Humans are evolving more quickly than at any time in history, researchers say. In the past 5,000 years, humans have evolved up to 100 times more quickly than any time since the split with the ancestors of modern chimpanzees 6m years ago, a team from the University of Wisconsin found.

The study also suggests that human races in different parts of the world are becoming more genetically distinct, although this is likely to reverse in future as populations become more mixed.

"The widespread assumption that human evolution has slowed down because it's easier to live and we've conquered nature is absolutely not true. We didn't conquer nature, we changed it in ways that created new selection pressures on us," said anthropologist Dr John Hawks, who led the study.

The researchers analysed data from the international haplotype map of the human genome, and analysed genetic markers in 270 people from four groups: Han Chinese, Japanese, Africa's Yoruba and northern Europeans.

They found that at least 7% of human genes have undergone recent evolution. The changes include lighter skin and blue eyes in northern Europe and partial resistance to diseases such as malaria among some African populations, according to the study in Proceedings of the National Academy of Sciences.

Some of the changes were tracked back to just 5,000 years ago, and "today they are in 30 or 40% of people because they [are] such an advantage," said Hawks.

Many Chinese and African adults cannot digest lactose in milk, but across Europe a lactose-tolerance gene is now widespread. One reason is thought to be that at northern latitudes sunlight is weaker, so people make less vitamin D in their skin. Vitamin D is crucial for absorbing calcium, so being able to digest milk throughout life made people in colder climes healthier.

The surge in global population had also led to faster evolution since more mutations occur, the researchers said.

They believe that in future, the tendency to start families later in life will drive evolution. "People are having problems with infertility, so any kind of genetic variation that increases the success of later fertility will be selected for," said Hawks.