How fast can a species adapt to a new environment?  What evidence isthere that humans are evolving?

These are two common questions that usually come up during classroom discussions of evolution. Most people do not have a problem recognizing that insects adapt to new environments by evolutionary change that provides resistance to certain chemicals, or that bacteria do the same with antibiotic resistance, but often it is difficult to make the connection that the same thing must be occurring for humans. Maybe this is because of the same problem that Aristotle and Plato faced when they proposed the Chain of Being -  as far as one can tell, life (and especially humans) has changed little over the relatively brief period of recorded history. The organisms that people are familiar with - oak trees, lizards, and humans, appear to be the same now as they were several thousand years ago. For humans, this unfortunately has resulted in the idea that we are a "fixed" species, operating outside the laws of evolution.

Therein lies a the fundamental problem - that if you can't "see" evolution, it isn't happening. But now, due to studies of evolutionary change in human populations living in high-elevation areas of Tibet (see "High Elevation Humans - Evidence of Adaption "), we now know that it is possible to detect the genetic basis of specific adaptations in humans. But what is really interesting about this discovery is not the fact that humans are evolving - since that is a basic characteristic of all life - but rather that this adaptation probably occurred over less than 3,000 years . If we use a 25 year generation time for humans, that means that the high-elevation occurred in less than 120 generations. While not as fast as the evolution of adaptations in the bacteria, or even some insects, this is still fast. More importantly, it can be pointed to as a definite example that humans evolve, and that this evolutionary change can be measured.

Additional Links

• University of Berkeley article on rate of change in high-elevation humans.