Last night’s post on the Canadian polygamy ruling included a quote from an “expert” witness in evolutionary psychology, Joseph Heinrich. I didn’t break it down at the time, largely because I was dealing with a migraine and every sound in the room was a major distraction. Let me fix that now. Here is the quote again, now with commentary.

First, like other animals, human males and females have different mating strategies rooted in the nature of primate sexual reproduction.

This is an incredibly ugly sentence. Beyond its infelicities, however, it’s also a muddled mess of an idea. Other animals include fish whose parental investment ends when they spread their eggs and sperm in the same area. It also includes Darwin’s frog, in which the tadpoles grow within the safety of the father’s mouth, while the mother wanders away.

Even among primates, there is no one simple mating strategy, as Greg Laden hilariously demonstrated in a post on what we have to contend with if we adopt the naturalistic fallacy as a guide:

So, given the chimp model, we should all be bisexual and disregard age or gender of our sexual partners. Almost all baby making sex should involve a gang bang lasting several days. We should have strong male hierarchies and female hierarchies that determine, ultimately, who gets to be the father of each child (more or less) not by who has sex with whom, but by regulating exactly when in the ovulatory cycle intromissive sex with male orgasm happens. If we lean towards the common chimp model, all males should be dominant over all females. If we lean towards the bonobo model, all females should be dominant over all males.

Making assumptions about what human sex and parenting should look like based on other animals, even other primates, only tells us that there are a vast number of mating strategies. It doesn’t tell us which mating strategies may be ours, and it doesn’t tell us what part culture may play in shaping those strategies.

Back to Heinrich:

Females are limited in their direct reproduction to the number offspring they can rear to maturity in their lifetimes, and are necessarily committed to high levels of investment, at least in the form of providing the egg, gestation and lactation. In contrast, with little investment (sperm and a small effort), males can potentially have thousands of offspring that they can decide to invest in, or not, based on the costs of obtaining mates vs. the impact of additional investment in their offspring.

Ah, parental investment. So convenient for humans that it ends with weaning.

Yeah, that’s snark.

If your concern is to see that your offspring’s genes are optimally passed on to another generation, you, as a parent, have so much work ahead of you in a complex society that the calories, etc. expended on gestation and lactation are trivial. And this is true whether you’re the parent who gestated and lactated or the one who didn’t.

“Oh,” say the evolutionary psychologists of this particular stripe, “but we’re talking about early, primitive human societies, in which we evolved.”

This is why evolutionary psychologists are not anthropologists, or even evolutionary biologists. There is nothing primitive about early societies, particularly about the social interaction. Anyone with a tight-knit group of friends knows that a small social group is not necessarily a simple social group. Similarly, a group in which rules are enforced collectively instead of by a designated leader or leaders is not doing something simple. And even if “primitive” societies were simple, we’re a few generations of evolution away from that point.

Because human offspring benefit from the investment of both parents (at least in ancestral human societies) females seek to form pair-bonds with those males who are best able to invest in their offspring (males possessing high social status, wealth and valued skills).

I’m sure the fathers of my acquaintance who are or were primary caretakers of their children (seven I can think of off the top of my head) would be happy to hear that the attributes they needed to make a go of it had nothing to do with the nurturing they provided.

Look, there are a number of ways for children to become successful. Only one of those ways is for them to have started successful. That means that there are a variety of attributes in males that would be attractive to women looking for fathers for their children. In fact, the attributes listed here are useless without one that evolutionary psychologists never seem to attribute to men–constancy. With divorce rates among those with children being only slightly lower than among those without, and with approximately a quarter of those due child support in the U.S. not receiving it for a reason other than inability to pay, means are hardly the only important issue.

A female does not generally benefit from establishing simultaneous pair-bonds with multiple males because (1) she can only have one pregnancy at a time (so lots of sex with different males does not increase her reproductive success),

Given the means to control fertility, this isn’t necessarily true. There are benefits to bonding and sex that extend well beyond reproduction.

(2) this brings males into conflict (sexual jealousy)

There have been enough polyandrous societies to indicate that this sort of jealousy is largely enculturated. It may do that in this culture, but it doesn’t need to happen. As evidence that polygamy is doomed, this sort of assertion is worthless.

and (3) this creates confusion regarding male paternity (and greater paternity confidence increases paternal investment).

For the first time in our history, humans are able to determine paternity with certainty. If there were ever a time when this was a non-issue, it is now. Even in explicitly polyandrous relationships.

In contrast, males benefit both from pursuing additional pair-bonds with different females at the same time,

Recall that there is much more to raising humans to adulthood than providing food and shelter. Humans have an amazingly extended childhood. While one effect of this is a longer period during which children must be supported, the purpose appears to be an increased education. The benefits of additional education in skills, wealth, and attendant social status are so well understood that one would think this would be a primary concern for any father driven to pass on his genes to further generations.

That limits the number of offspring in which a father can effectively invest as well.

and from additional extra-pair copulations (short-term sexual relationships).

This is essentially irrelevant to any argument about polygamy, but it’s worth noting that only now, when paternity can be settled definitively, is there no similar benefit to women from extra-pair copulation on the sly.

So, once again, we’re left with evolutionary psychological “reasoning” that is based on overly broad generalizations and uninformed assumptions about early societies, assumes we stopped evolving several thousand years ago, and doesn’t explore more than one degree of logical progression. It’s rather astonishing that any decision could be printed that relies on this.