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This is: The Psychological Diversity of Mankind , published by Kaj_Sotala on the AI Alignment Forum.
The dominant belief on this site seems to be in the "psychological unity of mankind". In other words, all of humanity shares the same underlying psychological machinery. Furthermore, that machinery has not had the time to significantly change in the 50,000 or so years that have passed after we started moving out of our ancestral environment.
In The 10,000 Year Explosion, Gregory Cochran and Henry Harpending dispute part of this claim. While they freely admit that we have probably not had enough time to develop new complex adaptations, they emphasize the speed at which minor adaptations can spread throughout populations and have powerful effects. Their basic thesis is that the notion of a psychological unity is most likely false. Different human populations are likely for biological reasons to have slightly different minds, shaped by selection pressures in the specific regions the populations happened to live in. They build support for their claim by:
Discussing known cases where selection has led to rapid physiological and psychological changes among animals
Discussing known cases where selection has led to physiological changes among humans in the last few thousand years, as well as presenting some less certain hypotheses of this.
Postulating selection pressures that would have led to some cognitive abilities to be favored among humans.
In what follows, I will present their case by briefly summarizing the contents of the book. Do note that I've picked the points that I found the most interesting, leaving a lot out.
They first chapter begins by discussing a number of interesting examples:
Dogs were domesticated from wolves around 15,000 years ago: by now, there exists a huge variety of different dog breeds. Dogs are good at reading human voice and gestures, while wolves can't understand us at all. Male wolves pair-bond with females and put a lot of effort into helping raise their pups, but male dogs generally do not. Most of the dog breeds we know today are no more than a couple of centuries old. There is considerable psychological variance between dog breeds: in 1982-2006, there were 1,110 dog attacks in the US that were attributable to pit bull terriers, but only one attributable to Border collies. Border collies, on average, learn a new command after 5 repetitions and respond correctly 95 percent of the time, while a basset hound needs 80-100 repetitions for a 25 percent accuracy rate.
A Russian scientist needed only forty years to successfully breed a domesticated fox. His foxes were friendly and enjoyed human contact, very unlike wild foxes. Their coat color also lightened, their skulls became rounder, and some of them were born with floppy ears.
While 50,000 years may not be enough for new complex adaptations to develop, it is enough time for them to disappear. A useless but costly adaptation will vanish in a quick period: fish in lightless caves lose their sight over a few thousand years at most.
An often-repeated claim is that there's much more within-group human genetic variation than between-group (85 and 15 percent, to be exact). While this is true, the frequently drawn conclusion, that phenotype differences between individuals would be larger than the average difference between groups, does not follow. Most (70 percent) of dog genetic variation is also within-breed. One important point is that the direction of the genetic differences tends to be correlated: a particular Great Dane may have a low-growth version of a certain gene while a particular Chihuahua has a high-growth version, but on the whole the Great Dane will still have more high-growth versions. Also, not all mutations have the same impact: some have practically no effect, while others have a huge one. S...
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