first began to systematically classify living things in the 1700s according to a system laid out by Swedish naturalist Carolus Linnaeus, inventor of Linnaean Classification. Linnaeus noted (obviously enough) that many life forms had anatomical and (in the case of animals) behavioral similarities to other life forms, and he began grouping them according to those similarities. Dogs and horses, for example, shared the characteristic of having hair-covered skin and suckling their young; although dogs and horses are different in many other ways, those characteristics made dogs and horses more similar to each other than either was to some other life forms like fish. Despite their differences, dogs and horses are both mammals. Anatomical similarity is still the basis of life-form identification, but genetic data increasingly factor in as well.
The four main levels of the hierarchical classification system used today are significant to understanding primates:
The order: All primates are in the Primate order, which is different from the order Canidae (the dogs and dog-like animals), the order Felidae (all the cats, from lion to Tom), and so on.
The family: The Primate order contains several families of primates, including the Pongidae (chimpanzees, gorillas, and orangutans), the Hominidae (humans and our ancestors), and the Colobinae (the primates of South America).
The genus: Several genera (plural of genus) are members of the Primate order, including the genus Papio (the baboons) and the genus Homo (humans and their ancestors).
The species: About 200 species of primates exist. If two individuals are sexually viable (can interbreed and have healthy offspring that themselves can have healthy offspring), the two individuals are in the same species.
Humans, then, are in the order Primate, the family Hominidae, the genus Homo, and the species sapiens. Subspecies designations exist as well, and all humans today are in the subspecies sapiens. Therefore, humans are Homo sapiens sapiens, whereas Central African chimpanzees are in the genus Pan, and the species troglodytes; they’re known as Pan troglodytes.
Today’s fossil and genetic records allow us to reconstruct the evolution of the primate order. This includes about five major adaptive radiations (see the sidebar “You can’t go home again”). In those ancient events, older forms became extinct, replaced by new forms of primates. These radiations include the origins of the primate focus on vision as the most important sense (as opposed to olfaction, or smell, in many mammals), and the origins of the prehensile tail, used to aid climbing among South American primates. Other such radiations are still being discovered.
You Look Like an Ape: Primate Species
Biologically speaking, you’re an ape. So am I, and so is everyone else in the world. It’s true. This section shows you the general characteristics of all primates and then focuses in on the main groupings of primates, including the apes.
What’s in a name? General primate characteristics
As primates evolved after 65 million years ago, they developed the more distinctive characteristics seen in the living species as well as their fossil ancestors. Today, although the many kinds of primates vary a great deal, they do share some basic traits:
Wide range of body size, from 100 grams (1⁄3pound) to 200 kilograms (more than 400 pounds). On average, primates are about 10 pounds, which is a little larger than most rodents and a little smaller than most hoofed animals.
Large eyes with three-dimensional vision, allowing keen depth perception.
Lack of emphasis on a snout. Primates focus on vision rather than sense of smell, which appears in other animals’ snouts.
Large brain case containing the largest brain — relative to body size — of any land animal.
Heterodont (differentiated) teeth, indicating a varied diet. For example, the incisors can clip one kind of food, and the molars can crush another.
Nails rather than claws, allowing more sensitive grasping of tree limbs.
Today, the primate order contains about 230 living primate species (give or take a few, depending on whom you ask). Although you could spend a lifetime studying them in all their diversity (not to mention the fossil record of the ancestry of each living species), for most purposes it’s enough to recognize four main subgroups in the primate order: the prosimians, the Old World monkeys, the New World monkeys, and the apes. I take a closer look at these subgroups in the following sections. You can see how they relate to one another in Figure 4-2 (refer to the nearby sidebar for a refresher on biological classification), and Figure 4-3 shows how some of them appear. Regarding Figure 4-2, note that different physical anthropologists classify the primates in slightly different ways, and some don’t even consider the loris — shown in this figure but not discussed in the text — a primate. Although variations like this exist, the classification shown here is widely used.
© John Wiley & Sons, Inc.
FIGURE 4-2: The Primate order.
The primate dental formula is a notation of the number of various tooth types in the individual mouth, counting incisors, canines, premolars, and molars, in each quadrant of the mouth (upper left, upper right, lower left, and lower right). Different dental formulas can tell anthropologists about the relationships between species. For example, humans have two incisors, one canine, two premolars and three molars, for a dental formula of 2.1.2.3, whereas New World monkeys (a very different group) have an extra premolar, for a formula of 2.1.3.3. Figure 4-4 compares the dental formulas of an Old World ape and a New World monkey.
Although you read lists of separate species characteristics, like body weight or diet, those characteristics always intertwine. Therefore, diet can have effects on body weight and vice versa, and exactly how one characteristic affects another isn’t always easy to understand. In fact, I’d say that although anthropology today has very good lists of these characteristics and can very clearly describe the primate species, as a field anthropology doesn’t always have a good explanation for how the characteristics interact. That doesn’t mean that anthropology can’t ever understand them, but at the moment I’d say that anthropologists are just now working out the interactions of the anatomical and behavioral characteristics.
© John Wiley & Sons, Inc.
FIGURE 4-3: Sketches of the main varieties of primates.
Illustration courtesy of Cameron M. Smith, PhD
FIGURE 4-4: Comparison of the dental formula of a New World monkey and an Old World ape (human).
