In comparison to many closely-related species, the human child takes a long time to grow up and requires a high degree of parental investment(亲情投资). Human children need more time to reach maturity(成熟)than other closely-related species.
A new study finds that one reason is the large amount of energy that the brain requires as it grows.
Christopher Kuzawa, first author of the study, explained: “Our findings suggest that our bodies can’t afford to grow faster during the toddler(幼童)and childhood years because a huge quantity of resources is required to fuel developing the human brain. As humans we have so much to learn, and that learning requires a complex and energy-hungry brain.”
Data from the study shows that at the moment when children’s bodies are growing the least-on average, at four years old-their brains are using the highest percentage of glucose(葡萄糖). That means that 40% of the child’s total energy expenditure is being used by its brain.
The findings support the theory that children take so long to mature because of the energy-intensive task of growing a massively over-sized brain in comparison to the brain-to-body weight ratio of other species.
Kuzawa continued: “After a certain age it becomes difficult to guess a toddler or young child’s age by their size. Instead you have to listen to their speech and watch their behavior. Our study suggests that this is no accident.”
Body growth nearly stops at the ages when brain development is happening at a lightning pace, because the brain is using up the available resources.”
“The mid-childhood peak in brain costs has to do with the fact that there are a huge number of synapses(神经元突触), connections in the brain, at this age, when we learn so many of the things we need to know to be successful humans.”
【小题1】Why does it take people so long to grow up?| A．They need to store energy to grow later. |
| B．They need time to adapt to their environment. |
| C．Most of the energy is used for brain development. |
| D．They need a high degree of parental investment. |
| A．At about four years old. | B．At about two years old. |
| C．At about one year old. | D．At about five years old. |
| A．Why toddlers and children need plenty of resources. |
| B．The reason why it takes human infants a long time to grow up. |
| C．The reason why human infants are similar to other animals. |
| D．Why the brains of people need a large amount of energy. |
| A．age | B．their size |
| C．listen to their speech | D．guess their age by listening and watching |
