Lost DNA made us human: losing penile spines allowed for prolonged sex, fostering emotional bonds.
Gill Bejerano, a biologist at Stanford University School of Medicine, and colleagues investigated the differences between humans and closely related primates. They discovered more than 500 regulatory regions, sequences in the genome responsible for controlling genes, that chimpanzees and other mammals have, but humans do not.
They found switches that had been lost in humans such as those which turn on an androgen receptor where sensory whiskers develop on the face and spines develop on the penis.
The researchers speculate that the loss of such spines allowed humans to prolong sex and helped establish the emotional bonds between partners necessary for the long task of raising human infants.
Another switch examined in this study, the GADD45G regulator, has to do with the expansion of brain regions in humans. Bejerano and colleagues believe they have found a place in their genome comparisons where the loss of DNA in humans may have contributed to the gain of neurons in the cortex of the brain.
The researchers found another 508 lost regions they are investigating.
Bejerano and his colleagues intend to delete some regulatory sequences from mice to see if they grow human-like features.
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