Ever wonder why the human body matures much slower than other mammals? Me neither. Even though this isn’t anything I’ve ever even thought about, the reason is fascinating.
According to a new study, young children grow much more slowly than other mammals because their developing brains require so much energy to prepare for challenges they will face later in life.
Researchers analyzed data from PET and MRI brain scans and found that the human brain uses enormous amounts of energy during the first few years of life, which means physical growth has to take a back seat during that time.
The brain’s energy use peaks at about age 4 causing the body’s growth to slow down. At about this age the brain is burning on all four cylinders at a rate equaling two-thirds of what the entire body uses at rest.
"Our findings suggest that our bodies can't afford to grow faster during the toddler and childhood years because a huge quantity of resources is required to fuel the developing human brain," first author Christopher Kuzawa, a professor of anthropology at Northwestern University, said in a university news release.
"As humans we have so much to learn, and that learning requires a complex and energy-hungry brain," he added.
That could explains why it’s difficult to tell a young child’s age simply by looking at them.
"After a certain age it becomes difficult to guess a toddler or young child's age by their size," Kuzawa said. "Instead you have to listen to their speech and watch their behavior. Our study suggests that this is no accident. Body growth grinds nearly to a halt at the ages when brain development is happening at a lightning pace, because the brain is sapping up the available resources."
Earlier clinical thought on the topic suggested that the brain’s demand for energy was highest at birth, when the brain size is more relative to the body.
The study's finding that the brain's energy needs peak at age 4 "has to do with the fact that synapses, connections in the brain, max out at this age, when we learn so many of the things we need to know to be successful humans," Kuzawa said.
Other studies have looked at the functions of the 3 to 4 years-old age group and brain development. Experts say that this is the first stage of enlightenment. It’s during this time that preschoolers begin to use problem-solving skills during activities. They are interested in learning about their bodies and other living things. They begin to understand the order of events during the day and start figuring out how to take things apart and put them back together again.
It’s a pretty amazing time for brain development and identity processing. Good nutrition and exercise at this critical time can also help the brain maximize its potential, along with a nurturing environment.
The study was published in the journal Proceedings of the National Academy of Sciences.