The genetic changes have related to numerous different human characteristics, the researchers say in the journal Proceedings of the National Academy of Sciences.

Two genes involved in determining the size of the human brain have undergone substantial evolution in the last 60,000 years, researchers say, suggesting that the brain is still undergoing rapid evolution.

The scientists make their claim based on the recent evolutionary history of two genes microcephalin and abnormal spindle-like microcephaly-associated, which appear to regulate brain size.

Over thousands of years, both genes seem to be generating new and improved versions of themselves - beneficial mutations that are spreading rapidly among the human population to reshape and strengthen brain capacity.

Many of the recent genetic changes reflect differences in the human diet brought on by agriculture, as well as resistance to epidemic diseases that became mass killers following the growth of human civilizations, the researchers say. For example, Africans have new genes providing resistance to malaria. In Europeans, there is a gene that makes them better able to digest milk as adults. In Asians, there is a gene that makes ear wax drier.

“The changes have been driven by the colossal growth in the human population, from a few million to 6.5 billion in the past 10,000 years, with people moving into new environments to which they needed to adapt. The central finding is that human evolution is happening very fast, faster than any of us thought,” - says Professor Henry Harpending, a University of Utah Anthropologist.

Most of the acceleration is in the last 10,000 years; basically corresponding to population growth after agriculture is invented.

Gene mutations

The researchers looked for the appearance of favorable gene mutations over the past 80,000 years of human history by analyzing voluminous DNA information on 270 people from different populations worldwide.

Data from this International HapMap Project, short for haplotype mapping, offered essentially a catalogue of genetic differences and similarities in people alive today. Looking at such data, scientists can ascertain how recently a given genetic change appeared in the genome and then can plot the pace of such change into the distant past. Beneficial genetic changes have appeared at a rate roughly 100 times higher in the past 5000 years than at any previous period of human evolution, the researchers determined. They add that about 7% of human genes are undergoing rapid, relatively recent evolution. Even with these changes, however, human DNA remains more than 99% identical, the researchers note.

Harpending says: “the genetic evidence shows that people worldwide have been getting less similar rather than more similar due to the relatively recent genetic changes.”

Genes have evolved relatively quickly in Africa, Asia and Europe but almost all of the changes have been unique to their corner of the world.

This is the case, because since humans dispersed from Africa to other parts of the world about 40,000 years ago, there has not been much flow of genes between the regions.