Monday, March 30, 2009

What Apes Can Teach Us Pt I

After watching Cave Baby sitting up, I found myself wondering if her development is affected by anything we as parents do. If she had not spent many happy hours sitting in her Bumbo, would she have taken longer to sit unsupported? If she had been carried less and left to play on the floor, would she have sat up more quickly? If a baby was always carried in a sling would it learn to sit up at the same time as it would have done if it spent more time supporting its own body? The acquisition of new skills is due to a combination of muscle development and brain development but my question really is: is this development innate (so the muscles and brain would develop in the same way regardless of the experiences of the child) or is it learnt (so development would be dependent on practice)? Or, as is more likely, is it a combination of the two? The answer to this question has implications for standard advice given to mothers, such as to let baby have plenty of kicking time on its back, and later to have tummy time to allow baby develop its muscles for crawling. I have always had an inkling that these pieces of advice are based on nothing more than popular wisdom but I am willing to be proven otherwise.

On the one hand, many animals' young are born with the ability to walk. The muscular and brain development necessary for this clearly takes place in the womb and was hard coded into the animal's DNA. So it may be the case that humans are also hard-coded to walk and that in time, every child will walk irrespective of the input of its parents. Or, on the other hand, are we different? Since our ability to learn is so much more advanced than that of cows, deer and sheep, have we abandoned this hard-coding in favour of gaining skills through learning? In an effort to investigate these questions I carried out a brief bit of research on the development of infants of our closest genetic relatives - chimpanzees, gorillas and orangutans. Assuming that their childcare methods are primarily based on instinct, rather than societal norms as human methods currently are, how do their young "learn" to sit up and walk?

Though I probably could not answer my original nature/nurture question without running highly unethical trials with pairs of identical twins, I did find some fascinating things out about our ape cousins. To begin with gestation - we all share very similar periods of gestation (gorilla - 8.5 months; orangutan - 8.5 months; chimpanzee - 7.5 months). It has been suggested that human babies are born at a relatively immature stage compared to other large mammals due to the difficulty of birthing our large heads through our twisted birthing canals; however great ape babies are also born fairly helpless. Newborn orangutans cannot even raise their own heads and certainly neither chimpanzees, gorillas or orangutans can sit or stand up. However all have a strong grasping reflex (like human babies) and have the innate ability to hang on to their mothers' bodies, though all require additional support from the mother at first. Chimpanzees are then carried almost continuously for 5 months, gorillas for 6 months and orangutans for longer. The carrying period lasts until walking begins (at least for gorillas and chimpanzees - orangutans move primarily using their arms and hands). Chimpanzees walk at around 6 months and gorillas at around 8 months. During this carrying period, great ape babies develop much more quickly than human babies. The actual development depends to some extent on the characteristics of the species, but for example the infant orangutan learns to sit up at around 2 weeks, and the infant gorilla crawls at 9 weeks.

It is no surprise that all apes sleep with their infants for security and convenience. For orangutans, nest sharing goes on for at least 3 years - around the same time period that infants nurse for. Chimpanzees remain in contact with their mothers both night and day and nurse until around 4 years. Gorillas also nest share for the nursing period which lasts around 3 years. A silverback, the dominant male in a group, has even been documented sharing his nest with an orphaned infant. Although nursing lasts a long time, consumption of solid food does begin early for all these animals. Orangutans eat soft fruits at around 3 months (which their mothers apparently chew for them first) and gorillas begin to eat vegetation at 2.5 months.

I hope that any readers of this are already beginning to draw their own conclusions about what natural, instinctive human childcare would really be like if we were not so strongly influenced by so much ill-founded advice. Click here for the second part of this post.

1 comment:

Joxy said...

Fascinating :)

I look forward to reading the next post.

I do think children will learn to walk regardless because as they develop they want to be more independent and do things themselves and walking allows a child a lot fo freedom. Whether a child who was isolated and never saw a person walk, would learn is debatable. And not an experiment I would want to conduct.