Strength by outbreeding

I am reading Robert Trivers’s The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life. I will review in the next few days, but these passages on the benefits of outbreeding are particularly interesting:

US history has many virtues, among which is the fact that the US population is reconstituted every generation through a roughly 10 percent admixture by external immigration from throughout the world. Although in its history rules of immigration have favored some groups over others, all have had some opportunity. And with illegal immigration, such opportunities are sometimes greatly enhanced. From a biological standpoint, the resulting outbreeding (insofar as it takes place, as it inevitably must) will tend to be genetically beneficial. The US population is perpetually heterogeneous, about to be infused with 10 percent more genes from around the world. …

The later history of African Americans was in some ways more dreadful than under slavery, since not counting as property they could be hanged or “lynched” by the thousands as a form of social control. Nevertheless, the subpopulation had become strong enough by the middle of the twentieth century to begin a political and social movement that led to eventual legal liberation, and with this yoke lifted, the intrinsic benefits of strong outbreeding associated with strong selection has produced a vibrant and powerful subgroup. African Americans are the melting-pot population par excellence in the United States, genetically roughly 25 percent European in origin, 70 percent African, and the remainder Amerindian and Chinese. At the same time, social policies such as the war on drugs amount to a war on lower-class African Americans, greatly increasing incarceration rates, with destructive effects on their communities. So the racist attack continues, but in the long run it can only strengthen the biological power of its target.