Washington, Sep 2 - Humans and chimpanzees are genetically very similar yet clearly distinct in many ways. Scientists have isolated genes that evolved in humans after branching off from other primates, making us uniquely human.

The prevailing wisdom in molecular evolution was that new genes could only evolve from duplicated or rearranged versions of pre-existing genes. It seemed highly unlikely that evolution could produce a functional protein-coding gene from what was once inactive DNA.

However, recent evidence suggests that this phenomenon does occur. Researchers have found genes that arose from non-coding DNA in flies, yeast, and primates.

No such genes had been found to be unique to humans until now, and the discovery raises fascinating questions about how these genes might make us different from other primates.

In this work, David Knowles and Aoife McLysaght of the Smurfit Institute of Genetics at Trinity College Dublin, undertook the painstaking task of finding protein-coding genes in the human genome that are absent from the chimp genome.

Once they had performed a rigorous search and systematically ruled out false results, their list of candidate genes was trimmed down to just three. Then came the next challenge. 'We needed to demonstrate that the DNA in human is really active as a gene,' said McLysaght.