Women’s faces are rated as more attractive than men’s, even by other women, but the perceived gap declines with age and all but vanishes by the time people reach their 80s, researchers have said.

The work appears to confirm the existence of a “gender attractiveness gap”, an observation reflected in centuries of language that present women as “the fairer sex”, “das schöne Geschlecht”, “le beau sexe”, and far more beyond Europe.

“This is a super robust effect and we see it across cultures. Female faces are evaluated as more attractive than male faces regardless of all the other factors,” said Dr Eugen Wassiliwizky, a research fellow at the Max Planck Institute for Empirical Aesthetics in Germany. “What is most surprising is that women give other women the highest ratings and give the lowest ratings to men.”

When Charles Darwin, the Victorian naturalist and father of evolution, looked across the animal kingdom, he saw males adorned with dark manes, brightly coloured faces and fancy plumage. These were, he said, products of sexual selection, where those with the fanciest adornments got to sire the most offspring.

But Darwin saw humans as bucking the trend. Rather than female preferences driving sexual selection, he believed men fought men for the most desirable women or found that wealth and power achieved similar ends. Evolutionary biologists have debated the peculiarity ever since.

“They took it for granted that women are the fairer sex and theorised about what evolutionary principle could have led to this phenomenon, but the existence of the gap itself was never actually tested,” said Wassiliwizky.

For the latest study, Wassiliwizky and his colleagues compiled the world’s largest dataset on facial attractiveness ratings from 52 studies in 76 countries. The final dataset contained more than 1.5 million ratings of 17,000 faces from nearly 30,000 raters.

Their analysis found that the average female face is rated more attractive than about 60% of male faces. The size of the gap was strongest in the west and varied slightly with sexual orientation, but was still evident across heterosexual, gay, bisexual and lesbian raters. When men and women rated themselves, the gap disappeared.

Some of the effect is driven by sex differences in facial structure. On average, men have more rectangular faces while women have more rounded faces. The results suggest both men and women tend to find rounder faces more attractive. Details are published in Proceedings of the Royal Society B.

The study doesn’t explain the reason for the general preference for female faces, but Wassiliwizky believes there is more than culture at play. “Usually when we see an effect across the whole world it’s hard to see a purely cultural explanation for that,” he said.

It is possible that hundreds of thousands of years of sexual selection have shaped female faces, but “we can’t infer that from our data, we have to be cautious,” Wassiliwizky added. It may be that more rounded faces appeal for other reasons, perhaps because they are more similar to babies’ faces.

In her 1972 essay, The Double Standard of Aging, the American writer Susan Sontag argued that society equated the value of women with beauty and their beauty with youth, but did not impose the same standards on men. In the study, the preference for female over male faces dropped steadily from 18 years old until vanishing at about 80 years old.

“The older the faces, the less we see a gap between the perceived attractiveness of male and female faces,” Wassiliwizky said. “Male and female faces become more and more similar with age, the structural differences shrink, and this might be the reason the gap is melting.”