Evolutionary theorist Gregory Cochran and anthropologist John Hawks claim to have found evidence of a huge increase in the rate of human evolution in the more recent period of human evolution of the last 40,000 years.
Human evolution has been speeding up tremendously, a new study contends—so much, that the latest evolutionary changes seem to largely eclipse earlier ones that accompanied modern man’s “origin.”
Contrary to the common view that humans have changed little since out-of-Africa Cochran and Hawks think big changes have come since humans emerged as a distinct species.
“The origin of modern humans was a minor event compared to more recent evolutionary changes,” wrote the authors of the research, in a presentation slated for Friday in Philadelphia at the annual meeting of the American Association of Physical Anthropologists.
Cochran and Hawks see a 2 orders of magnitude acceleration in human evolution in the last 40,000 years.
Hawks and Cochran analyzed measurements of skulls from Europe, Jordan, Nubia, South Africa, and China in the past 10,000 years, a period known as the Holocene era. They also studied European and West Asian skulls from the end of the Pleistocene era, which lasted from two million years ago until the Holocene.
“A constellation of features” changed across the board, Hawks and Cochran wrote in their presentation. “Holocene changes were similar in pattern and... faster than those at the archaic-modern transition,” the time when so-called modern humans appeared. But these changes “themselves were rapid compared to earlier hominid evolution.” Hominids are a family of primates that includes humans and their extinct, more ape-like though upright-walking ancestors and relatives.
Hawks and Cochran also analyzed past genetic studies to estimate the rate of production of genes that undergo positive selection—that is, genes that spread because they are beneficial. “The rate of generation of positively selected genes has increased as much as a hundredfold during the past 40,000 years,” they wrote.
Humans were already spread over large areas of land 40,000 years ago and were evolving to better fit their local environments. If human evolution has been rapid then different population groups likely possess important unique adaptations to local circumstances and the differences between groups are larger than politically correct people would like us to believe.
This reminds me of a recent paper in Nature Genetics that found a quarter of genes show different expression levels in Europeans and East Asians.
Ethnicity stems not just from differences in genetic sequence, but also from differences in the expression of genes shared by ethnic groups, according to a new study in Nature Genetics. The authors found that 25 percent of genes show different expression levels in Asian and European individuals, and single-nucleotide polymorphisms (SNPs) in regulatory elements likely account for many of these variations.
To see if some of these polymorphisms could cause differences in gene expression levels, researchers led by Richard Spielman of the University of Pennsylvania in Philadelphia assayed gene expression differences between ethnic groups.
Spielman and his colleagues measured expression levels of more than 4,000 genes in lymphoblastoid cell lines derived from individuals from three different populations: Chinese, Japanese, and European. They found that gene expression levels from the Chinese and Japanese groups were largely the same, but that expression levels between the Asian groups and the European group differed significantly for more than 1,000 genes.
Local selective pressures produced so many differences.
Also see the March 2006 Plos Biology paper A Map of Recent Positive Selection in the Human Genome by Jonathan K. Pritchard and colleagues at the University of Chicago.
Cheaper DNA testing technologies are going to produce a huge flood of reports on human evolution and human differences.
March 2009 Update: This work has since become the basis for an excellent book by Cochran and Harpending entitled The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.
|Share |||Randall Parker, 2007 March 28 07:50 PM Trends, Human Evolution|