Once thought of as junk, noncoding sequences of DNA fill in the gaps between genes and make up more than 90 percent of our genome. Recently, scientists have discovered that these stretches of DNA contain regulatory elements that control how and when nearby genes are turned on and off (ScienceNOW, 16 August). An international team led by genome researcher Edward Rubin of the Lawrence Berkeley National Laboratory in California wondered how many of these noncoding regions might play a role in human evolution.
The team looked at 110,549 human noncoding DNA sequences that seem to have been conserved during mammalian evolution. Using statistical tests, Rubin and his colleagues found 992 sequences that appeared to have undergone changes during human evolution that were not due to simple chance, suggesting that the genetic alterations were due to natural selection. The team then used two existing gene databases, called Gene Ontology and Entrez Gene, to match the noncoding sequences with the functions of the coding genes closest to them.
The strongest evidence for accelerated evolution on the human line was found in noncoding sequences next to genes involved in helping neurons adhere to each other. The team found 69 such sequences, suggesting that changes in these regulatory elements may have contributed to the evolution of uniquely human cognitive talents.