How Humans Evolved Textbook Notes: Part 2 Primate Ecology and Behaviour Chapter 5, 6, 7, 8

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12 Apr 2012
Primate Ecology and Behaviour: Part 2
Chapter 5
Primate Diversity and Ecology: Two Reasons to Study Primates
Help us to understand human evolution:
o Closely related species tend to be similar morphologically (they share
traits of decent through a common ancestor)
Reasoning by homology
o Natural selection leads to similar organisms in similar environments
We can see how evolution shapes adaptation in response to
different selective pressures
Reasoning by analogy
Primates Are Our Closest Relatives
Because humans and other primates share many characteristics, other primates
provide valuable insights about early humans
Humans are closely related to nonhuman primates than to any other animal
Primates Are a Diverse Order
Diversity within the primate order helps us to understand how natural selection
shapes behaviour
Animals closely related to one another phylogenetically tend to be very similar in
morphology, physiology, life history and behaviour
Differences observed among closely related species are likely to represent
adaptive responses to specific ecological conditions
Similarities among more distantly related creatures living under similar ecological
conditions are likely to be the product of convergence
o Comparative method: used to explain the patterns of variation in
morphology and behaviour observed in nature
Sexual dimorphism: differences in male and female body size
**Features that Define Primates
1. Flexible movement of hands and feet
2. Nails as opposed to claws and sensitive tactile pads with “fingerprints” on fingers
and toes
3. Movement is hind-limb dominated
4. An unspecialized olfactory (smelling) apparatus that is reduced in diurnal
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5. Visual sense is highly developed, stereoscopic/binocular vision
6. Females have small litters
Longer pregnancies
7. Large brain compared to the brains of similarly sizes mammals
8. Unspecialized molars, maximum of two incisors, one canine and three premolars
and three molars on upper and lower jaw
Teeth used to process food
Used as weapons in conflicts with other animals
None of these traits make primates unique
Not every primate possesses these traits
Primate Diversity
The Strepsirrhines
Divided into two infraorders
o Lemuriformes
Only found on Madagascar and the Comoro Islands
Evolved in total isolation from other primates
Underwent adaptive radiation
Half are diurnal, others are nocturnal and some are active during
the day and night
Females dominate males
o Lorisiformes
Small, nocturnal, arboreal residents of the forest of Africa and Asia
Includes two sub-families with different types of locomotion and
activity patterns
Ex: Galagos, lorises
The Haplorrhines
Containes three infraorders
o Tarsiiformes
Includes tarsiers
Live in rain forests
Small, nocturnal, aboreal, move by vertical clinging or
Often more than one breeding female (not always pair-
Rely exclusively on animal matter, insects and vertebrate
o Platyrrhini (New World Monkeys)
Found in South and Central America
Divided into 5 separate families (Aotidae, Atelidae, Callitrichidae,
Cebidae and Pitheciidae)
Considerable diversity (size, diet, social organization)
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Most are quaddrupedal
o Catarrhini (Old World Monkeys)
Found in Africa and Asia
Marmosets and tamarins
Very small, claws instead of nails, two molars, often give
birth to twins, single breeding pairs
Others are often larger than marmosets and tamarins
Includes humans
New World monkeys have round nostrils, have 3 molars
Divided into 2 super-families (Cercopithecoidea, Hominoidea)
The super-family Cercopithecoidea encompasses great diversity in
social organization, ecological specializations and biogeography
The super-family Hominoidea includes two families of apes
o Hylobatidae
Gibbons (lesser apes)
Living members found in Asia
o Hominidae
Southeast Asian islands
Largest and most solitary species of all primates
Feed primarily on fruits and also some leaves and bark
Females do not often socialize with other orangutans
(except their young)
Males often spend time alone, but will defend a range that
contains several adult female
Males mate opportunistically with females
Largest of the apes
Mountain gorillas
o Eat herbs, vines, shrubs and bamboo
o Eat little fruit due to their habitat
o Males sometimes remain in their natal groups to
breed, but most draw females away from other
males during intergroup encounters
Lowland gorillas
o Eat much fruit due to their habitat
o Form less and larger cohesive social groups than
mountain gorillas
Researchers have found the study of chimps to be
important for hypthese about the behaviour of early
Research conducted in sites across Africa
Jane Goodall (1960s, Tanzania)
Female chimps leave natal groups when they have reached
sexual maturity while the males do not
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