Reading about human evolution is an interest I’ve developed in recent years and it has given me a lot of pleasure. A downside to my enthusiasm, however, is that family and friends have to suffer my occasional mansplaining outbursts about the evolutionary roots of human nature. It hasn’t – as yet – led to marital breakdown.
Which reminds me, did you know that there is a correlation between the extent to which different primate species, including humans, are monogamous, and the difference in body size between the adult males and adult females of each species? I was first introduced to this idea when reading the late great Edmund O Wilson, whose specialist area was ants but who wrote about social animals generally. Male gorillas are twice the size of their female counterparts and are polygamous. At the other end of the spectrum gibbons, who are similar in size whether male or female, are monogamous.
Human adult males are, approximately, 20 per cent bigger than their female counterparts, suggesting we are as a species almost monogamous, but not quite. Which seems to fit the evidence.
More recently, while reading Human Evolution, by Robin Dunbar, I’ve been introduced not just to suggested reasons for the existence of our capacities for laughter and gossip, but to the argument that the evolution of these capacities is an important part of the story of how we came to be the species we are.
Dunbar puts a great focus on time budgets and using them to explore our deep past. There are only so many hours in the day and our distant forebears, just like us, needed to gather and eat food, and to rest. They also, just like us, needed to maintain relationships with others if they were to flourish, and this also took time. When early hominids came down out of the trees and began scouring for food on the ground, they made themselves more vulnerable to predators, and sought to counteract this by operating in groups.
But operating in groups requires bigger brains – handling multiple relationships is challenging – and brains consume a lot of energy. So, where to find the extra time needed, in an already stretched time budget, to gather more food to allow for bigger brains? Well, I’m glad you asked.
Primates like chimps and gorillas bond by grooming, Dunbar explains. I groom you, producing endorphins in you and giving you a sense of well-being. Then you groom me, making me feel good too. We bond. It takes time out of our daily time budgets, but bonding is essential if the group is to flourish.
Laughing also produces endorphins, and because it can produce them in more than one person at a time, it is a more efficient way of bonding than grooming. What Dunbar suggests is that by evolving a capacity for laughter we freed up time to collect more food, which we used to fuel bigger brains. The evolution of laughter probably pre-dates sophisticated language, the scientist believes. When sophisticated language came along, it allowed for jokes, which are even more efficient tools for bonding. We could walk along in a group, telling jokes, having a laugh, and all the time scouring for food. With our big brains.
There is some debate about whether the evolution of sophisticated language was driven primarily to help us convey information, such as how to cultivate bees, or by the need to gossip. One of the cheering things about reading good popular science is learning how scientists have set about exploring such seemingly impossible questions. Researchers have tested people’s capacity to recall stuff they are told and have found that people are less likely to remember information, such as how to cultivate bees, than they are to remember gossip, such as who’s sleeping with who, or the latest scandal in the workplace. For reasons I’ll skip over here, they believe that this indicates that gossip, and bonding, may have been the driving force for the evolution of language, rather than the capacity to convey utilitarian information.
It is an interesting suggestion and one that I personally find attractive. It may well explain why, in the middle of an entertaining gossip, an intervention by one member of the group to share some fact they’ve just come across in a book about evolution can be met with an outbreak of silence and blank stares. Evolution explains a lot.