Sex at Dawn part 2

This covers part 2 of the book Sex at Dawn: The Prehistoric Origins of Modern Sexuality. (You can see my reaction to part 1 here.) There are 6 chapters in this section.

Chapter 5: Who Lost What in Paradise?

This chapter makes 3 primary arguments:
1) Agriculture is more work than foraging.
2) Humans have more sex than any other animal.
3) Humans are more social than any other animal.

Data is not really provided to back these claims. This is most troubling to me on point 1, and I'm hoping that data is provided on this in future chapters.

On point 2, it is probably not necessary to provide substantial data; the authors mention that only humans and bonobos have sex throughout the entire menstrual cycle, and that chimps and dolphins have been observed engaging in sex for pleasure instead of reproductive purposes. On the other hand, most animals have sex relatively rarely, constrained to times of estrus. While that is largely true, I feel that a discussion of sex for pleasure (as opposed to solely for reproductive purposes) should include information about masturbation and same sex coupling, both of which are widely observed across animals, particularly in captivity or domestication. While there are cases where the actual intent is not clear -- is a mounting being performed for sexual gratification, as a dominance display, both, or neither? -- their omission is odd given the context of asserting that sex outside of these four species is confined to reproductive purposes.

For point 3, I would quibble only with the superlative. Humans are an intensely social species on the whole. I don't think it's obvious that we are the single most social species, however. Many species of the eusocial insect -- ants, bees, termites, and wasps -- live in markedly larger social groups than we do, and with reproduction confined to a much smaller percentage of the individuals in society. A variety of mammals live essentially their entire lives in social groups, from the complex groups of cercopithecine primates (think baboons) and spotted hyena to the cooperatively breeding wolves and naked mole rats to the matrilineal groups of elephants and orcas, to name just a few. European starlings form flocks that can number over a million individuals, and a large number of fish species spend their entire lives in shoals/schools. Humans are clearly social creatures, and even more social than most mammals, but I don't think it's clear that we are the single most social species.

Chapter 6: Who's Your Daddies?

This chapter discusses the notions of partial paternity found in a number of South American hunter gatherer societies, though mentions that they are found elsewhere in the world as well. This is the idea that babies can have more than one genetic father. I get the impression that the authors think that these notions refute what they see as the standard narrative of male sexual jealousy. I disagree. As I stated in my first post about this book, evolution of behavior doesn't require consciousness of the genetic impacts of this behavior. In societies in which sharing of material resources in mandatory and largely equal, the notions of cuckoldry do not apply as they do in socially monogamous societies/species in which adult investment in the young is directed toward just specific individuals known or assumed to be kin. The largest cost to males in the latter type of social organization is when they invest heavily in offspring to which they are genetically related, and thus there would be an evolutionary pressure to either increase likelihood of relatedness (through, for example, mate guarding), or to decrease investment in specific offspring and increase the number of sexual partners. Communal groups would seem to be following the last of these listed strategies. That doesn't change the fact that sexual jealousy is expected in societies where children are not invested in communally.

It is asserted again that foraging bands in our evolutionary past likely had multiple overlapping sexual relationships throughout the band, and that these relationships were likely required for the level of social equilibrium and communal standards needed for survival. Again, no evidence is presented, this is merely an asserted position.

This is a small point, but one that has irritated me so far in this book: the authors keep talking about gibbons as if they're a single species. They're not. There are more species of gibbons than there are all other apes combined. So when they say things such as "the three most closely related apes: chimps, bonobos, and their conflicted human cousins" (p. 97), they're wrong -- the species within the Nomascus genus in gibbons are more closely related to each other than chimps and bonobos are to each other.

Not quite as small of a point is their tendency to assume that anything shared between humans and bonobos, but which differs from chimps and gorillas, represents the ancestral state of humanity. As I noted before, it is equally parsimonious to get two independent beginnings of something as it is to get one beginning and one loss. We can potentially distinguish between these two options on likelihood grounds, but we're not going to get there on parsimony alone.

A final point at the end of the chapter is that they state that if one views sex as a way to build and maintain mutually beneficial relationships, non reproductive sex makes a lot more sense, and that things like homosexuality become a lot less confusing. From an evolutionary standpoint, same-sex sexual interactions are no more confusing than masturbation is: individuals who enjoyed sex were more likely to leave descendents, leading to sex in general being enjoyable, leading to individuals finding ways to tap into that enjoyment. What is confusing is exclusive homosexuality -- individuals who only have sex with others of the same sex, because, by nature, that doesn't result in passing one copies of one's genes. Group cohesiveness doesn't address that issue at all.

Chapter 7: Mommies Dearest/

This chapter is a bit unfocused. It starts out with retelling a few anecdotes about how some societies embrace not only the idea of multiple paternity, but also multiple maternity, which any woman who nurses a child is seen as one of that child's mothers. This then segues into anecdotes of societies in which children are raised communally, with all adults being viewed as father and mother. From there, it goes on to discuss the decline of the nuclear family structure within Western societies, and how if the nuclear family were the natural unit in humanity it wouldn't need laws to back it up.

The problem is that these arguments are not well-constructed. The authors state "One wonders, in fact, why marriage is a legal issue at all -- apart from its relevance to immigration and property law." (p. 110), and then in the very next paragraph cite the decline of the percentage of legally married households and the concomitant rise of unmarried couples living together over the past 4 decades in the US as evidence of people not living as nuclear triads (mother, father, children). That isn't evidence for their argument at all -- it's evidence of a) a declining rate of marriage, and b) an increasing age at first marriage. Logical flaws such as this make this chapter underwhelming.

Chapter 8: Making a Mess of Marriage, Mating, and Monogamy/

The point of this chapter appears to be to show that the word marriage means many different things to many different societies. Specific examples are discussed, from temporary arrangements and no fault divorces to permanent bondings which don't require sexual fidelity. I have no issues with this chapter; it is manifestly true that what we call "marriage" differs across societies, and even over time within a given society.

Chapter 9: Paternity Certainty: The Crumbling Cornerstone of the Standard Narrative

This chapter largely has two points:
1) Patriarchy is not universal among human societies.
2) Many species formerly believed to be monogamous are not exclusively so.

Both of these points are true. However, I feel that the authors -- particularly in regards to point 2 -- are either running into a terminology issue, or are falling afoul of a false dichotomy. From my reading of the behavioral literature (which is far from expansive, as this is not my field of study within evolutionary biology), paternity certainty doesn't actually refer to certainty. That is, it doesn't require 100% knowledge. Instead, it refers to the notion that certain behaviors -- and, in organisms recognized as having cultures, certain culture norms -- increase the likelihood that the offspring of a male's social partner are his genetic offspring as well. These are things that increase the certainty, but that doesn't mean that they raise it to 100%. Most often, this falls under the general category of mate guarding, which in this context is essentially the male being around the female during the time period in which she is fertile and ensuring that other males do not mate with her. It also also refer to physical adaptations, such as the formation of a coital plug that prevents future males from inseminating a female until it dissolves. But unless a female is fertile for only an exceptionally short window, males will not be able to absolutely ensure their own paternity in her offspring, and we humans tend to be horrified when we come across some strategies involved (such as groups of 2 or 3 male bottlenose dolphins forcing a female away from the rest of the pod, denying her sleep until she accepts copulation and/or physically forcing the issue, and keeping her prisoner for up to several weeks -- dolphins aren't the gentle creatures of our childhood lore). While many songbirds previously thought to be monogamous turn out to have an appreciable rate of extra-pair paternity, that rate is still well under 50%. That makes it more probable that a given male is the genetic father of a chick in his nest than that he is not, and thus there is a more positive expected value in reproductive fitness for provisioning the offspring than is true for most solitary species.

In regards to point 1, it is good to note that there are human matriarchies, and thus patriarchy is not universal. I assume most biologists already knew or suspected this. I don't yet see what bearing this has on notions of what is the proper way for humans to orient their societies or individual lives.

Chapter 10: A Beginner's Guide to Coveting Thy Neighbor's Spouse

I like the beginning of this chapter. It points out the shortcomings in many cross cultural surveys of people's attitudes about specific things. Namely, such surveys are very commonly limited to university students, who are in turn a non-random sample of the population due to considerations of age, class, and status. And particularly in regards to questions about relationships, their youth is a likely strike against them being a universal sample -- most have had few relationships at the time they are answering hypothetical questions about how they might react under certain circumstances. The respondents are also nearly all embedded within cultures of private property and individualism, which make them distinct from many modern foraging groups. These are quite valid criticisms.

Where I feel the authors go wrong is assuming that modern foraging groups accurately represent the distant past of humanity. As I've pointed out in my previous post, I take issue with the authors' assertion that modern foraging groups "thoughts and behaviors have not been shaped by the effects of modern life and whose perspectives represent the vast majority of our species' experience?" (p. 144). These modern groups do not exist in a vacuum. The land they inhabit is due in part to the results of past conflicts with other peoples, including agriculturalists. Many have dealt with years, even decades, of missionaries seeking to convert them to specific faith adopted by much of the agriculturalist world.

This chapter also includes one of the most interesting finding they provide a citation for: namely, that both men and women state that they would be more upset by the idea of a sexual relationship between their partner and their sibling than between their partner and a random stranger. The authors take this as a blow against the standard model of sexual jealousy. In my interpretation, it is completely expected that women would be more hurt by the idea of their spouse sleeping with their sister than with a stranger. The standard model presumes that women are more troubled by their spouse forming an emotional attachment to another woman, and thus provisioning her and her offspring. Women are going to, as a rule, know their sisters better than they know strangers, and have at least a likelihood of liking them. As such, it is likely easier to imagine her spouse forming such an emotional bond with her sister than with a stranger. On the other hand, I do view men being more disturbed by their spouses having an affair with the man's brother than with a stranger to be a blow against the standard model. If the fear is based on provisioning an unrelated offspring, a child that is genetically a niece or nephew is a lot less problematic than a child who is a genetic stranger. I think this could provide an interesting avenue of research, such as whether men are more bothered by affairs with their brother than with their friends, who presumably they would know well enough to be able to easily imagine the scenario.

The authors present an appeal to the notion that erotic love need not be exclusive, as many other forms of love are not, and that it does not have to follow a zero sum game expectation. This is true, but it depends on the society in which children exist in many ways. These include both the obvious ones -- such as the discussions throughout this book of societal mechanisms by which various forager societies have mitigated sexual jealousy with ritualistic requirements on extra pair sex -- and the less obvious ones such as enforced provisioning of all children by all adults within a group. Without these societal structures in place, significant reproductive conflict within a sex will exist, as one individual gaining resources will come at the cost of another individual losing them.

There is also, at the end of this chapter, another instance of what I feel is an assumption that a behavior must be conscious in order to count. The authors look at forager societies in which sexual bonds are not exclusive, and conclude that the women in them do not have to barter access to sex for food or protection or investment in their offspring. That is one way of looking at it, and potentially valid. It's not the only one. It is also valid to look at this as an example of paternity confusion, where men do not know which children are related to them genetically and which ones are not so they contribute to all of the offspring in the group. In this view, the women are bartering sexual access for resources, but they are doing so so constantly that they do not recognize it as such. I do not know that this is what is occurring, but I see it as at least as consistent with the evidence presented, and it's starting to feel like an elephant in the room.