I recently read Wendy Shalit’s “Is Infidelity natural? Ask the apes” for CNN.com and a barrage of thoughts invaded my mind, including; Who is Wendy Shalit and what makes her qualified to comment on anything scientific? Why does it seem that every time a male researcher proposes an evolutionary explanation for a male behavior he is attacked in the popular press? What does personal choice have to do with our evolutionary history as a species? Who the hell is Chris Ryan and what is he doing determining what is natural or unnatural for our species? What do pendulous breasts and a thick penis have to do with pair-bonding? There were a multitude of other questions, but I will only deal with some of them here and now.

After a little further research I discovered that Chris Ryan is a psychologist with a fair amount of background and knowledge on the subject. While his article is mistaken in a few places [a topic I will deal with shortly] most of his statements in “Monogamy unnatural for our sexy species” are right on the money. Not surprisingly, Ms. Shalit chose to only include parts of statements from Dr. Ryan’s article that supported her position, and she thought, helped prove her point. It’s unfortunate that Ms. Shalit appears to have been so threatened and/or angered by the ideas put forth by Dr. Ryan in his article that she couldn’t, or wouldn’t, stop and consider the ideas and data being presented. This happens all too often when questions about the nature of human sexuality are brought up. What seems even more apparent, from her comments, is that Ms. Shalit doesn’t understand how evolution works, or much about science in general.

When Ms. Shalit questioned the use of bonobos to understand human sexuality, she stated that she would like to consider *all* species, and suggests that data from gorillas or orangutans [or any other primate] are just as useful for understanding the behavior of our early ancestors as those from chimpanzees and bonobos. Ms. Shalit’s error comes from the fact that she doesn’t seem to understand that when scientists reconstruct the behaviors of our ancestors they choose the species they do based on evolutionary relationships. Bonobos, along with chimpanzees, are our closest living relatives, sharing 99+% of their DNA with us. In fact, gorillas are as closely related to us as they are to chimpanzees and bonobos, and all of us [chimpanzees, bonobos, gorillas and humans] are more closely related to each other than we are to orangutans. To make matters worse, Ms. Shalit seems to be confused about whether or not bonobos and chimpanzees are the same thing – they’re not. Chimpanzee and bonobo populations separated from each other about 1.5 million years ago. Either Ms. Shalit doesn’t understand the relationship between these two ape species, or she chose to only use the information that bolstered her position.

The reality is there are questions about the behavior of our ancestors that we will never be able to answer fully. I call these time machine questions, because until we figure out time travel, that allows us to not only go back in time but survive the trip, survive the new environment we find ourselves in and survive the return, we won’t be able to know for sure how our ancestors behaved. However, if we use the fossil evidence [of which there is some] and modern human behavior, combined with the behaviors of our closest living relatives [bonobos and chimpanzees] we can get a good idea of how our ancestors probably behaved. We just have to make sure that we are careful, conscientious and consistent in our approach.

Unfortunately, Ms. Shalit doesn’t seem to understand this process, and instead just attacks it and tries to belittle it, from what I interpret as an angry, defensive position. This is all too apparent when we look at her comparison of pendulous breasts to pendulous earlobes in men, which is just silly. Breasts in human females are sexual signals to men all over the world. It doesn’t matter what culture they’re from, men find breasts attractive, and use them as proxies for the reproductive potential, or fertility, of women. Further, breasts are erogenous zones and are part of sexual stimulation in many, if not most, females. Men’s ears, which are sometimes larger than women’s, do not indicate anything about listening. Ms. Shalit uses a weak example to attempt to “prove” a point that is moot, and she continues it, further damaging her own position.

Despite the errors in her argument, Ms. Shalit does make a good point about monogamy and Dr. Ryan’s reported evidence for it. Pendulous, or permanent, breasts, the “thickest, longest, primate penis” and the ability of females to have multiple orgasms say nothing about whether or not our ancestors were monogamous. Permanent breasts appear to be a proxy for fertility, as mentioned above. Meanwhile, a “thick, long” penis indicates nothing about multiple partners, and instead could have evolved in response to females who were selecting males that could provide them with enhanced pleasure through both anatomical fit and endurance during intercourse. The female orgasm continues to be a mystery, on multiple levels, but it appears to increase the chances of fertilization while enhancing bonding between a female and male. This does not, necessarily, point to promiscuity. While it is true that human males have relatively larger testicles than monogamous primates [like gibbons] or harem living primates [like gorillas], our testicles are nowhere near as large, relative to body size, as the highly promiscuous chimpanzees or bonobos [or bonnet macaques for that matter]. Our testicles seem to be adapted to produce significant amounts of sperm, which allow for multiple matings in any given day, but it is our behavior, and the survival of our children that tell a stronger story here. On average, human relationships around the world last seven years. That’s right, the old cliche of the seven year itch appears to exist for a reason. Now, this doesn’t mean that relationships can only last seven years, it’s just the average across human cultures. Interestingly, seven years appears to be a significant amount of time in human development as well, which may give some clue as to why we are “serial monogamists” cycling through subsequent seven year long relationships.

When children reach age seven, several things happen physiologically, anatomically and behaviroally. Physiologically, seven year olds get exposed to new hormones that prime them for sexual maturation and the ability to reproduce. We often experience this in our 7-10 year olds in new body odors accompanied by increased sweating. Anatomically, the brain nears its completion in growth. While neural connectivity continues to change and mature, the overall brain size is almost complete by seven years of age. These changes are reflected in behavioral expectations of children when they reach age seven. Children from cultures all over the world are considered capable of finding their own food, taking care of themselves and accepting more responsibility. These changes relax the demands on the parents of children at this age, allowing them to focus their energies elsewhere. All of these changes are reflected in child survivorship, which may be the real key to the nature of our romantic relationships. Kim Hill and Magdalena Hurtado from the University of New Mexico have found that among the Ache child survivorship is most strongly impacted by the survival of their mothers. While this is not surprising, the real surprise was the second biggest determinant of child survival – the presence of the father. Among the Ache, children survived, and thrived, most often when their father was present, and that affect diminished after the age of seven. Similar data are coming out from other cultures around the world. If the pattern remains consistent, it might indicate that human males and females form relationships that, on average, promote the survival of an offspring from a single reproductive event. If that seems to be the case, the next question will be, why only one offspring?

While I think that Ms. Shalit is misguided in her approach to this critique, and don’t think most researchers are out to justify male behavior through evolutionary approaches, I agree that those of us involved in modeling the behaviors of our ancestors need to be careful in our approach. We need to understand that there are those who will take our data and twist it to justify, or condemn, the behaviors they champion or despise. Our job as scientists, and the job of those in the media who use our research for stories, or print opinions is to make sure that the public is being exposed to the most thoughtful science available. When it comes to the “naturalness” or “unnaturalness” of human sexuality, feminists and their antagonists will continue to argue their positions with great vigor, which they should. What they don’t need to do is to mislead the public while they do it.