Teenagers: A Natural History Chapter Summary

Due to immense interest in evolution, the brain, and sex, Biologist David Bainbridge wrote Teenagers: A Natural History to discuss the uniquely human concept of adolescence. His book is divided into sections, beginning with the context of human development over the ages and how it compares to that of similar species. Bainbridge then moves into the main topic of his book, which resides in the topics of biological development in teenagers, mental differences in the sexes, and comparisons of adolescences to children and adults. Throughout his book, the author’s focus remains on the crucial period of human development, showing that the ages between ten and twenty treated as an ordeal might be much more positive than anticipated. The origins of adolescence are seen in the history of modern humans, notable in the development of the “three-orange brain.” Chronologically, the creation of adolescence came before the growth in human brain size and gives evidence that it paved the way for this brain increase. Bainbridge explores how adolescence is seen in the fossil records as a period of slowed human development, where humans were sexually immature past the age of twelve. This phenomenon, in addition to many sexually related characteristics, illustrate the special features in human development that is unheard of in any
other species. Of course, sexual development in humans differs between the sexes, beginning with brain development after contraception.
In the center of the brain is the hypothalamus, or the “breeding center,” which releases neurons that in turn release hormones are unique to either sex. Puberty, directly affected by hormones, occurs in different rates in males and females as well, as females begin the process approximately two years earlier than males. These hormones also cause differences in outward male and female appearances, in addition to the theory of sexual selection over time (which suggests that certain characteristics are retained due to widespread
attraction). Prior to adolescence, the childhood stage of life serves as a period of immense brain growth, where almost 95% of total brain growth is complete by the age of six. However, the size of the brain peaks at adolescence and shrinks slightly into adulthood, resulting in adolescence technically having the largest brains of humans. Adolescent brain development is a period of time critical to humans, seen through evolution, A mass part of the brain is unused by children, and this is the part that grows into usefulness to provide an adult-functioning brain by the time of adulthood. Bainbridge refers to this perception of the teenage brain as it being a “behavior establishing machine,” where differences between adolescent and adult brains is clear in the prefrontal cortex. Author David Bainbridge, in his book, clearly depicts how the period of adolescence is one that is key in the process that makes Homo sapiens such a unique species. Through the pre-established complex signals given by the brain, the human body is able to mature from childhood in the areas of bodily growth, sexual development, and mental progression during the “wonderful, valuable time of adolescence.”