Chapter 5: Living Primates
INTRODUCING THE PRIMATES
The primate order consists of two suborders, the prosimians, which are pre-apes, and the anthropoids, which are monkeys and apes. Modern humans are part of the primate order because we are a type of ape. We study non-human primates because they provide clues about our own ancestors and because of their close biological and behavioral links to modern humans. Like other anthropologists, primatologists, or those who study primates, also conduct long periods of fieldwork.
PRIMATES AS MAMMALS
Humans are classified within the primate order and all primates belong to the class called Mammals. All mammals share certain traits, including giving live birth, producing milk to feed their young, long periods of offspring dependency, and near constant body temperatures.
The Primate Order
Records of fossilized primates start around the time of the dinosaurs, roughly 65 mya. These early primates were rodent-like animals that evolved into a vast array of modern organisms that vary widely in look, habitat and behavior. Humans are the primates that have the largest habitat. We inhabit nearly every continent and landmass on earth.
Despite their great range of physical differences, primates tend to share some basic features.
- Flatter, non-projecting faces
- Brains that are large in relation to body size
- Most have five digits on both hands and feet, with nails at the end
- Our hands, and sometimes our feet, can be used to grasp, often with opposable thumbs
The similarities in our physical form are related to shared behaviors.
- Most primates are arboreal (tree-dwellers).
- Most are also quadrupedal (move about on all fours).
- Most are diurnal (active during the day) instead of nocturnal (active during the night).
- As a result of our diurnal habits, we tend to rely on sight more than other senses. This is where our stereoscopic vision (three-dimensional) is important as well.
- Finally, most primates have a high degree of sociality (the tendency for group living).
Primatologists study the environments in which non-human primates live in order to provide a context for their behaviors and features.
- Most contemporary primates live in forested tropical or sub-tropical areas, at low altitudes.
- These environments often provide a range of ecological niches for the animals to make use of and also allow multiple species of primates to make use of the same area.
- The different species don't have to compete for resources because they evolved different features such as size, diet, and behavior, as a result of adapting to different ecological niches.
Having to search for food affects how an animal moves about, the size of their habitat and even their behavior. All non-human primates forage, or get food by gathering, hunting or scavenging. Different primates make use of different kinds of foods. All primates fit into five feeding types based on what the majority of their food intake is.
- Frugivores mainly eat fruit, which is often seasonally available and in great demand.
- Folivores mainly eat leaves that are plentiful so there is little competition.
- Insectivores mainly eat insects which are high in protein and energy and for which there is little competition but they provide little food for the amount of time it takes to gather them.
- Gumnivores mainly eat gums and saps that are plentiful, but which are difficult to digest.
- Omnivores eat pretty much anything and this allows them to adapt to habitat changes.
VARIETIES OF LIVING PRIMATES
Prosimians consist of the primates that are most distantly related to humans, in an evolutionary sense, and which are mostly found in Southeast Asia and Sub-Saharan Africa, including Madagascar.
- Most prosimians are small, arboreal, insectivores that are nocturnal and solitary in their daily lives. They also tend to groom one another with teeth instead of hands.
- This group includes lorises, lemurs and tarsiers, although recent genetic evidence shows tarsiers are more closely related to anthropoids than the other prosimians.
- Lemurs are the one major exception to generalizations in this group in that they tend to be larger, diurnal and terrestrial (ground dwelling). They also have a larger variety of diets and live in groups. Their differences are probably related to the fact that they are found on Madagascar and have been the only primates on the island for most of their history.
Anthropoids include New and Old World Monkeys, Humans and Apes. They are different from prosimians in that they have nails and not claws on their digits, forward facing eyes, larger brains, dry noses and flatter faces. They also use their hands, not their mouths, for grooming.
New World Monkeys
- New World monkeys exist only in tropical Central & South America. All of them are arboreal, small and have rounded nostrils. Some have prehensile (gripping) tails. Because of the lack of competition from prosimians or apes, there are a wide variety of New World monkeys as they spread out into all areas and ecological niches. Capuchins are the only New World monkeys to use tools regularly.
Old World Monkeys
- As a group, Old World monkeys are more uniform in appearance and behavior than their New World counterparts. They are broken into two main groups. Cercopithecines are omnivores who use cheek pouches to store and carry food and mostly live in Africa. Baboons are the largest and most terrestrial. Colobines are folivores who have complex stomachs and who live in both Africa and Asia (Colobus Monkeys).
- Apes are members of the superfamily of primates known as hominoids.
- Apes differ from other primates by not having tails, having large brains relative to body size, using brachiation (forelimbs to swing), having long strong collarbones and long fingers and arms.
- There are lesser and great apes. The Lesser Apes are the Gibbons and Siamangs. The other group, those most like humans, is considered the Great Apes, and includes Gorillas, Orangutans, Chimpanzees and Bonobos.
- Gibbons and Siamangs are two of the smallest apes and are the most distantly related to humans. They are frugivores and live in tropical forests in Southeast Asia. They are habitual brachiators. They have small pair bonded family groups with 1 male, 1 female and offspring.
- Orangutans are the only great apes in Asia. They live on Borneo and Sumatra. Sexual dimorphism (differences in appearance linked to sex genes) is great and they are orange in color. They are primarily arboreal frugivores and use a distinct form of fourhanded tree and ground travel. They are the most solitary of the great apes with the mother-child bond being the longest lasting.
- Gorillas are the largest primates and live in sub-Saharan Africa. They have 3 different groups (Western & Eastern Lowland & Mountain Gorillas). Each subspecies differs in diet and appearance. They eat a variety of plants and sometimes insects; all 3 types are folivores, frugivores or a combination. They exhibit a high degree of sexual dimorphism, are terrestrial, quadrupedal and use knuckle-walking. They live in small, tight-knit groups of adults, typically with one male and multiple females and offspring. Some are silverbacks.
- Chimpanzees and Bonobos -There are two species of chimp, the chimpanzee and the bonobo. They are found in sub-Saharan Africa. Both species spend a large amount of their time in social interaction, with grooming being the primary activity.
- Chimps are found in West and Central Africa, are smaller than other apes and live in humid tropical forests or woodlands. They are knuckle-walkers on the ground but also arboreal. They are mostly frugivores, but also eat meat and vegetation. Chimps have large communities that frequently split into smaller groups for feeding. The mother-child bond lasts the longest. They are patrilocal, with males staying in their birth group for life.
- Bonobos are only found in the D.R. Congo, are slightly smaller than chimps and live mainly in rainforests. They are knuckle-walkers and frugivores, they sometimes hunt and they eat meat and plants. Bonobos have groups that consist of many males and females and offspring. They have a lot of fluidity in their group composition. Their social groups are more stable than those of chimps and it is the females who usually leave to mate. Females tend to dominate many aspects of bonobo life, as they create strong bonds and alliances with other females. They are also extremely promiscuous, with sex occurring between all combinations of ages and sexes and number of partners. They are more social and less violent than chimps.
Not all primates behave in the same way and this allows them to adapt and be flexible when they encounter changes in their environment.
- There are many different types of primate groups, which vary in composition and size. Females and offspring usually are the core of the group.
- Groups often have a home range, or a place with their primary sources of food, water and nesting trees. Animals often move seasonally because of food.
- Males are not always the most dominant, nor do they always dominate females. Many things besides size and aggression determine rank. Hierarchies affect access to mates and resources.
- Individual interaction includes grooming as a social activity, touching and hugging for friendship and to comfort each other, and a strong mother infant bond.
- Sexual Behavior: They have estrus (heat), are non-monogamous and hierarchy dominates access to females (among most animals, except bonobos).
- Play is a means of learning about the environment, testing strength and learning how to behave as an adult (socialization).
- Their learning abilities are much like humans; they are inventive, parents pass skills on to their young, they can deceive and even make use of human communication systems. Because behavior is a prime method of adaptation, they have advanced learning skills.
- Some great apes, including chimps, will hunt small to medium sized mammals and it is usually the males and they cooperate and share the kill.
All primates have complex communication and signaling systems. It allows individuals to band together and live in groups.
- Primate communication involves smells (olfactory), touch (tactile), visual and vocal communication. Complex facial muscles allow primates to have a large range of expressions that convey meaning. Primates also use body language to convey ideas.
- Those primates who are arboreal have the most advanced vocal communication because they have a harder time seeing one another through the trees.
- Their communication systems include calls for food, territorial, contact, warning and fear.
- Non-human primate communication systems are not as complex as human's. Most of their communication is emotional rather than intellectual.
For much of our discipline’s history, we thought making and using tools was a distinctive feature of human behavior. We were wrong. Tool use is found among all chimpanzee and bonobo groups and some groups of gorillas, orangutans and capuchin monkeys. No wild prosimian regularly makes or uses tools. In captivity though, all the great apes and even capuchins can be trained to make and use tools. It is likely that modern humans and our ancestors inherited the ability to make and use tools from the last common ancestor we shared with the other primates.
THE QUESTION OF CULTURE
Non-Human Primate Culture
Culture was also thought of as a distinctly human trait for much of our discipline’s history. Since culture is broadly defined as behavior that is learned and shared, non-human primates are often viewed as having something like a rudimentary culture. Analysis of chimp groups revealed 39 behavioral differences that can only be explained as different cultures. By passing on specific tool making, food getting or other behavioral skills, great ape communities are creating cultural traditions.
Endangered Non-Human Primates
Because of their own value and their value to our understanding our past and present selves, we must be mindful of the fact that out of over 300 non-human primate species, over half of them are at risk extinction. Rapid economic growth and globalization, massive resource consumption and unequal access to the basic necessities of life all contribute to conditions that threaten these primates.
Threats From Humans
Human activities are now a greater threat to non-human primate survival than wild ones. Most primates live in tropical forests in less developed nations. New consumption patterns and population growth lead to the need for wood, land, and even bush-meat. Environmental degradation also harms the habitats where they are found. While logging and other commercial interests can create massive habitat loss, even small, patchy destruction of areas of forest can harm these primates because it fragments and isolates their populations, reducing the genetic diversity of their gene pools. They are also threatened with live capture for zoos, pet stores or research.