Four Observations About Mating

I have been too busy to do much reading recently, so here is something from my Human Nature course.  I offer four observations that lay out one of the general theories of sociobiology. 

Observation 1: Males are larger, stronger, better armed, and more aggressive, across a wide range of species. 

This is not universally true.  Spiders are a conspicuous exception.  There the reproductive machinery resists reduction in size.  Ask a black widow male what he thinks about this.  It is however true of a vast number of species including elk, gorillas, walruses, and human beings.  Why? 

Observation 2: Males compete with other males for reproductive opportunities. 

In most species that I am aware of, almost all of the females can successfully mate.  They may compete with other females for access to the most competitive males, but they get to mate with someone.  By contrast, males will often go without mating opportunities at all.  This is especially true in harem species, where males enjoy access to a considerable number of mates so long as they can defend their position against other males. 

In harem species the sexual dimorphism is rather large.  In promiscuous species, larger males may not enjoy exclusive access but they often enjoy the first opportunity to mate with a fertile female.  In some monkey species, the males compete not with size and offensive weapons like antlers, but with large testes, the better to flush out the work of the last suitor.  In yet another strategy, males compete by features that attract females, such as color or flamboyant tail features. 

In the case of harem species, female choice is limited but not extinguished.  A female may cry out to arouse the dominate male if an interloper appears.  She doesn’t want to mate with the Johnny-come-lately unless he can stand his ground.  Where females can easily flee, female choice is accordingly increased.  Hence the colorful male birds. 

In all such cases, males with weapons leave more offspring than males without or with lower caliber weapons.  Accordingly, they sire sons with the same weapons. 

Observation 3: females are choosy but males are eager. 

Across a wide range of species, males will take any opportunity to mate that they can get, whereas females will resist any suitor that they regard as unsuitable.  While female choice will be more or less constrained depending on the mating system, they will exercise as much choice as possible.  Males will mate with anything that looks vaguely female.  Mount a female turkey’s head at the appropriate level and a male turkey will move behind it and try to mate. 

Observation 4: sperm is cheap; eggs are expensive.  

 The male’s minimal investment in a single reproductive act is often very minimal.  For most males, each mating is chance to sire more offspring.  Hence eagerness to mate is selected for.  For females of many species, the minimal investment in a single reproductive act is very large.  Indeed, the universal definition of female in biology is the sex with the largest sex cell. 

We can see this spread across a number of mating systems.  Where the female lays eggs to be fertilized externally by the male, her investment is relatively small for a female.  However, it is still larger than the males.  In hermaphrodite fish, where each individual produces both eggs and sperm, the eggs are more precious.  This fact results in a social contract called parceling.  When two such fish meet, each lays a parcel of eggs for the other to fertilize and then they repeat the exchange.  A fish that managed to fertilize all the eggs of another without giving up any of its own eggs would be able to cheat many other fish before he/she finally released his/her own cache of eggs. 

Females that develop an egg within their own bodies must devote a lot of time and resources to each reproductive opportunity.  Those that allow the young to develop to live birth must devote even more. 

The result is that the minimal cost of each reproductive act for females is much larger than it is or can be for the male.  More coupling does not result in more offspring.  Accordingly, the female is inclined to make sure that each coupling counts and that means being choosy (when she can) about whom to mate with. 

Thus the four basic observations can be arranged so that each one helps to explain the previous one.  Males are better armed because they compete with other males; they compete because males are choosier than females; males are choosier because their minimal investment is less.  Given Darwinian theory, we can now understand a lot about the sexual behavior of elk and the guys down at the Elks Lodge. 

Boehm's Moral Origins

There is a fine review of Christopher Boehm’s recent book at the Evolutionary Psychology site.  The book is Moral Origins: The Evolution of Virtue, Altruism, and Shame.  The review is by Dennis L. Krebs and Kaleda K. Denton. 

I have the heavy version on the book on my desk.  It is third on my reading list right now.  To judge by the review, it will be a very interesting read.  Here is the reviewers’ synopsis:

Boehm seeks to trace the origins of morality in the human species back to the very beginning. He begins by identifying traits shared by chimpanzees, bonobos, and humans (and going back further, by gorillas) under the assumption that these species probably inherited such shared traits from a common ancestor. 

He goes on to employ findings from archeological research and from ethnographic accounts of contemporary hunters and gatherers to draw inferences about culturally-universal aspects of the social behavior of early humans who lived in the late Pleistocene era, about 45,000 years ago. 

Then, moving to an explanatory level of analysis, Boehm uses evolutionary theory to develop “working hypotheses” that account for the differences between archaic humans and humans who lived in the Pleistocene era. Finally, Boehm notes differences between the social behaviors of modern humans and the social behaviors of hunters and gatherers, and offers a brief explanation for these differences.

I am not sure about that “very beginning” language, but the general strategy seems right.  Why do I and my brother have hands?  Because our father had hands.  Why do I and a chimpanzee share a capacity to be socialized by the group we are raised in?  Because a common ancestor of both of us had trait.  Why did I “pair-bond”, i.e., marry for life, whereas chimpanzees do not?  Because at some point human and chimpanzee evolution diverged.  Figuring out how and why that divergence occurred goes a long way toward explaining the evolution of morality. 

Boehm’s most important argument, which he has been elaborating for some time, is described by Krebs and Denton in these terms:

Central in Boehm’s analysis is the inference that the social order of archaic human groups was hierarchical, dominated by Alpha males. Dominant members of groups are relatively well equipped to induce subordinate members to obey the rules, but this method of social control inevitably gives rise to a significant social problem, namely, how to induce the dominant members of groups to resist the temptation to bully subordinate members of the group and to hog all the resources for themselves.

Boehm suggests that in response to this problem, mechanisms evolved in subordinate members of groups to constrain the domineering behavior of Alpha males. Power comes from numbers. As in living primate groups, subordinate members of archaic human groups formed coalitions that enabled them to gang up on Alpha males to reduce their power and access to resources.

In other words, human evolution produced two traits that are at odds.  One was the dominance and submission schema that is familiar to anyone who is the least bit familiar with chimpanzees.  Alpha males dominate the group, which makes for political order but allows the dominant individual to take unfair advantage and bully pretty much everyone.  The other is the tendency of the subordinate members to resist that domination. 

Boehm believes that early human communities were largely egalitarian because the group resistance to the power of dominant individuals was sufficient to limit that power.  That is a plausible and very interesting thesis.  Whether it is true or not, remains to be seen.  It certainly gives a lot of material for any Biopolitical theory to work on.  To state the obvious, limited government appears as a highly refined expression of the politics that played out in the simplest human communities.  That is worth chewing on.  

 ps.  Doesn't Boehm look smashing under that hat?