In “Culture may trigger evolution of human features, study finds” (MSNBC Live Science , 12/19/2011), Charles Choi reports that “Research helps solve mystery of Amazonian tribe’s divergent head shapes”:
scientists analyzed genetic, climatic, geographic and physical traits of 1,203 members of six South American tribes living in the regions of the Brazilian Amazon and highlands. Their research found that one group, the Xavante, had significantly diverged from the others in terms of their morphology or shape, possessing larger heads, taller and narrower faces and broader noses. These characteristics evolved in the approximately 1,500 years after they split from a sister group called the Kayapo, a rate that was about 3.8-times faster than comparable rates of change seen in the other tribes.
The major changes the investigators saw apparently occurred independently of the effects of climate or geography on the Xavante. Instead, cultural factors appear responsible. For instance, in the Xavante village of Sao Domingo, a quarter of the population was made up of sons of a single chief, Apoena, who had five wives. The tribe’s sexual practices allow successful men in that group to father many offspring, which in turn means that any traits of theirs can quickly dominate their population
Of course, girls going to high school, getting jobs in the city, and joining a monogamous religion will end this particular experiment in evolution pretty quickly.
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