A recent University of Texas study discovered that evolution clearly programmed men to have a preference for curvy women in terms of a big "back-to-buttock" curve. The researchers' theory is that the ideal angle of hips is based on an ancient belief related to humans' evolution.
The study asked 100 men to rank how attractive photos of different females were to them. Researchers learned that men greatly preferred a particular back-to-buttock ratio: 45.5 degrees. The researchers referred to this figure as a hypothetically perfect angle of "lumbar curvature," according to The Market Business
The theory of the researchers is that in ancient times this angle was significant. At that time the belief was that women with this physique were more likely to have successful pregnancies.
David Lewis, one of the study's UT researchers explained that the 45.5-degree ratio would have allowed pregnant women to "balance their weight" over their hips, according to Time. This would have reduced the likelihood of injuries to their spines.
As a result, men would have preferred such women because they would be better suited to provide for the fetus. They also could have several pregnancies "without injury."
The researchers then carried out a second study to determine if men preferred the 45.5-degree back-to-buttock angle because they preferred big bottoms or wide hips. It turns out they preferred the ideal spinal curvature even if women had a smaller backside.
Interestingly, while ultra-thin female bodies are fashionable today, it is a relatively new trend. Until the early 1900s, women with extra body weight were considered to be healthier and wealthier.
Lewis explained that social scientists' previous theories were wrong. Beauty is not totally "arbitrary" or biased, but instead seems to have a rational "adaptive logic." Cavemen liked curves.