Washington, Sep 5 (IANS): A team led by Indian origin scientist Shyam Prabhakar has discovered a gene enhancer, HACNS1, that may have helped in the evolution of human thumb that gave us our identity.

The study offers the first ever evidence of the existence of human-specific gene enhancers, which are switches near genes in the human genome.

Shyam Prabhakar, co-author of the paper and senior scientist at the Genome Institute of Singapore (GIS), said "opposable thumbs, manual dexterity and ankle or foot adaptations for walking on two legs are hallmarks of our species.

"We think we may have discovered one of the pieces of the genome that encodes some of these definitive human traits.

"This is just the first step - we need to characterize HACNS1 in more detail, and also test the hundreds of other HACNSs we have identified in the genome to figure out what role, if any, they play in making us human."

Human-accelerated conserved non-coding sequence 1 or HACNS1 showed statistical signatures of being an enhancer, and also had the most surprising amount of sequence change during human evolution of all the 110,000 such sequences identified in the human genome - it was by far the most striking candidate.

Remarkably, HACNS1 was found to play a unique human-specific gene-activating role in a region of the developing limb that eventually forms the junction of the wrist and thumb, and also extends partially into the developing thumb.

A similar, though weaker activating role was also observed in the corresponding ankle/foot-forming regions of the developing hind limbs.

Thus, the many observable differences between humans and chimpanzees, such as brain size, hair density, tooth patterns, pelvic structure and hand and foot modifications, could have arisen partly through changes in the way developmental genes are turned on.

The discovery provides significant insights into the genetic differences between humans and chimpanzees - though the species are 99 percent similar in genetic make-up.

These findings have been reported in the Friday edition of Science.