SUNDAY, 6 OCTOBER 2024
Eight mice look up at me, just a few weeks old. I’ve distracted them from their play and now they are curious, but wary. Fair enough, really - an alien in a lab coat just lifted the lid off their whole world. They give a few tentative sniffs before realising I am no threat and return to playing monkey bars with the food rack and chasing after their friends.But I am anthropomorphising. Are they really playing? Do mice have friends? Neither play nor friendship serves any immediate purpose in the sterile eyes of evolution yet in non-human animals, play behaviour is widely studied while friendship remains strictly out of bounds.
We’ve come to attach so much gravity to the word ’friendship’, shutting us off from exploring it scientifically. Bound up with love, centuries of philosophers and poets would have us believe that it is right at the core of what it means to be human. Just like everything about us, though, it emerged through our evolution so perhaps we are not such a special case.
THE FIRST CONNECTIONS
The evolutionary origins of friendship lie in cooperation, a trait which is rife across the animal kingdom. With the gift of retrospect, the advantages of cooperation are clear - protection, reliable access to resources, more reproductive opportunities - but this was not an obvious or easy adaptation to be made through evolution.
Evolution is not a conscious process with foresight to predict useful traits. Instead, genetic variation from generation to generation gives rise to individual quirks. Most are neutral but some may be useful and some quite the opposite. When a trait provides a survival or reproductive advantage, the chance of its underlying gene being passed on to the next generation is higher - we say that trait has been ‘selected for’. This makes cooperation unlikely to emerge given that its positive effects are only felt when all members of a group are behaving cooperatively. If only one has cooperative tendencies, it may help the group but they themselves will see no benefits, and so that tendency will not be selected for.
Evolutionary biologists have two theories for why cooperation emerged regardless. The first is kin selection. In this case, by helping a close relative, you are indirectly improving the chance of your genes being passed on because you share largely the same set. Sensible, but how can we explain the cases in which cooperation extends beyond your closest family, such as within a herd? The herd passing on their genes is irrelevant for you, so you need a personal motive. Two phenomena must have emerged at the same time: a cooperative behaviour, and a reward for that cooperation. Perhaps against our intuition, these are not fundamentally entwined.
Imagine the case of communication. Its evolution requires the simultaneous emergence of signal generation, such as making sounds, and signal reception, such as hearing. One trait is useless without the other and would never be selected for, but if at the same time one individual is born with the ability to squawk and another with squawk-tuned ears, suddenly each has a purpose.
We can apply this to cooperation. This time, imagine an unusually cooperative creature born into a society of lone wolves. He shares the spoils of every hunt with others around him who, of course, gobble it up but never do anything in return. That unusually cooperative creature is disadvantaged and so his rogue cooperative trait is selected against. Now imagine instead that at the same time, another creature pops up with an inclination to protect the first creature’s land when he is off hunting. One hunts and shares food while the other protects. These are different traits but the circumstances mean that both are indirectly useful and so this time, they are both selected for.
This laborious recipe makes complex behaviours like cooperation seemingly unlikely to emerge, but luckily evolution is an infinite experimental playground. Given that we see forms of cooperation across so many species, from lions hunting in packs to take down larger prey to my eight mice giving tiny ultrasonic squeaks to alert the others of a potential threat, biologists can conclude that cooperation was heavily selected for by natural selection, and so must be a hugely beneficial adaptation.
BEYOND COOPERATION
We clearly share cooperative tendencies with many other animals, but it’s only the first step towards friendship. The next is attaching a positive emotional component to cooperation. Inside the brain, we humans share the same reward and pleasure systems with other mammals. We cannot ask animals how they feel when these pathways are active, but we see that during positive activities like eating, having sex, or socialising, those pathways light right up. We know that animals desire these experiences because they can be used as rewards to train other undesirable or neutral tasks. My mice could be trained to navigate a maze or pull levers by offering food as a reward, but researchers have shown that social interaction can be used as a motive just as successfully.
Zooming out of the brain to behaviour, we see that after a successful cooperative hunt, animals like wolves engage in bonding behaviours such as grooming and close contact, suggesting a shared positive experience. There is no need for them to do this from the evolutionary perspective of cooperation – it doesn’t increase the chances of a successful hunt or keep them extra safe from predators – but there is a clear desire to establish closeness with their pack which in turn strengthens cooperation.
It’s easy to see why these emotions are a common phenomenon across animals. They are a powerful motivator for an evolutionarily important behaviour, comparable to fear driving predator escape and bonding driving maternal care. As such, these have all been classified as ‘basic’ emotions and their ubiquitousness points to a relatively early evolutionary origin.
Animals can have social bonds with a strong emotive aspect, but those emotions can ultimately be traced back to personal survival and reproduction. This is still not quite the picture of friendship we revere, of selflessness and generosity. For this we must search for evidence of ‘complex’ emotions that appear to overrule fundamental self-preservation instincts: empathy and sympathy.
OVERCOMING INSTINCTS
Ethologists have reported wild animals behaving in ways that support this sense of care beyond the self. One story reported on two male chimps, Hare and Ellington, who were unrelated but hunted together, protected each other and shared food. These are unquestionably survival activities, but this pair also spent time travelling the forest together and when one died, the other retreated for weeks. A similar story followed, reporting three elephant matriarchs of three different families, Grace, Eleanor, and Maui. Eleanor fell ill and in the days before her death, collapsed to the ground. Grace stayed with her for hours, calling out and trying to lift Eleanor back onto her feet. Eleanor soon died, and this time Maui came and again tried to get her up. When realising this wasn’t possible, Maui stood over her, rocking in apparent distress. Elephants continued visiting her body for some time. These stories are representative of many reports, each niggling us towards the idea that a bond can exist between animals far beyond any rational personal gains.
This can be tested in the lab by letting animals choose between helping another or a personal reward, or by testing whether an animal is willing to exert a high effort to help another. The study of empathy remains contentious, always returning to the problem that we cannot ask an animal how they actually feel, but there are a handful of studies giving credibility to reports of animal empathy in the wild. They have shown that if a rat has experienced an aversive condition themselves, such as a small electric shock, they will act to save another from that same situation. In one experiment, rats who had experienced being soaked in water themselves quickly learned to pull a lever that would allow other soaked rats to escape the water, even forgoing a food reward to do so. A similar study saw rats work to open a tube that another rat was trapped inside, even when they did not then get to socialise with the rescued rat. Their tendency to rescue each other was strongest when they were already acquainted.
Do animals have friends, then? The greatest challenge of this question is defining friendship. With no objective definition or measure, we cannot evaluate friendship systematically in ourselves, never mind compare between species. It is, however, clear that many animals – at least mammals – have a pleasurable component to their social relationships and can even care for those outside their immediate family without expecting anything in return. But do these relationships take up cognitive space beyond the moments spent physically together? This is incredibly difficult to test in animals under scientific conditions, but stories of apparent grief reported in animals like chimps and elephants may be our first sign that animals are capable of more complex internal lives than we once believed.
I clip the lid back over the mice’s little world and watch as they dash around the cage like tiny bumper cars, bouncing off in the opposite direction each time they see another. It’s predictable, exactly the same routine every time they are interrupted like this. It looks to me like they are counting each other. It looks like, maybe, before settling down in their nests, they are checking up on their friends.
Article by Ailie McWhinnie. Artwork produced using Dall-E.
