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Neutral theory: the relative importance of drift and selection

It might seem like everywhere we look, we see evidence of natural selection: organisms seem to be pretty well adapted to their environments. But the neutral theory of molecular evolution suggests that most of the genetic variation in populations is the result of mutation and genetic drift and not selection.


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The neutral theory is easily misinterpreted. It does NOT suggest:

  • That organisms are not adapted to their environments
  • That all morphological variation is neutral
  • That ALL genetic variation is neutral
  • That natural selection is unimportant in shaping genomes
