Isn't it odd that a young, high school couple successfully growing a young child up is considered appalling?
Emerging adults, or late adolescents, are where our bodies are the strongest in terms of fertility and strength
One's genes, neighborhood grow, and health habits all play a role in one's adulthood. Some grow faster than others and we're able to see this at age 26. To really understand this, we need to dive into three fields in relation to aging.
Organ reserve - The ability of the organs to help the body deal with stress.
Homeostasis - Body's ability to adjust and reach a balance that "keep physical function in sync with each other".
Allostasis - Long-term homeostasis. Allostatic load [not good effects of something] supports this as the effects of lack of sleep, dental hygiene, and certain Vitamins can add up.
For example, if one does not get enough sleep for a night: they're tired the next day (homeostasis). Years of poor sleep lead to a rise in allostatic load and other functions (such as cognitive speed) adjust. Sooner or later, the effects add up.
Historically, adults would have children before their 20s. But now, adults usually have children in their late 20s (or get involved in marriages). This conflicts with one's cognition and sex drive. Many ages ago, premarital sex used to be taboo - but now young adults are as sexually active than ever before! Adjustments have been made to accommodate this rapid sex drive by implementing same sex colleges. But even then, that's not enough to counter the present issues. The rates of STDs are increasing. Due to organ reserve and homeostasis, young adults don't die early of HIV. Ignorance of STDs allow STDs to spread exponentially. Unwanted pregnancies are also an issue.
According to studies conducted, as one grows up, they weigh certain risks from a good risk to take, to a bad risk. Risky sports, like rugby, are dangerous in of it itself, but people like it! Risks, such as unprotected sex, drug abuse and carrying guns are common from ages 18-25, who are balanced out with more violent deaths vs. low disease rates. Illegal drug abuse increases during this period.