Congratulations! You are one of the 7.041 billion people currently breathing on this planet. You have about 1.3 kg of immensely complex and hard working brain tissue consuming 20-30% of your daily calorie intake. That is more than any other organ in your body.
Why the human brain grew large enough to let you read this, and wonder where this is all leading to, is a puzzle keeping more than one evolutionary biologist awake. To be intelligent is nice, to some extent, but do we really need the capacity to reflect about the meaning of life in order to propagate our genes and maintain the human species? In terms of bodily energy expenses, a brain is costly to produce and expensive to run. Wouldn’t life be better with a smaller brain?
There is a species of sea-squirt that uses its brain to find a suitable rock to cling to; once found, there is no need for a brain any more, and the brain is absorbed back into the rest of the body as fuel. In other words: brainfood. So what has happened to us during human brain evolution? About 2 million years ago, the brains of our hominid ancestors underwent a rapid expansion. The size of our brain started to increase faster than the size of our body. By now, compared to the relation between body volume and brain size, our brains are at least seven times larger than expected for a mammal of our size. In comparison, imagine a mouse with the head about as big as a tennis ball!
But why all these brains? Where other species adapted to their environment by physical adaptation, primates specialized by developing their cognitive skills. Several theories address the question why primates are – according to our human measures of intelligence – more intelligent than other mammals. A popular theory is that group-living requires considerable mental skill and complexity, with which I can heartily agree.
Recently, at a party, I introduced myself to the same girl three times. Obviously, the third time, the girl seemed a bit grumpy: “Yes. I know. You have told me two times already.” With embarrassment and blushing cheeks, I tried to convince her that she should not take it personal and that I always have trouble remembering new faces. Luckily, a friend of mine who understood what was going on, helped me out by confirming that this was indeed the case, “She always forget the faces of people she have met”, he said. With this confirmation the girl now seemed to accept my explanation and apology, and started a more neutral topic of conversation.
This is only one of the many situations demonstrating that our brain-capacity is crucial for our everyday lives. We don’t just sit on a rock like that sea-squirt: our memory, tactfulness, strategic and empathic skills are all essential cognitive ingredients, allowing us to live as successful social human beings in a social society.
But has the evolution of the human brain stopped? Alternatively, will our brains grow bigger in order to cope with a world that is rapidly expanding on a social, economical and technological level? Or will technological progress allow an artificial form of evolution?
In our modern world of overwhelmingly clever technology, where we are surrounded by ubiquitous artificial intelligence such as robots and computers, I am wondering when the limit between human intelligence and artificial intelligence will fade away. When will the first hybrid robot-human, the first cyborg, be born? And when will the first chip, replacing a part of the human brain, be implanted?
Imagine replacing your amygdala – a part of the brain that plays a key role in our emotional life – with an ingenious chip producing exactly the same feelings and behavior as the real amygdala. Are you still human? Intuitively, I would say ‘yes’. Now, imagine replacing your brain, part by part, until your brain is entirely electronic, while still letting you act, think and feel exactly the same as you did before any brainpart was replaced. Would you still call yourself human? What distinguishes you from a robot? At what point do you cross the line between being human and robot, and what does the line consist of?
Currently, a dominating view in neuroscience is the idea that ‘we are our brains’. In this view, every single aspect of our behavior, every single thought or emotion, results from a chemical, mechanical, physical process. If this is the case, if all the processes in our brain could at some point be perfectly understood and replicated, couldn’t the brain be replaced, like an artificial leg?
Due to brain-computer interface research it is already possible for people (often paralyzed patients) to control technology such as computers or a robot arm with their own mind. Only time will tell (us) what this technological progress will mean for the evolution of the human brain and our definition of a human. What does being human mean to you? Will you update your prefrontal cortex and download the first ‘amygdala-app’ when the iPhone 384 will be on the market? Brainfood, I’d say..
If you crave for more food for thought:
Evolution and human behavior, Darwinian perspective on human nature, 2nd edition, John Cartwright, 2008, A Bradford Book, MIT Press.
Shulman RG, Rothman DL, Behar KL, Hyder F. (2004) Energetic basis of brain activity: implications for neuroimaging.
To read more about brain-computer interface research: http://www.nick-ramsey.eu/pages/bci.html
Illustration: Erica Lindstedt