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http://www.newscientist.com/article/dn16579-ape-faces-reveal-family-bonds.html

Who's the daddy? Ape faces reveal family ties

12:25 11 February 2009 by Ewen Callaway

If apes could talk, would they cluster around a newborn and say, "Aw,
he looks just like his dad"? Perhaps so, hints a new study that finds
that humans can discern family resemblances in great apes and some
monkeys.

If humans can garner enough information from primate faces to tell kin
from stranger, then perhaps closely related animals can do the same,
says Alexandra Alvergne, an anthropologist at the University of
Montpelier, France, who led the study.

"We do not know if the others species use [facial recognition], but we
know that it is possible," she says.

This could help explain how, among promiscuous species such as
chimpanzees, fathers determine which children are their own. Facial
recognition might also help closely related individuals avoid
inbreeding, Alvergne says.
Kith or kin?

A previous study found that captive chimpanzees can distinguish
related mothers and sons, but not mothers and daughters, by pictures
alone. However the authors have since backtracked on this conclusion.

To see if other primate faces convey enough information to determine
relatedness, Alvergne and her colleagues tested whether humans could
see a family resemblance in chimpanzees, lowland mountain gorillas,
mandrills and chacma baboons.

Her team showed volunteers – 618 in all – a picture of one individual,
followed by three different members of the same species. One of the
three was the parent of the first animal.

Take the test yourself with our primate family photo album

On average, volunteers picked the related chimpanzee, gorilla and
mandrill at rates well above chance, but not so for baboons. This
could be because baboon faces convey few obvious giveaways to kinship.
"In baboons the colour is always the same," she says.

Next, Alvergne aims to determine whether other primates can discern
relatedness by vision alone and – more importantly – whether they act
differently when presented with the face of a family member versus a
stranger.

Peter Kappeler, a researcher at the German Primate Center at the
University of Göttingen, says that humans may have evolved to pay
closer attention to facial resemblances than other primates.

"Given the unusual importance of cooperation in human societies, it is
reasonable to presume that the ability to recognise kin is highly
developed in our species," he says.

Journal reference: International Journal of Primatology (DOI:
10.1007/s10764-009-9339-0)