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New favorable traits evolve when genetic mutations arise that offer a survival edge. As the survivors of each generation pass on those beneficial mutations, the mutations and adaptive traits become more common in the general population. Though it may take millions of years for complex traits , say allowing humans to walk on two legs, evolution itself happens with each generation as adaptive mutations become more frequent in the population. The genomic revolution has allowed biologists to see the natural selection process by making the genetic blueprint of hundreds of thousands of people available for comparison. By tracking the relative rise and fall of specific mutations generations of people, researchers can infer which traits are spreading or dwindling.
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