Teenagers go through dramatic physical changes as a part of puberty. But something odd is happening: puberty is starting earlier each generation. In this lesson, we'll look at the secular trend of puberty and its possible causes.
Ellie is 13 and her body is changing rapidly. A few years ago, she started developing breasts, and her hips are growing larger, too, as her body becomes more and more like a woman's. A few of her friends have even started their periods, and Ellie knows she's not far behind.
Ellie is in adolescence, or the period of life between childhood and adulthood. People go through many changes in adolescence, including physical, emotional, intellectual, and social changes. The physical changes that take place in adolescence are called puberty, which lasts for about four years and ends with the ability to reproduce. For girls, this means that they get their first period. For boys, it means that they are able to produce sperm.
Puberty has always been a part of human development. Ellie is just the latest in a long line of people who have gone through it, all the way back to caveman days. But puberty is different now than it was in caveman days. In fact, puberty is different now than it was just a hundred years ago. Let's look at the 'secular trend' in puberty that has happened over the past century and the possible causes for it.
Like generations of women before her, Ellie is going through puberty. But there's a difference in Ellie and her ancestors. Ellie's great-grandmother didn't start developing breasts until she was 13, and Ellie began puberty at age ten.
The secular trend in development is the fact that puberty is starting earlier for boys and girls now than it did a hundred years ago. The end of puberty (when girls get their period, for example) has leveled off somewhat, but the beginning of puberty is still getting earlier, especially for girls. So, Ellie is not unusual. It's common for girls today to start developing breasts (which is often considered to be the onset of puberty) much earlier than their ancestors did.
This would seem to be counterintuitive because the onset of puberty is largely influenced by genetics. That is, girls and boys have a genetic predisposition for when they go through puberty. And since that's the case, then it makes sense that Ellie would start and end puberty at a similar time to her great-grandmother because they are related and share genes.
So why is the secular trend happening? Genes aren't destiny, and environmental factors can play a large role in human development, including puberty.
Nutrition is a key factor in the secular trend. In the early days of the 20th century, the average American diet changed drastically and has continued to change since. Take Ellie and her great-grandmother, for example. Ellie eats lots of meat and dairy products and gets a good amount of calories every day. She never wants for food. Her grandmother, though, ate meat and dairy much more sparingly and lived on fewer calories because, often, there just wasn't a lot of food to go around.
Ellie's food, too, is often more processed and has hormones and chemicals in it that were not in her great-grandmother's food, which may have an impact on how quickly Ellie develops. Whatever the specific reasons, studies have shown that nutrition is linked to the secular trend and early onset of puberty.
Besides nutrition, there's another difference in Ellie and her great-grandmother: Ellis has more exposure to endocrine-disrupting chemicals, or EDCs for short, which are chemicals that affect the endocrine system of the body. The endocrine system of the body is responsible for sending hormones throughout the body, and thus, it is largely responsible for puberty.
Since she was a baby, Ellie has had exposures to EDCs, particularly those in plastics, like cups and toys, as well as in things like hairspray, nail polish, and some home furnishings. They are everywhere in modern life! In contrast, most of the EDCs that Ellie is exposed to weren't around in her great-grandmother's day. As a result, her great-grandmother wasn't exposed to them in the same volume that Ellie has been.
Puberty is the period of physical development that leads to being able to reproduce. For the past century, the onset of puberty has started earlier and earlier for people in developed nations, which is called the secular trend of puberty. There are many reasons why this might be the case, including nutrition and endocrine-disrupting chemicals.
After completing this lesson, you should be able to:
- Define puberty
- Understand the body changes to boys and girls during this time
- Recognize what has caused the secular trend in puberty