A new study in the journal Nature has generated a great deal of titillation this week as Cory McLean and colleagues have revealed a sequence of DNA that promotes these penis spines, a sequence that humans appear to have lost. The genetic mechanism involved has already been explained extremely well by Ed Yong and John Hawks. However, the interpretation of what the loss of this DNA reveals about human evolution is perhaps the most provocative claim and has resulted in a flurry of media attention.
"Simplified penile morphology tends to be associated with monogamous reproductive strategies in primates," write the authors. According to their study, the loss of these spines would have resulted in a reduction in sexual sensation (because the spines are thought to be connected to nerve endings) and would therefore have allowed our ancestors to engage in more prolonged sexual activity that the authors associate with pairbonding and the evolution of social monogamy (citing Owen Lovejoy's Ardipithecus ramidus paper from 2009 as a model).
As Nature News wrote in their summary of these results:
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.
Read the rest of the post here and stay tuned for the next entry in the Primate Diaries in Exile tour.
McLean, C., Reno, P., Pollen, A., Bassan, A., Capellini, T., Guenther, C., Indjeian, V., Lim, X., Menke, D., Schaar, B., Wenger, A., Bejerano, G., & Kingsley, D. (2011). Human-specific loss of regulatory DNA and the evolution of human-specific traits Nature, 471 (7337), 216-219 DOI: 10.1038/nature09774