Disease Resistance

After a few more studies that have piled up in my inbox that have to do with mixing of populations, let me propose a general rule.  When one population has pretty much outcompeted another, so that there are no more Denisovans/Neandertals/Western Hunter-Gatherers or most of the high-altitude populations but their markers keep showing up at rates of 5% or so, this is nearly always because of disease - malaria, local viruses in Europe or South America - or multiple responses to single environmental pressures like altitude or cold.

So when you see science stories about "they're gone now, but they left some genes behind," those are often going to be disease resistance. These days anthropologists, and especially science writers are going to hit hard on the fact that you are a racist person for not recognising that you have these genes in you, but that is "just the bull elephant trumpeting to the herd," as Garrison Keillor said years ago. They have to say that.

Update:  Oh right.  And they are also obligated to point out that these Others had more complicated cultures, tool sets, diets, economies, and satellite dishes than you thought, you racist, because you likely still thought that "Indians" say "How, paleface."