DNA Clues to Our Kind: Regulatory Gene Linked to Human Evolution
Bower, B., Science News
A gene that exerts wide-ranging effects on the brain works harder in people than it does in chimpanzees and other nonhuman primates, a DNA disparity that apparently contributed to the evolution of Homo sapiens, according to a new study.
The gene participates in production of prodynorphin, an opiumlike protein that serves as a building block for chemical messengers in the brain known as endorphins. Studies have implicated endorphins in the anticipation and experience of pain, in the formation of intimate emotional bonds with others, and in learning and memory:
All primates possess a virtually identical prodynorphin gene, say geneticist Matthew V. Rockman of Princeton University and his colleagues. However, a separate stretch of DNA regulates the extent to which the gene generates prodynorphin. This regulatory DNA displays a handful of mutations in people that must have evolved by natural selection and aided human survival, the scientists propose. The new findings appear in the December PLoS Biology.
"This is the first documented instance of a neural gene that has had its regulation shaped by natural selection during human origins," says geneticist and study coauthor Matthew W. Hahn of Indiana University in Bloomington.
Rockman's team first compared chemical sequences of prodynorphin-regulating DNA from 74 people and 32 nonhuman primates. The latter group consisted mainly of chimps but included gorillas, orangutans, baboons, and macaque monkeys.
The people generally possessed two to four copies of the regulatory sequence, in contrast to just one copy for each nonhuman primate. Moreover, the people displayed distinctive rearrangements at five spots along the DNA sequence. …