Читать книгу Anthropology For Dummies - Cameron M. Smith - Страница 74

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).