen isotopes...

Human Adaptation

Although the genes involved in the expression of the complex skeletal and dental traits we track through the hominin fossil record are still being identified, examples of selection-driven adaptation in living humans illuminate the recent and continuing evolution within our species, and exemplify the speed with which evolution can transform human populations. The maintenance of a harmful allele like that for sickle cell trait shows how humans can adapt with their own biology to fight diseases....

The Earliest Hominins

Until very recently, little pertinent fossil evidence was known from the late Miocene epoch when chimpanzee and human ancestry diverged. Now there are a few contenders for the title of earliest hominin Sahelanthropus, Orrorin, and Ardipithecus and there will need to be more fossil discoveries for paleoanthropologists to reconstruct the root of the hominin tree. Some questions paleoanthropologists ask about the earliest hominins include Were they woodland creatures If so, did bipedal-ism evolve...

Geology And Dating Methods

Before mounting an expedition, paleontologists first look to geologic maps of a region to determine if the right time period is actually present. Then, ideally, they look at aerial photographs or they make a visit by airplane, automobile, or foot to determine if those rocks are exposed and accessible and free of thick vegetation or water cover. Often paleontologists and geologists will explore regions of interest together. If they are interested in fossil hominins they look at rocks dating to...

Homo Erectus

Turkana Boy Anatomy

The first H. erectusfossils to be discovered were a skullcap (the top portion of the cranium that does not include the face or the bottom where the foramen magnum is located), a molar, and a femur from Trinil, Java, in 1891. These finds comprise the missing link that Eugene Dubois set out from the Netherlands to find. Since then, paleoanthropologists have collected H. erectus specimens from Ethiopia, Kenya, Tanzania, South Africa, Morocco, Italy, India, China (Peking Man), and Indonesia (Java...

Homology and Analogy

Dog Scratches Human Leg

The relationship between form and function in animals reveals how ancestry, or shared origin, affects the forms of animals. For instance, the human, whale, dog, horse, and bat forelimbs are similar despite their Figure 2.1 The human arm and the forelimbs of a whale, dog, horse, and bat are homologies because they all evolved from a common ancestral tetrapod. However, the wings of bats and birds are considered analogies because they did not evolve for flight from a common flying ancestor....

Body Size Shape And Strength

Many human adaptations follow the same patterns as other mammals around the world, especially those that are determined by thermoregu-latory rules. There are general mammalian-wide relationships between a body's surface area and volume (SA V) that are controlled by climate. Bergman's Rule states that mammals in colder climates tend to have larger bodies than animals in warmer ones. A larger body size decreases the SA V ratio and thus reduces heat loss. Based on a similar need for heat...

Paranthropus Robust Australopiths

It is becoming more popular to refer to the robust species of the australopiths with their own genus Paranthropus. According to the rules of Linnaean classification, groups must share a single ancestor, but it is possible that robust australopiths evolved independently in East and South Africa from the australopiths in each region (A. afarensis and A. africanus respectively), meaning they could have separate roots. But for clarity and for continuity with current trends, here the robust...

What Is A Fossil

Although they are usually hard to find, fossils are not hard to see. What is surprising to many first-time fossil hunters is how life-like a fossilized animal or plant appears. There is no need to use your imagination to spot fossils in the ground, as if conjuring animal-shaped clouds in the sky. Biological organisms are symmetrical, mathematical, patterned, and in most cases they fossilize having retained much of the appearance they had in life, even if they become flat and resemble...

Speciation

Accumulated microevolution, or changes in allele frequencies in a population, leads to macroevolution, which is speciation. In this sense, variation that exists within a population eventually increases to become variation between populations. Evolution at the species level is the result of cumulative microevolution. Fishes did not and do not evolve into humans, instead a fish-like ancestor gave rise to all amphibians, reptiles, birds, and mammals, including humans. Step-wise changes accumulated...

Scavenging And Hunting

Humans share a common herbivorous, or plant-eating, ancestor with living apes and early hominins were mostly vegetarians who ate fruit, nuts, tubers (roots), and also ate insects like termites. Like other herbivorous mammals, including monkeys and apes, humans cannot synthesize vitamin C an unnecessary skill with a diet comprised of vitamin C-rich vegetable matter. But the drastic shift in hominin brain and body size around 2 Mya is linked to a shift in diet toward carnivory. Scavenging and...

Archaic Homo Sapiens

Hominins that lived all over the Old World between 800 and 125 Kya belong to a category called Archaic H. sapiens. Archaics are a transitional group between H. erectus and modern humans and include the Neanderthals, which are discussed separately. Archaics were still anatomically distinct from modern people, mostly in their skulls, which were thick-boned and low-vaulted, and featured prominent browridges, sloping foreheads, and small chins. Reminiscent of earlier H. erectus, their skulls retain...

Teeth

Because tooth enamel is made of sturdy material (hydroxyapatite), teeth make good candidates for fossilization. As a consequence, teeth are the most common part of hominin skeletons that are discovered and collected. Teeth are distinguishable by species because their shape and size are linked to body size, diet (for shearing, cutting, crushing, grinding) and social behavior (long, sharp canines for mate competition). Differences in the number, size, shape, cusp patterning, and placement of the...