Sunday, June 17, 2007

Altruism: from genes to primates

Interesting notes on primate altruistic behavior

As primates go, human societies have an incredibly complex, nuanced, and dynamic structure that sometimes makes beautiful sense and other times leaves you scratching your head. From very basic forms of gregarious behavior human society has evolved breathless levels of elaborate cooperative- and not so cooperative behavior.

This makes it difficult to pin down specific and clear cut correlations between person to person interactions making it even harder to formulate any generalized species specific behaviors for our “deep and brooding” ways. However, fascinating evolutionary theories regarding human social behavior have begun to shed light on why we do what we do.

The social behavior of other primate species can offer revealing insight into the workings of our own far more complex social structure as well as humble us with many of the startling similarities observed. Most primate species, like humans, live in large groups and generally maintain a familiar social pattern. The mother- infant bond acts as the primal social glue and from this core, a variety of social structures exist depending on what species is studied. In general primate group systems involve a core of matrilines (females and their female offspring) and males tend to migrate to other groups.Some primate species have a reverse make up such as chimpanzees and spider monkeys where the core of a group is male and the females do the migrating. In general though, all these large groups have relatively stable social make ups.

The significant migration between groups of individuals allows for a whole new world of complex interactions to flower. This added layer of behaviors between individuals are ultimately dependant on relatedness and give rise to wondrous primate versions of social interactions and altruistic behaviors opening the door to a broader understanding of the maddening quagmire that are the human social systems of today.

Through the work of J.B. Haldrane and later W.D. Hamilton (late 1950’s and early 1960’s) an evolutionary theory developed involving genetic continuity among groups. This provided an evolutionary basis for a variety of animal behaviors including primate altruism. This “genes eye” view of group behavior gave rise to a variety of theories that take into account genetic, biological, and sociobiological phenomena in group interactions and eventually coined the now familiar term "the selfish gene."

Obviously, this is a simplistic and anthropomorphosized description of natural gene to gene interactions. However, these genetic interactions do provide a framework for developing an evolutionary basis for many animal interactions and in this case, primate social behaviors.

Kin Selection and cooperation

Since the concept of kin selection was formulated (that related individuals come together in the interests of maintaining the survival of like genes in a gene pool) it has taken on a bit more nuance with respect to primate social behavior. Seemingly logical predictions turn out to be more complex than previously thought. The larger goal of genetic “selfishness” though still remains a core incentive.

For example, during fights animals regularly come to each others aid forming coalitions often between close genetic relatives. This simple concept can get rather complicated depending on the given circumstance. Female rhesus macaques are less likely to support even an ally closely related to them if the opponent is highly ranked. This seems to be a form of calculating the risk vs. benefits for offering aid and brings to mind very human traits and justifications such as “living to fight another day.”

One form of kin selection and altruism can be observed when older offspring fore go their breeding opportunities in order to help their parents raise a younger litter. This behavior seems to stem from crowded conditions and harsh environments where the benefits of passing like genes are weighed towards this “selfless” behavior.

Another interesting form of kin selection in primate social groups relates to male migratory behavior. Male vervet monkeys migrate into groups where older brothers or cousins have already migrated as they are more likely to support each other in conflicts and it may also be more likely to successfully integrate into the group.

Reciprocal altruism

This interesting behavior seems to be widespread among primate groups and involves cooperation between unrelated individuals where both parties exchange mutual benefits on a reciprocal base.

In one example, male baboons form coalitions for mutual protection against larger and more powerful males. Another example involves a seemingly “political” association where a low ranking male chimpanzee supported the second –ranking male against the top male permitting the second-ranking male to become dominant. The reward for the low-ranking male was access to receptive females he would otherwise not have access to- sound familiar?

Evolutionary stable strategies

This fascinating sociobiological concept, derived from game theory mathematics, offers a malleable and effective mechanism by which animals resolve conflicts. It predicts that given a choice an animal behaves in such a way as to achieve the most profitable situation- but what this is will vary depending on what the other individuals in the population are doing.

Dunbar (Human Evolution) gives this example: “…male gelada baboons acquire harems of females in two ways. One option is to fight a harem-holder so as to take over his entire harem…A second is to join another male’s unit as a subordinate follower without challenging his ownership; a follower can then build up relationships with one or two peripheral females who make a small harem that eventually separates off from the parent unit. The best strategy is clearly to take over an entire unit, because by doing so a male gains many more breeding females than he can as a follower. However, there are only a limited number of units in the population large enough to be worth fighting for. Consequently, as an increasing number of males opt to take over a unit, so a male’s tenure as harem- holder declines. Reproductive success depends not on just the number of females that a male can mate with …but also on the time over which he can do so. The initial advantage a male gains from taking over a large unit is hence soon offset by the fact he cannot survive very long as harem-holder. It then pays some males to become followers. A balance may be maintained between the two reproductive strategies…”

These interactions are not as simple as they might sound when extended to other primates, especially humans.It does, however offer a small glimpse of how complex human social behavior might come about. Incidentally, new inroads into understanding the intricate behaviors of human society are coming from expanding game theory experiments. They are providing insight into the curious interplay between human instinctive and cognitive interactions as well as on the balance between apparently rational and irrational behaviors.The discovery of incredibly complex “meta-rational” behaviors (where individuals skip over apparently rational choices and basic logic to make apparently illogical choices that in fact end up reaping even greater rewards) that ultimately benefit all involved parties is shedding new light on the deeper nuances of human society. This is reminiscent of the R. Dawkins “nice guys finish first” concept of mutual and cooperative behavior predominating in many evolutionary stable strategies.

In essence, by acknowledging the rich tapestry and variable nuances of primate social behavior, we as a species can begin to understand how and why we interact the way we do. This confirms to us the fact that we are inextricably and evolutionarily linked to our primate cousins- an appropriately humbling experience. Additionally, we are provided valuable information allowing perhaps for the discovery or reinforcement of more constructive forms of human interactions that may go a long way towards limiting our more destructive behaviors.


R Dunbar.Social behavior and evolutionary theory. Human evolution. Cambridge Univ Press. UK.2005

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