Books, magazines, and television shows have all narrowed down the qualities of any man’s ideal woman: sexy, smart, and funny. Now, while all men have different preferences when it comes to physical traits, men of all ages can agree on one thing: a woman’s age. According to a recent study published in the journal Evolution and Human Behavior, men who are looking for love prefer women who are in their mid-20s because they are most likely to be fertile and have the highest odds of bearing the man’s child, passing on his genes.

"This means that in our evolutionary past, men who have had sex with women in their mid-20s have had more offspring than other men," said the Finnish research team in the Academy of Finland press release. Based on their interpretation of evolutionary theory, the researchers believe because women are more selective than men in their sexual behavior, men are therefore more unlikely than women to have sex with their ideal partners. This means men’s actual behavior mimics women’s preferences rather than men’s own preferences. Gender differences in age-related fertility is expected to shape the sexual strategies of both sexes.

In an effort to investigate sex differences in sexual interest and sexual activity in regards to the partner’s age, Jan Antfolk of Abo Akademi University in Turku, South Finland, and his team of researchers gathered observations from a population-based sample of more than 12,000 Finns. The survey was financed by the government-backed research funding group Academy of Finland. The study only looked at heterosexual preferences and heterosexual activity.

The findings revealed men have a tendency to be sexually interested in their mid-20s. This was notable when the men themselves are younger or older than this. Men younger than 20 prefer women older than themselves, while men older than 30 prefer women younger than themselves.

Antfolk and his colleagues suspect men’s sexual interests seem directed toward women in their mid-20s, between ages 24 and 25, because women of this age are most fertile. Most women hit their fertile peak between the ages of 23 and 31, although the rate at which women conceive begins to drop slightly in their late 20s, according to the Baby Center. Around age 31, fertility starts to drop fairly quickly by about three percent per year, until women hit 35 or so.

The study also observed women’s age preferences when it comes to finding a partner and found women think men their own age, or slightly older, are the most attractive. The biggest age gap was for women in their late teens and early 20s, who were intrigued by men around four years older. Antfolk suggests a slightly older male is more likely to have the money and stability to bring up a family than a younger man, the Daily Mail reported. However, although a much older “sugar daddy” may have more money, he is more likely to die while his family is still young.

Contrary to Antfolk’s findings, data from Are You Interested, a dating site, found out of about 24,000 American members ages 18 and up, with a 2:1 female ratio, women were more likely to respond to a man’s message the younger he was. Even slight age differences tended to play an influential role in a woman’s dating preference. A woman was found to be twice as likely to respond to a man two years younger as she was to one two years older.

This data can correlate with the financial realities of women under 30 who are found to be out-earning younger men. Women are less likely to be preoccupied with a man’s financial stability and prefer to date a younger one where they are about as much in control as the man. Justin Lehmiller, a Harvard psychologist, told Time about a recent story on data: “when the woman is older, it shifts the traditional heterosexual power dynamic toward greater equality,” and equality makes for happier couples.

Men’s sexual behaviors are dictated by women’s preferences, which are powered by the change in traditional heterosexual relationships.

Source: Alanko K, Antfolk J, Gergen E et al. Women’s and Men’s Sexual Preferences and Activities with Respect to the Partner’s Age: Evidence of Female Choice. Evolution and Human Behavior. 2014.