Let's put it this way. Opposable thumbs are such a massive fitness advantage, in so many ways that are obviously massively more impactful, that such a factor, if it even exists, would be utterly negligible.

So the only conceivable reasons to raise such a bizarre topic all involve you being a very unpleasant person to converse with -- the most generous I can think of being an unearned sense of intellectual superiority simply by the fact of raising an idea you see as taboo.