On the Evolution of Oral Sex: It's Actually Good News!

If you thought that fellatio was an entirely human thing, then think again! Naughty, naughty scientists have long been studying how the primates do it. There have been some documented cases of bonobos Pan paniscus performing it, but these little animals are well known to be really kinky, not to say very promiscuous. In terms of evolution, primates are very closely related to humans, so scientists expect them to be a heck lot more likely to be involved in non-vanilla sex than other species.



The short-nosed fruit bats Cynopterus sphinx are not the type of guys that you expect to be exactly...err...adventurous. But one day, a couple of scientists woke up and decided to put cameras in their rooms, without their knowledge. Call them voyeurs or call them explorers, the study was approved by a national panel on animal care.

The authors studied 20 couples and looked at how fellatio affected the length of sex. To be precise, as scientists often are, they defined length of copulation as "when the penis entered the vagina until when it withdrew completely." The males would normally approach from the back of the females who would then reach down and provide some lubrication to their partners, still behind. The males never seemed to object to it! Very rarely did some of the females run away, but they were quickly chased by the males and within 8 to 25 seconds, the sex continued.

The result:

Females were having sex for longer time when they performed fellatio on their partners. More specifically, for every 1 second of fellatio, the couples gained 8 seconds of copulation.

And yes, the scientists do think that there are evolutionary benefits to fellatio! What benefits you might ask? Well, at least for these bats, they hypothesize that the adaptations might provide evolutionary incentives ranging from the prolongation of copulation to the ability of females to taste whether they have made the right mate choice. Who knew?

But the humble authors would agree that we shouldn't stop looking at these types of behaviors just yet... because we do not know exactly, for sure, why fellatio happens. And that topic totally deserves some more exploration.



References:

Tan M, Jones G, Zhu G, Ye J, Hong T, et al. (2009) Fellatio by Fruit Bats Prolongs Copulation Time. PLoS ONE 4(10): e7595. doi:10.1371/journal.pone.0007595

De Waal FBM (1995) Bonobo sex and society: the behavior of a close relative challenges assumptions about male supremacy in human evolution. Sci Am 272: 82–88.

Palagi E, Paoli T, Tarli SB (2004) Reconciliation and consolation in captive bonobos (Pan paniscus). Am J Primatol 62: 15–30.

Schürmann C (1982) Mating behaviour of wild orangutans. In: Boer LEM, editor. The orangutan, its biology and conservation. The Hague: Junk. pp. 269–284.

Koyama N (1988) Mating behavior of ring-tailed lemurs (Lemur catta) at Berenty, Madagascar. Primates 29: 163–175.