How the Hell and Why Did the Chimp Penis Ever Develop Sharp Spines To Begin With?

How the Human Penis Lost Its Spikes - Thank Goodness



March 9, 2011

By Zoë Corbyn

Sex would be a very different proposition for humans if -- like some animals including chimpanzees, macaques and mice -- men had penises studded with small, hard spines. (Yikes!)

Now researchers at Stanford University in California have found a molecular mechanism for how the human penis could have evolved to be so distinctly spine-free. They have pinpointed it as the loss of a particular chunk of non-coding DNA that influences the expression of the androgen receptor gene involved in hormone signaling. Got that?

"It is a small but fascinating part of a bigger picture about the evolution of human-specific traits," said Gill Bejerano, a developmental biologist at Stanford who led the work along with colleague David Kingsley. "We add a molecular perspective to a discussion that has been going on for several decades at least."

Published in Nature today, the research also suggests a molecular mechanism for how we evolved bigger brains than chimpanzees and lost the small sensory whiskers that the apes -- who are amongst our closest relatives and with whom it has been estimated we share 96% of our DNA -- have on their face.

Monogamous strategy

It has long been believed that humans evolved smooth penises as a result of adopting a more monogamous reproductive strategy than their early human ancestors. Those ancestors may have used penile spines to remove the sperm of competitors when they mated with females. However, exactly how this change came about is not known.

What can be speculated, however, is why forcible rape became the sexual norm among certain mammals with spiked penises. Female chimps probably were not overjoyed about mating with a male chimp with sharp spikes adorning his penis. Ouch!

David Haussler, who studies the molecular evolution of the human genome at the University of California, Santa Cruz, added that our ancestors' loss of penile spines is our gain today."Couples everywhere can be thankful that this particular piece of DNA was ditched," he says.

Another theory for why the human penis lost its sharp spines is that females threatened to withhold sex if the males didn't make it more fun for the females, too. The female chimp in the above photo is making it clear to her guy that she doesn't care about continuing the family name until he gets a spinectomy.

Sheesh, guy....that hurts.....find someone else. I'm outta here.