121 The Living Primates

The Living Primates

The slides in the next two lectures and a study guide with additional information on the living primates are available on the Human Evolution web site.

Insectivores vs. Primates

Primate Traits • • • •

Grasping hands and feet Large brains Emphasis on vision De-emphasize of olfaction

Primate Classification

Primate Suborders •

•

Prosimii ¾ Prosimians ¾ Example: Ring tailed lemur ¾ Show some primitive traits ¾ Smaller brain to body size ratio ¾ Emphasis on olfaction Anthropoidea ¾ Anthropoids ¾ Example: Rhesus monkey, humans ¾ Show some advanced traits ¾ Larger brain to body size ratio ¾ Emphasis on vision

Grade vs. Cladistic Classification of the Primates

•Grade •Based on morphology •Prosimian vs. Simian •Clade •Based on phylogeny •Strepsirhine vs. Haplorhine

Haplorhine vs. Strepsirhine

Prosimians vs. Anthropoids

New Word vs. Old World Monkeys

Old World Monkeys vs. Lesser Apes

Lesser Apes vs. Great Apes

Great Apes vs. Humans

The tree shrew: insectivore or primate ?

Are tree shrews primates? • In the past, tree shrews have been considered primates – They show structural similarities to early primate – large brain for their body size – thumbs that tend to diverge from its fingers

• These features are probably either – independently evolved adaptations to similar environments or – A retention of primitive mammalian characteristics.

Infraorder: Lemuriformes (Lemurs)

Lemuridae (True lemurs)

Lemur dental specializations • Three premolars • One premolar less than the primitive mammalian condition. • Many species have incisors specialized into a tooth comb. • These are used for grooming and also to scrape nutritious, protein-rich sap off of the bark of trees.

Lemurs have a well-developed olfactory apparatus

Indriidae (Indris)

Sifaka Bipedalism • Indris such as the Sifaka are vertical clingers and leapers with long lower limbs. • On the ground they are often bipedal. • The long lower limbs associated with vertical clinging and leaping appear to be preadaptive to bipedalism.

Lorisidae (Lorises and Pottos)

Lorisidae

Galagidae (Bush babies)

Daubentoniidae (Aye-aye)

The Aye-Aye Adaptation • A wood pecker imitator. • Incisors are not continuously growing as in rodents. • Long finger impales grubs exposed by gnawing. • Wouldn’t be successful in doing this on the African mainland because of competition with regular woodpeckers.

Tarsiidae (Tarsiers)

Is the Tarsier a Prosimian?

Comparisons of a Tarsier and Lemur Skull

Suborder: Anthropoidea (anthropoids): Monkeys, apes, and Humans • The “higher primates” • Larger brain to body ratio than the prosimians • With a few South American exceptions have nails instead of claws • Eyes closed off in the back • Reduced olfaction • Adaptive emphasis on binocular vision

Infraorder: Platyrrhini (New World monkeys)

Two Platyrrhine Families • Callitrichidae (Marmosets and Tamarins) – Small – Lack prehensile tails – Some have claws on some of their digits • Cebidae (Cebids) – Larger – Most have prehensile tails – Nails instead of claws

Differences in Appendages

Marmosets and Tamarins

Callitrichidae (Marmosets and Tamarins)

Cebidae (Cebids)

Cebid characteristics • • •

Most cebids have prehensile tails Have nails on all digits Larger brain to body size ratio than marmosets

Howling Monkey • Has a leaf-eating adaptation • Specialized hyoid bone of males produces an impressive call that is used for territorial defense

Differences between Platyrrhine (New World) and Catarrhine (old world) monkeys

Cercopithecidae (Old World monkeys)

The Two Old World Monkey Subfamilies • Cercopithecinae – Cheek pouches – Frugivorous

• Colobinae – No cheek pouches – Folivorous

Cercopithecinae (Cheek Pouch Monkeys)

Cercopithecinae includes baboons, macaques, vervets, and other similar forms

Baboons

Baboon Adaptations • Quadrupedal adaptation with limbs of equal lengths. • Ischial callosities allow them to sleep in trees. • Troops with dominant males and a well developed social hierarchy

Baboon Meat Eating • Omnivorous • Opportunistic carnivores • Do not share meat, but instead fight over it

Colobinae (Leaf monkeys) • •

•

Leaf-based diet No cheek pouches, large sacculated stomachs that are divided into three or four Colobine molar teeth have high pointed cusps with sharp shearing crests adapted for shredding leafy material.

Langurs: Asian Colobines

Langur infanticide • Live in one male multi-female groups. • Peripheral males sometimes live alone or in multi-male groups. • Among Hanuman langurs, when a new male takes over a group, he frequently kills the unweaned infants of the previous male. • Males who kill infants will have more offspring than males who don’t. .

Hylobatidae (Gibbons)

Gibbon Brachiation • Gibbons have extremely long arms, hook-like fingers, and welldeveloped thumbs that fold out of the way against the palm of their hands. • These specializations are adaptations for swinging below branches (brachiation). • Long arms allow us to identify brachiator adaptations in fossil forms.

Gibbons in Action

Features Associated with Brachiation • Long arms • Chest flattened from front to back • Good grasping capabilities • Big clavicles to attach the arms to the torso • Bipedalism on the ground • Humans show many anatomical features suggesting a brachiating ancestor

Gibbon Bipedalism • On the ground, gibbons often walk bipedally. • This suggests the possibility that brachiation was preadaptive to human bipedalism

Gibbon Monogamy • Gibbons show strong pair bonding. • The social unit is a male, female, offspring and sometimes elder parents. • Sexual dimorphism is low because males and females cooperate in territorial defense.

Superfamily Hominoidea

An Alternative Classification

Pongidae (Great Apes)

The Orangutan

Orangutan Diet • Orangutans eat fruit, except during the dry season when they are forced to feed on bark and other lower energy foods.

Orangutan Locomotion • Excellent prehensile capabilities of both hands and feet allow these large-bodied apes to get fruit found in the the peripheral branches of trees. • Owing to their size, males spend more time on the ground than do females.

Orangutan Social Organization • Among orangutans, females associate with infants while males are solitary. • Males are solitary, but attempt to maintain a territory that includes several females. • Male-male competition probably explains the high size sexual dimorphism in orangutans.

Gorillas

Gorilla Diet • Gorillas specialize in eating foliage and have never been seen to eat mammals in the wild. • Canines are used in fighting and also for processing heavy plant foods.

Gorilla Social Organization • Gorillas live in groups containing one or two adult males along with several females and their offspring. • Young male gorillas leave their natal group at adolescence.

Gorilla Locomotion • Owing to their size, gorillas spend much of their time on the ground. • When walking quadrupedally they support the front of their body on the middle of their fingers in a specialized mode of locomotion called knuckle walking . • They sometimes brachiate in the trees

Chimpanzee Brachiation • Chimps are brachiators, but not as athletic as gibbons. • On the ground, they knuckle walk like gorillas

Chimpanzee Diet • Chimpanzees are predominantly frugivorous • However, in some areas they frequently kill and eat animals, especially other primates.

Chimpanzee Social Organization • Chimpanzees live in multimale-multifemale communities with a fluid social organization.

Chimp Body Language

Hominidae • • • •

“Know Thyself” Bipedal Big brains Dependant on culture

Strepsirhini vs. Haplorhini

•The rhinarium is dry; nostrils are more rounded and continuous •The upper lip is continuous and not attached to gums •Free upper lip allows for more expressive face •Eyes lack tapetum and do not reflect light •Larger brain •Reduced snout and less reliant on sense of smell •Binocular and stereoscopic vision •Delayed sexual maturity •Usually one offspring, with extended maternal care •Extended life span •Trend towards longer arms than legs