If you bury money in your garden, you won’t get any interest on it, nor help build any new homes or companies. You might think the risk of losing money is lower in the garden than in a bank, but someone or something else might dig it up, or it might stop being a valid form of currency, or you might lose track of where it is, or die without giving it to someone else. Memory is similar – we save it for a purpose, a purpose that changes it. As children we develop our ability to plan at roughly the same time we develop our ability to remember. We use the same parts of our brain to remember as to imagine or plan. Just as the purpose of money is transferring wealth, the purpose of memory is action.
The most basic problem an animal has is what to do now, what to do next. Since the world at any instant does not provide us with enough information to make the best decision about what to do next, we need an active memory. Even simple animals and plants have a kind of memory, although some species use their own memory less than others. Trout can find food, mating partners, and fresher water by smell. So a fish brain takes in smell, translates it into goals, then pushes that information into movements of its spine: memory is barely required. Birds have small brains but travel fast, and can direct more information from memory into the goal-choosing forebrain than fish can. So they spread out through their environment and figure out which trees are fruiting right now, leaving fruit yet to ripen until later.
Primates also work in niches where the immediate environment offers few clues about where the next meal is coming from, and so they have more in common with birds than fish in this respect. Humans evolved from fish and our brains are shaped that way too – our goals are selected by our forebrain which is right up near the olfactory lobe and the nose. However, if you look at a human brain, information from ears, touch and eyes have to go via the locations used to associate information with memory before they come back forward to the planning. The olfactory lobe is still in its evolved location, but humans have worse sense of smell than most other species and other abilities like memory play more of a part in our actions. We call species that integrate memory into plans to choose their behaviour cognitive. They can work on hard problems like how they can successfully collaborate to survive because they’ve co-evolved bigger brains with their adaptive behavioural strategies.
When we humans are born, we cannot perceive or understand most of what happens around us. In fact, even as adults the complete complexity of the world is well beyond our perception. But by adulthood we have learned an amazing range of things that makes us the most cognitive of all species. Not only do we learn from our own experience, but we learn from the experience of others. This is also true of other animals, such as just chimpanzees, and we’re coming to realise, in fact, that many species mine information from the memories of others. But humans do more than this. Humans also share stories – we can learn about actions we haven’t observed, even synthesised summaries of actions and situations that never took place. This is what makes our cognition exceptional.
The advantages of memory might make you think that holding onto it would be the best plan. But the fact is, if memory is for acting, then there is no reason to remember things that no longer affect our behaviour. In fact, it’s worse than “no reason”. There is a computational and therefore cognitive cost to remembering too many things. It takes time to search through memory, and we don’t want to accidentally apply a principle that no longer holds. Forgetting is our brain’s method of automatically losing access to that which no longer applies. However, generally speaking cognitive animals live longer than non-cognitive ones, perhaps because our memory is such a resource, not only to ourselves but to our children. Because we are a part of a social and a cognitive genus that has lasted for millions of years, it may be that we have evolved patterns of varied strategies. Our genes may be able to rely on the fact that some family members will have long memories to help us if an old problem comes back, while others will always be ready to try new things.
Of course, stories are more than just memory about useful ways to operate in the world. Stories are also a form of art, and as such, they contribute to our identity. Group-level identity allows us to achieve both great and terrible things, but overall the effect of our incredible capacities has been our ability to vastly increase our numbers and to dominate almost every ecology on the planet. Before the evolution of contemporary levels of art, language, writing and agriculture there were more macaques on the planet than humans.
The evolution of cooperation is not a mystery (as it is sometimes portrayed in the press), but it is one of the most exciting and challenging areas of research with more understanding emerging every day. My group is one of many working to understand where our society comes from and how it works. If you would like to read more academic papers about the evolution of human society and language, I have a list.