Humans are not "all one." There is multiple different hominid species.

There's Cro-magnon. Denisovans and Neanderthal. Sub saharan Africans contain DNA from an unknown hominid species. There's the "hobbit man" a tiny little hominid that until recently lived on a South Pacific island. They hunted miniature elephants.

RH negative blood will reject a fetus from RH positive sperm. That means they are incompatible. A different species. Sure they are close enough that modern medicine has found a way around that.

The group that has the highest percentage of neanderthal DNA is very good with numbers and money. They are often very short and stocky with sloped foreheads. (See Henry Kissinger images.)

Cro-magnon is tall and often very attractive. (Think of Tom Brady and his wife Gisela.)

All very political correct to mention this, but we're a mix and match of hominids. There probably used to be a lot more, including those giants that seem to escape the history books.