Last week I solicited friends and family to help me initiate a new feature for the blog: Ask the Biological Anthropologist! I invited people to submit any and all queries related to primates and/or evolution, and I received so many great questions that I’ll be making ‘Ask’ a regular feature henceforth.
For this initial installment, I’m going to tackle a couple of ‘softballs.’ This isn’t to say they’re not great questions — I actually really enjoy the opportunity to discuss things that may be common knowledge to primatologists but are completely new to people outside the field — but the answers are relatively straightforward. So without further ado…..
Q: What are the differences between monkeys and gorillas, and how do you tell them apart? -Gladys, Cambridge
A: I’m so glad someone asked this question because it is a pet peeve of mine that most people refer to all primates as monkeys. In fact the Primate order, which is only one of many orders of the Mammal class (some others include Carnivores, Rodents, and Cetacea (better known as whales)), consists of over 200 species, ranging in size from the mouse lemur (approx. 1 ounce) to the mountain gorilla (400+ pounds), and new species continue to be discovered .
As primates, all of these species share certain characteristics; for example, five digits on each hand and foot, a grasping (prehensile) thumb, good depth perception (stereoscopic vision), and a large brain relative to body size. But, as the above image illustrates, the Primate order also includes a great deal of diversity. Not all primates are alike, and not all primates are monkeys!
Other than size, what differentiates all of these species from one another? Quite a bit, actually. Different species have different diets (some eat mainly fruit, some eat mainly leaves, and the tarsier is entirely carnivorous), social structures (some primates are mostly solitary, others live in large groups), mating systems (chimpanzees are highly promiscuous, whereas marmosets and tamarins are mostly monogamous), and degrees of intelligence/behavioral complexity. Some of it is geographic, too. Lemurs, for example, are found only on the island of Madagascar, off the east coast of Africa, while monkeys are divided into two primary taxonomic groups: the “Old World Monkeys” (Cercopithecoidea), which are found in Africa or Asia, and the “New World Monkeys” (Platyrrhini), which are found in Mexico and Central & South America.
Gladys’s question, though, is about gorillas, and gorillas are apes, a subgroup of the Primate order that also includes gibbons, orangutans, chimpanzees and bonobos, and humans.
So how do you tell an ape from a monkey? The easiest way is to look for a tail. While all monkeys (with the exception of Barbary macaques) have a tail — some of them prehensile — none of the apes does. This is far from the only difference between the two groups (I have listed a few more below in case anyone is curious), but it is the most obvious, and an excellent example of how pop culture so often gets primates wrong.
Additional differences between monkeys and apes:
1. Apes are adapted for suspensory locomotion — hanging from beneath tree branches rather than walking on top of them — which means they have a broad chest, arms that are longer than their legs (in monkeys arm & leg length is roughly equal), and a highly flexible shoulder joint.
2. Apes tend to rely more on vision than smell. New World monkeys in particular have a better olfactory sense than apes, but they tend to have dichromatic rather than trichromatic vision.
3. Apes tend to be more intelligent than monkeys. They also mature more slowly, and tend to live longer.
Q: At what point did tool use first become a primate characteristic? –Diana, Chicago
A: In the not too distant past, it was thought that only members of our own species had the cognitive sophistication to make and use tools. We now know, however, that chimpanzees, orangutans, and gorillas all make and use tools in the wild*. Moreover, in 2007 researchers documented finding stone tools of the type chimpanzees use to crack open nuts that date to 4,300 years ago, suggesting that tool use in apes is not a recent innovation (though whether it was characteristic of the last common ancestor of chimps and humans 6 million years ago, or possibly the last common ancestor of all the living great apes 15-20 million years ago, remains unknown).
In the hominin lineage — that branch of the primate evolutionary tree on which the genera Australopithecus and Homo lie — the earliest stone tools date to approximately 2.6 million years ago, and are found in east Africa. Production of these Oldowan tools, named after Olduvai Gorge in modern-day Tanzania, in which they were found, is most often attributed to Homo habilis, one of the earliest members of the genus Homo. It’s worth noting, however, that circumstantial evidence suggests that Australopithecus garhi, a contemporaneous species in east Africa, may also have been a tool user.
*Capuchins — New World monkeys notable for having a brain to body size ratio comparable to a chimpanzee — are also capable tool users in the wild.
Q: Please explain this:
A: That, of course, is one of natural selection’s most fabulously awesome achievements: the star-nosed mole. It is fabulous. And awesome. So awesome, in fact, that the only way I can do it justice is to offer you a very short list of facts about it, and a video so you can see it in action.
Star-nosed mole facts:
1. The mole’s snout consists of 22 tentacles, which are used as a touch organs. Each tentacle has over 25,000 sensory receptors known as Eimer’s organs, which enable the mole to forage faster and more efficiently than any other mammal on Earth.
2. They smell underwater by blowing bubbles.
Check the little guy out here (the real magic starts at 1:00):
And that’s it! I hope you’ve all enjoyed this first installment of Ask the Biological Anthropologist!, and please keep the questions coming.