"Rightly or wrongly, in today's environment, looking sexy can generate large returns, economically, socially, and personally," wrote the study's lead author, Khandis Blake from UNSW Science's School of Biological, Earth and Environmental Sciences.
"Think of her as a strategic player in a complex social and evolutionary game. She's out to maximise her lot in life, just like everyone."
The study examined more than 68,000 "sexualised self-portrait photographs" posted on Instagram or Twitter from 113 different countries.
They found more of such photographs were taken in areas with acute economic disparity, suggesting competition to "get ahead" was the prime motivator.
Researchers also argue that gender inequality, or "the patriarchy," is not to blame, contrary to popular belief.
"We found no association with gender oppression," the study read.
Blake added that women are "more likely to invest time and effort into posting sexy selfies online in places where economic inequality is rising, and not in places where men hold more societal power and gender inequality is rife."