why humans don’t have sex with their relatives? Inbreeding study reveals

Surprisingly even 34,000 years ago, ancestors avoided having sex with the close relatives. The study, led by Cambridge University and the University of Copenhagen says, after analyzing an ancient human remains discovered in Russia has revealed that even among a small remote society incest avoided inbreeding deliberately sought partners beyond their families.

Professor Eske Willerslev, Cambridge, said in a statement: “What this means is that even people in the Upper Paleolithic, who were living in tiny groups, understood the importance of avoiding inbreeding"

Through this study we can now tell why anatomically-modern humans proved more successful than other species such as Neanderthals  from the Altai Mountains who lived about 50,000 years ago thought inbreeding was okay to them

Researchers examined genetic remains of four anatomically-modern humans from Sunghir, Russia who were found buried together but surprisingly the individuals were not closely related in genetic terms. If not they were probably second cousins. This is valid even in the case of two children who were buried head-to-head in the same grave.