Sexually transmitted infections, peer pressure may have turned humans into monogamists

Prehistoric humans may have developed social norms that favor monogamy and punish polygamy thanks to the presence of sexually transmitted infections (STIs) and peer pressure, according to new research. As hunter-gatherers began living in larger populations of early settled agriculturalists, the spread of STIs could explain a shift towards the emergence of social norms that favored one sexual partner over many.