By far, brain is the most recognizable feature that split humans apart from animals. Mutations in genes related to brain function and structure seem to explain the vast differences between human and chimp cognition.

Scientists have now found that DNA non gene coding sequences, once seen as junk and forming 90 % of the genome, can be just as important. They have discovered that these stretches embark regulatory elements that control the activity of nearby genes.

An international team at the Lawrence Berkeley National Laboratory in California assessed the role played in human evolution by these DNA zones looking at 110,549 of them kept during our mammalian evolution. Statistical tests showed that 992 sequences suffered natural selection. The team discovered an accelerated evolution in 69 noncoding stretches close to genes involved in neuronal adhesion. It seems that changes in these regulatory keys might have primarily led to our high cognitive abilities. "Neuronal adhesion molecules play a major role in wiring the brain, such as the formation of connective synapses between nerve cells." said genome researcher Edward Rubin.

"These processes are important in early brain development and also crucial for learning, memory, and cognition in adults."

"For example, one of the noncoding sequences is next to a gene called CNTN4, which appears to be involved in the development of both verbal and nonverbal communication abilities in humans, while another is adjacent to CHL1, which is linked to cognition in both humans and mice."

Anyway, some researchers pinpoint to the fact that we still do not know the exact role of every gene in the human genome, so some precautions must be taken in interpreting the results.

Image credit: Mediscan/Corbis