The Evolution of Life History

In This Chapter

^ Exploring life histories

^ Understanding fitness trade-offs and constraints ^ Appreciating the many ways to be fit

The specific details of an organism's life cycle and reproductive strategy are its life history, which includes longevity, age at reproductive maturity, how often the organism reproduces, and how many offspring are produced. Life histories are fascinating to evolutionary biologists because so many of them exist and can be so different. Of course, all this information is interesting at the individual level, but evolutionary scientists look at life histories at the species level.

An oak tree will make thousands of acorns over its life, but it's not likely you're going to make more than one minivan full of children. The human life history is very different from the oak tree life history, yet both strategies have been very good at getting offspring into the next generation. There are lots of people and lots of oak trees, but from a life history perspective, these two species go about it in different ways.

This chapter introduces you to the current theories concerning life-history evolution, theories that seek to answer questions such as these:

^ Why is it best sometimes to make lots of eggs once, but at other times it's best to make one egg lots of times?

^ Why do some animals live for weeks and others for decades?

^ Why do we grow old, and why do we die when we do?

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