Transcript Chapter 5: Primates

Chapter 5: Primates
What is a Primate?
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First, primates are members of the
vertebrate class: Mammalia
+ 4000 mammals
Primates are part of the subgroup of
placental mammals
Three types of primates
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Prosimians (pre-monkeys)
Monkeys (Old World and New World)
Apes
Common Mammal Traits
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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
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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
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Tendency towards erect posture
But, primates utilize a number of types of
locomotion
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Bipedal
Brachiation
Knuckle walkers
Fist walkers
Limb jumpers, etc.
Hands & Feet
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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
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Why are Human Feet different?
II. Diet & Teeth
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Lack of dietary specialization – most
primates are generalized feeders eating a
wide variety of foods
Therefore, primates have a generalized
dentition
III. Senses & Brain
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Vision enhanced
Olfaction reduced
Complex brain
Vision
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All primates rely heavily on vision
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Color vision in Diurnal primates.
Stereoscopic vision
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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
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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
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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
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Traditionally, the arboreal adaptation seen
as the primary factor in primate evolution
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Selected for 3-D and color vision (why?).
Grasping prehensile hands/feet to grasp
Tropical arboreal environment = varied foods
Visual Predation hypothesis
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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?
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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
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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?
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What’s so great about trees?
Diet & Teeth
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Omnivorous w/generalized dentition
Although some primates prefer some food
items over others, most eat a combo of
fruit, leaves, and insects.
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Some do eat meat (chimps & baboons)
Some are leaf specialists (Colobine monkey)
Teeth
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Most have 4 types of teeth
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Incisors and canines: biting and cutting
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Premolars and molars: crushing and grinding
Each Primate species has a specific
dental pattern
Locomotion
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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
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Vertical clinging & leaping (prosimians)
Brachiation (apes)
Semi-brachiation (combo leaping/brachiating)
Quadrapedalism
Bipedalism (us)
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Taxonomies organized from general to
more specific
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All primates grouped in the
Order of Primates
Two Suborders
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Prosimii
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Lemurs, Lorises, Tarsiers
Anthropoidea
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Monkeys, Apes, Humans
Purposes of Taxonomic classification
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To show evolutionary relationship
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Animals grouped together or close by more
closely related
Organize Diversity
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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
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SURVEY OF LIVING PRIMATES
Prosimians: Lemurs & Lorises
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Most primitive
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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
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Madagascar
Many different species
(diversified in absence
of competing
primates)
Became extinct in
other areas
Lemurs
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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
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Similar in appearance to Lemurs
Tropical habitats (Sri Lanka, India, SE Asia,
Africa)
Survived by adopting nocturnal habits
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Competition avoidance with monkeys
Lorises
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Slow, cautious climbing form of
quadrupedalism
Bushbabies active vertical climbers and
leapers
Almost entirely insectivorous
Diet supplemented with fruit, gum, leaves
L&L
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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
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Nocturnal
SE Asia
Mated pair & offspring
Diet: insects & small
vertebrates they catch by
leaping from branches
Tarsiers difficult to classify
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Prosimian traits:
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Small size
Grooming claws
Unfused mandible
Anthropoid traits
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Lack of Rhinarium (moist nose pad)
Orbits fully enclosed by bone
Anthropoids (monkeys, apes, H.s)
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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
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~ 70 % of all primates are monkeys
Two types:
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Old World or Catarrhini (downward-facing nose)
New World
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Callitrichidae
Cebidae
New World Monkeys
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Wide flaring noses with nostrils
that face outward
Almost exclusively arboreal
Prehensile tails
With one exception, diurnal
Two Groups:
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Callitrichidae
Cebidae
Callitrichids
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Small Marmosets and
Tamarins
Marmosets and Tamarins
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Most primitive monkeys
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Retain claws instead of nails (used like squirrels
to climb trees)
Twins rather than single births
Family groups
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Mated pair
2 males & 1 female
Males very much involved in infant care
Cebids
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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
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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.
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One family: Cercopithecidae
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Two subfamilies:
Cercopithecines and Colobines
Cercopithecines
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More generalized than Colobines
More omnivourous
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Cheek pouches to store food while foraging
Most found in Africa
Altho, a number of macaques are found in Asia
Colobines
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Leaf diet
Colobus monkey exclusive to Africa
Langurs found in Asia
Probiscus in Borneo
Old World monkeys
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Variety of locomotion
Guenons, macaques, langurs: arboreal
Baboons, patas, macaques: terrestrial
quadrupeds
Colobus: semibrachiation and leaping
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Significant sexual dimorphism, esp. in
terrestrial quadrupeds (baboons)
Females of several have genitalia that
changes according to reproductive cycle
Estrus– hormonally induced cycle
Homoplasy
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Evolutionary principle that explains
similarities between NW & OW monkeys
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Genetically distinct populations responding to
similar environmental pressures.
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NW & OW monkeys have been separated
for ~ 30 million years
But, derived from same African ancestors
Perhaps they “rafted”
Hominoids (apes & humans)
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Super-family includes:
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Less apes: gibbons and siamangs
Great apes: gorillas, orangutans, chimps
Humans (family Hominidae)
Hominoid traits
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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
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Tropical SE Asia
Extremely long arm limbs
Curved fingers
Reduced thumbs
Powerful shoulder muscles
Most efficient brachiator
Gibbons & Siamangs
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Monogamous pairs
Lack of sexual
dimorphism
Males share equally in
child care
Mated pairs are very
territorial
Orangutans
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Borneo & Sumatra
Almost completely arboreal
Solitary animals
Mainly frugivorous
Very large
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(males = 200 lbs, females = 100
lbs)
Gorillas
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Larges of living primate
Knuckle walkers
Exclusively vegetarianism
Marked sexual dimorphism
Males = 400 lbs, females 200 lbs.
Family group: Silverback male &
harem
Chimps
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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
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Large social groups of up to 50
Fluid membership
Males form the core of the community,
females leave, often during estrus
Bonobos
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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
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It has been speculated that frequent sexual
behavior serves to minimize stress
between individuals