Above is an image of Sexual Market Value broken down by age and gender. What is sexual market value? It's how attractive you as a romantic and sexual option. The higher your SMV, the easier it will be to attract partners, and higher quality partners as well.
You may notice something if you look at the graph. Women tend to peak in their twenties, and then around the age of 30, men's and women's SMV intersects with each other. There's are two major reasons for this. The first reason is that what determines a woman's sexual market value is primarily her physical appearance. Men tend to be attracted to youth, beauty, and a fit body, since men are primarily visual by nature. For this reason, women in their twenties are in their prime in terms of sexual market value. Another reason is because women, unlike men, have a shorter window of time to have children. So men who want to have children will look for younger and more fertile women to start a family with.
What determines a man's SMV is a combination of looks, status, and wealth. Even though men do tend to lose looks as they get older, if a man has status and wealth, his sexual market value isn't as negatively impacted. As a result, men tend to peak in their thirties or early forties. A 35 year old man can date a 26 year old woman and it's not that weird.
What can you learn from all of this? If you're a young guy, take your education and your career seriously, and you can be a lot more successful with women in your thirties then in your twenties.