Becoming Human Flashcards
Where is the fossil evidence found of the first hominins?
Great Rift Valley, East Africe
The first Hominins: Difference in the skull
- brain size, cranial proportions, reduction in bony crest
- facial size decrease
The first Hominins: Sahelanthropus tchadensis (aka chad)
- 5.2- 7 mya
- earliest pre-australopithecine
- brain size 350 cc
- massive browridge
- bipedal
- lived very near time of ape-human divergence
- lived in a forest near a lake
The first hominins: Orrorin tugenesis
- 6 mya
- lake Turkana, Kenya
- bipedal
- curved fingers
- apelike canines & premolars
- spent time in trees
- lived in forest
The first hominins: Ardipithecus kadabba
- 5.2-5.8 mya
- teeth intermediate between ape & human
- middle Awash Valley, Ethiopia
The first hominins: Ardipthecus ramidus (aka “Ardi)
- 4.4 mya
- Awash River Valley, Ethiopia
- lived in a forest
- hominin chewing complex, small canines
- tooth enamel intermediate
- opposable big toe
- part-time biped, part time quadruped
Ardi’s story
- female adult
- weighed 110 lbs
- 4 feet tall
- 300-350 cc brain size
- projecting face
- nonspecialized teeth (omnivore diet)
- primate arms & hands, legs & feet (did not knuckle walk)
* Long toes, divergent big toes - Hominin pelvis (walked bipedally on ground
-“the breakthrough of the year”
Australopithecus & kin
- 4.2- 1.0 mya
- “southern ape” (raymond Dart, 1920s)
- small bodied (30-45 kg)
- small brained (340-500 cc)
- moderately prognathic faces
- several species
- robust australopithecines had massive jaws and molars, strong chewing
Australopithecus anamensis
- 4.2- 3.9 mya
- most primitive australopithecine
- earliest incontrovertible evidence of bipedality in postcranial skeleton
- woodland enviroment
Australopithecus afarensis
- 3.9- 2.9 mya
- Awash valley, Ethiopia (Don Johansen, 1974)
- brain size 350-500 cc
- prognathic face
- funnel-shaped thorax
- arms longer relative to leg length
- arms not used for walking
- some level of arboreality
- biped with aboreal characteristics
- retreated to trees to escape predators, forage and sleep
- lived in woodlands
- likely lived in polygynous groups
- extreme sexual dimorphism
Lucy (Australopithecus Afarensis)
- both humanlike and apelike features
- 1 metre tall
- brain size of adult chimpanzee
- most complete fossil hominin skeleton
Dikka Baby (Australopithecus afarensis)
- 3.3 mya
- Awash Valley
- small brain
- apelike upper body
- biped lower body
- probably no speech
Australopithecus bahrelghazali
- 3.5-3.0 mya
- found in chad
- known from one single fossil, a mandible with 7 teeth
- proves that hominins lived in areas other than easten Africa
Kenyanthopus platyops
- 3.5 mya
- “the flat-faced hominin from kenya”
- flat faced
- small molars
- woodland habitat
- lived at same time as A. afarensis
Australopithecus garhi
- 2.5 mya
- small brain
- prognathic face
- large canines
- sagittal crest
- found in same beds as early stone tools
- ancestral to Homo?
- may have made & used stone tools
- oldawan tool complex
- earliest tool culture
- primitive tools
- used for butchering & other functions
Australopithecus africanus “Taung child”
“Taung child”
- type specimen
- found in Tuang limestone quarry near Johannesburg, 1924
- fossilized impression of interior of skull (endocast) revealed general appearance and size of brain
- apelike
- 2.3 years old
What is a type specimen
the anatomical reference specimen, the species definition
Australopithecus africanus
- 3.5- 2.4 mya
- short, broad iliac blade (pelvis)
- spine, leg, feet adapted to habitual bipedality
- 24- 40 kg
- lived in woodland enviroment
- may have evolved from A. afarensis that migrated south
- brain size 450- 550 cc
- no cranial crests
- less prognathic face
- flexed cranial base
- generalized teeth
- gracile
The robust Australopithecines (paranthropines)
- an evolutionary dead end?
- extreme specialization
- shared cranial features, sagittal crest, flared zygomatics (cheeks), smaller front teeth, large molars
Paranthropus aethiopicus
- 2.7- 2.5 mya
- “the black skull”
- Lake Turkana
- large sagittal crest
- flaring cheekbones
- prognathic face
Paranthropus boisei
- 2.3- 1.2 mya
- brain size 500 cc
- body size 34-50 kg
- strong chewing adaptations
- shape of nasal bones & brow-ridges like that of P. aethiopicus
Paranthropus Robustus
- 2.0- 1.5 mya
- Kromdraai, Swartkrans, Drimolen
- brain size 500-550 cc
- body size 30-40 kg
- animal protein in diet- termites?
Australopithecus sediba
- 2- 1.5 mya
- Malapa Cave, South Africa
- brain size 420 cc
- Small face, jaws, teeth
- pelvis like Homo
- long arms like australopithecines
Earliest evidence of stone tool use is an association of?
A. garhi and butchered animal remains 2.5 mya
Hand and thumb anatomy show what?
A capability for making stone tools.
Paranthropines are probably too specialized to be ancestral to Homo. An ancestor should:
- exist early enough to give rise to later groups
- not be more derived than those later groups
- have characteristics that look as if they could give rise to later groups
Evolution & Extinction of Australopithecines
- early evolutionary trend was to cranial robusticity & strong chewing musculature
- robust australopithecines (paranthropines) perhaps unable to adapt to changing vegetation & became extinct
- the lineage that led to Homo was perhaps more adaptable & survived
