Convoluted human evolution: Still evolving? (Introduction)

by David Turell @, Tuesday, July 12, 2016, 14:58 (498 days ago) @ David Turell

A statistical study tires to show that we are, but the evidence appears thin:

Harvard economist Jonathan Beauchamp has conducted a study of lifetime reproductive success (rLRS) of a small segment of the U.S. population and has concluded that there is evidence that humans are still evolving. In his paper published in Proceedings of the National Academy of Sciences, he describes the study he conducted, his results and why he believes we are still evolving despite our control over our environment.

As Beauchamp notes, many in the scientific community have come to believe that humans stopped evolving approximately 40,000 years ago—shortly after the advent of agriculture. But he notes there is also evidence that refutes such claims, such as studies that have shown that people developed an ability to digest milk and to live at high altitudes much more recently.

To learn more, he conducted an analysis of records on 20,000 people he obtained from the Health and Retirement Study, which has compiled data on people born between the years 1931 and 1953. He chose this group because the vast majority of them were past child-bearing age—thus he was able to calculate a rLRS for each of them. Besides counting how many children they had, he also looked at body mass index, schizophrenia, age of onset of menstruation and education level—all traits that have genetic roots.

After studying the data, Beauchamp found evidence of evolution in two phenotypes—a slight uptick in the age of first menstruation and a trend toward a lower rLRS for people who had more education—conversely, people with less education had more kids and thus more opportunity to pass on their genes.

But, as Beauchamp acknowledges, his study was based on a very limited dataset, and it was constricted in that it left out the possible children that might have been born to the people in the database who died before growing old, for example. There is also an issue with the increased age of first menstruation, as recent studies have shown that it is actually going down, not up. And there is evidence that even if evolution is still at work, it appears that it is being overridden by our ability to control so many factors of our lives, such as saving people who would have died a natural death, or artificial fertility measures for educated people who have children later in life.

Comment: Adults drinking milk is an enzyme adaptation, as is high altitude living, not real evolution. We may be the end point.

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