So asked Charles Darwin in 1859, seeing cooperative behavior as a challenge to his theory of evolution. Such behavior is still one of science’s largest outstanding problems, and our study, published in Ecology Letters, set out to address it with the assistance of a highly gregarious bird, the sociable weaver.
It’s simple to see why animals are selfish: if you want to pass on your genes to the next generation, you should focus on taking care of yourself, protecting your resources, finding a spouse, and reproducing – why would you care about others?
Conflict is common in nature as a result of such selfish objectives.
Cooperation, on the other hand, is pervasive and may be detected at practically any level of biological organization.
Since Darwin, significant progress has been made, and we now know a lot more about how creatures might profit by cooperating. Although various key ideas have been created and tested over the last several decades, kin selection theory may have resulted in the biggest progress in our knowledge of animal cooperation.
Bill Hamilton proposed in the 1960s that if an individual cooperates with its relatives, that individual may indirectly pass on its genes to the following generation. This is now widely acknowledged as the primary explanation for family cooperation.
Cooperation, on the other hand, may be seen on a far broader scale, with enormous social groupings effectively working together to build and preserve a common good outside of the context of reproducing. Because of the often low average degrees of relatedness and the social challenges encountered by individuals inside those groupings, it is much more difficult to see how kin selection may favor such big social groups. The tragedy of the commons is a well-known and often observed societal predicament.
According to the tragedy of the commons, societal benefits are greatest in cooperative groupings, while selfish individuals fare best inside cooperative groups. If selfishness reigned supreme, public goods would be over-utilized, and society would implode. Overfishing of fish stocks, our inability to address climate change effectively, and the demise of the original inhabitants of Easter Island are all examples of human culture. How can animals prevent catastrophic collapse while keeping freeloaders at bay?
To discover, our University of Sheffield research team, led by Professor Ben Hatchwell, used sociable weavers (Philetairus socius) as a model system.
This little passerine bird is incredibly sociable and creates the biggest nest of any bird, sheltering hundreds of people, weighing more than a tonne, and lasting decades.
Individual nest chambers are integrated within a common thatch of their huge nest. The latter necessitates independent investment from colony members and is unrelated to investment in individual nest chambers. We can learn about how birds collaborate to preserve their public good by analyzing the thatch.
We discovered that the birds contributing to thatch building did so above their own nest chamber after comprehensive observations of their behavior and tests to determine the genetic ties among the colony members. This denotes self-directed thatch construction.
However, we discovered that these thatchers’ neighbors were frequently relatives and the fact that they profited shows that the thatch-building may be aimed toward family. We discovered that relatedness to near neighbors predicted thatch building: the more related a person is to their neighbors, the more likely it is to contribute to the common benefit.
Finally, we discovered that related individuals tend to share the usage of nest chambers, so sharing the rewards of their community investment among relatives. So these gregarious birds benefit from excellent neighbors and solid family ties – a lesson for us all, no doubt. Despite minimal relatedness at the colony level, the social organization of relatives within the colony leads to community investment and contributes to the overall thatch vital for the nest as a whole.
This is the first study to show that kin selection may support the animal effort necessary to communally build and maintain a building, and as such it may be applicable to the many other species that build structures. However, the process discovered in our study is unlikely to apply directly to humans, the most cooperative of creatures.
There are alternative answers to the problem of collaboration, such as the enforcement of laws and agreements. Perhaps it is to these, such as the regulation of sustainable fishing techniques, that we must look to guarantee that the tragedy of the commons is not repeated on a global scale.
