On Human Sexuality
I recently read Cristopher Ryan and Cacilda Jethá's Sex at Dawn: The Prehistoric Origins of Modern Sexuality and it's definitely at the top of my recommended reading list.
It challenges both of the common (but competing) theories of what type of sexuality has been produced in humans by evolution: monogamy (with cheating) and ("mild") polygyny. Monogamy is a well-known word, so I won't waste time defining it. Polygyny is what we reflexively think of when we hear "polygamy": one male with some kind of harem.
Sex at Dawn does so by providing a laundry list of anatomical features, studies of current foraging (hunter-gatherer) societies and historical records of then-contemporaneous foraging societies from the Colonial Era. It delves into evolutionary biology, evolutionary psychology, anthropology, religion, and even touches on economics, and manages to remain interesting and humorous throughout. I was already familiar with most of the items on the list, but had picked them up piece-meal, so finally having a single source to refer to is a great help.
This books joins Sarah B. Hrdy's Mothers and Others: The Evolutionary Origins of Mutual Understanding (which, sadly, I currently only have a book extract for, with the full thing at the top of my books to buy list) in providing a compelling argument that humans are wired for cooperation rather than competition as many assume. Not even the common model of interpersonal cooperation but inter-group competition, either, but full-blown, end-to-end cooperation.
After all, if altruism is statistically advantageous within the context of natural selection, then it would produce an impulse for resource sharing within any social species. Indeed, in Mothers and Others Hrdy illustrates that humans are unique among primates in giving to each other, even choice food items. That is to say, that it is the holder of the resource that initiates the transfer, rather than merely tolerating when another swipes a piece. This is so deeply ingrained that both recipient and donor get a dopamine jolt when such an interaction occurs.
Hrdy also delves into the lack of private property among foragers and that most of the things individuals carry around - what we would at first assume to be personal possessions - are to be given to new acquaintances from neighboring bands (their new owners, in turn, will eventually regift them to somebody else) as tokens of mutual friendship ties that both know they can call upon in the future if their home group ever falls on hard times. In addition, both books point out that the low population density of the pre-agricultural world made it far more advantageous to simply pack up and move rather than raiding or invading one's neighbors. It's only after populations became tied to a specific plot of farmland or grazing area and began producing surpluses of food to drive higher than natural population growth that inter-group competition would become advantageous.
Mothers and Others focuses on child-rearing and argues that humans are obligate allomothers dependent on help from others to support our unusually slow-developing and care-needing children to adulthood, especially considering that it's not uncommon for a woman to have more than one at different stages of development, even in foraging societies where children tend to be spaced out at one every five years or so.
Sex at Dawn focuses more on reproduction, as you'd expect from the title, but also picks at the Malthusian and Hobbesian - Hobbes' famous claim that prehistoric life was "solitary, poor, brutish, and short" is used for the outline of Part III, with each adjective getting a chapter dedicated to a raft of counter-evidence against it - view, argued by Ryan and Jethá to be a case of projecting the ills of Malthus and Hobbes' own time back onto prehistory, a tendency they refer to as "Flintstonizing" prehistory. Its basic premise is that humans are neither monogamous nor polygynous, but polygynandrous - with every adult, male or female, having multiple partners.
Although both agree that the natural state for humans is one of cooperative child-rearing, with all adults and older children in the group chipping in to help take care of all the young children, they do disagree on the cause. Sex at Dawn takes the tact that human's natural promiscuity drives this child-rearing as it obscures paternity, while Mothers and Others argues that it is a consequence of the total foraging lifestyle, with young children being a liability while gathering and hunting and therefore needing to be left at camp under the care of babysitters. I personally agree more with the latter interpretation, with this shared parenting enabling promiscuity rather than the other way around as pooling all resources like that would eliminate the zero-sum game that drives males in many other primate species to kill other males' offspring. Sharing sex partners would simply be an extension of the fierce egalitarianism and punishment of stinginess characteristic of these societies, reinforced by the genetic advantages of not putting all your eggs in one basket, as it were.
One thing that I really like about Sex and Dawn's challenging of both the monogamous and polygynous views of human nature is that both assume that females are monandrous, and differ only in whether they share their single partner with other females or not, perpetuating a subtle type of slut-shaming in their not-explicitely stated, but just-under-the-surface narrative of female promiscuity being unnatural. This entry is already pushing into TL;DR territory, so I won't get into the evidence presented in Sex at Dawn comparing various parts of human anatomy and behavior to monogamous (gibbons), polygynous (gorillas and orangutans) and polygynandrous (chimps and bonobos) apes, with one exception as a way to finish off this entry.
We accept female copulatory vocalizations as being a way to announce that the train is in the station and accepting passengers - i.e. as a sign of female promiscuity - in other species, but not our own. Vocalizing during sex attracts predators and conspecific males alike, and is a useful quality in neither monogamous nor polygynous species. Basically, if the females of your species do this, it's a safe bet they're not naturally monandrous. Stop trying to force them to behave contrary to their nature.
