the goal of much of modern medicine and culture is effectively to stop evolution. Is that happening?
Although the evolution of measurable traits such as modern human skull shape may be due to random drift, some changes have more to do with cultural and environmental factors such as diet. Over the past 10,000 years, there has been a trend toward rounder skulls and smaller faces and jaws. Most of the change is probably due to how we use our jaws rather than genetic evolution. With the rise of farming, humans began to eat much softer food. The resulting relaxation of stress on the face and jaw triggered changes in skull shape. The dramatic and worldwide increase in tooth malocclusion, tooth crowding, and impacted molars are also signs of these changes: Our teeth are too big for our smaller jaws. Non-Western people who eat harder textured foods have low rates of malocclusion. It is not genetic, but reflects the great plasticity of bone. It is a biological change but heavily influenced by culture.
What future for evolution by natural selection? Shifting rainfall patterns, increased rates of evaporation and melting of glaciers, combined with population and economic growth, are expected to increase the number of people living in water-stressed water basins. Rough calculations suggest increases from about 1.5 billion in 1990 to 3-6 billion by 2050. By the 2090s, climate change may bring a doubling in the frequency of extreme drought events, a six-fold increase in mean duration, and a 10 to 30-fold increase in the land area in extreme drought.
Ray Kurzweil imagines humans merging with technology to become cyborgs so that biological evolution finally becomes obsolete.
The evidence points to continuing natural selection, backed by other mechanisms like sexual selection and random genetic drift. This is an era of rapid technological progress and a fast changing environment, and these are conditions under which natural selection can continue to act. Technological change has driven natural selection in the past and there are other selection pressures that could be acting today. In any case, you can be sure that we have no idea where we are taking evolution, or where evolution is taking us.
Professor Christopher Dye was speaking at Gresham College last month