chapter 5: primates. what is a primate? first, primates are members of the vertebrate class:...
TRANSCRIPT
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
Lemurs, Lorises, Tarsiers
Anthropoidea 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