Yale University image
After running experiments on mouse embryos (pictured above), scientists concluded that the HACNS1 gene sequence affected developing limbs.
Scientists believe that a certain genetic sequence, which is uniquely unstable in human beings, may explain how humans became so good at using tools and walking upright. The gene sequence, named HACNS1, is thought to regulate both hand and limb formation in embryos.
James Noonan, assistant professor of genetics at the Yale University School of Medicine.