While traveling around Mexico I’ve noticed Mexicans either spoil dogs or put them on the street. The street dogs appear to be pretty sound specimens, probably because mixing breed lines provides them with superior traits.
Human genetic investigations are reveling our genetic past and it’s more mixed up than you might imagine. It’s possible now for regular folks to economically have their gene line sequenced and they’re finding they have surprising contributors to their genes.
The first big revelation is that we’re all Africans, descended from common ancestors who spread out of Africa around the world.
As modern man settled outside of Africa, we lived near Neanderthals. Most people think of Neanderthals in a negative way, that they were the dim-witted dwellers of a long ago abandoned evolutionary cul-de-sac. But it turns out that the Neanderthals’ time overlapped with ours and they weren’t dim, they were strong and robust. And they had children with us, modern man.
Here’s an example of how some of the investigation works. The more generations that pass, after new genes were introduced to your genome, the shorter that additional piece becomes. So by looking at the length of any Neanderthal genes present, we can make a good guess about when Neanderthals and our ancestors had kids, some as recently as 37,000 years ago.
Another archaic and distinct human group called Denisovans were recently discovered in Russia (in the Denisova cave). There was enough material to produce a genome. And guess what? The Denisovan gene snippet shows up in the mix of some modern humans too. Our ancestors were interminglers.
The fine tuning of our background is still happening and so far it looks like we’re all mixed up.