In many cultures, men are often found caring for their sister’s children, sometimes more than their own children. Nobody quite understood why a man would not care as much for his own offspring, until now.
In certain societies where extramarital sex is accepted behavior, a man is far more likely to care for his sister’s children because he knows they are more closely related to him, a study by the University of Utah has found. Anthropology professor Alan Rogers showed mathematically that if a man is likely to be father of fewer than half of his own kids, he will turn his attentions to his sister’s children. Previous long-held assumptions were that a man had to be father of less than a quarter of his own children to trigger this behavior. Rogers’ study appears in the November 27 Proceedings of the Royal Society B.
The study shows how humans—men in this case—attempt to further their own traits to the next generation through other relatives. In societies such as those in Central Africa and South America, extramarital sex isn’t considered cheating—it is expected, in fact. The study also may show why relatives tend to care for each other more than non-relatives.
Rogers made his finding by tweaking two assumptions in previous mathematical predictions of this behavior:
Both assumptions incorrectly made the probability of fathers—niece/nephew relationships much lower than they were.
Which means it’s not about knowing who the mother is. It’s all about knowing who your mother is.
Source: University of Utah