With her drop-dead curves, Marilyn Monroe's voluptuous figure has long been regarded as the absolute essence of what it means to be an attractive woman.
But the hourglass shape that made her so desirable is linked to a hormone that, scientists claim, lay behind her inability to hold down a steady relationship.
They believe the hormone they have identified is a major factor in establishing why beautiful women are more likely to be unfaithful.
Those with the most oestradiol, a form of oestrogen, are usually more physically attractive and find it easier to snare a man.
But they are also less satisfied with their current lovers - and therefore more likely to cheat, according to the findings published in the Royal Society's journal Biology Letters.
Marilyn Monroe's hourglass figure was caused by the same hormone that triggered her affairs according to scientists
The ovarian steroid hormone is also associated with having a symmetrical face, large breasts and a low waist-to-hip ratio.
Such women are also likely to be physically attractive - and the researchers found that beautiful women are more likely to play on their desirability to snare the best mates.
Elizabeth Taylor was married to Richard Burton when she had an affair with Eddie Fisher
Dr Kristina Durante said: 'Physically attractive women may not only have more alternatives but also high standards that are difficult to satisfy.
'Accordingly, they have fewer reasons to be committed to any particular partner if higher quality potential mates are available.'
Dr Durante, of the University of Texas in the U.S., measured levels of oestradiol - a form of the hormone oestrogen - in 52 female students.
The women were also asked how attractive they found themselves to be and some university staff were also asked to rate their appeal.
This showed that the students deemed the most attractive had the highest levels of oestradiol.
Those in relationships were also asked how satisfied they were and how likely they were to cheat.
The analysis showed that the most beautiful women felt the least satisfied with their lot.
However, they would choose a long-term affair over a string of one-night stands, the Royal Society journal Biology Letters reports.
The researchers said: 'Without necessarily being consciously aware of their motives, highly attractive women are probably able to capitalise on their desirability and continually acquire valuable resources and a higher quality long-term mate by trading-up when the opportunity arises.'
'Marilyn Monroe is actually a really good example of a woman who was almost certainly high in oestradoil,' Australian scientist Dr Frances Quirk said in response to the research.
'She was a classic hour-glass figure and because of her relationship pattern - she was a serial monogamist.
'Her relationships last three or four years or slightly longer, and if you look at the men she had relationships with, they increased in status."
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