AsianScientist (Apr. 2, 2015) – Research published in Evolution and Human Behavior suggests that the more competition a fellow has to deal with, the more flamboyant he gets—at least in primates.
A team of researchers led by Dr. Cyril Grueter from the University of Western Australia investigated the hypothesis that in big, multilevel societies, male primates have developed more ostentatious ‘ornaments’ or ‘badges’.
These include the elongated noses of proboscis monkeys, cheek flanges in orang-utans, capes of white and silvery hair in hamadryas baboons, reddened chests in geladas, upper-lip warts in golden snub-nosed monkeys—and beards in humans.
They found that at least some of these badges may enhance male sexual attractiveness to females. For example, male rhesus macaques with darker red faces receive more ‘come-ons’ from more females during the mating season.
They also showed that male-male competition could even be a stronger reason for the evolution of badges than female choice. For instance, men with beards could be seen as more aggressive and dominant than those without beards and might also be attractive to women drawn to seemingly powerful men.
In their investigation of 154 species of primates representing 45 genera, the authors found more conspicuous badges in males of species in multilevel social organizations where social and physical conflict were common and individual recognition was limited.
The authors suggest the flamboyant badges were of benefit to males in large and complex social organisations to signal their identity, rank, dominance and attractiveness. Species that live in smaller groups, on the other hand, had less need of badges as individual recognition and more frequent interactions allowed animals to better assess the social status, strength and quality of their contemporaries.
“When you live in a small group where everyone knows everyone because of repeated interactions, there is no need to signal quality and competitiveness via ornaments,” Grueter said.
“In large groups where individuals are surrounded by strangers, we need a quick reliable tool to evaluate someone’s strength and quality, and that’s where these elaborate ornaments come in. In the case of humans, this may also include phenotypic extensions such as body decoration, jewelry and prestige items.”
The authors explain that primate group-sizes vary dramatically: Bornean orang-utans are non-gregarious, whereas mandrills move in hordes of up to 800 animals.
In their paper, the authors argue that the popularity of moustaches and beards among British men from 1842—1971 rose when there were more males in the marriage pool and beards were judged to be more attractive.
The article can be found at: Grueter et al. (2015) Are Badges of Status Adaptive in Large Complex Primate Groups?
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Source: The University of Western Australia; Photo: Nicole Kasper/Flickr/CC.
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