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Chapter 9: Early Hominins (Oldowan Tool Tradition (Cultural Processes…
Chapter 9: Early Hominins
Oldest African hominin fossils
Sahelanthropus tchadensis
7 mya Chad, West-central Africa
Hominoid (ape-like traits): small brain, elongated skull, sloping face, prominent brow ridges
Hominin (human-like traits): foramen magnum central, suggests partial bipedalism, small canine teeth, short mid face
Orrorin tugensis
~ 6 mya Kenya
Chimpanzee sized
Overrall humanlike appearance
Small teeth with thick enamel
Bipedal
Ardipithecus ramidus
~ 4.4 mya, Ehtiopia
Possible hominin common ancestor
Hominoid dentition: small cheek teeth, thin enamel, large canines
Hominin bodies: big toe, rigid foot, central foramen magnum, bipedal/arboreal
First Hominins
Great Rift Valley
Ethiopia, Kenya, Tanzania
4-3mya
First hominin groups (Genus): Ausrtalopithecines (Australopithecus), Paranthropoids (Paranthropus)
General Traits
Dentition: small canines , flat and thickly enamelled molars
Fully bipedal
Not completely terrestrial, partially arboreal
Australopithecines (5m to 2mya)
Variation, 6+ species
Diversity: adaptive radiation to dynamic environment
Volcanic eruptions and geological uplifting, forests giving way to grasslands and savannahs
Australopithecus anamensis
~4.2 mya Kenya
Small, bipedal hominin
Teeth similar to A. afarensis
Humanlike lower body(e.g. tibia)
Australopithecus afarensis
4-3 mya Laeotli, Tanzania, and Hadar, Ethiopia
Laetoli: 3.6 mya
Large number of individuals recovered (24+)
Clear evidence of bipedalism
Hadar, Ethiopia: 3.2 mya
"Lucy" 40% complete skeleton
Completely bipedal (hominin body), occasionally arboreal
Retained ape-like skull jaw & dentition
Australopithecus africanus
South Africa ~3.2 mya
1924: Taung child, 3.5 years old
Rounder cranium, larger brain
Smaller teeth (similar shape as humans)
S-shaped lumber curve, bipedal
Australopithecus sp.
Australopithecus Bahrelghazali
: 3mya Chad, first hominin recovered outside of Rift Valley
Australopithecus Garhi
: 2.5 mya, Ethiopia, Possible first tool use
Australopithecus Sediba
: 2 mya, South Africa, facial features, dentition & dedicated bipedalism as Homo
Paranthropoids
South Africa, East Africa 2.7-1mya
Body size similar to robust A.
africanus
, slightly larger brain(490-530cc)
Thicker jaws with larger molars, smaller incisors
Massive muscle attachments to jaws and skull, well developed sagittal crests to support heavy chewing
Paranthropus aethiopicus
Southern Ethiopia and Northern Kenya, 2.5mya
Similar to contemporary A .
africanus
, very robust in jaw size and dentition, faces were broad/dish shaped
Large sagittal crests for muscle attachments
Paranthropus robustus
Kromdraai Cave, South Africa, 1.8-1mya
Robust teeth and jaw, large cheek teeth, thick enamel, dish face
Likely vegetarian diet
Paranthropus boisei
2.3-1.2mya
Not ancestral to Homo sapiens
possibly associated with stone tools
Homo habilis and Homo Rudolfensis
Western Kenya, Tanzania, Ethiopia, South Africa
2.5-2.3mya
Homo habilis 'Handy man'
Larger brains 630-640cc
Reduced molars, premolars, thick enamel, omnivorous
body ~ to Australopithecines, still partially arboreal
Not sure if they made and used stone tools they were found with
Homo rudolfensis
Larger brain - 775cc, compared to H. habilis
larger premolars,/molars, longer face
Body ~ to Australopithecines, still partially arboreal
Handy man 2.0? also associated with tool use
Modelling Human Evolution
1) 2 separate hominin lines 3-1mya
2) Paranthropoids not ancestral to modern humans
Australopithecines ancestral to line leading to
Homo sapiens
3) Homo species direct line of ancestry to modern humans
Review: Trends in hominin evolution
Bipedalism
Habitual walking on two legs, spinal column centred on foramen magnum, s shaped spine(spring), bowl shaped pelvis (gravity), legs angled in at knee (forward stride), arch in the foot
1) Adaptation to life in savannahs
Climate change to dry temperate forests & grasslands
advantageous in tall grass, better vision
2) Adaptation for better dispersion of body heat
Cooling effect (Bergman's rule)
Thermoregulation of brain
3) Adaptation to free hands
Carry food, efficient foraging
Tool manufacture and use
Long distance travel
Enlarging the brain
Brain development after bipedalism, starting 2 mya
Selected for tool making, group living
Reduction of the face, teeth, jaws
Simultaneous with increased brain size
Result of eating softer/cooked foods
Other trends
Hairlessness
Larger brain advantageous but made birthing more dangerous
Increased dependency of infants
Social living improves survivability of young
Oldowan Tool Tradition
2.6-1.7 mya East Africa, percussion tools (stone on stone)
Terms: Hammer stone, cobble (piece to be made into tool); core(remaining piece once flake comes off); flakes(pieces of rock removed from cobble; expedient tool(what flake biomes); chopping tools(what core becomes)
Alternative to sharp teeth & claws: processing plants, skinning carcasses, cutting meat, smashing bone
Experimental Archaeology: interpret past behaviour by: archaeologically observing modern human behaviour, replicate ancient tools
Cultural Processes
Purpose made tools, accumulation of bones/stones
Tool cut marks; deliberate broken bones (v shaped)
Wear patterns on tool edges to infer function
Natural Processes
Crushing and gnaw marks by carnivore teeth(wide shallow grooves)
Naturally fractured rocks
Accumulations due to erosion/deposition processes
Olduvai Gorge
Oldest H. habilis encampments 1.8-1.6mya
Layers of smashed animal bone, stone tools & basalt cobbles
Functions: windbreak shelter, processing site, stockpile of throwing stones
CultureL a set of interrelated social processes, shared and learned by a group. Generally adaptive, ever-changing, integrative