Why does it take so long for human children to grow up? A male chimp and male human, for example, both end up with the same body weight but they grow very differently: at year one the human weighs twice that of the chimp but at eight the chimp is twice that of the human. The chimp then gains its adult weight by 12 – six years before the human. A male gorilla is also a faster growing primate – a 330-pound male gorilla weighs 110 pounds by its fifth birthday and 265 pounds by its tenth.
Clues to the answer can be found in the young human brain’s need for energy. Radioactive tracers allow scientists to measure the glucose used in different areas of the brain but this procedure is only used rarely when it is justified by investigating neurological problems. However, the few cases we do have reveal how radically different the childhood brain is from that in adults or infants.
From about the age of four to puberty, the young brain guzzles glucose – the cerebral cortex, its largest part, uses nearly (or more than) double that used earlier or later in life. This creates a problem. A child’s body is a third of the size of an adult but its brain is nearly adult-sized. Calculated as a share, a child’s takes up half of all the energy used by a child.
link.
No comments:
Post a Comment