Active site: selection acting where it matters
Other: neutral drift where it doesn’t matter
‘Neutralists’ and ‘selectionists’ for a while grew quite exercised about their respective beliefs, and when the dust settled Kimura was left with a respectable following. Much variation does indeed seem to be neutral in its effects. In particular, the closer scientists look at how proteins change, the more they conclude that most changes do not affect the ‘active site’ where the protein does its chemical tricks.
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An example where the ‘whole truth’ reveals Either-Or Thinking