More lumbar curvature increased perception of attractiveness of girls, men looked longer & fixated more on the hip region

Pazhoohi, F., Doyle, J.F., Macedo, A.F. et al. Evolutionary Psychological Science (2017). https://doi.org/10.1007/s40806-017-0123-7

Abstract: It is common in studies of human mate preference to have participants judge the attractiveness of photographs in which models adopt a neutral facial expression or a neutral body posture. However, it is unlikely that humans adopt neutral expressions and postures in normal social circumstances. One way in which posture can vary is in the curvature of the lower spine. In some non-human animals, a “lordotic” posture (in which the lower spine is curved towards the belly) is associated in females with readiness to mate. In humans, this posture may serve a similar function, attracting heterosexual men. In this study, participants were presented with computer-generated images of female bodies in which the back curvature was systematically manipulated. The result showed that small changes in lumbar curvature are associated with changes in the perception of attractiveness. Specifically, the result showed that there is a relationship between the range of the back curvatures used in this study and attractiveness, such that increasing the curvature increased the perception of attractiveness. Additionally, as the curvature increased, participants looked longer and fixated more on the hip region of the female bodies. This paper argues that the attractiveness of women in lordotic posture is due to a conserved mechanism across the taxa which signals proceptivity to men.

Check also: Behavioral display of lumbar curvature in response to the opposite sex. Zeynep Şenveli Bilkent University, Graduate Program in Neuroscience - Master's degree thesis. http://www.bipartisanalliance.com/2017/08/behavioral-display-of-lumbar-curvature.html

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Carl J. Armstrong Jr.'s comment on this >>> Counter-explanation: Lumbar curvature may be a critical factor in mobility during late pregnancy. Lordotic posture--demonstrating lumbar mobility--may signal healthy mobility during reproduction.

Likewise, given that spinal asymmetry drives breast asymmetry, breast fullness and symmetry may also indicate part of the same mobility-during-pregnancy by telegraphing spinal health and motility....