Introduction (Order of appearance)

Many animal forms inhabit the world, and humans have come to view themselves as one of them. The taxonomic order, Primates, to which humans belong includes at least 50 genera and 250 species and subspecies of living apes, monkeys, and prosimians. As these animals are humans' closest relatives, it is understandable why they hold a particular fascination for us. This film, Survey of the Primates, has been produced to give the viewer access to the richest array of primate forms ever assembled for a motion picture.

Primates are essentially dwellers of the tropics and semi-tropics. With the exception of man they are found typically within areas bounded by 40 degrees North and South latitudes. All continents, with the exception of Australia and Antarctica, either have or have had nonhuman primates. The main threat to continuation of their existence and reproduction is man, who continues to encroach upon their environs for the purposes of obtaining natural resources and accommodating his own populations.

Nonhuman primates are a valuable natural resource in their own right, unique forms of life which if lost will never re-evolve in their present forms. It is hoped that this film will encourage all viewers to respect nonhuman primates and to support those efforts of conservation intended to sustain all extant forms in the field or, as a last resort, in captive breeding colonies.

Primate Characteristics

Authorities generally agree on the definition and characteristics which set primates apart from other mammals. Le Gros Clark (1959) has characterized them by noting that they possess (1) a generalized skeleton, including a clavicle, (2) highly mobile digits, especially on the hands, (3) highly sensitive tactile pads on the tips of fingers and toes, frequently shielded by nails rather than claws (all primates have at least two nails), (4) in general, rather short snouts, (5) overlapping visual fields which enhance depth perception, (6) vision as a dominant sense, (7) relatively few teeth, as compared with primitive mammals, (8) a well-developed brain with a complex cortex, which facilitates learning, and (9) enriched mechanisms for nourishment of the developing fetus.

Napier and Napier (1967) add two additional characteristics to Clark's list: (1) a tendency toward upright posture and (2) prolongation of infant dependency, both physically and psychologically.

Man has not linearly descended from contemporary monkeys and apes, but he shares with them many physical traits and behavioral propensities as old as the very roots of the primate order.

As example of a form that is equivocal so far as classification in the primate order is concerned is the small animal called the tree shrew (Tupaiidae). Let us consider them in some detail.

Tree Shrews: Tupaiidae

The tree shrews are forest-dwelling mammals of Southeast Asia. The consensus is that they are not true primates, but they suggest important evolutionary developments which led ultimately to man. Authorities generally agree that it has been from some now-extinct form of tree shrew-like insectivore that the contemporary primates evolved.

Tupaiids are partial to insects, but they do eat a wide variety of foods; they are omnivorous. Their high metabolic rates require large quantities of food. They are very active, belligerent, quick to attack, and likely to bite if handled.

Primates have a least some nails which cover the tips of their fingers and toes. As the tree shrews have only claws they lack a characteristic which holds true for all other animals classified as primates.

They have 38 permanent teeth, in contrast to man's 32. In comparison to true primates they have two additional lower incisors.

Most of the 12 tupaiid species have an elaborate visual system compared to true insectivores. The tupaiid's visual area in the brain is larger, but the olfactory area is smaller than those of most insectivores. Tree shrews lack binocular vision generally found in true primates.

Some tupaiid species have a placenta which in its later stage assumes a character which has led Meister and Davis (1956) to conclude that a haemochorial type is extant just prior to birth. (The term "blood-bearing" in the film refers to this trend toward a haemochorial placenta in some tupaiids. The placentation of apes and man is haemochorial, which allows the vascular structures to have maximum and most direct contact with the mother's blood. This type of placenta has less tissue between the maternal and fetal blood streams than either the endotheliochorial or epitheliochorial types.)

The tupaiid's gestation period is just under seven weeks. Characteristically a litter of two or three young is delivered and placed in a nest separate from that of the parents. The close mother-infant relationship so characteristic of monkeys, apes and man is missing in the tree shrew. The infants remain alone in the nest and are attended to only a few minutes every 48 hours for nursing by their mother. The infants emerge from the nest at the end of a month and rapidly become independent.

For these and other points of deviation from primate characteristics, it is concluded that the tree shrew is an equivocal from, possible as the first link in the primate chain, but still suggesting an early, remote ancestor.

Prosimians: Lemuridae, Indriidae, Daubentoniidae, and Lorisidae (of the suborder Strepsirhini/infraorder Lemuriformes), and Tarsiidae (of the suborder Haplorhini/infraorder Tarsiiformes)

Prosimians are true primates, yet primitive and distinct from monkeys and apes. Some 50 million years ago they existed even in the New World. Today they are found only in Africa, on the island of Madagascar off the east African coast, and in the Far East. Most of them are highly arboreal.

Ring-tailed lemurs, of the Lemuridae family, are found along with all other lemurs only on the island of Madagascar, probably because no monkey or ape lives there to compete with them. Lemurs are presumed to be the least intelligent primates, not likely to survive in direct competition with higher intelligence. All but one of the lemur forms have 36 teeth.

Although small-brained, they have an excellent sense of smell. By means of scent glands they mark objects in and bordering the territories which they define and defend against intrusion by others of their kind.

Each year the ring-tailed lemurs have only one breeding season of a brief few weeks. During this season the otherwise peaceful males become very hostile and dangerous to each other. Gestation is about 130 days. Most births are single, but twins are not uncommon. The newborn weighs only 3 ounces, but within 6 months it becomes independent and at 18 months it is sexually mature. Lemurs live about 25 years.

The galago or bushbaby of the family Lorisidae is another prosimian. Their sensitive eyes are important for their nocturnal activities. Their young are hidden in well concealed nests. The mother carries an infant by use of her mouth which grasps onto a fold of the infant's lateral abdominal skin.

The tiny tarsier is still another primate form, of the family Tarsiidae, that is a nocturnal dweller of tropical rain forests. By reason of their elongated tarsal bones, they can jump about 6 feet.

No specimens of two of the Malagasy families, Indriidae and Daubentoniidae, are portrayed in the film.

The prosimians are an important primate group between the insectivores and true monkeys and apes. Prosimians are the most primitive of all primate forms.

Cercopithecidae: Colobinae and Cercopithecinae (infraorder Catarrhinii)

All Old World monkeys are grouped into one family: Cercopithecidae. Compared with the prosimians they manifest higher intelligence and learning ability. This family has adapted to a wide variety of ecological conditions.

The Colobinae is one of the two subfamilies of Cercopithecidae. The Colobinae subsist primarily on a leafy diet. Representative of them are the Douc langur of Viet Nam, the Hanuman langur of India and Ceylon, the proboscis monkey of Southeast Asia and the colobus of Africa. All of them have large and sacculated stomachs to accommodate amounts of leaves up to 1/3 of the animal's own weight. This type of stomach is necessary to provide sufficient nutrition, for leaves are low in food value. The Colobinae are primarily arboreal. Their intelligence is generally lower and their social systems less intricate than the other Cercopithecidae subfamily, the Cercopithecinae. The Cercopithecinae are represented by such Asian terrestrial forms as the macaque, the baboon, the gelada, and the patas monkey. Also, they are represented by such African arboreal forms as the talapoin, the guenon, and the mangabey. They are more omnivorous than the Colobinae, a characteristic which facilitates adaptation to areas outside of the rain forests. Some of the Cercopithecinae, but none of the Colobinae, have cheek pouches which facilitate food intake and storage.

In some respects the development of the Cercopithecinae is superior to that of the leaf eaters. The improved thumb opposability of Cercopithecinae is a valuable aid to manipulation of the environment. Also, the Cercopithecinae are more varied than nurturing and protecting their infants and pregnant females. Their adaptation to life on the ground is seen in their walk, in which their dexterous hands are used palm-down in a quadrupedal style.

The majority of Cercopithecinae have sitting pads (ischial callosities) that cover the rough ends of the ischial bones. Many Cercopithecinae, particularly the males, have formidable canine teeth with which to defend, compete, and eat tough foods.

Old World monkeys have 32 teeth, the same in number and basic dental formula as that of apes and man.

The color vision of the entire Cercopithecidae family is excellent, and their eyes are positioned for enhanced stereoscopic depth perception. Compared to prosimians their sense of smell is less important.

The genus Macaca ears special attention. Other than man, this Old World monkey is the most successful primate form if adaptability is taken as the criterion. From Gibraltar where the regional macaque is misleadingly called an ape (the "Barbary ape"), through Pakistan and India where the well-known rhesus monkeys abound, through the forests of Southeast Asia, China and Formosa where various forms of Macaca thrive, and finally into Japan where Macaca fuscata survives winter snows and rigors of summer ocean swimming which yields fish for its dietary staple, the macaques are the most widely ranging of all nonhuman primates. And if the baboons were to be grouped with them--as some taxonomists maintain they should--the range would extend even more dramatically into the arid wastes of Arabia and North Africa.

Learning is an advanced mechanism of adaptation. In Cercopithecidae, and particularly in its subfamily Cercopithecinae, a variety of learned social organizational patterns attest to their intelligence and probably account in part for their success in survival. This variety of social patterns illustrates the principle that biology provides for latitude of behavioral expression, so that usually more than one adjustment pattern is available to enhance the likelihood of surviving environmental demands.

Ceboidea: Callitrichidae and Cebidae (infraorder Platyrrhinii)

All New World monkeys, members of the superfamily Ceboidea, are embraced within two families: Callitrichidae, represented by such as marmosets and tamarins, and Cebidae with its familiar capuchins, squirrel monkeys, and spider monkeys, among others.

New World monkey distribution in South and Central America and into Mexico is characterized by considerable overlapping of many species. New World monkeys are more primitive than Old World monkeys and are only distantly related to them. Nonetheless, they resemble them in many ways.

As do lemurs, the several marmoset species of the family Callitrichidae use their scent glands and tactile facial whiskers. Also as with lemurs, the marmosets' relatively undifferentiated facial musculature allows little facial expression.

Marmosets typically bear fraternal twins at the end of a gestation period of about 140 days. The marmoset male plays a unique and vital role in infant care. During the first week of life infants normally cling to the mother, but during the next three months they cling to the father, being transferred back to the mother at intervals for nursing. At about four months they are quite independent, eating plant food and insects. They achieve adult size by the age of one year. Though the marmoset brain is relatively large considering the diminutive size of the animal, it is not convoluted, a factor related to restricted learning skills. Even so, the beautiful golden lion marmoset, the most intelligent of the Callitrichidae, probably equals the squirrel monkey in learning skills. It is highly arboreal and lives on insects, fruits and small lizards. Its fingers are remarkably long. Its hands are prehensile, but the thumbs are nonopposable.

Woolly monkeys are typical of the other Ceboidea family: the Cebidae. They may attain 20 lbs. when full-grown, whereas the squirrel monkey is not likely to weigh more than 3 lbs. Though the Cebidae have excellent color vision, there is often some reduced sensitivity to red light.

Most striking in certain cebids is the prehensile tail. Functionally it is a fifth limb with which the animal can hang, balance, and pick up bits of food. Capuchin, woolly, howler, and spider monkeys all have prehensile tails. No Old World monkey has such an appendage.

Unlike the Old World monkeys, all New World monkeys are restricted to arboreal habitats. There are no ground dwelling New World monkeys. With the exception of Lotus, all are diurnal.

Gestation periods of New World monkeys range from about 140 days in the golden marmoset and 165 days in the squirrel monkey to an estimated 225 days in the woolly monkey. Among the cebids twins are uncommon. Their diet of fruit, leaves and shoots is enriched by lizards, insects, and bird eggs.

The New World monkeys comprise a broad spectrum of primate forms. In general, they maintain less rigid social organizations than do the Old World monkeys. In general, they are considered less advanced.

Hylobatidae: Hylobates and Symphalangus

Though there are several distinguishing factors that separate apes from monkeys, the most obvious one is the absence of a tail. Together the gibbons (Hylobates) and siamangs (Symphalangus) comprise the lesser apes, so called by reason of their size when compared to the other apes. They are dwellers of the jungles of Southeastern Asia and are probably the most adept of all primates at brachiation, a hand-over-hand form of locomotion. When on the ground, the lesser apes walk bipedally. In contrast to some of the monkeys, apes appear to have an aversion to even small pools of water. All of them lack the ability to swim. Deep water barriers effectively isolate them, both in the wild and in captivity.

Apes are the latest-maturing and the longest-living nonhuman primates. Lesser apes might live to about 35 years.

Probably all lesser apes are highly territorial. Gibbon groups are known to defend fiercely their territory against other gibbon groups. In the early morning hours the lesser apes make the jungles ring with their vocalizations, an activity which serves to communicate locations of the groups in the area.

Only in the gibbon is the natural grouping that of a "monogamous family": a male-female breeding pair and their immature young. Ironically, they have not learned or performed well in formal tests of intelligence.

Pongidae: Pan, Pongo, and Gorilla

The great apes, like the lesser apes, are tailless. In addition, there is a number of more significant characteristics which distinguish them from monkeys and the lesser apes.

The three great ape genera are Pan, the chimpanzees; Pongo, the orangutan; and Gorilla, the generic name used also popularly. The chimpanzee and gorilla are confined to the African mainland; the orangutans are found only in the southeast Asian islands of Sumatra and Borneo. Great apes might live to beyond 50 years.

Both the scope of learned behavior and the rate of learning are highly advanced in the great apes. They are superior to all other nonhuman primates in these regards.

Their finger dexterity is quite precise. The gorilla approaches man in the use of the thumb (it is even superior to the chimpanzee in this capability). Nevertheless, gorillas have not been observed to use tools in the wild, although chimpanzees and orangutans have.

Orangutans are highly arboreal and are quite awkward on the ground. Chimpanzees are equally at home on the ground or in trees. Both orangutans and chimpanzees exhibit modified brachiation. The gorilla has been erroneously assumed to be strictly a ground-dwelling animal. Such is not the case. They frequently climb trees, but they have not been observed to brachiate in the wild.

The normal ground gait of all great apes is quadrupedal, but like the lesser apes, they frequently move in a bipedal fashion. The male gorilla and chimpanzee frequently stand erect while displaying with "intimidating" exuberance.

Unlike the lesser apes, great apes do not exhibit territorial defense. Their aggressive behavior is surprisingly minimal and is limited to such infrequent instances as the challenge of strangers of their own kind or predators and the competition for choice items of food or a desired object.

In primate evolution, vision has become highly developed. Apes, as well as most monkeys, are endowed with high visual acuity, well developed color reception, and excellent binocular depth perception. The entire range of sensory experience of great apes closely resembles that of man.

Of all nonhuman primates, the great apes are the most highly evolved. One other form, man, significantly threatens their survival, and he does so with frightening effectiveness!

The primates encompass a great range of life. They originally evolved from a now-extinct form of the tree shrew-like insectivore. The prosimians are the most primitive primates and are represented in the film by such forms as the ring-tailed lemur, tarsier, and galago. More advanced than the prosimians are the Old World monkeys, represented by the baboons, langurs, colobus, mangabeys, and macaques. Less advanced than the Old World monkeys are the New World monkeys, represented by the spider monkey, capuchin, squirrel monkey, marmoset, and howler monkey.

The apes are most highly evolved. The lesser apes (gibbon and siamang) and the great apes (the orangutan, gorilla, and chimpanzee) comprise the apes.

All of the primates, man included, are basically adapted for life in the trees. To varying degrees, some Old World monkeys, most apes and man have come to assume a terrestrial way of life.

Primate behavioral patterns may distinguish families and species from one another as surely as do their morphological characteristics.

With progression from the most primitive--the prosimians--to the most highly evolved primates--the apes and man--there has come an increased capacity for solving problems, for learning concepts, and for perceiving relationships among objects and events. From such skills, which rest upon refinement of the brain, especially the cortex, we infer intelligence which allows even for adaptive and creative use of implements: what we call tool-usage. The enlarged and refined cortex also provides for language uniquely in man.

Intelligence also surely allows for the formation of increasingly complex social organizational patterns where such are required for effective coping with presses of the environment. Consequently, some terrestrial forms have social organizations which provide even for (1) effective defense against predators through coordinated reactions among the adult, powerful males, (2) prolonged periods of dependency through which the young learn social patterns and methods of securing food, water, and shelter, (3) maintenance of peaceful relationships among individuals, otherwise lethal to one another, and (4) the maintenance of territories by some forms of forceful denial of certain geographic areas to others of their own kind.

With higher evolutionary standing has come prolongation of all critical intervals of life: gestation, physical growth and maturation, sexual maturity, social maturity, and life expectancy itself.

For all primates the bonding between individuals is critical. The mother-infant bond, invariably strong, affords security and protection and enhances access to food. It also may serve to instruct the infant in behavior which will eventually determine in part its role in its group's social hierarchy. Further, as infants interact with one another, critical sexual and social modes are defined and given full expression.

Primates provide a remarkable array of closely related forms; study of them reveals much regarding the role of environmental adaptation upon the evolution of both physical and behavior characteristics. But an complete understanding of prosimian, monkey, ape or man requires a broad evolutionary perspective of all animal forms.

For those who desire to understand man, with his keen talents and burdensome problems, the key principles ultimately will be revealed by a full knowledge of man's alternatives--his fellow, nonhuman primates.