At the end of this article about human cooperation, West, El Mouden and Gardner (WEG), ask “Are Humans Special?”  The authors specifically consider two questions:

1) Do humans have especially high levels of altruism?

2)  Are humans special because cooperation occurs between non-relatives?

After reviewing the literature, they answer both of these questions in the negative, suggesting that human cooperation is not so special after all.  However, their argument misleads because they answer two questions separately that really should be answered together:  The special thing about cooperation in humans is that we have especially high levels of altruism that occurs between non-relatives.

Allow me to illustrate with a Venn diagram:

The left circle in the diagram represents altruistic cooperation.  This is normally defined as cooperation where an individual pays a cost and confers a benefit on another individual. In evolutionary biology, these are normally considered as reproductive costs and benefits at the level of the individual (some like to do the accounting at the level of the gene, but that is outside the scope of this post).  WEG give examples of non-altruistic cooperation:

…a number of organisms have higher levels of altruism than humans, ranging from social amoebae and bacteria to ants and cooperative breeding vertebrates… An extreme example at the altruistic end of the continuum is the long tailed tit, where helpers never reproduce and so
cooperation has been favoured purely by indirect fitness benefits.

Something to notice is that in each example (social amoeba, ants, and long-tailed tits) altruistic behavior occurs between close genetic relatives. For example, in most ant colonies workers are all the offspring of a single queen or multiple closely-related queens. And on top of that most ants are haplodiploid which makes workers even more genetically related. Because altruism promotes the fitness of similar genes in close relatives, this allows for large-scale altruistic cooperation in ants.  This is what WEG means by “purely indirect fitness benefits.”

In contrast, the right circle represents cooperation in non-kin. WEG write:

…cooperation between nonrelatives occurs in a range of organisms. Many forms of cooperation occur between nonrelatives in birds and mammals (Clutton-Brock, 2002). In cooperative breeding vertebrates, there are several examples where non-relatives cooperate, the indirect fitness benefits of cooperation appear to be negligible and it is thought that cooperation is driven by direct fitness benefits…

They do not give specific examples but this review by zoologist Tim Clutton-Brock describes cooperation between meerkats, pied babblers, and African wild dogs.  Something to notice about these examples is that cooperation is not altruistic. Instead, it is what is called mutualistic cooperation, which occurs where an individual’s behavior provides reproductive benefits to both itself and another individual. This is what WEG mean by “direct fitness benefits.”

For example, if an African wild dog goes hunting by itself, it can capture food which will help it reproduce. If more dogs join in the hunt, the expected return to the hunt increases with the number of dogs. If the returns to the hunt are only shared by participants, there is no reproductive cost to cooperation and, thus, cooperation is not altruistic (more about this in my encyclopedia article.)

But don’t take my word for it.  Here is WEG earlier in their paper:

Cooperation is defined as a behaviour which provides a benefit to another individual (recipient) and which is selected for because of its beneficial effect on the recipient (West et al., 2007b). This definition of cooperation therefore includes all altruistic (–/+) and some mutually
beneficial (+/+) behaviours.

If you were paying close attention to the Venn diagram you will notice that there is only one animal that is enclosed in both circles – humans – and this is the only animal described by WEG as being a member of both. This seemingly unique position is what makes human cooperation special – our willingness (or even eagerness) to cooperate altruistically with very distant genetic relatives. You see this type of cooperation all around us and we mostly take it for granted. There are extreme examples, like the willingness to sacrifice oneself for unrelated comrades in war, but also everyday examples like throwing trash in a can instead of on the street. Economic experiments have long established that individuals will often behave altruistically even when their behavior is completely anonymous and one-shot.

So why do humans cooperate altruistically with non-relatives? I am of the school that thinks this is a result of the unique properties of human social learning (i.e., human culture) – a topic I will discuss in a Part II of this post.