Random Evolution and Genetic Drift Sometimes Its All about Chance

In This Chapter

Understanding genetic drift: What it is and when it's important ^ Seeing how genetic drift reduces variation ^ Navigating the adaptive landscape

Charles Darwin (see Chapter 1) had natural selection nailed, even though he didn't have the tools to test his ideas that evolutionary biologists have today. A great deal of modern evolutionary biology has been about confirming and refining Darwin's hypotheses. Since Darwin, one of the most important advances has been the recognition of the role of genetic drift as an evolutionary force. Genetic drift refers to the power random events can have in influencing whether genes increase or decrease in future populations.

Here's the take-home message of this chapter: Genetic drift can result in evolution, even in the absence of natural selection. If two critters are equally well suited to their environment, only chance determines which one leaves more descendants. Genetic drift also can work in the presence of natural selection. Even when some individuals are potentially better than others, chance events still occur. If lightning strikes the fastest cheetah, it won't be contributing its genes to the next generation.

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