Historical Geology 102
Hominid Evolution


Primates Characteristics

1) lack of specialization
2) skeletal structure
3) increased brain size vs. body size
4) stereoscopic vision
5) grasping hand with opposable thumb
6) smaller, fewer, less specialized teeth

Primates

Two suborders
Prosimians - shrews and lemurs
Anthropoids - monkeys, apes and humans

Order Suborder Superfamily Family Common Names
Primates Prosimii
Prosimians
Tupaidoidea Tree Shrew
Lemuroidea Lemur
Lorisoidea Bush Baby, Loris
Tarsioidea Tarsier
Anthropoides
Anthropoids
Ceboidea New World Monkeys
Cercopithecoidea Baboon, Macaque, Langur
Hominoidea
Hominoids
Hylobatidae Gibbon
Pongidae Gorilla, Chimpanzee, Orangutan
Hominidae
Hominids
Humans

Prosimians

Mouse- to cat-sized
Nocturnal, Arboreal (live in trees)
5 digits on all limbs
Large, forward looking eyes adapted for night vision
Descendants of the oldest primates
Only found in tropical regions of Asia, India, Africa and Madagascar

Anthropoids

Evolved in the late Eocene
3 Superfamiles within this Suborder - New World Monkeys - Old World Monkeys - Hominoids

New World Monkeys

Central and South America
Prehensile tail, flat faces, widely separated nostrils
Howler monkeys, spider monkeys and marmosets

Old World Monkeys

Asia and Africa
Close-set, downward directed nostrils, grasping hands, non-prehensile tail
Baboons

Hominoids

Evolved during the late Oligocene ~25 m.y.
3 Families
1) Great Apes - chimpanzees (skull-profile, skull-frontal), orangutans (skeleton), gorillas
2) Lesser Apes - gibbons (skeleton) and siamangs
3) Hominids (4 m.y. - present) - humans and their ancestors

Hominids

Differ from other hominoids
1) locomotion is bipedal - vs. quadrupeds and brachiates
2) brain size - larger than other hominoids
3) reduced face - more vertical profile
4) reduced canines
5) increased manual dexterity

Hominids

Traits shared with some hominoids
1) construction and use of tools
2) omnivores

Australopithecines

Oldest known hominids - four species

Australopithecus afarensis

Common ancestor of all later hominids - 4.0 to 2.75 m.y. - 1.2 m tall, bipedal, strong sexual dimorphism, ape-like features, massive brow ridges, low forehead, forward jutting jaw
Brain capacity - 380-450 cc - 10-20% larger than modern chimps - 30-35% of modern hominids

Australopithecus africanus

3.0 to 1.6 m.y.
Minor differences from afarensis
1.4 m tall, slightly flatter face
Brain capacity - 400-600 cc

Australopithecus robustus

2.3 to 1.3 m.y.
1.5 m tall, massive skull with flat face,strong jaw with broad, flat molars
Sagital crest - provides stronger attachment for jaw muscles
Brain capacity - 500-600 cc

Australopithecus boisei

2.5 to 1.2 m.y.
Similar to robustus but even larger features

Skull - profile view
Skull - frontal view

Genus Homo

Four species

Homo habilis

- 3.0 to 1.4 m.y.
- earliest known Homo genus
- similar to Australopithecines
- brain capacity - 700 cc

Homo erectus

- 1.8 m.y. to 300,000 yrs.
- prominent brow ridges
- brain capacity - 1,100 cc
- Africa, Europe, India, China and Indonesia
- constructed and used handaxes, flakes, scrapers
- believed to have used fire

Skull - profile view
Skull - frontal view

Homo sapien

- 300,000 yrs. to present
- higher, rounder cranium, smaller teeth and jaw
- brain capacity - 1,300 cc
Two subspecies
- Homo sapien sapien - modern man
- Homo sapien neanderthalensis

Skull - profile view
Skull - frontal view

Homo neanderthalensis

Regarded by some as a separate species
- Homo neanderthalensis
150,000 to 32,000 yrs.
- Europe and Near East
Skull differs from Homo sapien sapien: lower forehead; prominent, heavy brow ridges; weak chin.
Body tends to be more massive and more heavily muscled with shorter limbs.
Lived in caves in Europe
Made highly specialized tools of stone and bone
Buried their dead in ritual burials

Skull - profile view
Skull - frontal view

Human Ancestry

1) cyanobacteria evolve 3.8-3.6 b.y.
2) metazoans evolve 1.8-.9 b.y
3) fish evolve (agnathids) L. Cambrian
4) amphibians evolve Devonian
5) reptiles evolve Pennsylvanian
6) therapsids evolve Permian
7) mammals evolve Triassic
8) placental mammals evolve Cretaceous
9) primates evolve Paleocene
10) anthropoids evolve late Eocene
11) Australopithecus evolves Miocene - Pliocene
12) Homo habilis evolves Pliocene
13) Homo erectus evolves Pliocene - Pleistocene
14) Homo sapien evolves Pleistocene

Additional Reading in This Topic