Humans have the longest childhood of any animal on the planet – a remarkable fact. Since children are very vulnerable in the wild, why would evolution risk such a long childhood?
The reason is that there has been a big payoff – a net adaptive advantage – in giving the brain time, during childhood, to learn a vast number of things, and to become trained to be capable of the additional learning during adulthood that enables a person to adapt to and thrive in his or her environments.
All this learning means that the actual structure of the brain must change over time, in a dynamic unfolding process enabled by mechanisms like these:
- Neuronal pruning from the moment of birth: a kind of natural selection within your own brain in which inactive neurons die (“use it or lose it”)
- Greater excitability of individual neurons due to increases in their activity
- Increased blood flow to active neuronal regions
- Stronger synapses between neurons that are firing
- New synapses – “arborization” – among active neurons, like eager spring growth of twigs and buds stretching toward each other in the great forest of the brain
Interestingly, the part of the brain that takes the longest time to fully develop is the prefrontal cortex, which is centrally involved in the “executive functions” of planning and the regulation of feelings and actions.