에 대한 답변 [Forecast Q2-2025] - The Study of Teens

A   5Our ancestor, Homo Erectus, may not have had culture or even language, but did they have teenagers? For reasons unknown, humans continue to be the only animals on the Earth to have a teenage phase. Determining exactly when adolescence first evolved and the sorts of changes in our bodies during adolescence as well as the lifestyles associated with it, could help us understand the reasons for adolescence. It would be interesting to learn why we alone have a growth spurt so late in life.

B   1Until recently, the dominant explanation was that physical growth is delayed by our need to grow large brains and to learn all the behaviour patterns associated with humanity-speaking, social interaction, and so on. While such behaviour is still developing, humans can not easily fend for themselves at a young age, and a youthful appearance will make it more likely for parents and other adults to continue looking after younger ones who are still in the major stages of development. 6What's more, studies of mammals show a strong relationship between brain size and the rate of development, with larger-brained animals taking longer to reach adulthood. Humans are at the far end of this spectrum. If this theory is correct and the development of large brains accounts for the teenage growth spurt, the origin of adolescence should have been evident in the evolution of Homo sapiens and Neanderthals almost 200, 000 years ago. But, surprisingly, the fossil evidence does not support the existence of adolescence.

C   2The human fossil record is extremely sparse, and the number of fossilised children is minuscule.That being said, anthropologists have recently begun to try to find out if we can learn anything about our ancestors from the remains of these children.7Among the most studied is the famous Turkana boy, an almost complete skeleton of Homo Erectus from 1.6 million years ago found in Kenya in 1984. However, it is not easy to determine someone's age from a skeleton. Even with a modem skeleton, you can only make a guesstimate of the age based on the developmental stage of teeth, bones, and skeleton size.

D   8You need as many developmental markers as possible to get an estimate of age. The Turkana's teeth made him 10 or 11 years old. The features of his skeleton put him at 13；however, he was as tall as a modern 15-year-old. 11Susan Anton, a New York University anthropology professor refers to a research carried out by Margaret Clegg who studied a collection of 18th-century and 19th-century skeletons whose ages at death were known. When Anton tried to age the skeletons without checking the records, she found similar discrepancies to those of the Turkana boy. For example, one 10-year-old boy had the dental age of a 9-year-old； his skeleton was thought to be of a 6-year-old yet had the height of an 11-year-old. “The Turkana kid still has a rounded skull and needs more growth to reach the adult shape, ”Anton adds. She thinks that the Homo Erectus had already developed modern human growth patterns, with a late adolescent growth spurt that was not as drastic as the growth spurts of modem day adolescents She believes that the Turkana boy was just about to enter adolescence.

E   If Anton is right, her theory differs from the conventional thinking that linked late growth with the development of a large brain. Anthropologist Steven Leigh from the University of Illinois goes further. He believes the idea of adolescence as a catch-up growth does not explain why the growth rate increases so dramatically. 12He says that many apes have growth spurts in particular body regions that are associated with reaching maturity, and this makes sense, because by timing the short but crucial spells of maturation to coincide with the seasons when food is plentiful, they minimise the risk of being without adequate food supplies while growing.  What makes humans unique is that the whole skeleton is involved.  For Leigh, this is the key.

F   According to his theory, adolescence evolved as an integral part of efficient upright locomotion, and to accommodate more complex brains. We have learned from fossils that our ancestors walked on two legs about six million years ago. If proficient walking was important for survival, perhaps the teenage growth spurt has very ancient origins. While many anthropologists will consider Leigh's theory stretches too far, he is not the only one with new ideas about the evolution of teenagers.

G   Surprisingly, the study of tooth growth, has helped anthropologists in their studies regarding teenage evolution. 9Every nine days or so, the growing teeth of both apes and humans acquire ridges on their enamel surface. Similar to rings in a tree trunk, the number of ridges in teeth can tell us how long it took the crown of a tooth to form. With mammals, the rate at which teeth develop is correlated with how fast the brain grows and the age at which the mammal matures. 3Teeth are good indicators of life history because their growth is less related to the environment and nutrition than the growth of the skeleton.

H   The published findings based on a study of Neanderthal teeth by researchers in France and Spain offered a more decisive piece of evidence. 13The Neanderthals had a faster tooth growth than the Homo Erectus who were before them, and hence, possibly, a shorter childhood as well. 10Lead researcher Fernando Ramirez-Rozzi thinks the average life expectancy for Neanderthals was 25 years. This was mainly caused by the hostile environment of the glacial Europe where it was usually cold and harsh. 4Both the Neanderthals and Homo Erectus evolved to grow up faster than their immediate ancestors.They probably had to reach adulthood fairly quickly without delaying for an adolescent growth spurt.