When Charles Darwin articulated his theory of evolution by natural selection in On the Origin of Species in 1859, he focused on adaptations — the changes that enable organisms to survive in new or changing environments. Selection for favorable adaptations, he suggested, allowed ancient ancestral forms to gradually diversify into countless species.
That concept was so powerful that we might assume evolution is all about adaptation. So it can be surprising to learn that for half a century, a prevailing view in scholarly circles has been that it’s not.
Selection isn’t in doubt, but many scientists have argued that most evolutionary changes appear at the level of the genome and are essentially random and neutral. …
But now some scientists are pushing back against this idea, known as neutral theory, saying that genomes show much more evidence of evolved adaptation than the theory would dictate.
As useful as the neutral theory has been in its various forms over the past half-century, the future of evolutionary theory may inevitably depend on finding ever-better ways to do the hard work of figuring out exactly how — and how much — selection is inexorably shaping our genomes after all.
Read full, original post: Theorists Debate How ‘Neutral’ Evolution Really Is