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I will never forget Gordon Gallup’s invited presentation at the 2007 meeting of the NorthEastern Evolutionary Psychology Society. I had never heard him speak prior to this particular talk, but I’d heard that his presentations are in a class of their own.
His talk, titled Competition for Paternity: The impact of evolution on human genital morphology and behavior, was based on a now-famous paper (Gallup et al., 2003) arguing that the human erection is shaped as it is primarily for the purposes of displacing any seminal fluid in a woman’s reproductive tract that may have been deposited by a competing male. In short, he argued (and provided strong evidence for) the idea that the coronal ridge at the end of the erection serves the purpose of pulling out any seminal fluid that is already in the female’s tract. The research by his storied team of behavioral scientists found, using artificial male and female genitalia (along with artificial seminal fluid), found that anatomically correct and textured phalluses removed substantially and significantly more artificial seminal fluid (from artificial female parts) compared with phalluses that did not replicate the standard texture of a human erection.
This research essentially answers the question as to why the human erection is shaped with the unique characteristics that it has. From an evolutionary perspective, any adaptation that increases the likelihood of an individual being able to achieve reproductive success at a cost of the reproductive success of competitors will be naturally selected. And this explanation accounts for the unique nature of the human erection in a way that matches the data, along with the accompanying evolutionary framework, quite well.
But What About Men Displacing Their Own Semen in the Process?
Dr. Gallup’s talk at this conference in 2007 was more than a little provocative. When he finished, it was almost like people didn’t know what to say. This research sheds light on just so much about human sexuality and, in some ways, the human experience more generally.
I was fortunate to have sat behind a woman with big hair during this talk because some of the slides were quite graphic, and at times I felt a need to look away.
During the question and answer session, a young male student asked an interesting question. He essentially asked about the possibility of a male pulling out his own seminal fluid. And, in addition, he asked if this clear possibility posed something of a problem for Dr. Gallup’s framework.
Dr. Gallup, a seasoned academic, did not hesitate in his response. He first acknowledged that it was a good question. He then paused, looking for the right words, and said essentially this: You may have noticed that after an ejaculation, an erection dissipates quickly. And it becomes uncomfortable for the penis to be touched at that state. I hypothesize that this is an adaptation to reduce the likelihood of the male pulling out any seminal fluid that he, himself, has just released