There are many things believed to make a woman more attractive in a man’s eyes – but a curved spine isn’t usually thought to be one of them. However, researchers claim men are particularly attracted to a women with a back that curves exactly 45 degrees above the top of her bottom. The findings provide a new explanation as to why voluptuous celebrities such as Kim Kardashian and Jennifer Lopez are considered to be so attractive, with extra mass around the buttocks enhancing the curvature of the spine. Such an angle would have given a woman an advantage while pregnant in early hunter-gatherer societies and so has evolved as being seen as attractive around the world, they claim. Perfect angle: Jennier Lopez has an attractive curve as scientists discover that extra mass around the buttocks can often enhance the curvature of a woman's spine . J-Lo, pictured above, may have the ideal spine curvature that evolved to be attractive in early hunter-gatherer societies because it gave women an advantage to forage for food while bearing children . Kim Kardashian, shown above, has become famous for her curvy figure and buttocks, but her appeal to men may be tapping into something rooted in our evolutionary past when they gave an evolutionary advantage . The scientists found that extra mass around the buttocks could often enhance the curvature of a woman's spine. However, the researchers also found that a physical curvature of the spine - known as vertebral wedging - was seen as more attractive than extra buttock mass. Curvy hips and buttocks may provide vital 'fat banks' that help to fuel the development of newborn babies' brains, claim scientists. Researchers say the fat stored around the buttocks provides extra energy for babies when they are breast feeding. The scientists at Pittsburgh University say the fat there is rich in DHA (docosahexaenoic acid), which is a particularly important component in the human brain. Over the past five million years, the average human brain has trebled in volume from 400ml to 1,200ml. It could therefore follow that women have had to become fatter to keep up with the growing demands of babies’ brains. The researchers argue that mothers who breast-feed typically lose one pound of fat (half a kilo) a month. Dr David Lewis, a psychologist at Bilkent University in Turkey, said: 'It's an independent and previously undiscovered standard of attractiveness. '(The curve) would have enabled ancestral women to shift their centre of mass back over their hips during pregnancy, a time during which there is a dramatic forward shift of their centre of mass. 'This benefit is critical: without being able to do this, women would experience a dramatic increase in hip torque (pressure) subjecting them to risk of muscular fatigue and injury. 'Consequently, ancestral women who possessed this degree of lumbar curvature would have been able to forage longer into pregnancy and would have been able to carry out multiple pregnancies with a reduced risk of spinal injury.' Dr Lewis said that this trait would have become sexually attractive to men due to the evolutionary advantage it gave. Without such a curve, the pressure on a woman's hips during pregnancy increases by nearly 800 per cent, rendering her largely immobile and increasing the risk of health problems. An example of the silhouettes shown to men during the study with different curvature of the spine. A curved angle of around 45 degrees was rated the most attractive and is also an optimum angle during pregnancy . Dr Lewis said: 'One can think of vertebrae that aren't wedged like (ice) hockey pucks - they are the same height in the front and the back,' he said. 'A dorsally wedged vertebra, on the other hand, is taller in the front of the body than it is in the back. 'When you stack hockey pucks on top of and underneath a vertebra that is taller in the front than it is in the back, you end up with a curved stack.' A 45-degree angle was optimal because it would have aided movement, yet would not have been so great so as to expose women to the back pain and risk of slipped discs that can come with excessive spinal curvature. These silhouettes all exhibit identical buttock protrusion but it is due to different reasons such as excess muscle (a), fat (b) and vertebral wedging( c). The participants found the vertebral wedging was most attractive . For the study, which was published in the journal Evolution and Human Behaviour, the psychologists showed 300 men silhouettes of women with different angles of curvature. They were then asked to rate the images according to how attractive they found the silhouette. Most of the men were significantly more attracted to those with a spine curve of 45.5 degrees, the researchers found. Analysis of the results also found that the preference for this level of spine curve was 'unequivocally not a by-product of a preference for buttock mass', they added. Men who think they like big bottoms may actually be more into spines, Dr Lewis said. He said: 'Men may be directing their attention to the butt and obtaining information about women's spines, even if they are unaware that that is what their minds are doing. 'Alternatively, men may have preferences for both lumbar curvature and buttock size. 'Future research is needed to better understand the latter.'
Curved spines would have allowed women to forage longer into pregnancy . Trait would have been seen as preferable in early hunter-gatherer societies . Scientists at Bilkent University, Turkey studied the preferences of 300 men . They were shown  silhouettes of women's bodies and asked to rank them . A curved spine with an angle of 45 degrees was the most attractive to men .