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Evolution, Stanford News

Hey guys, sometimes less really is more

Developmental biologists David Kingsley, PhD, and Gill Bejerano, , PhD, have published some very interesting research (subscription required) in today’s issue of Nature showing that humans are missing snippets of regulatory DNA shared among other mammals. The upshot is that the loss of these regulatory regions appears to have led to some uniquely human features, including our bigger brains and our lack (thank God) of penile spines. From our release:

The resulting changes may have paved the way for monogamous pair-bonding and the complex social structure necessary to raise our species’ relatively helpless infants, the scientists speculate.

Coupled with bigger brains, that monogamous pair-bonding is likely to occur at least in part due to the fact that penile spines increase sensitivity of the male genitalia and shorten the duration of intercourse. Less stimulating sex may have led to a greater bond between partners, evolutionary biologists theorize. (As long as you’re spending the time, you might as well have a chat?) Discover blogger Ed Yong, who wrote about the research this morning, explains:

We might have facial hair, but we lack the sensitive whiskers that many other mammals use. That’s understandable for vision is our main sense. But why did we lose penis spines, and why do other animals have them in the first place? The spines aren’t there to inflict injuries (as those of many insects are). They’re hair-like and sensitive. Without them, sex is probably a less stimulating activity for human men than for other male mammals, and it takes relatively longer.

It’s possible that by evolving to have less arousing sex, lengthy human intercourse creates a stronger social bond than chimp quickies. “Penile spines are often found in species with competitive mating systems, where multiple males [aggressively] compete for fertilization success,” says Kingsland [Kingsley]. “Humans have evolved a more monogamous, long-term bonding system, which involves many changes.“

The research is getting a lot of play online today, in part due to Nature’s no-holds-barred title of their own news feature about the work. In particular, some science writers are outdoing themselves on Twitter.

Joking aside, however, this is really interesting stuff with implications reaching far beyond genitalia structure. Apparently, less *is* more in many arenas, at least when it comes to being human.

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