About Primates

Defining the genus Primates

LeGros Clark

Arboreal adaptation
Dietary plasticity
Increased parental investment

Specific trait

Emphasis on vision over scent
Unspecialized skeleton
Nails, not claws; tactile pads on digits
Grasping hands and feet; opposable first digits
Postorbital closure or bar
Larger brain for body size
Dental reduction
Prolonged gestation & life span

r/K selection

For most primates: live in social groups
Dietary plasticity

Taxonomy

Anatomical: classic, Linnean-based

Anatomical & adaptive/ecologicalcharacteristics basis for distinguishing taxa

Cladistic: taxa defined by genetic divergence

Consequences: example –chimpanzees more closely related to humans than the other apes. Differs from the anatomical/ecological model where apes are grouped together.

Key terms

Derived vs. primitive
Homologous vs. analogous
Hominoid vs. hominid
Locomotor categories

Bipedalism
Quadrapedalism
Knuckle walking (difference between chimpanzees and gorillas)
Brachiation
Vertical clinging and leaping

Anatomical classification

Primates

Prosimians

Tarsiers are a special case!

Anthropoids

Platyrrhini
Catarrhini

Cercopithecoidea
Hominoidea

Early Primates

Geologic time

Eons -- Eras -- Periods -- Epochs
Precambrian Eon:4.6 BYA-545 MYA

Origin of life –both single and multi-cellular

Phanerozoic Eon: 545 MYA –present

3 geological eras

Paleozoic –545-245 MYA
Mesozoic –245-65 MYA
Cenozoic –65 MYA –present

Opportunities for mammals

K-T mass extinction/boundary
Continental drift changing environments

Cenozoic era

“Age of mammals”
Mammals replace reptiles as dominant land form
Epochs of the Cenozoic era

Paleocene 65 mya
Eocene 55 mya
Oligocene 34 mya
Miocene 23 mya
Pliocene 5 mya
Pleistocene 1.8 mya
Holocene 0.01 mya

Primate origins

Models of primate origins

Arboreal model
Visual predation hypothesis
Angiosperm radiation hypothesis

Primates and geological time

Paleocene epoch (65-55 MYA)–plesiadapiformes
Eocene epoch(55-34 MYA)–prosimian radiation

Adapoids vs. Omomyids

Oligocene epoch (34-24 MYA)–anthropoid radiation (monkeys)

ayum, Egypt

Parapithecidae & Propliopithecidae
Aegyptopithecus
Transition to diurnal living

Evolution of New World monkeys –Branisella
How did platyrrhines get to South America?
First clear catarrhine species –Victoriapithecus

Miocene epoch(24-5 MYA) –Hominoid radiation (apes)

“Planet of the apes!”
What characteristics would help you recognize a fossil ape?
Proconsul–1stape genus, quite diverse, “dental apes”
Important genera: Dryopithecus, Gigantopithecus, Sivapithecus, Khoratpithecus

Taphonomy and Dating

Fossils and fossilization

Fossil: remains transformed into ‘rock’

Calcium replaced with hard minerals like iron andsilica

Taphonomy: deposition of plant/animal remains and the environmental conditions affecting preservation

Fossilization is rare
Requires an oxygen free environment
Many concerns: immediate burial necessary

Sampling

Species abundance as a concern

Common taxa are most represented
To identify rare species, need large samples
How well are we identifying rare species?

FAD and LAD

Example: Presence of hominids in the African fossil record

Dating methods

Relative dating: establishes age based on comparison(s) t other sites/formations

Stratigraphic correlation
Flourine dating

Only works with data at a specific site that has been tested

Biostratigraphy

Requires prior absolute dating of a species’morphology
Index fossils
Examples: Suid dentition, Irish Elk

Cultural dating

Example: stone tools

Absolute dating: provides a chronological age

Dendrochronology: requires a series of templates
Radiocarbon dating

Organic materials
40 kya –1500 AD
Incorporation of 14C into plant tissues that are consumed by animals
Decay of 14C into 12C is measured

otassium-Argon dating

Inorganic materials –Example:Volcanic rock
2 billion+ –100kya
Following volcanic eruption, argon is released. Upon cooling, potassium is sealed in the rock. Decay is measured accordingly.

Paleomagnetic dating: Shifts in the earth’s magnetic fields are recorded in igneous rock

Early Hominids

Defining hominids

Important traits in the early fossil record

Bipedalism
Non-honing canine complex
Thicker dental enamel

Later important traits

Brain expansion
Culture

Origins of bipedalism

Recognizing bipedalism

Pelvis
Limb proportions = Intermembral index
Knees
Feet –example of how the “Burtele foot” changes our ideas of the origins of bipedalism
Bicondylar angle of the femur
osition of the Foramen magnumo
"S” shaped curve in the spinal column

Differences existed in bipedal ability

Occasional
Habitual
Obligatory

Hypotheses for the origins of bipedality

Darwin’s tool use
Patchy forest
Scavenging
Carrying
Male provision
Temperature regulation

Early hominid evolution

Variability selection hypothesis –tie in with climate fluctuation and key adaptive events in hominid evolution like bipedalism and encephalization

Gracile Australopithecines

Sahelanthropus tchadensis

7-6 mya
Found in Chad
Characteristics:

No diastema
Anterior foramen magnum
Cranial Campacity: 350 cc
Thin enamel
No honing complex

Orrorin tugenensis

6 mya
Found in Tugen Hills, Kenya
Characteristics

Femoral neck and postcrania indicate bipedality

Ardipithecus ramidus

4.4 mya
Found in Middle Awash, Ethiopia
Characteristics

Pirmative hominoid
Long upper limbs
Abducted big toe
Samll canines
No diastema
Foramen magnum location

Australopithecus afarensis

3.9-2.8 mya
Found in East Africa
Famous fossil Lucy!
Characteristics:

High sexual dimorphism
Nonhoning complex
Reduced canines
Pelvis and post crania are adapted for bipedalism but retains aboreal features
Think enamel
Medium molars

Kenyanthropus playop

3.5 mya
Found in Lake Turkana, Kenya
Characteristics:

Cranial Capacity: 450cc
Flat face
Emphasis on masticatium

Australopithecus africanus

3.3-2.5 mya
Found in South Africa
Charcteristics:

Cranial Capacity: 461cc
Higher forehead
Less pronounced brow ridge
Small canines
Large molars
Bipedal

Australopithecus garhi

2.5 mya
Found in Bouri Ethiopia
Oldowan tools found neeaby
Characteristics:

Cranial Capacity: 450cc
Longer arms than legs
Strong subnasal prognathism
Large cheek teeth
Small sagittal crest
Hominid modification of bovid bones
Possibly bipedal

Robust Australopithecines

Parathropus aethiopicus

2.7-2.3 mya
Found in Lake Turkana, Kenya
Characteristics:

Cranial Capacity: 410cc
Sagittal crest
Flat face
Large postcanine dentition

Paranthropus boiser

2.3-2.1 mya
Found in Olduvai Gorge Tanzia, Koobi Fora Ethiopia
Characteristics:

Cranial Capacity: 530cc
Sagittal crest
Large mandible
Flat face

Paranthropus robustus

1.7-1.2 mya
Found in South Africa
Charcteristics:

Sagittal crest
Large molars
Concave midface
Squared orbits
Bipedal
High sexual dimorphism

Early Homo

Homo habilis

2.5-1.6 mya
Found in Tanzania, Kenya, Ethiopia, Malawi, South Africa
Stone tools (oldowan) were found to be used, butchered animals
Characteristics:

Cranical Capacity: 650cc
Similar body plan as australopithecines
Increased brain size
Reduced dentition and face size
Precision Grip

Homo erectus

1.6 mya -100 kya
Diverged from H. Ergaster around 1.6 may and spread throughout Africa
Evolutionary dead end but related to genus homo
Charcteristics:

Cranial Capacity: 1000cc
Large brow ridge with sulcus
Think skull bones
Teeth similar to ours

Homo heidelbergensis

600-400 kya
Characteristics:

Cranial Capacity: 1280cc
Smaller postorbital
Rounder occipital and forehead
Smaller teeth and jaw
Tool use

Homo neandertalensis

75-30 kya
Found in the Middle East and Europe
Lived in cave and efficient hunters
Complex tools, cultural lifestyle, and burials
Charcteristics:

Large superorbital ridge
Round orbits
Rounded zygomatic arches
Broad nasal aperture
Vertical mandibular symphysis
Large limbs

Homo floresiensis

60-18 kya
Found in the Island of Flores
Charcteristics:

Cranial Capacity: 380cc
1m tall
Used tools for butchery
Island swarfism for isolation

AMHS

100-35 kya
Charcteristics:

Cranial Capacity: 1200-1700
Vertical forehead
Small super orbital ridge
Angular orbits
Squared off zygomatic arches
Chin
Smaller teeth and jaw

Proconsul

Sahelanthropus tchadensis

Australopithecus afarensis

Australopithecus africanus

Paranthropus aethiopicus

Paranthropus boisei

Paranthropus robustus

Homo habilis

Homo erectus

Homo heidelbergensis

Homo neanderthalensis

Homo floresiensis

Anatomically Modern Homo sapien (Cro Magnon)