A striking cover photograph on the 4 September issue of Science: Ants build a living bridge, using their bodies as structural elements to enable other ants to traverse a vertical gap. The cover introduces a review essay on the evolution of cooperative behavior among members of a family, a clan, a species, and even between species.
Cooperation has always been a problem for strict Darwinists. Darwin himself considered it an almost insurmountable problem for his theory, which emphasized the competitive fitness of individuals. Since Darwin's time, much work has been done to show that cooperation between genetically related groups can enhance the inheritability of beneficial mutations., but a full understanding of cooperative behavior remains to be explored.
Some biologists include cooperation as one of three pillars of evolutionary theory, along with mutation and natural selection. One thing is sure: cooperative behavior is ubiquitous -- from microbes to meerkats. It's a dog-eat-dog world out there, as Darwin supposed, but often it pays to cooperate in the scramble for the top.
These days everyone worries about the loss of biodiversity and destruction of the environment. What no one talks about is the fact that the destructive exploitation of the planet by humans is a consequence of cooperation. A single human hunter would have a hard time killing a mastodon or saber-toothed tiger, but hunting in packs, like hyenas, helped drive those animals to extinction. The rise of agriculture, cities, war, science and technology are all examples of cooperative behavior. Language, music, dance, art, religion -- all have a social dimension. Humans have become the dominant species on the planet because we, like ants, have exploited "living bridges" to rise to the top.
In a zero-sum world, our gain is someone else's loss. What seems to be uniquely human is the fact that we worry about the consequences of our success. Cooperation and group altruism may well be compatible with natural selection. It will be interesting to see if evolutionary theorists can account for a guilty conscience.