Good news girls: you're getting more beautiful. But the forecast isn't so rosy for men.

Scientists have found that evolution is driving women to become more attractive, while men are not likely to advance in the looks department at all.

A study, led by Markus Jokela from the University of Helsinki, found beautiful women had up to 16 per cent more children than their plainer counterparts.

The research used data gathered in a US study, which involved 1,244 women and 997 men being followed through four decades of life.

Their beauty was assessed from photographs and data was also gathered on the number of children they had.

Evolution expert Dr Jack da Silva, from the University of Adelaide, says even though 16 per cent is not a huge difference, a "beauty race" is being formed.

"From an evolutionary perspective, there's a selection in women to be more beautiful," he told ABC News Online.

"The study showed that women on a whole are more attractive than men."

And not only that, these more attractive women are producing more beautiful women.

"Attractive parents have been found to have a higher ratio of daughters to sons," Dr da Silva said.

"For women, beauty was strongly correlated with the number of children they have, but it wasn't for men.

"One of the predictions is that if you are an attractive woman, you will have more daughters because being more attractive is more beneficial to women than it is to men."

And why is that? Dr da Silva says research shows men choose their mates on the basis of beauty, while women pick their partners based on behaviour.

"Women are not primarily choosing their partners based on beauty," he said.

"They're choosing their mates based on other characteristics ... whereas men choose genetic success based on looks.

"Women often choose men based on behaviour that is successful."

And Dr da Silva says there could be a genetic excuse for the stereotype of older wealthier males going for young attractive women.

"Really, really successful men often are serially monogamous," he said.

"They often trade up for younger, more fertile women. You often see very rich, powerful men with very young attractive women hanging off their arms.

"In these men, their genetic endowment probably determines their success [and] women may choose a certain man because he's a good provider."

Hunter gatherers

Dr da Silva says even though we now live in a very urbanised world, humans behaving as hunters gatherers is stuck in our roots.

"In humans, we've been hunter gatherers for most of our history so we still really behave as hunter gatherers," he said.

"And for most our history women's resource gathering potential hasn't been as important.

"The importance of a mate as a female would be that she could bear lots of children and be able to raise these children.

"Whereas, the importance of a male as a mate would be to bring stuff back from the hunt and provide protection. That sounds really old fashioned in an urban society, but for the vast majority of our history, that's how we lived."

But why is beauty so important anyway? Dr da Silva believes humans link beauty with genetic perfection.

"There's a theory that certain characteristics reflect a person's genetic quality and in humans that is beauty," he said.

"If you have children with someone, you're going to think your children will carry these qualities."

You're so symmetrical

And if you think stocking up on beauty products will help, think again. Dr da Silva says it has been found that humans judge beauty based on symmetry.

"One reason we think certain people are beautiful is because of certain features like symmetry of the face, because possibly that reflects the genetic quality of the person," he said.

"Symmetry is seen as a good indication of genetic quality because genetic mutations interrupt with that. It's very difficult to be born symmetrical."

But Dr da Silva says not being "too old" or having extreme features also helps.

"Another aspect of faces that makes them more attractive is that they don't have any extreme features. So any average face without extreme features - so the nose isn't too big or too small, the ears aren't too big or too small, the eyes aren't too far apart or too together," he said.

"And because women's fertility peaks in their mid 20s, if you want to be the ideal beautiful woman, you want average features, a symmetrical face and you want to be about 25."

"When a man's choosing a mate, he wants a fertile mate - for evolutionary reasons, but he's not necessarily doing this consciously."

Dr da Silva says that even though there are slight differences in what people find attractive, it is generally pretty much the same across the board.

"In just about everything you measure in terms of human behaviour, there's a lot of variations but people do generally agree on who's beautiful and who's not," he said.

"Look at celebrities. People generally agree that some celebrities are beautiful and some are not. Everybody tends to think Angelina Jolie is beautiful."