Politeness and civility do not pay off for chimpanzees. According to a new study from researchers from Duke University and Arizona State University, male chimps that consistently slap females around sire more offspring over their lifetimes than those that take a gentler approach to interacting with the opposite sex, Duke Today reports. Nature, in this case, rewards what we humans would label as bad behavior.
Researchers arrived at these conclusions after analyzing 16 years of chimp behavior observation from Gombe National Park in Tanzania. They categorized aggression across a gradient, from charges meant to frighten females to physical assaults that resulted in injury, and overlaid those data on the number of babies each male produced, Duke Today describes. The researchers also noted whether the female receiving that negative attention was fertile or not, as indicated by her swollen genitals. Finally, they also ran genetic paternity tests on the 31 babies that were born throughout the study period, just to be certain.
The results were surprising. When a female was receptive to mating, males that acted aggressively did indeed have a better chance of taking her up on that invitation. But they did not have an edge on actually siring her young. Instead, the males who consistently bullied her regardless of her receptivity had the paternity edge, Duke Today reports. "It is certainly not a happy message," one of the authors told Reuters.
That said, it's a strategy that apparently works well for chimps—though thankfully not for humans. As the researchers noted to Duke Today, while chimps are our closest relatives, "mating behavior varies significantly between our two species."