Bruce Hood - The Domesticated Brain - A Pelican Introduction (Pelican Books)

That analysis could rely solely on the costs and benefits of social behaviours, but then we would miss the important point that people are emotional animals with feelings. It is not enough to read others and synchronize with them in some coordinated tango to achieve optimal goals. There is also an imperative to engage with others through positive and negative emotions that motivate us to be social in the first place. Taking that perspective casts a better light on understanding why humans seem to behave so irrationally because sometimes they care too much about what others think.

One of the more controversial issues that The Domesticated Brain addresses is the extent to which early environments can shape the individual and even pass on some acquired characteristics to their offspring. For most Darwinians committed to the theory of natural selection, whereby the environment alone operates to select genes that confer the best adaptations, this idea sounds heretical. Yet we examine the evidence that early social environments leave a lasting legacy for developing our temperaments through what are known as epigenetic processes – mechanisms that change the expression of our genes that can affect our own children.

Every child at some point has been told that they must ‘behave’ and when they do not, they are ‘misbehaving’. What parents really intend when they scold their children for misbehaving is that they must learn how to control their thoughts and actions that conflict with the interests or expectations of others. Self-control is a feature of our developing frontal lobes of the brain and is central to our capacity to interact with others. Without self-control we would never be able to coordinate and negotiate by suppressing the urges and impulses that could interfere with social cooperation. This capacity for self-control is critical when it comes to being accepted and without it we are likely to be rejected – labelled anti-social because we fall foul of the moral and legal codes that hold our societies together.

That danger of rejection is the flipside of the benefit of living in a group and the devastating consequence of becoming an outsider. Ostracism and loneliness not only register as pain in our brain but also make us both psychologically and physically ill. Rejection can make individuals behave in destructive ways not only against themselves when they self-harm, but also against others. We may be more connected through social networking on the Internet, but this digital village also makes it much easier to become isolated.

Considering the vast size of the different territories covered in The Domesticated Brain , from human evolution, brain growth and child development to genetics, neuroscience and social psychology, any attempt to bridge these regions will be ambitious – yet it is a goal worth pursuing. When we recognize the importance of others in shaping who we become and how we behave, we can begin to understand what makes us human.

‘Why do you need a brain?’ Initially, this seems like a silly question with an obvious answer. ‘You need a brain to stay alive,’ is a fairly common response and indeed this is true. 1You would be dead without your brain. When someone is ‘brain dead’, they lack the vital signs of breathing and a heart beat – functions that are automatically controlled by structures deep at the core of the brain. However, keeping you alive is neither the sole function nor responsibility of the brain. There are many other organs you need to keep you alive. There are also many living things that do not have brains, such as simple organisms like bacteria, plants and fungi.

When you take a closer look at our planet and consider all its different life forms, it soon becomes apparent that the original reason why living things evolved brains was for movement. Life forms that do not move or those that are swept around by the ocean currents or carried in the wind or even transported on or inside the bodies of other animals do not need to have brains. In fact, some start off with brains that they later abandon.

The best example of this is the sea squirt that begins life as a tadpole-like creature, swimming around the ocean in search of a suitable rock upon which to attach. It has a rudimentary brain to coordinate movements and even a simple eye spot to ‘see’, but when it finally attaches to the rock, it no longer needs to search for a home and so loses its own brain. 2Brains are expensive things to operate so if you no longer need one, why keep it?

Arguably, the main reason that the brain evolved was to navigate the world – to work out where you currently are, remember where you have been and decide where you are going next. The brain interprets the world as patterns of energy that stimulate the senses, generating signals that stream up into our brain where they are analysed and stored. With experience, these patterns become learned so that the brain knows how to respond more appropriately in preparation for future encounters. As you progress up the tree of life to animals with increasingly complex brains, you find that they have a much larger library of patterns they have stored. This provides greater flexibility, giving the animal more skills and knowledge to deal with potential problems rather than being stuck with a limited set of actions. Without the ability to act, organisms would be completely at the mercy of the environment. They would be easy pickings for any predator, unable to forage or capture their own food and vulnerable to the elements. Some creatures live their lives like this – the inevitable food for others – but many evolved a brain to lash out at the world or scamper away if the threat was too fierce.

The human brain, on the other hand, is not just for solving practical problems of finding food and avoiding danger; it is also a brain exquisitely engineered to interact with other brains. It evolved to enable humans to seek out others who are similar to form social relationships. Many of its specialized operations address the complexities of the social spheres we inhabit. We require a brain with finely honed skills to process different individuals who may be family, friends, workmates or the multitude of strangers we encounter in everyday situations.

In our ancestral past, these encounters would have been few and far between, but in the modern era we need to be expert socializers. We need to recognize who people are, what they are thinking, what they want and how to cooperate – or not – with them. We have to read others in order to understand them. These social skills that may seem trivially easy for many of us turn out to be some of the most complicated calculations our brains can perform. Some people never master them, such as individuals with autism, and others lose these capabilities through the effects of damage and disease to their brains. Our brain may have initially evolved to cope with a potentially threatening world of predators, limited food and adverse weather, but we now rely on it to navigate an equally unpredictable social landscape. The human brain enables each of us to learn about, and from, each other – to become domesticated.

Our brain is equipped with the mental machinery to live together, to breed, to raise our children and to pass on information about how to become a valued member of society. Many animals live together in groups but only humans have brains that enable them to transmit knowledge and understanding from one generation to the next in a way that is unparalleled in the animal kingdom. We can learn the rules about how to behave in ways that are acceptable to the group. We can adopt a moral code about what is right and wrong. We raise our children not only to survive to an age where they are capable of reproduction themselves but also to benefit from the collective wisdom of others that is passed on as culture.