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New observational research on chimpanzees indicates that children are also more prone to risky behavior, but less parental supervision of teenagers gives them more opportunities.
Teenagers are known for their risky behavior, and in the US they are more likely to die as a result of injuries than younger children. But what is responsible for this increased propensity to take risks during puberty?
New findings on physical risk-taking propensity in chimpanzees suggest that increased risk-taking propensity in human adolescence is not due to a new inclination to danger. Instead, decreased supervision gives teens more opportunities to take risks.
A team of scientists studied locomotion in chimpanzees, one of humans’ closest relatives. It is difficult to study people’s propensity to take physical risks, as it is unethical to put anyone in danger. Chimpanzees make good alternative study subjects, since wild chimpanzees of all ages have to move through the treesoften at great heights.
Bryce Murray, a graduate student at the University of Michigan, noticed that some of the movements chimpanzees perform in trees are more dangerous than others.
Typically, chimpanzees climb or swing, keeping a firm grip on branches. However, they also jump over gaps and sometimes let go of a branch completely, falling onto another branch or onto the ground. Unfortunately, they don’t always land correctly. Years of observations in nature have shown that falls are one of the leading causes of injuries and even death among chimpanzees.
After observing these behaviors in chimpanzees, Bryce began to wonder whether their propensity for taking physical risks follows the same patterns we see in humans. Will chimpanzees start taking more risks – like jumping and falling from branches – when they enter puberty? Because there is evidence that men take more risks than women, although this varies across cultures, researchers have questioned whether male chimpanzees are more likely to take risks than females.
Young adventurous chimpanzees
The study group consisted of more than 100 wild chimpanzeesaged between 2 and 65, from Ngogo, Kibale National Park, Uganda.
They found that chimpanzees showed their most daring locomotion behaviors in late childhood (between 2 and 5 years old), with jumping and falling rates at progressively decrease with age.
Compared to adults (over 15 years old), older babies were three times more likely to engage in risky behavior. Juveniles (between 5 and 10 years old) were 2.5 times more likely, and adolescents (between 10 and 15 years old) were twice as likely. Babies under 2 years old spend most of their time clinging to their mothers and were therefore not included in the study.
Thus, adolescence does not represent a peak in risk-taking for chimpanzees, but rather a point within a gradual age-related decline. Furthermore, there were no significant differences between the sexes in risk-taking at any age, which is in line with previous work, which showed that male and female chimpanzees do not differ much in the way they move in trees.
The results corroborate previous laboratory studies that focus on gambling risks rather than physical risks. Researchers ask chimpanzees to choose between safe and risky options – for example, a box that guarantees an acceptable treat, like peanuts, versus a mystery box that might contain a very desirable treat, like a banana, or a bland option, like cucumber. Chimpanzees tend to choose the safest option – peanuts – as they get older. A similar pattern occurs in humans, who become more risk averse with age.
In both contexts, in trees and in the laboratory, chimpanzees did not show a peak in risk propensity when they reached puberty.
Implications for risk propensity in humans
Chimpanzee mothers cannot effectively restrain their offspring’s behavior after the age of 2. At this age, cubs cling less frequently to their mothers and they no longer maintain constant contact. In observations of jumps and falls, 82% of the cubs were out of the mother’s arm’s reach.
In contrast, the human children are accompanied closely by their parents and by what social scientists call “alloparents”: other adult caregivers, such as grandparents and older children, especially siblings. Although approaches to parenting vary greatly around the world, in all cultures children are constantly supervised and restrictions ease as they become teenagers.
Our hypothesis is that if parents and other caregivers watched children less closely, younger children would take more physical risks, even before they become teenagers. Studying chimpanzees therefore helps us understand how supervision can shape physical risk-taking in humans.
What is not yet known
It is important to consider other factors that may influence whether chimpanzees take fewer physical risks as they mature. For example, this pattern can reflect a need for adults to be more careful. Although younger primates break bones more often in falls, adults are heavier and have less flexible bones, so injuries from falls are generally more fatal.
The study of chimpanzees offers clues about the roles that both evolution and culture play in human development.
Balancing parental supervision with children’s need for play is a challenge. While concerns about injuries to children are valid, little ones injuries can be a normal part Playing during childhood, when bones are more resistant, can allow children to practice risky behaviors more safely. Some anthropologists advocate increasing children’s access to thrill-provoking games – including traditional monkey bars – as a way to help them develop motor skills and bone strength.
