DNA studies indicate that Humans and chimpanzees carried on interbreeding for thousands, perhaps millions of years after the two species diverged.

The researchers say human evolution seems to have been much more complex than previously thought. This exchanging of genes probably helped both species survive more successfully in their environments.

Team member, Prof. D Reich says that this is just a hypothesis as it has not yet been proved. However, he said it would explain multiple features of their data. Their hypothesis is that there was an exchange of genes between our human ancestors and chimpanzees after the two species diverged.

This study was carried out at the Harvard Medical School and the Broad Institute of MIT and Harvard. You can read about the study in the journal Nature.

Chimpanzee DNA sequences are the most similar to humans in the animal kingdom. After divergence, the differences took place as a result of tiny mutations over time. If scientists can pinpoint these differences in human's and chimp's genomes, it is possible to map out a history of each species' evolution.

The researchers say divergence happened between 6.3 - 5.4 million years ago. This clashes with some fossil findings and calculations. The Toumai fossil of Chad places man before Chimps and Humans diverged, 6.4 - 7.4 million years ago.

If the Toumai fossil calculations are right, then the human-chimp speciation may have taken place over a long period with episodes of genetic exchanges between the two emerging species. It is possible, say the researchers, that the Toumai datings are wrong.

How the two emerging species, one walking upright while the other moved around on all-fours, managed to view each other as attractive mates - is something we will probably never know.

Written by: Christian Nordqvist
Editor: Medical News Today