A good one is the Minnesota Trans-racial Adoption Study. Bit it's not hard to find more. It was a very popular research topic a few decades ago.

> honestly, just think about it a little longer

It's arrogant of you to assume that more thinking will lead to your thinking. It's possible that I did think of your idea and dismissed it as wrong, or that you and cogman10 have different ideas without realizing it. So you should say what you mean if you want to communicate that.

I did think about it enough to realize that all non-human life collectively has more genetic diversity than humans, yet every single other species has less intelligence. So more diversity doesn't necessarily mean equal intelligence.