Are Humans Still Evolving?

The popular view is that humans have ceased to evolve as advances in medical care, better housing and welfare, etc. etc. have leveled the playing field and eradicated the essential variability in humans upon which selection can act. The view that human evolution is grinding to a halt is cogently argued by Prof. Steve Jones, from University College, London, who points out that a former great source of mutational change was the sperm of older men. Cell division during sperm manufacture provides plenty of opportunity for mutational mistakes to occur - and in men over 50 those mistakes are far more numerous. But, says Jones, elderly fathers are rare these days - there is a dearth of aged patriarchs fathering children by multiple wives - and this is allied to far greater survival rates among offspring.

I counter that view in NOT A CHIMP by championing the arguments of John Hawks, Greg Cochran and Henry Harpending, who calculate that human evolution stagnated for much of hominin history but has dramatically speeded up in the last 40,000 years. Also, that, if you take a population geneticists viewpoint there are very many more genomes in circulation around the globe today thanks to human population explosion over the last few millennia - all potential sites for mutation.

Now, as reported in The Scientist, life history evolutionist Stephen Stearns, from Yale University, has got his hands on a wealth of longitudinal medical data collected in the famous Framingham study which has been running since 1948 - several generations' worth. With a number of colleagues he is developing an evolutionary twist to the Framingham data-bank where they are correlating variables like lower cholesterol, lower blood pressure, earlier conception and later menopause, with reproductive success (having controlled for social factors that might influence fertility). They have shown clear changes in the levels of these genetically-controlled traits in only 2 to 3 generations and are now expanding the study to include parameters like high-density lipoproteins, triglycerides and bilirubin, and to look at male reproduction. They are due to publish a detailed review of their findings on contemporary human evolution in a special issue of PNAS later this year.