Are some primates wired for sexual harassment?

According to a new study, male baboon harass and assault females are more likely to mate with them, add more evidence shows that sexual intimidation may be a common mating strategy among promiscuous mammals. The study’s authors even argued that these findings could shed light the evolutionary origins of our species behavior, though others are not convinced theses results don’t imply about human.

To study, Elise Huchard, a zoologist of National Center of Scientific Research in Montpellier, France and colleagues have examined a group of baboon living in Tsaobis Nature Park in Namibia over a 9-year period. These brownish dog-sized primitives live in troops of dozens of males and females. Female will mate with multiple male throughout the year.  Males are about twice the size of female and aggressively fight one another and engage in howling competitions to establish dominance. The more dominance a male is, the more he likely he is both to succeed in looking for a mate and sire offspring.

Males rarely force females to mate, but after years spent observing animals in wild, Huchard noticed that a subtler form of sexual coercion appear to be going on. Males usually chase and assault several females in their group when meeting other groups and often aim to receptive females on such occasions. He spent a lot of time to study female mate choice, and her main impression was that many females don’t have much room to express any preferences.

A research published in 2007 shows that male chimpanzees sometime sexually coerce females – attacking and chasing as a type of violent, bullying courtship – Huchard and her colleagues wondered whether baboon behaved similarly? So that, they meticulously catalogued the interactions between individuals in two troops in Tsaobis’s rocky grassland.

Males often chase, bit, struck and fertile females (easily distinguish by bright red, swollen hindquarters), but not pregnant or lactating females. These assaults were not immediately followed by sex. Instead, after weeks when females were likely to be ovulating, they tended to mate with attackers. If a male attack a fertile female, he was 10%-50% more likely to mate with her than were non-aggressive male.

Not all females liked aggressive male in genera. Instead, they gravitated to the specific males that harassed them. The authors conclude that the baboon’s behaviour amounts to sexual  intimation. Though the researchers don’t know precisely why females liked their coercers, they speculate the females fear further injury if they refuse.

The fact that such intimation has now been seen both chimpanzees and baboons suggests that it may be common in primates with promiscuous social structures and and pronounced size differences between males and females. The sexual intimidation of human may have an evolutionary origin as a mating strategy.

But others say that baboon behaviour may have no implications for human. Alberts is sceptical of any evolutionary implication from that study, because human biology and social motivation are different from that of baboons. Though  we are all primates, the two species are very different in key things, like how much bigger males are than female in baboon and how much male to male competition there is? And though sexual customs and freedom vary widely across human society, women have more choice in who they mate with than female baboon.

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