New research by Yale University researchers, led by J. Noonan, points to the so-called junk DNA to be actually wroking as active switches that regulate gene expression on and off. In fact, it could have been critical to the evolution of humankind as such.
Source: Science Daily: Yale Researchers Find 'Junk DNA' May Have Triggered Key Evolutionary Changes In Human Thumb And Foot.
Noonan and his colleagues looked for sequences with more base pairs in humans than in other primates. The most rapidly evolving sequence they identified, termed HACNS1, is highly conserved among vertebrate species but has accumulated variations in 16 base pairs since the divergence of humans and chimpanzees some 6 million years ago. This was especially surprising, as the human and chimpanzee genomes are extremely similar overall, Noonan said.
Using mouse embryos, Noonan and his collaborators examined how HACNS1 and its related sequences in chimpanzee and rhesus monkey regulated gene expression during development. The human sequence activated genes in the developing mouse limbs, in contrast to the chimpanzee and rhesus sequences. Most intriguing for human evolution, the human sequence drove expression at the base of the primordial thumb in the forelimb and the great toe in the hind limb. The results provided tantalizing, but researchers say preliminary, evidence that the functional changes in HACNS1 may have contributed to adaptations in the human ankle, foot, thumb and wrist-- critical advantages that underlie the evolutionary success of our species.