Saturday, June 27, 2015

The future of human sex: gorilla, gibbon, or bonobo?

Sex at Dawn, a 2010 book published by HarperCollins

I stumbled into this book almost by chance and, at first, I hated it. The authors start with creating a true army of straw men and then proceed to attack almost everyone who has been saying something on the topics of human sexuality. They start with Darwin, poor guy, he was always faithful to his wife, what could he know about sex? Then, they take a wide sweep to people like Dawkins, Gould, Diamond, and many others, including a remarkable sneer at Richard Wrangham who studied chimps for his whole career, but they know so much more than him about chimps. Truly, that put me off to the point that I was seriously tempted to throw the book out of the window.

But, eventually, I didn't throw the book away and I can say that it is worthy reading despite its many defects. It is biased, preposterous, prolix, and poorly organized; yet, the authors managed to put together a remarkable assessment of the current knowledge on the sexuality of primates.

So, what is the thesis of the book? It takes some work to disentangle it from the mass of the text, but, eventually, it comes out loud and clear. I could summarize it starting from a rough classification of the three sexual strategies used by apes.

1. Gibbons: male-female pair bonding (monogamy)

2. Gorillas: alpha males and large harems of females

3. Bonobos: complete male-female promiscuity

Of the remaining ape species, Chimps behave similarly to bonobos, but they are more aggressive and more hierarchical. Humans, then, are supposed to tend to pair bonding, but that's only theoretical and they can adopt also, in various degrees, the other two strategies.

The thesis of Ryan and Jethà, the authors of the book, is that the "original" human strategy, widely adopted in pre-historical times, is the bonobo strategy, that is male-female promiscuity. Not only that, but they maintain that bonobo strategy is the "natural" sexual strategy of humans and also the optimal one for various reasons.

All that is, of course, not completely new, but it had not been discussed, so far, in a popular book. Then, it is clearly also very questionable, but the authors do manage to show elements in support for their thesis.

Let's start from the beginning: it cannot be proven that our hunting/gathering ancestors would practice the bonobo sexual strategy. However, in some conditions, promiscuity makes a lot of sense in evolutionary terms. In ancient times, one of the main existential threats for a human female was the death of her male companion and we have sufficient evidence that even today human stepfathers do not behave very kindly toward their stepchildren (to say nothing of how lion stepfathers behave). In this view, for a human female, mating with several males is the equivalent of a life insurance for her and her children. If there is a reasonable possibility that her children could have been fathered by a male other than her husband, then, that male has an interest in helping her and her children. Even a husband has some interest in not stopping his wife from mating with other males (or at least for not making too much fuss about that), for the sake of his (probable or possible) children. Extrapolated to its logical conclusion, this leads to the bonobo strategy: complete promiscuity.

This strategy still exists today in some small and isolated tribes and, in modern society, we call it "swinging" (also "wife swapping"). Ryan and Jethà report that it was a fashionable game in the 1940s with American military pilots, whose job carried high risks. As a consequence, it made sense for them to share their wives in order to help them to survive in case their husbands would die in battle.

Up to here, we are on a relatively firm ground; these matters are known in anthropological studies, although not so often popularized. The problem comes if we try to follow the authors in their more audacious propositions, that is, that the bonobo strategy is not just natural but, rather, something that should be widely adopted worldwide by humans. This idea may be appealing under some respects. Bonobos are peaceful creatures because their promiscuous sexual habits remove the need for males to fight for females. If we could develop something like that it in our society, then many of our current problems with wars and violence would disappear.

Here, unfortunately, we have moved to a very, very slippery ground. It is possible that the bonobo strategy is optimal for a small tribe of hunters/gatherers, but things change a lot when we move to the more complex and hierarchical societies that appeared in the past 10,000 years or so. A certain degree of hidden promiscuity persists in all human societies, but the full bonobo strategy is very rare and not exactly praised or considered to be morally acceptable.

There are many possible reasons for the disappearance of the bonobo style sexuality in humans - assuming that it existed. One could be the effect of sexually transmitted diseases, others, simply, the diffusion of alternative sexual strategies. In a complex society ruled by laws and tradition, a human female may not need promiscuity to gain support in an emergency situation. Rather, she can rely on a network of relatives, or - in modern times - on the state. That may be one of the reasons for the diffusion, in relatively modern times, of strict monogamy and of strictly regulated polygamy, both linked to the diffusion of monotheistic religions. At the same time, the increasing complexity and the increasing hierarchical structure of modern society led to the appearance of "super-alpha males" such as Gengis Khan and Ismail Ibn Sharif, who can muster harems that not even the strongest silverback gorilla could dream of. In some cases, these super-alpha males are the very embodiment of the concept of "demonic males" described by Wrangham.

Given this situation, it is naive, to say the least, to think that the bonobo-style sexuality will return with humans simply because we would like to live in a happier and more peaceful world. Evolution is not here to make people (or any creature) happy. Evolution simply moves forward and changes keep occurring as the result of adaptation. We are evolving fast, as a species, and we'll keep evolving. And this evolution is surely affecting also our sexual behavior. So, what is the future of human sex?

In principle, humans could evolve toward any of the three known primate sexual strategies (gorilla, gibbon, and bonobo). A move to bonobo-like promiscuity seems to be improbable, but it may not be excluded if we manage to build a relatively peaceful and stable society. More likely, monogamous pair bonding  could remain the (theoretical) rule for some time. On the other hand, the monstrous "super-alpha" male could expand their role and become the widespread rule, forcing most other males to be unable to reproduce. Finally, humans could evolve in completely different ways, including the possibility of developing a completely "eusocial" society in which sex and reproduction would be reserved for a small group of specialized individuals, as it is the case for some insect and mammal species.

As usual, we cannot tell what the future has in store for us; but one thing is certain: the future is never the same as the past.

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