If you watch chimpanzees from different parts of Africa, you’ll see them doing very different things. Some use sticks to extract honey from beehives, while others prefer leaves. Some use sticks as hunting spears and others use them to fish for ants. Some drum on branches to get attention and others rip leaves between their teeth.
These behaviours have been described as cultural traditions; they’re the chimp equivalent of the musical styles, fashion trends and social rules of humans. They stem from the readiness of great apes to ape one another and pick up behaviours from their peers. But a new study complicates our understanding of chimp cultures. Kevin Langergraber at the Max Planck Institute for Evolutionary Anthropology has found that much of this variation in behaviour could have a genetic influence.
Their astounding selflessness is driven by an unusual way of handing down their genes, which means that females actually have more genes in common with their sisters than they do with their own daughters. And that makes them more likely to put the good of their colony sisters over their own reproductive legacy.
The more related the workers are to each other, the more willing they will be to co-operate. So you might expect colonies of social insects with fairly low genetic diversity to fare best. But that’s not the case, and Heather Matilla from Cornell University has found that exactly the opposite is true for bees.
Bee queens will often mate with several males (a strategy called polyandry). It’s an unexpected tactic, for it means that the queen’s daughters will be more genetically diverse and slightly less related to each other than they would be if they all shared the same father. And that could mean that selfless co-operation becomes less likely.
Despite this potential pitfall, social insect queens do frequently sleep with many males, and all species of honey bee do this. There must be some benefit, and Mattila has found it. Together with Thomas Seeley, she showed that a genetically diverse colony is actually a more productive and a stronger one.