Via the Cornell Chronicle Online, Evidence that up to 10 percent of human genome may have changed very recently revealed by CU researchers:
A Cornell study of genome sequences in African-Americans, European-Americans and Chinese suggests that natural selection has caused as much as 10 percent of the human genome to change in some populations in the last 15,000 to 100,000 years, when people began migrating from Africa.
The study, published in the June 1 issue of PLoS (Public Library of Science) Genetics, looked for areas where most members of a population showed the same genetic changes. For example, the researchers found evidence of recent selection on skin pigmentation genes, providing the genetic data to support theories proposed by anthropologists for decades that as anatomically modern humans migrated out of Africa and experienced different climates and sunlight levels, their skin colors adapted to the new environments.
While the study in question, lead by Assistant Prof. Scott Williamson (in biological statistics and computational biology), didn’t turn up too many areas of selection in human genetics that we didn’t already suspect (e.g. skin color, nervous system function and development, immune system genes, lactose tolerance, etc.). They did however have a couple of surprises, such as the lack of selection in critical brain functions (e.g. the frontal lobe and language centers), genes that control proteins that help muscle cells attach to surrounding cells (mutations of this gene lead to muscular dystrophy), and receptors that relate to hearing.
“It is important to emphasize that the research does not state that one group is more evolved or better adapted than another,” said co-author Carlos Bustamante, a Cornell assistant professor of biological statistics and computational biology. “Rather as humans have populated the world, there has been strong selective pressure at the genetic level for fortuitous mutations that allow digestion of a new food source or tolerate infection by a pathogen that the population may not have faced in a previous environment.”
Humans migrate, diversify, and undergo selection, too.