Thursday, November 26, 2009
Humans, Bonobos, and Ants
Chimpanzee politics is a bloodsport in which male chimps fight to become alpha males. This does not happen with bonobos because the females have disguised fertility. It is relatively easy for male chimps to monopolize sexual access to the two or three females in the group who are fertile. It is harder for male bonobos to monopolize sexual access to all eight or ten females. Guarding more people is tougher than guarding fewer. The upshot is that the incentive to become an aggressive status seeking alpha male is lower for male bonobos. Females take up the slack which is why bonobos are female-dominated.
My point was that while the "disguised fertility plus promiscuity" strategy successfully tamed the aggressiveness of males it came with a price. Bonobo males do not have an incentive to invest hard for the welfare of the group. They do not have children as an incentive to work hard gathering food. An anonymous commenter made a very perceptive comment:
On the contrary, the most peculiar thing about (systematically) disguised paternity is all males are genetically incented to cooperate towards the same group goal. It’s a form of higher-level selection–sort of like the worker ants in a colony. You’re not going to see anything like this with chimps or humans.
The commenter is talking about group selection (I have a bit to say about group selection here). D.S. Wilson has the best way to think about group selection. Imagine an island filled with half good people and half evil people. The good people would be shark food and then the island society would collapse into a Hobbesian "war of all against war." But now imagine two islands. The first is filled with good people and the second is filled with bad people. The first island would thrive and the second would collapse. That's group selection.
In a eusocial species like ants the group level dominates. The way that happens is by creating a reproductive caste. The queen(s) and male drones reproduce whereas the legions of female workers slave away for the good of the group. Since the female workers can't have babies of their own the best they can do is spread their genes indirectly. Work hard so that their little island prospers. That is basicaly what the anonymous commenter is proposing. There is basically nothing that the male bonobos can do to intentionally reproduce because female fertility is disuised. So they can work hard for the group like good little worker ants.
But as the primatologist Frans De Waal points out in Our Inner Ape, this is not what male bonobos do. Although the incentive to monopolize sexual access to females is lower, it still exists. Males do divert their energies into gaining access. De Waal explains in Bonobo: The Forgotten Ape:
There is a sharp decline in sexual involvement during a male’s adolescence due to the tendency of dominant males to occupy the core of the traveling parties, where the females are. Only when they enter adulthood and rise in rank do males regain access to receptive females. Not that male bonobos are egalitarian with respect to sexual privileges. In contrast to its peaceable image, the species conforms to the general patterns in the animal kingdom of male competition for females. Bonobo males may compete less fiercely than chimpanzee males, but a recent report from Wamba leaves no doubt that dominant males mate more often than others. Since the two top-ranking males in any traveling party generally do most of the mating, it is assumed that they suppress the sexual activity of other males.
This explains the difference between bonobo males and ant female workers. Eusocial species like ants are highly inegalitarian. We can imagine a queen saying the following to a worker female, "Listen. Here's the deal. You will never reproduce. I've been emitting a pheremone that makes you sterile. But if by some miracle you do manage reproduce then we will kill you and kill your larvae. What you will do is work hard for the group. Do that and your genes will be passed on indirectly." The worker has no choice. She will work hard and even sacrifice her life for the good of the group. That's the power of group selection.
Monogamy accomplishes the same thing but it is egalitarian. We can anthropomorphize God and imagine Him saying, "Listen. Here's the deal. You can reproduce if you want. But except for some fine print, you can only have sex with one person. Anything more than that is selfish and immoral."
The unifying theme between monogamy and the eusocial species is clear boundaries specified ex ante about reproductive opportunity. If you don't have these strong boundaries then you create a free rider problem. People will try to increase their reproductive opportunity. But that is a (1) a zero sum game. Each male who gains social status causes others to lose status. (2) it takes energy away from developing a cooperative surpluss for the good of the group. The crucial difference between monogamy and a eusocial species is that the latter are highly inegalitarian. Their essential feature is the creation of a separate reproductive caste.
Monogamy is better than promiscuity because it is group-minded. Monogamy is better than a caste system because it is egalitarian. My take on alternatives to monogamy: "A strange game. The only winning move is not to play". But of course, that assumes a group-oriented perspective.
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