Ancient hominid fossils not accepted as ancestors Biases in fossil record from 19 th century Fossil remains of species not that old Homo erectus amp Neanderthal Found in Asia and Europe ID: 544133
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Slide1
Hominid Evolution in Context
Ancient hominid fossils not accepted as ancestors
Biases in fossil record (from 19
th
century):
Fossil remains of species not that old (Homo erectus & Neanderthal)
Found in Asia and Europe
Had relatively large brains
Cultural biases:
Big brains, intelligence emphasized
Resistance to ancestors with primitive features
Resistance to Africa as cradle of humankind
Humans viewed as unique (culturally & biologically)Slide2
Hominid Evolution in Context
Occurs in a series of
ADAPTIVE RADIATIONS
The evolution & spreading out of related species into new environmental niches
What “ingredients” are needed for natural selection/evolution to work?Slide3
Will the Earliest Hominid Please Stand Up?
Earliest representatives of our lineage lived at end of Miocene & beginning of Pliocene epoch
6 – 4.5
myaSlide4
Geological Context of Hominid Sites
East African Sites
Volcanic ash/sediments
Can be dated by Argon/Argon (chronometric) dating, relative dating techniques (stratigraphy) &
paleomagnetism
South African Sites
Mostly limestone (no volcanic sediments)
Cave sites with bone accumulations
Dated with biostratigraphy &
paleomagnetismSlide5
First Adaptive Radiation
L
ate Miocene (6-7
mya
)
Produces potential/possible LAST COMMON ANCESTORS These are the earliest (possible) Hominids
Forest adaptedSlide6
Sahelanthropus
tchadensis
Found in central Africa, country of Chad
7
myo
Nearly complete cranium
Mix of human & ape-like traits
Small braincase: 370-380 cc
Massively built, heavy browridges, crest in back, large muscle attachmentsReduced upper canineSmall, vertical faceCannot determine bipedality
OLDEST possible hominidCommon ancestor?Slide7
Orrorin
tugenensis
aka
“
Millenium Man”
Discovered: 2001 in western Kenya
Age range: 6
mya
Remains: Fragmentary arm & thigh bones; lower jaws & teethFeatures: Limb bones larger than later hominid speciesCranial capacity: Not yet determinedSlide8
Orrorin tugenensis
, cont.
Notes: Some evidence of
bipedality
& tree climbing; dental & some skeletal features more human than ape like
Significance: More evidence that bipedalism may have originated in the trees Slide9
Second Adaptive Radiation
Early Pliocene (4-5
mya
)
New species & new genus evolves
Dense forest environmentAll exhibit bipedalism – established hominidsRepresent a challenge to the established “Savanna Hypothesis”Slide10
Ardipithecus ramidus
Discovered: 1994 in Ethiopia by various research teams
Age range: 5.8- 4.4
mya
Features:
most complete ancient hominid skeleton
– bones of hand, feet, limbs, pelvis, most of skull & teeth; remains of males, females, juveniles
Slide11
A. ramidus
, cont.
Ape-like traits
Grasping
big toe (only biped w/ this
feature)
Long
arms, short legs Small brain
Human-like traits:
Small caninesSmall molarsHand bones NOT adapted for knuckle-walkingSlide12
Ardipithecus ramidus
Diet
: omnivorous - plants, fruits, insects, nuts, seeds
Environment: lush woodlands, forests
Significance
:
1 my older than Lucy
Closest
established hominid to Last Common Ancestor with chimpsArboreal AND Bipedal Adaptations