The findings don't determine the exact genetic mechanisms that control development of limbs, but do provide the first genome-wide view of candidates to analzye, the researchers said.
"We now have a parts list that may account for these biological changes," study senior author James Noonan, an associate professor of genetics at the Yale School of Medicine, said in a university news release.
He and his colleagues compared gene regulatory sequence activity that occurs in humans, rhesus monkeys and mice during limb development in the womb. While activity was generally similar in all three species, certain regulatory sequences were active only in humans.
The study was published online July 3 in the journal Cell.
Noonan plans to transfer some of gene regulatory elements specific to humans into mice to see what aspects of human limb development they may control.
"It has been difficult to understand how human traits evolved, because we didn't have any idea where the important genetic changes might be," Noonan said. "Now we do, and we have the experimental tools to determine what biological effects these changes may have. Our study also provides a roadmap for understanding other human-specific traits that arise during development, such as increased brain size and complexity."
The March of Dimes explains how a baby grows.