Agner Fog: Cultural selection © 1999

7. Digression: Social organization among baboons

Two markedly different patterns of social organization have been observed among baboons. The hamadryas baboon (papio hamadryas) living on the dry steppes of Africa is organized into groups comprising a single dominant male with a harem consisting of two or more females and their young. The most important social relations are between the harem leader and the adult females. The surplus of adult males, having no harem, live in all-male groups. The groups are joined into larger troops which often sleep together.

The closely related savanna baboons (papio cynocephalus) live in bigger groups and are rather promiscuous. The females have more influence than the males, and the most important social relations are female-female alliances (Byrne et.al. 1989).

Recent studies have shown that the chacma baboon (papio cynocephalus ursinus), which is a subspecies of the savanna baboon, will approach the social organization pattern of the hamadryas baboon under certain living conditions, although its normal pattern is the same as for the savanna baboon (Byrne et.al. 1987). One group has even been observed to change from the mating pattern of savanna baboons to the harem pattern in a few years as a result of the presence of a leopard (Anderson 1989). The change in organizational pattern took place in less than one generation, so it is impossible that genetic changes can have played any part. If we assume that this change in organizational pattern is adaptive, then it must have been controlled by vicarious social, psychological or intellectual mechanisms as a reaction to the changed ecological conditions, e.g. the risk of being eaten by a leopard.

The most probable reason why savanna baboons assemble into big troops is that it is the best defense against predators. The hamadryas baboons live on the dry steppe where food is sparse so the baboons have to forage in smaller groups. The chacma baboons live in the mountains where food becomes more and more scarce the higher up you go, and accordingly the social organization resemble the hamadryas pattern more and more the higher the altitude (Byrne et.al 1987, 1989; Wrangham 1987).

It may seem illogical, then, that a group of chacma baboons switched to a pattern resembling the organizational form of the hamadryas baboons owing to the presence of a leopard, as observed by Anderson (1989). The explanation may be that the monkeys have to stay together in larger troops during the summer in order to protect themselves against the predator. This makes foraging ineffective and the competition within the troop is sharpened. A female has no chances of feeding her young in this situation unless she allies herself with a strong male. This promotes the splitting of the social organization and mating pattern into harem groups, and the competition within the troop becomes a competition between harem groups.

The reproduction of the baboons is limited first and foremost by the scarcity of food on the dry steppe as well as on the savanna. Many young die from starvation or malnutrition, and the competition for food therefore plays a big role for the parents who have to feed their young. There is also a fierce competition between the males for access to mate with the females. These conflicts are regulated by a strict hierarchy of dominance and by the formation of alliances. The difference between the two organizational patterns with respect to competition is that with the hamadryas baboons there is competition between single-male harem groups, whereas the savanna baboons compete primarily within their troop because they are not divided into small groups. In other words, the hamadryas organization is dominated by group-external conflicts, whereas the savanna pattern is dominated by group-internal conflicts. This is the background for why I compare these two patterns with cultural r- and k-selection.

Wasser and Starling (1986) have found a considerable amount of competition between the females among the savanna baboons, which is seen in the females attempting to suppress each other's reproduction. Not surprisingly, there is also a high degree of rivalry between the males, and it is not unusual for males to kill young that are not their own in order to increase their own chances of reproducing. Females often mate with all available males during a single period of heat in order to avoid this. The males determine their paternity from the time of mating (Busse 1985), and the females create uncertainty about the paternity by mating with multiple males, thereby minimizing the possibility of the males killing their young.

Unlike this savanna pattern, there are seldom any conflicts between females among baboons living by the hamadryas pattern, and neither are any alliances between females seen (Byrne et.al. 1989). The dominant male decides everything and, due to the small size of the group, internal conflicts are rare. But when one hamadryas group comes near another then a tense situation arises. The dominant male spends a lot of energy on herding his females away from rival males from the other group (Byrne 1987).

In a hamadryas group there is a single male sitting on top of a strict hierarchy deciding everything and being able to suppress most conflicts within the group. Not so for the savanna baboons where decision processes are less simple and where females have at least as much say as the males. The similarity of these two patterns with regal and kalyptic human cultures, respectively, becomes particularly striking when we look at the sexual behavior. Mating is very rule-governed by the hamadryas baboon, and even though the male is polygamous he only mates with females belonging to his harem, and the females never mate with other males. Any uncertainty about paternity is therefore ruled out and the young can receive the full care and protection from their father.

Not so on the savanna, where there is almost complete promiscuity. The females seek 'deliberately' to create confusion about who is the father of their young in order to make all possible fathers sympathetic to their young.

Comparing with human societies, we similarly find a strict sexual moral in regal societies where adultery is severely punished, whereas there is considerably more freedom for promiscuity in kalyptic societies. Exclusive harems are only found in regal societies. A male may have mistresses in a kalyptic society, but he does not own them, and the females may at the same time have several lovers. The sexual behavior of humans in regal and kalyptic societies is the topic of chapter 10.

It must be emphasized that our knowledge about the social life of baboons is insufficient, and the above account is based on a limited number of studies. It is difficult to distinguish between cause and effect and there is considerable uncertainty about which factors determine group size and organizational pattern of the baboons. We have no empirical data that can throw light on the supposed social or psychological mechanisms leading to changes in organizational pattern. The observations about conflicts and alliances are regarded as more reliable, so that there are reasonable grounds for asserting a connection between sexual behavior and the ratio between group-internal and group-external conflicts. This connection is indeed interesting since a similar connection is observable among humans, as I will explain in chapter 10.

Of course, the comparison between humans and baboons cannot be used for proving anything about the social or sexual lives of humans, but the study of baboons shows that a causal mechanism connecting social conflict patterns with sexual behavior is indeed biologically possible.