The Gombe chimpanzee war: a non-human clan struggle

The Gombe chimpanzee war took place from 1974 to 1978 and pitted relatives against each other.

One of the greatest impediments to studying animal behavior is, paradoxically, the human mind itself. It is a fact that we tend to humanize other living beings: if we see a cat run over in the street and another one moving its paws over the corpse, we automatically think that it is trying to revive it and feel sorry for it. However, there is also the likelihood that it may be arranging a warm space to lie down to rest, in order to take advantage of its companion's body heat.

The same is true when observing almost any living being interacting with the environment, but the reality is that the "feeling" is confined to very few animal species. Living things experience basic emotions in the short term (fear and disgust, for example), as these are adaptive behaviors that maximize the long-term survival of the community. However, we find it hard to believe that a lizard is capable of loving its offspring or that an insect feels pain in the same way as a human does.

Ethology, the branch of biology that studies animal behavior, comes up against a big wall every time it tries to explain a behavior or hierarchy in the animal kingdom: is the character exhibited a product of natural selection and serves a specific purpose or is it a trait of the individual that is not adaptive, but personal? Based on these interesting premises, we tell you, from a Biological perspective what happened in the war of the chimpanzees of Gombe..

What was the Gombe chimpanzee war?

The Gombe chimpanzee war was a conflict between two chimpanzee communities ( a conflict between two chimpanzee communities (Pan troglodytes), which occurred in the Gombe Stream National Park in Tanzania between 1974 and 1978.. The groups involved in this conflict remained at the time in the Kasakela community, the study population of the famous primatologist Jane Goodall. Due to her follow-up since the 1960s, this has become the animal population with the longest study history in the history of biology.

It all began with the split of the main group. Six males, three females and their offspring separated from the established population, receiving the name "Kahama community". The Kasakela nucleus was left with a total of eight males, 12 females and their offspring. Later we will delve into the possible reasons for this division, but for now it is enough to keep the name of both nuclei.

The first bloodshed occurred on January 7, 1974, when a group of six males from the Kasakela nucleus ambushed and killed one of the Kahama males while he was feeding. while it was feeding.

This was the first recorded instance of a chimpanzee being killed by another of its family members. Brawls are common among populations of the same species in many taxa, but to end the life of an individual that shares a genetic load is completely counter-intuitive.

We will spare you the details, as it is sufficient to know that each of the Kahama males fell over the years. In the end, the Kasakela population completely conquered the land of their murdered former relatives, although stability was not possible until some time later.. Other chimpanzee populations bordered Kahama's territory, so the partition of territories was irregular.

Chimpanzee warfare and kin selection

As we have seen, the fact that two different populations attack each other is nothing new, even though they may belong to the same species. The biological unit to keep in mind is always the population.The biological unit that must always be kept in mind is the population, because two nuclei of specimens separated by an ocean, no matter how much they belong to the same species, will never exchange genes nor will they be exposed to the same environmental impositions.

What is most interesting about the Gombe chimpanzee war is that what has happened challenges, to some extent, the ideas of kin selection.. According to this theory (Kin selection) some living beings favor the reproductive success of their closest relatives, even if this means a decrease in the biological fitness of the individual in the process.

Kin selection could be confused with altruism, since it seems that one individual helps another in a disinterested way, but this is not the case: the more similar the genome between the two individuals (e.g. siblings), the more likely it is that this "altruistic" behavior will be present. This theory is based on the concept of "inclusive fitness", i.e., that it is not only the offspring produced by a specimen that matter, but also those conceived by its relatives.

The Hámilton rule explains this interaction. R refers to the kinship between the recipient of the aid and the donor, B represents the "benefit" of the donor acting as an altruist, and C refers to the biological cost of the donor. If helping a relative presents more benefits than costs, sociality and community living may be encouraged.

The war already described challenges this idea, as we can assume that the chimpanzees in conflict were inbred. By killing a male from the same population (at least it was a few months ago), the killers are "shooting themselves in the foot", as part of their inclusive fitness (genes in the form of relatives) is being destroyed for no apparent reason.

So why did this confrontation between animals happen?

At this point, it is necessary to explain the concept of "population fission". It is more than documented that, iin many species of mammals (including humans), population splits occur when living in groups is no longer beneficial.. This happens when the following parameters are met:

• The cost of competition between individuals exceeds the benefit of living in society. In many cases, males or females of the same population attack and attack each other in order to establish hierarchies. If this has only negative effects, the population may break up.
• The cost of maintaining relationships outweighs the benefit of living in society. Again, a population in which conflict is continuous may not be evolutionarily viable.
• The cost of maintaining spatial cohesion outweighs the benefit of living in society. For example, a plot of land that is too small or too large may make it very difficult to maintain family cohesion.

When any of these parameters are met (or all at once), it is postulated that a population may be at risk of breaking up, regardless of how hardy it was in the past. For example, imagine that in a field where there is a population of 200 chimpanzees there is a fire and half of the foraging areas are lost. If there is no food for all the members, there are two options: kill the weakest ones or allow them to leave..

To this day, there are multiple subsequent studies that have tried to explain the reason for the population fission of the Gombe chimpanzees. Some professionals argue that the Kasakela population could have been composed at its conception by two different groups and, therefore, the genetic relationship between individuals was not as great as it was believed. According to this postulation, the fatal outcome was only a matter of time, since it was only a matter of time to maintaining a hierarchy between unrelated individuals is complex to say the least..

However, other sources argue that there is no evidence to believe in this dual community theory. According to them, all those involved were members of the same population, but the first signs of fission became evident in 1971, three years before the first bloody conflict.

It is believed that the trigger for this event could have been the lack of dominance established between males in the same population or, alternatively, the increase of males in the population with respect to the total number of females. If the operational sex ratio is greatly disrupted, the population is endangered.If the operational sex ratio is too high, the population is endangered: if there are too many males, one of them has to leave or be expelled.

Summary

What this tour shows us is that the Gombe chimpanzee war is an extremely interesting event, but less "poetic" than its name might suggest. In the process of humanizing the rest of the living beings, we forget that they have a restlessness that goes much further. have a concern that goes far beyond hatred, rancor or lust for power: survival..

In nature, everything is a matter of genes and adaptations: if something endangers the population, it is discarded, whatever the cost. Therefore, the most plausible explanation for this conflict is the lack of females in the Kasakela population, which started to become effective in 1972. If the sex-ratio becomes unbalanced, some of the surplus must leave the nucleus, as their chances of having offspring are drastically minimized.