Early Eocene

(~56-34mya)

• Early radiation of small arboreal primates
• Common across North America, Asia, Europe, and Africa
• Discovery of Darwinius "IDA", from Messel site in Germany, dates 47 mya

Late Eocene

• Abrupt cooling and drying trend
• Isolation of N. America and Eurasia and extinction of N. American primates
• Lowering sea levels and formation of ice caps, reduced available habitatsMost surviving primates lived in tropical zones
  

Oligocene Anthropoids

(34-23mya)

• From Fayum (fossilbed), Egypt
• Two anthropoid types:
• Monkey-like
• Ape-like
• Aegyptopithecus: possessed a mosaic of features (monkey-like skull and body; ape-like dentition); possible ancestor of later hominoids 2-1-2-3 dentition

The Oligocene

• Major ecological change
• The great rift valley of E. Africa is a 1200 mile long volcanically active fault zone between large tectonic plates
• India crashed into Asia and began forcing up the Himalayas and the Tibetan Plateau

The Miocene 

(23-5 mya)

• Early Miocene: Proconsul
• Miocene Hominoid radiation: During the early Miocene the African and Eurasian landmasses collided
1. Resulted in volcanos, earthquakes, changing climates, and migrations
2. Hundereds od new species evolved throughout Africa & Eurasia

Proconsul

(21-17mya)

• Early Miocene hominoid, found in sites in Kenya, East Africa, possible LCA of extinct and extant apes
• Possible ape ancestor

Aegyptopithecus

• Possessed a mosaic of features (monkey-like skull and body; ape-like dentition); possible ancestor of later hominoids
• 2-1-2-3 dentition
• From the Oligocene era found in Fayum, Egypt
• 34-23 mya

Sivapithecus

(12-7mya)

• Looks a lot like modern Orangutan
• Miocene ape
• Found in the foothills of the Himalayas

Gigantopithecus

(6m-300kya)

• Miocene Ape
• Found in China, India, Vietnam
• ~10ft tall and weighed as much as 1200 pounds
• Was probably a quadruped and a herbivore, existing on a diet primarily of bamboo, possibly supplemented with seasonal fruits

Molecular Clock Hypothesis

A hypothesis that dates of divergences among related species can be calculated through examination of the genetic mutations that accrued since the divergence

Late Miocene Evolution

• 8-10mya, choroapithecus (possible gorilla ancestor) diverged from the rest of the miocene apes
• 5-8mya, human ancestors diverged from ancestors of modern chimps and bonobos

Miocene Ape Descendants

Gorilla, Orangutan, Bonobo, Chimp

1. Habitual bipedalism
2. Reduced dentition and jaw musculature
3. Larger brains
4. Slow development, long juvenile period
5. Elaborate culture, spoken language

Anatomical Adaptions for Bipedalism

1. Anteriorly placed foramen magnum (hole at the base of the skull)
2. A short bowl-shaped pelvis
3. Lumbar curve in spine
4. Elongated legs
5. Arch in foot (longitudina) shock absorber
6. Big toe in-line (non-grasping) 4myo

Drawbacks to Bipedalism

• significantly slower
• leg or foot injury seriously hinders a biped
• bad balance
• organs exposed
• makes an animal more visible to predators
• Interferes with the ability to change direction
• Frequent lower back problems

• Use of hands for tools, offspring, food, etc.
• Habitat variability- cooler, dryer, open woodlands (Savannah hypothesis)
• Further sight distance over tall grasses
• Energy efficiency- able to travel longer distances (movie promotes this hypothesis)
• Body temperature- thermoregulation- keeps brain from overheating
• Allowed early himinins to brandish and throw objects at attackers

Sahelanthropus tchadensis

(6-7mya)

• Discovered in 2002, southern Sahara Desert, Chad
• Modern: flat faced, u-shaped dental arcade, small canines, anterior foramen magnum
• Ancient: heavy brow ridges, small brained
• No post-cranial remains
• Thought to be the oldest biped

Orrorrin tugenensis

(~6mya)

• Found in Tugen Hills, Kenya E. Africa
• Second oldest 'potential' hominin species
• Cranial features: gracile teeth
• Post cranial: bipedal, size of modern chimp
• 5 individuals represented

Ardipithecus ramidus

(4.4mya)

• "Ardi"
• Discovered in Ethiopia E. Africa
• Cranial traits: prognathic face, dentition transitional from apes and australopithecines, small brain
• Post cranial traits: grasping big toe (arboreal trait), bipedal
• Inhabited Forested environment- defeated savannah hypothesis

Ardipithecus kadabba

(5.8-5.2mya)

Australopithecines

Hominid genus as a whole (4.2-1mya)

• Found only in Africa

Australopithecine Sites?

• *East Africa- great rift valley
• South Africa
• Chad

Gracile Australopithecines

• A. anamensis- Kenya (3.9-4.2 mya)
• A. afarensis (lucy)- Ethiopia, Tanzania, Kenya (2.9-3.9mya)
• A. africanus- South Africa (2.3-3mya)
• Thought to be the best candidate for ancestor of genus homo
• no sagittal crest

Robust Australopithecines

• Often referred to as genus Paranthropus (splitters)
• 3 species
• A. boisei- Kenya
  
• A. robustus- S. Africa
• A. aethiopicus- Kenya
• Younger than gracile Australopithecines, so might descend from them
• Known for the rugged nature of their chewing apparatus (large back teeth, large chewing muscles, and bony ridge on their skull tops for the insertion of these large muscles)

A. anamensis

(4.2-3.9mya)

E. Africa (Kenya and Ethiopia)

• Oldest Australopithecine
• Cranial features- prognathic face, thick enamel on molars, sectorial premolars
• Bipedal, with climbing capabilities
• Gracile

A. afarensis

(2.9-3.9mya)

Ethiopia, Kenya, Tanzania 

• "Lucy" and "Selam"
• Laetoli footprints: deposited in volcanic ash; discovered by Mary Leaky
• Gracile
• Sexually dimorphic
• Cranial features: low sloping forehead, large canines in males, thick tooth enamel, prognathic face
• Bipedal, with climbing capabilities

A. africanus

(3-2.3mya)

S. Africa 

• First Australopithecine ever discovered by Raymond Dart
• Gracile
• Cranial features: prognathic face, smaller front teeth, parabolic dental arcade
• Bipedal, with climbing capabilities
• 3.8-4.5 ft tall

A. boisei

(2.3-1.2 mya)

Olduvai Gorge, Tanzania by Leaky's in 1959

• Very robust
• Cranial features: Sagittal crest, dished face, large teeth chewing apparatus
• 4.1-5ft tall, bepidal 

A. aethiopicus

(~2.5mya)

Kenya

• By far the most prognathic, most robust sagittal crest, megadontia (oversized teeth), Teeth used for processing food- no tools
• The 'Black' skull- minerals in soil made discoloration
• 410-530 cc skull

Kenyanthropus platyops

(3.5-3.2mya)

Kenya

• Cranial features: broad flat face, smaller teeth than most australopithecines, brain size similar, lack of prognathism (like sahelanthropus) may indicate its close relation to genus homo
• may be another astralopithecine

Homo habilis

• Smaller teeth that Australopithecines
• Thinner cranial bones
• Expanded brain case (500-750cc)
• Short stature (3.5-4ft tall)
• Splitters would call the more robust ones Rudalphensis

• Some populations of early hominins began making tools, making bigger brains

1. to butcher animals for their meat
2. Earliest tools date to about 2.6mya

• Expansion of the human brain coincides with tools and incorporating meat into their diet
• Genus homo- evolutionary offshoot of Australopithecus

Genus homo

(2.5-1.6mya)

• Fossils have been found since 1960 in E. Africa (Ethiopia, Kenya, Tanzania) and S. Africa
• Splitters add Homo rudolphensis species (more robust) may be sexual dimorphism
• Post cranial- skeleton of Homo habilis differs little from Australopithecus (small bodies, but skull shows increase in brain size) 
• Modern feet (small)
• Made first stone tools (oldowan tool), scavenged meat

Oldowan Tool Culture

• Oldest tool culture
• First known tools (~2.6 my)
• Recovered from Lake Turkana Kenya, Olduvai Gorge, Tanzania, and the Hadar region of Ethiopia by Leaky's
• First found using percussion method
• Flakes, scrapers, choppers

Percussion Method

• By 2.5mya, early Homo in Africa invented percussion method of stone tool manufacture
• Not hunters, tools to scavenge meat from already dead things

Carbon14 Half-life

5730 years

(Accurate to about 50 thousand years before present)

Potassium40 Half-life

1.3 billion years

(Useful in sites older than 200k years before present)

Ancestral Characteristics

Derived Characteristics

Characteristics that define a group of organisms and that did not exist in ancestral populations

• Humans- small dentition, habitual bipedalism, increased brain size, lack of body hair, chin (mental)

Relative Dating

&

Stratigraphy

• Relative Dating- determines the age of objects relative to one another (older than or younger than)
• Stratigraphy- strata or layers in relative position of one another

Chronometric Dating

Determines the absolute age of an object in units of time

• Use of Radiocarbon and Potassium Argon analysis