Debbie Bothwell, of Nayland College, asks :-
Karl Dear, of Manawatu College, asked:-
If the theory of evolution is true why have we stopped changing? Is there evidence that modern humans are still evolving.
Neil Gemmell, a zoologist at the University of Canterbury, responded.
The human species hasn't stopped changing. However, evolutionary change is so slow it would take thousands of years to see changes in the human population, and even then the changes would probably be minor.
To appreciate how evolution has worked on the human population we can compare ourselves with the fossils of our ancestors. For instance, in the early humans Homo habilis, who inhabited Africa 1.6 million years ago, the braincase was around 600 cubic centimetres, half that of modern humans. However, if we compare modern skulls to the skulls of humans living 30,000 years ago we see no difference in size.
Comparing modern human populations can also provide clues as to how evolution has affected us in the past. Much of the variation that we see in human populations probably arose as a result of natural selection, the principal force in evolution. For example mountain dwelling people, such as the descendants of the Inca in Peru, have thighbones that have more area for muscle attachment than average. This adaptation makes climbing easier and would have been advantageous for living in mountainous areas.
Humans will continue to evolve as mutations arise randomly and are acted upon by natural selection. However, natural selection may sometimes be sidestepped by our ability to adapt through cultural, rather than biological evolution. For example, should we enter another ice age in 10,000 years we will not evolve more body hair to stay warm, because we can bypass the action of natural selection by simply wearing more clothing. Only time will tell what the future holds for us as a species.