When Is A Monkey Really A Monkey?

A little boy pressed his nose on the glass where a Western Lowland Gorilla is interacting with the zoo-goers. He turns around to his parents with a big smile. “Oh look, the monkey wants to kiss you”, said his mother.

At the lemur exhibit, a girl asks her parents what those black and white primates were. Her dad picks her up and said, “It’s a monkey, sweetie … let’s go”.

A pair of gibbons gracefully swings around in their exhibit. Excited, a group of kindergarteners cheered as these gibbons maneuver around its habitat with great agility. “These monkeys are so active”, said the teacher.

If this sounds familiar to you then you are not alone. I spent a great deal of time near primate exhibits mainly because I love to observe their behaviors. I also enjoy watching interaction between humans and primates. However, there are times when I just can’t control myself and felt compelled to walk over to these people and explain to them that the word “monkey” is not a general term for primates (politely, of course). It shocks me that most of the time people do not read the information panel at the exhibit (aren’t zoo trips for educational purposes?). So when is a monkey really a monkey?

Monkey is a colloquial term for any cercopithecoids (Old World monkey) and platyrrhines (New World monkey). Monkeys are not hominoids (apes) or prosimians. One of the most distinctive characteristic that differentiate monkeys and apes is the presence of a tail in monkeys. Gibbons, siamangs, orangutans, gorilla, chimpanzees and bonobos are apes because they do not have a tail.

Gorillas do not have tails, so they are not monkeys but apes.

Differentiating monkeys and prosimians are a little tricky; all prosimians have grooming claws (toilet claws) but it is generally not visible within zoo exhibits. Prosimians include lemurs, lorises, galagos, aye-ayes and tarsiers.

A ring-tailed lemur is a prosimian. Although it has a tail, it also have grooming claws so lemurs are not monkeys.

A hamadryas baboon is technically a monkey because it has a tail but has no grooming claws.

The Barbary Macaque, Macaca sylvanus, was formerly named Barbary Ape due to the absence of a tail (to be more precise, they have a vestigial tail that looks like a stump). However, we know now that it is more closely related to macaques than to apes so its name was changed to correctly reflect what they are.

A Barbary Ape (notice the lack of tail). Flickr photo from Gerald Davison.

This brings us back to the question, “when is a monkey really a monkey’? The most straightforward answer would be “when it has a tail but doesn’t have grooming claws”. However, the most convenient answer usually lies in front of you … on the information panel.

Flickr photo taken by tim ellis at the Twycross Zoo, England.
The sign reads "Who are you calling a monkey?"

Humans Evolved From Tree Climbers

A research from Duke University by Daniel Schmitt, associate professor of evolutionary anthropology, and Tracy Kivell, a post-doctoral research associate, shows that human evolved from tree climbing ancestors, not from knuckle-walkers. Schmitt and Kivell examined and compared the wrist bones of humans and African apes. Their research, "Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor", was published in the Proceedings of the National Academy of Sciences on August 10th, 2009.

They also found that knuckle walking evolved at least two different times; gorillas fundamentally knuckle walk differently than chimpanzees and bonobos.

Kivell and Schmitt think this suggests independent evolution of knuckle-walking behavior in the two African ape lineages.

Some scientists point to features in the human anatomy as our own vestiges of a knuckle-walking ancestry. One notable example is the fusion a two wrist bones that could provide us extra stability, a feature we share with gorillas, chimps and bonobos.

But some lemurs have that feature too, and they do a variety of different movements in the trees but do not knuckle-walk, Kivell said.

Altogether, the evidence leans against the idea that our own bipedalism evolved from a knuckle-walking ancestor, the pair wrote. "Instead, our data support the opposite notion, that features of the hand and wrist found in the human fossil record that have traditionally been treated as indicators of knuckle-walking behavior in general are in fact evidence of arboreality."

In other words, a long-ago ancestor species that spent its time in the trees moved to the ground and began walking upright.

There are no fossils from the time of this transition, which likely occurred about seven million years ago, Kivell and Schmitt said. But none of the later fossils considered to be on the direct human line were knuckle-walkers.

Read more on Science Daily: Bipedal Humans Came Down From The Trees, Not Up From The Ground

Great Apes LOL Like Human Too

A baby orangutan being tickled. Photo from Discovery News.

We're not the only species that are capable of laughing according to new study. Great apes are able to laugh like humans too, and they do it frequenty. This finding suggests that the last common ancestor of humans and apes also laughed around 10 to 16 million years ago. The ability to laugh subsequently evolved among apes and human, resulting in distinctive ways of laughing among them.

"Orangutans produce a short laugh series of noisy calls. Gorillas, chimps and bonobos produce longer laugh series and the calls are produced more rapidly" said project leader Marina Davila Ross, a primatologist from University of Portsmouth. With partners Michael Owren and Elke Zimmermann, Davila Ross recorded over 800 recordings of 22 juvenile and infant apes, and also three human babies laughing as they were tickled in their palms, feet, necks and armpits.

Presented in the latest edition of Current Biology, the study shows that human laughter is most similar to that of chimpanzees and bonobos, followed by gorillas and orangutans. Human laughter is least similar to those of siamangs, a lesser ape. "These results coincide with the genetic topology of great apes and humans," said Davila Ross. She doesn't rule out if apes or monkeys have a sense of humor but said that "it is difficult to find a method to accurately test it".

Read the rest of the article from Discovery News: Chimps, Other Apes Laugh Like People.

I wonder what function does laughing serve in primates.

Mirror Mirror On The Wall, Who Is That Other Gibbon?

Gibbons (lesser apes) have no use for mirrors, studies had shown (Suddendorf and Collier-Baker, 2008). They are not able to recognize themselves in front of a mirror. Typical human children starts to recognize themselves in front of the mirror around two-years-old. Mirror self recognition or visual self recognition is not unique to humans, it was only documented in great apes (chimpanzees, bonobos, orangutans and gorillas). Humans and great apes are different than other primates because they can recognize themselves in front of a mirror. Self recognition in front of a mirror enable them to see areas of the body where they cannot see directly. Self recognition probably evolved in the common ancestors of great apes around 18 million years ago.

Primate phylogeny. The ability of mirror self awareness probably evolved around 18 million years ago with great apes (chimpanzees, bonobos, orangutans and gorillas) common ancestors Image from www. mun.ca

A gibbon seems to be interested in itself, but none tried to get at icing on their own faces (Image: Emma Collier-Baker) Photo from www.newscientist.com

The gibbons sometimes tried to reach around the mirror to get at the ape on the other side (Image: Emma Collier-Baker) Photo from www.newscientist.com

Read more about "The evolution of primate visual self-recognition: evidence of absence in lesser apes" by Suddendorf and Collier-Baker, 2008 (full article) (abstract).

"King of the swingers has no use for mirrors" by Ewen Callaway on Newscientist.com

Citation:
Suddendorf T. Collier-Baker E. 2008. The evolution of primate visual self-recognition: evidence of absence in lesser apes. Proceedings of the Royal Society B (doi: 10.1098/rspb.2008.1754 ) http://rspb.royalsocietypublishing.org/content/early/2009/02/21/rspb.2008.1754.full