Maybe not observable effects. There so many tiny things that must be in our genes that switches that affect anatomy are probably a small percentage. For example, the way people's laughs sound or the fact that almost everyone is attracted to paradisiacal places are probably influenced by genes and not just culture and nurture.
That is one possibility. But with subtle things like that, the trick is to come up with an experiment that either supports or falsifies them. Until such data exist, it remains a mere hypothesis.
