Anthro 101: Human Biological Evolution Lecture 3 & 4: Primate Adaptations & Comparative Anatomy

Classifying species into taxa

•  Linnaeus

u  physical similarity

u  Genus species, e.g. Homo sapiens

•  Darwin

u  similarity due to common descent VERTEBRATES

Birds Mammals

Sparrow Flamingo Lion Squirrel

Felis

Felis catus

Where do we fit in? Homo sapiens •  Kingdom: Animal •  Phylum: Chordata •  Class: Mammalia •  Order: Primates

•  Suborder: Anthropoidea •  Infraorder: Catarrhini •  Superfamily: Hominoidea •  Family: Hominidae •  Subfamily: Homininae •  Tribe: Hominini •  Genus: Homo •  Species: Homo sapiens

What is a primate?

Which of these animals are primates?

Galago

Tarsier

Possum

Loris

Which of these animals are primates?

Coati

Lemur

Red Panda

Sifaka

Some primates are easier to recognize

Gorilla

Capuchin

Rhesus

Primates are a diverse order

Basic primate phylogeny (relationships)

Lemurs, lorises Tarsiers

Prosimii Anthropoidea New World Monkeys Old World

Monkeys Apes & humans

Haplorhines

Strepsirrhines

Primates

(Hominoidea) Platyrhines

Cataryhines

Phylogeny for apes: Hominoidea

Gorillinae Panini

Bonobo

Chimpanzee

Gorilla Orangutan Gibbon

What makes an animal a primate?

•  Features of hand & feet u  Grasping big toe u  Grasping hands

¨  Some opposable thumbs u  Sensitive finger tips

¨  Finger prints! u  Flat nails u  Generalized limb structure

What makes an animal a primate? Features of the sensory organs - Vision

•  Forward facing eyes ¨  Binocular vision

•  Stereoscopic vision u  Information sent to both

hemispheres of brain •  Depth perception

•  Color vision

•  Limited olfactory senses (except prosimians)

Pygmy marmoset

Golden monkey

Binocular Vision

Stereoscopic Vision

What makes an animal a primate?

Features of life history •  K-selected

u  Large maternal investment in care

•  Small litters •  Long pregnancy •  Long infancy •  Long juvenile period

•  Long mother-infant bond

•  Long life span •  Long reproductive period Savanna baboon

What makes an animal a primate? Features of the teeth Generalized teeth, four kinds, many functions

Comparison:

•  Enclosed bony eye sockets

What makes an animal a primate? Features of the skull

•  Comparison: cat skull

What makes an animal a primate?

Large brain relative to body size & an emphasis on learning

Sociality Sociality

Figure 05.05

Primates are mainly restricted to the tropics

But, monkeys have also adapted to wide range of habitats

Primary tropical forest

Secondary forest

Desert

Temperate forests

What are these adaptations for?

1.  Arboreal Hypothesis u  Stereoscopic vision u  Grasping hands u  Nails = adapted for life in the

trees But squirrels do pretty

well without thumbs…

galago

What are these adaptations for?

2.  Visual Predation Hypothesis u  Analogy with insectivores u  Stalk and capture insects u  Depth perception u  Grasping hands = adapted to catch fast moving prey

What are these adaptations good for?

3.  Angiosperm Radiation hypothesis •  Adapted to eat flowering plants

•  Color vision •  Fine visual & tactile

discrimination

RECAP QUIZ

Question

•  What characterizes primates?

•  A prize for the person who can accurately name the most traits!!!!

Basic primate phylogeny (relationships)

Lemurs, lorises Tarsiers

Prosimii Anthropoidea New World Monkeys Old World

Monkeys Apes & humans

Haplorhines

Strepsirrhines

Primates

(Hominoidea) Platyrhines

Cataryhines

Prosimians are the most primitive primates (Strepsirhines)

The most different from us •  Many are nocturnal •  Many are solitary •  Some w/ claws instead of nails •  Some w/ acute sense of smell

u  Rhinarium u  Scent marking

Two types: Lorises Lemurs

Potto (Loris)

Bush Baby (Loris)

Prosimians divided into two groups: Lemurs

•  Only on Madagascar •  No competition from other

primates •  No large predators on island,

until humans 1500 ya •  Many different species

sifaka

dwarf lemur

avahi aye aye

Haplorhines: Monkeys, Apes, Tarsiers

Most of the primate adaptations •  Vision > Olfaction •  Eyes surrounded by bone •  Fused midline of lower jaw •  Diurnal

u  Except Tarsiers u  Except Owl monkey

•  Social u  Except Orangutan

•  Larger brain Red faced spider monkey

Tarsier: Prosimian & Haplorhine •  Mixture of anthropoid &

prosimian traits •  Dry nose •  Partially closed eye socket

•  Nocturnal

•  Only carnivorous primate •  Eat insects and small

vertebrates

Anthropoids: monkeys & apes

New World monkeys (Platyrrhini) •  Latin America •  Diurnal •  Arboreal •  Tropical forests

•  Dental formula (I.C.P.M.) 2.1.3.3

2.1.3.3

Anthropoids: monkeys & apes Old World monkeys & apes

(Catarrhini) •  Africa & Asia •  All diurnal •  Some arboreal, some

terrestrial •  Broad habitat range •  Ischial callosities •  Sexual skin •  Dental formula

2.1.2.3 2.1.2.3

Barbary Macaque © Karyn Sig

Spectacled langur Black and white colobus

Phylogeny for apes: Hominoidea

Gorillinae Panini

Bonobo

Chimpanzee

Gorilla Orangutan Gibbon

Apes: Hominoidea •  Bigger brains •  Extended life-history •  Complex social

interactions •  Large body size •  No tails •  Suspensory

locomotion

•  Hylobatidae (lesser apes) u  Gibbons & Siamangs

•  Ponginae (orangutans) •  Gorillinae (gorillas) •  Homininae

u  Panini (chimps & bonobos) u  Hominini (Humans)

RECAP QUIZ

Question: Match the traits with the taxonomic groups – a trait may belong to more than one group

1.  Strepsirrhines 2.  Platyrrhines 3.  Catarrhine Monkeys 4.  Hominoidea

a.  Color vision b.  Extended life history c.  Scent marking d.  Opposable thumb e.  Dental comb f.  No tail g.  Rhinarium

COMPARATIVE ANATOMY: LOCOMOTION

Forms of Locomotion •  Vertical Clinging & Leaping •  Arboreal Quadrupedalism

u  Use of prehensile tail in some species

•  Terrestrial Quadrupedalism •  Brachiation •  Knuckle walking •  Bipedalism

Horse Skeleton - specialized

Primate Skeleton - generalized

Colobus Monkey

In Class Activity

•  Skeletal features to note: u  Body position (upright (orthograde) or horizontal

(pronograde) u  Length & shape of trunk (torso – barrel or wide and

flat) u  Position of shoulder blade (scapula – side or back) u  Spine shape (C or S shaped) u  Limb length (arms vs. legs) u  Finger length (fingers, thumbs) u  Length of tail

Intermembral Index •  humerus + radius x 100

femur + tibia •  hindlimbs vs. forelimb

u  longer in the part that does the most work

•  Bipeds & vertical clinging and leaping u  hindlimb longer than forelimb

•  Quadrupeds u  Approx equal lengths

•  Brachiators u  forelimbs longer than hindlimbs

Vertical clinging and leaping - prosimians

•  Vertical body u  Orthograde

•  Push off branch with hindlimbs •  Turn midair and land vertically

again

•  Bush babies •  Sifakas •  Lemurs

Sifaka

Arboreal quadrupeds – monkeys •  Arboreal - run & leap •  Walk on palms on top of branches •  Push off with hindlimbs •  Stabilize with tail (long) •  Pronograde (horizontal) posture •  Longer fingers & toes to grab branch •  Approx. equal limb length •  Prehensile tails in NWM •  No terrestrial species in NWM

Owl Monkey

Squirrel Monkey Diana Monkey

Arboreal Quadrupeds

•  New World u  Hands + prehensile tail

•  Old World u  Hands, no tail use

Terrestrial quadrupeds - Old world monkeys •  Lots of time on ground, but also in trees •  Pronograde (horizontal) posture •  Walks on palm/toes (shorter digits) •  Rarely hang full weight from arms •  Scapula on sides of body (plane of motion,

shoulder rotation limited) •  Shorter tail – not balancing

baboon

Mandrill © Robert Young

Brachiation - gibbons •  Shoulder blade on the back

rather than top of torso u  Full range of arm motion

•  Long, curved fingers •  Small thumbs •  Long arms •  No tail

Siamang

Knuckle-walking - chimps & gorillas •  Great apes too large to brachiate frequently

u  Still use upper body and arms, suspend body when they do

•  Stronger wrists bones than brachiators in order to support weight on arms

•  Brachiating ancestors u  Longer arms u  Longer fingers u  No tail u  Scapula on back

Chimpanzee

Hominoids: Homininae: Hominini Bipedalism

•  Unique to humans (hominins)

•  Modifications to: u  Pelvis u  Knees & legs u  Feet

Changes in the pelvis narrowly center our weight

Human pelvis is a bowl

u  Maintains the center of gravity over one foot while walking

Chimp pelvis is longer and narrower

•  “S-shaped” curves in spinal column keep trunk centered over pelvis

•  Lumbar curve

•  C-shaped curve in chimps more

Changes in the spine center our weight over the pelvis

To walk efficiently, knees must be close to center line of body

•  Femur slants inward from wide pelvis u  Centers weight for balance

•  Longer leg bones u  Increased stride

chimp human

•  Arched foot u  “spring”-like shock

absorbers u  Heel-toe stride

•  Loss of opposable toe

•  Stiff foot makes better platform

Bipedality also causes changes in the feet

Changes in the skull: Foramen magnum

•  Hole in skull where spinal cord and brain connect •  Position indicates body posture •  Human skull is balanced on tops

COMPARATIVE ANATOMY: HANDS AND SKULLS

Comparative anatomy of manipulation

•  Apes long curved fingers & short thumb

•  Humans shorter fingers & longer thumb u  precision grip

Human hand

Brain Size

Lemur

Howler monkey (NWM) à

OWM

Features of the skull

Prognathism Enclosed eye Orbits Canine size

Features of the skull Sagittal crest Flared zygomatic arches

Postorbital constriction Sexual dimorphism

Male and female gorilla

RECAP QUIZ

Question

•  Which of these are characteristic of humans but not other primates? (you may choose more than 1) a.  Long fingers & short thumb b.  Large projecting canines c.  Largest brain d.  Bowl shaped pelvis e.  Long tails f.  Pronograde

Next Time …

•  Topic: Primate Behavior

•  Read articles: u  Primate Sociality and Social Systems u  Primate Cognition