There is a rea­son for so many mon­key faces !

pub­lished 16 Jan­u­ary 2012 | mod­i­fied 18 Jan­u­ary 2012

Researchers from the Uni­ver­sity of Cal­i­for­nia were also struck by the enor­mous diver­sity of New World mon­key faces, and stud­ied 129 of them belong­ing to adult males of dif­fer­ent species. The faces they stud­ied evolved over at least 24 mil­lion years, they report. Like big brother the fur­ther evolved ‘human being’ all other pri­mates are visu­ally ori­ented, and facial expres­sions pro­vides a lot of infor­ma­tion. But how and why did faces and facial fea­tures evolve into so many dif­fer­ent appearances?

new world monkey faces

Their find­ings led to the idea that when species live in larger groups, their faces evolve into quite bare (more sim­ple, more plain) faces. This could increase the abil­ity to com­mu­ni­cate using facial expres­sions. Because a plain face could allow bet­ter dis­tin­guish­ing of the dif­fer­ent fea­tures of these expres­sions, with­out dis­trac­tion by the colours for instance. Nev­er­the­less, it came as a sur­prise for the researchers as they ini­tially thought and expected the oppo­site accord­ing to Shar­lene San­tana, one of the authors. She said: “You might expect that in larger groups, faces would vary more and have more com­plex parts that would allow one indi­vid­ual to iden­tify any mem­ber of that group. That is not what we found. Species that live in larger groups live in closer prox­im­ity to one another and tend to use facial expres­sions more than species in smaller groups that are more spread out. Being in closer prox­im­ity puts a stronger pres­sure on using facial expres­sions.” (ScienceDaily)

Liv­ing in larger groups also means that a highly devel­oped social struc­ture exists, so if species are highly social, facial expres­sions are more impor­tant than highly com­plex pat­terns on their face. Which is what the researchers found in species liv­ing in smaller groups and liv­ing together with high num­bers of sim­i­lar species. In these species more com­plex pat­terns of facial colour have evolved.

Humans have pretty bare faces, which may allow us to see facial expres­sions more eas­ily than if, for exam­ple, we had many colours in our faces.

In addi­tion to these find­ings the sci­en­tists found that eco­log­i­cal fac­tors influ­enced the evo­lu­tion of facial pig­men­ta­tion and hair length. Species liv­ing closer to the equa­tor have darker skin and hair around their eyes. Fur­ther­more, facial regions around the nose and mouth get darker when species live in humid envi­ron­ments and denser forests, while facial hair gets longer as species live far­ther from the equa­tor and the cli­mate gets colder, which may be related to reg­u­lat­ing body tem­per­a­ture. (ScienceDaily)

The sci­en­tists, San­tana, Alfaro and Alfaro, envis­age that com­puter facial-​recognition soft­ware may become part of their tools to help quan­tify the faces in a more sophis­ti­cated way in the future. And even more inter­est­ingly, they plan to study the faces of car­ni­vores, includ­ing big cats.

(Sources: Pro­ceed­ings of the Royal Soci­ety B, 11.01.2012; Sci­enceDaily, 11.01.2012)

Goal: 7000 tigers in the wild

Tiger range countries map

Tiger map” (CC BY 2.5) by Sander­son et al., 2006.

about zoos and their mis­sion regard­ing breed­ing endan­gered species, nature con­ser­va­tion, bio­di­ver­sity and edu­ca­tion, which of course relates to the evo­lu­tion of species.
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