Chapter 5: Primates

What is a Primate? First, primates are members of the vertebrate class: Mammalia + 4000 mammals Primates are part of the subgroup of placental mammals

Three types of primates Prosimians (pre-monkeys) Monkeys (Old World and New World) Apes

Common Mammal Traits Fur (or body hair in Humans) Long gestation & live birth (relative to other types of organisms) Heterodontism (different kinds of specialized teeth) Ability to maintain constant body temp (Homeothermy) Increased brain size (greater ability for learning and behavioral flexibility)

Characteristics of Primates Difficult to define by one or two common traits Primates are generalized (rather than specialized) mammals. Defined by evolutionary trends Not all traits found in every member of the order.

I. Limbs & Locomotion Tendency towards erect posture But, primates utilize a number of types of locomotion Bipedal Brachiation Knuckle walkers Fist walkers Limb jumpers, etc.

Hands & Feet Great degree of Prehensility Five digits on hands/feet (contra horses) Opposable thumb In most- divergent & partially opposable big toe Nails on all or some digits Highly sensitive tactile pads on digit ends

Question to Ponder Why are Human Feet different?

II. Diet & Teeth Lack of dietary specialization – most primates are generalized feeders eating a wide variety of foods Therefore, primates have a generalized dentition

III. Senses & Brain Vision enhanced Olfaction reduced Complex brain

Vision All primates rely heavily on vision Color vision in Diurnal primates. Stereoscopic vision Eyes in front of skull, overlapping fields of vision Accurate 3-D vision Increased depth perception Point to Ponder: Why would this be an adaptive trait? (hint: think environment)

Stereoscopic vision

IV. Maturation and Learning As placental mammals, primates have relatively long gestation periods Also have few offspring, delayed maturation, longer lifespan than other mammals Greater dependence on learned behavior

V. Behaviors Tend to be diurnal Increased flexibility in behavior Tend to live in social groups In many primate social groups, males are permanent members – unusual among mammals.

Arboreal Adaptation Hypothesis Traditionally, the arboreal adaptation seen as the primary factor in primate evolution Selected for 3-D and color vision (why?). Grasping prehensile hands/feet to grasp Tropical arboreal environment = varied foods

Visual Predation hypothesis Alternative to the AA hypothesis Primates may have first evolved in bushy forest undergrowth relying on insect diet Grasping hands & vision for grabbing insects. Tree jumping came later a means of locomotion that grasping hands allowed.

How to choose which hypothesis is correct? Not necessarily mutually exclusive Many primate features may have been developed in non-arboreal settings Regardless, primates are primarily tree dwellers and whatever traits their ancestors had “preadapted” them for arboreal existences.

Geographical Distribution

Most primates are arboreal, living in forest or woodland areas Some Old World primates do spend considerable time on land. No primate, except for humans, is fully terrestrial – all spend some time in trees.

Point to Ponder? What’s so great about trees?

Diet & Teeth Omnivorous w/generalized dentition Although some primates prefer some food items over others, most eat a combo of fruit, leaves, and insects. Some do eat meat (chimps & baboons) Some are leaf specialists (Colobine monkey)

Teeth Most have 4 types of teeth Incisors and canines: biting and cutting Premolars and molars: crushing and grinding

Each Primate species has a specific dental pattern

Locomotion Almost all primates are quadrapedal Many use more than one form of locomotion Long, flexible lumbar spine which provides greater propulsion from hind legs

Types of Locomotion Vertical clinging & leaping (prosimians) Brachiation (apes) Semi-brachiation (combo leaping/brachiating) Quadrapedalism Bipedalism (us)

Taxonomies organized from general to more specific All primates grouped in the Order of Primates

Two Suborders Prosimii Anthropoidea Lemurs, Lorises, Tarsiers Monkeys, Apes, Humans

Purposes of Taxonomic classification To show evolutionary relationship Animals grouped together or close by more closely related Organize Diversity Make sense of differences & similarities

But, system is not necessarily perfect Studies of Orang chromosomes show it much different from African apes (and these are closer to Humans than Orangs). Humans & Chimps most closely related (based on DNA studies) Some researchers use a different scheme to show closeness of Chimp/Human

SURVEY OF LIVING PRIMATES

Prosimians: Lemurs & Lorises Most primitive Greater reliance on olfaction (long snouts) Mark territory with scent More laterally placed eyes Shorter gestation & maturation “dental comb” (projecting lower incisors & canines)

Lemur and Loris

Lemurs Madagascar Many different species (diversified in absence of competing primates) Became extinct in other areas

Lemurs Range in size from 5”, 2 oz. to +2’, 22 lbs Larger lemurs are diurnal, omnivorous Smaller lemurs are nocturnal, insectivores Many forms are arboreal, others are more terrestrial Some live in large social groups Others (Indri) are monogamous pairs

Lorises Similar in appearance to Lemurs Tropical habitats (Sri Lanka, India, SE Asia, Africa) Survived by adopting nocturnal habits Competition avoidance with monkeys

Lorises Slow, cautious climbing form of quadrupedalism Bushbabies active vertical climbers and leapers Almost entirely insectivorous Diet supplemented with fruit, gum, leaves

L & L Vision is stereoscopic, but less developed than anthropoids Color vision in diurnal, but not nocturnal Grooming claw on second toe (not fully nailed) Longer life spans than similarly sized mammals

Tarsiers Nocturnal SE Asia Mated pair & offspring Diet: insects & small vertebrates they catch by leaping from branches

Tarsiers difficult to classify Prosimian traits: Small size Grooming claws Unfused mandible Anthropoid traits Lack of Rhinarium (moist nose pad) Orbits fully enclosed by bone

Anthropoids (monkeys, apes, H.s) Generally larger body Larger brains in absolute and relative size Increased reliance on vision Fully forward placed eyes; bony plate back of eye socket; greater degree of color vision Fused mandibles; less specialized dentition Female anatomy different; longer gestation; longer maturation; increased parental care More social interaction

Monkeys ~ 70 % of all primates are monkeys Two types: Old World or Catarrhini (downward-facing nose) New World Callitrichidae Cebidae

New World Monkeys Wide flaring noses with nostrils that face outward Almost exclusively arboreal Prehensile tails With one exception, diurnal Two Groups: Callitrichidae Cebidae

Callitrichids Small Marmosets and Tamarins

Marmosets and Tamarins Most primitive monkeys Retain claws instead of nails (used like squirrels to climb trees) Twins rather than single births Family groups Mated pair 2 males & 1 female Males very much involved in infant care

Cebids Larger than callitrichids 30 species Diet varies with combo of fruits & leaves Most are quadrupedals Spider monkeys are semibrachiators

Old World Monkeys

Still finding new monkeys April 22, 2000: Conservation International announced the discovery 2 new marmoset species in the Amazon Basin of Brazil.  Both species are squirrel size.  They have been named Callithrix manicorensis and Callithrix acariensis.  Since 1990, ten new monkey species have been discovered in Brazil. 

One family: Cercopithecidae Two subfamilies: Cercopithecines and Colobines

Cercopithecines More generalized than Colobines More omnivourous Cheek pouches to store food while foraging Most found in Africa Altho, a number of macaques are found in Asia

Colobines Leaf diet Colobus monkey exclusive to Africa Langurs found in Asia Probiscus in Borneo

Old World monkeys Variety of locomotion Guenons, macaques, langurs: arboreal Baboons, patas, macaques: terrestrial quadrupeds Colobus: semibrachiation and leaping

Significant sexual dimorphism, esp. in terrestrial quadrupeds (baboons) Females of several have genitalia that changes according to reproductive cycle Estrus– hormonally induced cycle

Homoplasy Evolutionary principle that explains similarities between NW & OW monkeys Genetically distinct populations responding to similar environmental pressures.

NW & OW monkeys have been separated for ~ 30 million years But, derived from same African ancestors Perhaps they “rafted”

Hominoids (apes & humans) Super-family includes: Less apes: gibbons and siamangs Great apes: gorillas, orangutans, chimps Humans (family Hominidae)

Hominoid traits Lack of tail Larger body size (except in lesser apes) Shortened trunk Different musculature in shoulder joint More complex behavior Longer infant development & dependence More complex brains

Hominoids

Gibbons & Siamangs Tropical SE Asia Extremely long arm limbs Curved fingers Reduced thumbs Powerful shoulder muscles Most efficient brachiator

Gibbons & Siamangs Monogamous pairs Lack of sexual dimorphism Males share equally in child care Mated pairs are very territorial

Orangutans Borneo & Sumatra Almost completely arboreal Solitary animals Mainly frugivorous Very large (males = 200 lbs, females = 100 lbs)

Gorillas Larges of living primate Knuckle walkers Exclusively vegetarianism Marked sexual dimorphism Males = 400 lbs, females 200 lbs. Family group: Silverback male & harem

Chimps Equatorial Africa Also knuckle walkers Large social groups with no single,dominant male Sexually dimorphic, but not as pronounced as gorillas and organutans Omniverous (even will kill for meat)

Chimps Large social groups of up to 50 Fluid membership Males form the core of the community, females leave, often during estrus

Bonobos Bonobos are another species of chimps More arboreal Have been studies especially regarding sexual relations – including female to female Frequent copulation and male/female bonds are core

It has been speculated that frequent sexual behavior serves to minimize stress between individuals