understanding, and then describing (rather than comprehensively explaining) the variety of primate social behaviors.
Primates live in large, complex groups for three main reasons:
Protection from predators (protection in numbers): Predators can be put off by large, noisy, and dangerous groups of primates (like troops of baboons), and in a large group, one individual member is less likely to become lunch for a big snake or eagle.
Greater access to food: Larger groups who inhabit areas where food is distributed unevenly in the forest are more likely to find food patches because they have more eyes looking.
Raising offspring: Primates reproduce not by having vast numbers of offspring (like fish or frogs) but by having relatively few offspring that require a lot of care, both to protect them from predators and to teach the babies to socialize.
The following list describes the four main kinds of primate social groups:
Loners: This kind of social organization is called noyau. Only the nocturnal primates (like some of the prosimians discussed earlier in the chapter) and the orangutan have evolved noyau, in which males wander alone, staying with mates only long enough to mate. Females are also solitary, unless they have young, which they carry as they move around.
Families: Humans love families (or the idea of families) so much that we’ve been watching the Simpsons — Marge, Homer, Bart, Lisa, and Maggie — for 20 years (and they’re only one of a gazillion fictional families shown on television for the past 50 years); we’ve probably been telling stories about human families as far back as anyone can remember. In the primate order, monogamous families of a mated male and female with their offspring pop up among some gibbons and other kinds, but monogamy is actually quite rare in the primate order outside the human species.
Troops: Troops are multi-male, multi-female groups that contain no stable, long-term male-female mating relationships; males and females each have several mates. This situation is most common among the semi-terrestrial primates, whose groups may number into the low hundreds. These troops’ large numbers protect them from the big, terrestrial predators like leopards and lions and can help in finding food by sending scouts out on reconnaissance treks.
Harems: Groups that contain a single male, several females, and their offspring are known as polygynous groups or harems. Gorillas live this way; silverbacks, the dominant males, typically kick out male youngsters that are starting to come up in the ranks. They sometimes tolerate powerful young males for a while, but in the end the young guys normally have to leave. When they do, they have to find another group, defeat its silverback, and live to be the dominant male. It’s not an easy life.
Just when you have a handle on primate characteristics and behavior, another unusual situation arises. In this case, it’s polyandry, the social pattern among nonhuman primates in which a single female has several male mates. This tendency is only found among the tiny, nocturnal, insect-eating marmosets and tamarins.
Primate social behavior isn’t always sweetness and light. Like many animals, primates often threaten one another, but coming to actual physical blows is rare; it’s just too risky. A better tactic is to bluff, and plenty of that goes on: Chimpanzees scream, throw sticks, slap the ground, and bare their teeth, all in an effort to intimidate — and it works. Over the eons, intense competition among primates has favored those with large, intimidating canines; the baboons’ teeth can be knife-like and particularly scary. Among humans, most threats and displays of prowess are accomplished verbally or with objects that show our rank, and so the pressure for especially big canines has lifted. This pattern seems to go back at least 2 million years, where fossil evidence indicates that our early ancestors’ canines aren’t as large as they are in most primate species.
Primates Today (But For How Long?)
The living primates — anywhere between 233 and 290 species, depending on whom you talk to — are widely distributed from South America to Africa to Japan. (Figure 4-6 shows this distribution.) Most are found in the tropics or semi-tropics (within 1,500 miles north or south of the equator). New species still occasionally surface — for example, the sideburn-sporting titi monkeys of South America (found in 2002) and two new lemur species found in 2005 in Madagascar. Some species are flourishing in large wilderness areas, but development is steadily reducing and fragmenting these regions.
Illustration courtesy of Cameron M. Smith, PhD
FIGURE 4-6: Global distribution of primates today.
In 1996, the World Conservation Union reported on the many threats to primate species, and in 2003 they revealed that about half of the more than 200 primate species were under severe threat. The situation hasn’t gotten any better since that report. In October 2007, the International Primatological Society and Conservation International copublished a list of the 25 most threatened and endangered primate species. Astonishingly, these groups include chimpanzees, gorillas, orangutans, and some kinds of gibbons; essentially, aside from humans, all the great apes are facing extinction. Maybe we should be more ashamed than astonished, though; conservationists have been telling us for 30 years that these and other species were in trouble. But even pointing out that we share at least 95 percent of our DNA with most of these species hasn’t reduced the threats to our closest living relatives. These threats include
Habitat destruction from logging, particularly in Southeast Asia and Borneo, home of the orangutan
Habitat destruction from agriculture, particularly in the African Congo, where farms are encroaching on gorilla habitat
Poaching, much of it for meat, some of which sells for spectacular prices on the African “bush meat” market
Any conscientious anthropologist today will tell you that for the threatened and endangered species, right now research priorities must include conservation effort. If the species aren’t preserved, how can you find out about our species from them? And if humans let our closest living relatives go extinct without a real fight, what does that say about us?
CHIMPANZEES AND PEOPLE
One reason people may feel ambivalent about the fate of chimpanzees — and, by extension, other endangered primates — is that for a long time Western civilization has looked on the chimpanzee with suspicion, hatred, fear, and disgust. Medieval sculptures depict chimpanzees as gargoyle-like winged devils; in the Victorian era, captive chimpanzees disgusted many Londoners, who believed that the chimpanzee was a species locked in time, a throwback to a disgusting, primordial past. Of course, the Victorians were wrong: Chimpanzees are here in the present and have evolved for as long as we have. That they didn’t evolve the kinds of language and culture of modern humans is neither here nor there; each species adapts in its own way, and cross-species comparisons of this kind are pointless. Today, despite knowing that most of our DNA is identical to that of the chimpanzee, chimps are still dressed up for commercials and movies and essentially looked on as comical quasi-humans. But some scientists feel that, due to chimpanzees’ genetic and anatomical similarities to humanity, the chimpanzee genus — Pan — should be dissolved, and chimpanzees brought into
