Age 30 — Bone mass
If you're worried about running that marathon in old age, however, consider that your bones are at their strongest and densest when you're 30 years old.
Past age 30, take a vitamin D supplement to keep bones dense and strong.
Age 28 — Running a marathon at an elite level
According to one 50-year analysis of marathons, the average age to complete the race in just over two hours — widely considered the limit of human long-distance performance — was 28.
Of course, people of all ages can be fit enough to achieve that goal.
Age 26 — Chances of finding the ideal spouse
The 37% Rule of statistics says that at age 26 you'll have met enough people to have some solid options without waiting so long that they start pairing off without you.
And according to one recent study, divorce rates are lowest for couples who married between the ages of 28 and 32.
Age 25 — Muscle strength
If you want your muscles to be in the best possible shape in your 30s and early 40s, research suggests to keep them in good shape by age 25.
Your muscles are at their strongest at that age, and you can preserve much of their strength for the next 10 to 15 years.
Age 23 — Life satisfaction
A survey of 23,000 Germans between the ages of 17 and 85 found that 23-year-olds were most satisfied with their lives, "all things considered."
(However, life satisfaction actually has two peaks. The same study found people feel the most satisfied again around age 69.)
Age 23 — Female attractiveness to men
In the book "Dataclysm,"OKCupid cofounder Christian Rudder used his site's data to show preferences across race, religion, and gender.
According to the book's analysis of the data, men find women in their early 20s most attractive. Even as the men got older, their preference for 20-something women seemed to stay the same. Women in their 20s on the site, on the other hand, tended to like slightly older men (a year or two older than they were) and women in their 30s tended to like men a few years younger than them.
A disclaimer: OKCupid's data pool, which is based on its users, isn't a representative sample of the population.
Age 22 — The ability to remember names
Cognitive ability declines as people age, but recalling a stranger's name after meeting them is one skill that goes pretty quickly.
According to a 2010 study, people peaked in remembering others' names around age 22.
Age 18 - Brain processing power
One of the key ways cognitive scientists test brain processing power is through something called a digit symbol coding test.
A researcher will equate a number with a certain symbol before giving a subject a string of numbers and asking them to convert the numbers to the correct symbols.
On average, 18-year-olds fare best on the task, according to a study published in 2016.
Age 7 — Learning a new language
There's still some debate among linguists and psychologists about whether people lose their ability to absorb a new language as they age, but it's widely accepted that the brain is more malleable, or "plastic," before kids reach puberty.
If you want your child to learn a language, best to give them lessons as soon as possible.
Source: Business Insider India