Cooperative foraging

Many species live in environments in which they can not manage to find enough food by themselves in order to survive and reproduce. This can be because existing prey animals are too big, too strong or too fast to be hunted by an individual alone. On the other hand, competitors may be too big and strong or too numerous to protect a catch from them. These species can only survive and produce offspring if they cooperate with others in their food procurement.

Two lions cooperate to hunt down a big buffalo.

Image source: Corinata, Creative Commons CC BY-SA 3.0

Canadian wolves surround a bison.

Image source: Doug Smith, public domain

African wild dogs eat a shared prey.

Image source: Brain Gatwicke, Creative Commons BY 2.0

Cooperative foraging and human evolution

The environmental conditions in East Africa changed in the course of human evolutionary history so that the hominid species they increasingly needed a cooperative foraging strategy to survive. About 3 million years ago, the climate became drier, the vegetation became more sparse, and grazing ungulates such as antelope and buffalo were spreading. These were hunted by specialized predators, such as leopards, hyenas, and saber tooth tigers.

Some hominid species living at this time, such as Paranthropus boisei and Australopithecus africanus, specialized in plant foods such as nuts, grasses, tubers, fruits. Hominids, who could better utilize these sparse, hard, seasonal food sources, had a survival advantage. But this food became scarcer, and representatives of these species gradually died out.

With the help of fossile finds in East-Africa, scientists can estimate which kinds of species were abundant in the respective time period. The percentage of grazing bovid species increased from 2.5 Mio years ago. Source: adapted from deMenocal (2011)

At that time, some other hominids also began to exploit more of the animal food sources of the savanna. These were the first representatives of the genus Homo.

But it is not easy to compete as primate for prey animals with the specialized predators of the savannah . Bite marks on fossil bones indicate that our early ancestors exploited the last remnants of the carcasses hunted by other predators. There were probably times when this was the most important source of food for our ancestors. So they were first scavengers, and they were themselves hunted and eaten by these predators!

So they had to work together to some extent to mutually exploit found meat and bone marrow, while others in their group fended off predators. Then they had to share the food with everyone else in the group, including the female members and offspring. The groups in which members tolerated each other and did not become aggressive, and could coordinate their activities a little bit while exploiting the same carcass, had better chances of survival than groups in which members quarreled and fought each other when it came to sharing the food. The groups in which members could coordinate their roles in a joint activity (fend off predators, for example, while others separated meat and bones from the carcass) had better chances of survival and reproduction than groups where members were not so good at it.

Thus, anthropologists suggest that under these environmental conditions certain abilities for social cognition and an increased social temperament were beneficial. So these properties spread through natural selection in the populations of our ancestors.

  • Teaching material: Cooperative foraging reading text (in preparation)

Anthropologists like those at the Max-Planck-Institut for evolutionary anthropology in Leipzig, Germany, conduct different experiments and observations to investigate which behaviors are required for individuals to obtain food from a single source.

  • Teaching materials: Worksheets about the videos/experiments (in preparation)

Can chimpanzees, our closest relatives, coordinate their actitivies spontaneously in order to obtain food from a single source?

Causal map

The environmental conditions of the savanna were such that those had increased chances of survival and reproduction that could exploit animal food sources. Among those who began to exploit animal food sources, those had greater chances of survival and reproduction, that could procure food in a cooperative manner. Environmental conditions (predators and competitors) have also been such that primates had to cooperate with each other to protect themselves from predators and competitors, and to divide up found food among all in the group.

Better at cooperating with one another to exploit animal food, in turn, were those who had a good social perception and a relatively peaceful social temperament, so that they were less aggressive towards other group members and tolerated sharing the same food source with others.

Genes involved in the development of these traits were inherited to offspring, which in turn had increased chances of survival and reproduction due to the development of these traits.

Artifical selection of social temperament

This video is about domestication - or "taming by breeding" - of foxes, a Russian research project that has been conducted since the 1950s. It shows which behavioral patterns of foxes were selected during breeding, what was found out about the genetic makeup underlying these patterns of behavior and to what extent fox breeding is comparable to the breeding of dogs.

Possbile discussion questions about the video:

  • Which characteristics were selected or were of interest in the breeding of foxes (and also dogs), which were not?
  • What does "hyper-sociability" mean? What behaviors does it involve?
  • Describe the simple experiment breeders used in order to evaluate the sociability of dogs, foxes, and other domesticated animals.
  • Is tame and friendly temperament determined only by inherited genes? If not, by what other factors?
  • Why can geneticists use bred foxes rather than bred dogs to better study the genetics underlying a tame, friendly temperament?
  • What external characteristics/body features are associated with domestication in addition to social temperament?

References