Los Angeles, Oct 4 (IANS): Men - whether aged 13, 30 or more - fantasise about women who are in their 20s, according to a latest survey.

Researchers from Finland surveyed a total of 12,656 men and women aged 18 to 49 in an attempt to study age preferences in sexual partners. They asked each participant about which age group they were most sexually attracted to during the last 12 months and which age group they actually engaged in sexual activity with.

Just as the researchers hypothesised, the results varied by gender, reports huffingtonpost.com.

Women were seen to be interested in men who were similar in age or slightly older. Specifically, women in their late teens and twenties prefer male partners who are about four years older, and the age gap preference lessens as women get older.

Men tended to be interested in one single age group: women in their mid-twenties. This held true even in younger men in their late teens or early twenties.

Researchers argue that both male and female age preferences have roots in evolutionary biology. They hypothesise that women go for older men due to the "resources" they can offer, including the ability to help with offspring.

"Men mature later than woman and in our evolutionary past, raising human offspring to nutritional independence necessitated bi-parental care,” said one researcher.

The researchers also believe that men's sexual preference is shaped with offspring in mind -- they are especially interested in women who are fertile.

"The highest fertility has been estimated to occur in the mid-twenties, with a decline after the age of 35. Especially for short-term mating, men show a high interest in fertile women, that is, women in their twenties,” said another researcher.

This study was recently published in the journal Evolution and Human Behavior.