Cooperation is in our nature, for good and for ill, but there is still a nagging doubt that something biological in us compels us to be selfish—our genes. This is the paradox: genes are inexorably driven by self-replication, and yet cooperation continually rears its head. Not only are humans fundamentally team players, but all of nature has been teaming up since the dawn of life four billion years ago. The rules of cooperation that we encounter in our daily lives are fundamentally the same as those that apply to how our cells cooperate within the body, how the parts of the cell came to work together, and how selfish genes cooperate to make social beings. Though simple, these rules play out in complicated and fascinating ways that illuminate everything from the profound to the trivial.
Cooperation is defined as a social behaviour by one individual that benefits another at a cost to the cooperator. It evolves when the benefits to the cooperator exceed the cost of cooperation—a situation that might seem rare, but in fact is very common. Benefits can accrue to a cooperator in two ways, either directly or indirectly, through relatives. Benefits to relatives, or kin selection, explain why, for example, long-tailed tits will help their neighbours raise a brood when their own has been lost. Neighbours tend to be relatives. The cells of a multicellular organism cooperate for essentially the same reason: all are relatives. We don’t usually think of the cells of the body as being relatives of one another, but that is what they are, albeit genetically identical ones.
Uncovering the benefits as well as the costs to cooperation is key to understanding both its evolution and the situations in which it breaks down. Cooperative behaviour is conditional on there being a net benefit and it can disappear when the advantage is lost. Even an intimate symbiosis like a mycorrhizal association between a plant and a fungus will dissolve if the plant can obtain nutrients normally supplied by the fungus more easily from elsewhere.
I like to think of groups of cooperators as teams, because this idea is familiar and captures the essence of how cooperation produces benefits for individuals. Calling the plant and fungus in a mycorrhizal association a team may sound like a metaphor, but it is more than that because the individual benefits of cooperating in a team are the same, whether the game is football or natural selection.
Teaming up can produce direct benefits to team members in two distinct ways: through force of numbers and through division of labour. A team of 11 will beat a team of 2. This has to be how social insects with thousands of workers evolved. But force of numbers alone is not enough. The highest score that a team of 11 goalies can expect is nil-nil. A division of labour among the team, placing players in different positions according to their skills and the overall strategy, wins matches. Likewise, social insects have one or a very limited number of queens with the exclusive role of reproduction. Other castes such as workers assume different tasks, depending on their phenotype, age, and the size of the colony.
Individuals stick with the team so long as their interests are aligned with those of other team members, but this can never be taken for granted. Since cooperation involves costs as well as benefits, there is always the possibility that some individuals will try to take the benefits for free—or in other words—cheat. Tumour cells are cheats. Mutation breaks the alignment of interests that normally exists among the cells in a body, allowing a cancer cell to escape the many mechanisms that normally limit cell proliferation and to multiply at the expense of the host. The most dangerous and successful tumours recruit the assistance of normal cell types, acquiring a blood supply. Such cells cross the line from cooperation to parasitism.
Cheats may be found wherever there is cooperation, but cooperation thrives, nonetheless. Its most spectacular successes occur when members of a symbiotic team start to reproduce as a team, uniting their reproductive fates within a new kind of individual. This is what happened when the ancestor of the eukaryotic cell teamed up with the bacterial ancestor of the mitochondrion. The union of the two ancestral cell types produced a new kind of cell and a major transition in evolution.
Metaphors can help explain a difficult concept, but they can also mislead because at some point even good metaphors fail when taken literally. ‘Selfish gene’ is exactly such a metaphor. It has illuminated the science of social evolution for half a century since it was coined by Richard Dawkins, but it has also misled people into underestimating the importance of cooperation. Instead, let us think of natural selection as a team sport: on every level, from genes and cells to social beings, the team structure of life exists.
Featured image by Getty Images; CreativeJourney/ Shutterstock.com; Wikimedia Commons (Used with Permission).
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