1. Hominid Evolution in Context
Ancient hominid fossils not accepted as ancestors
Biases in fossil record (from 19th 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)

2. 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?

3. Will the Earliest Hominid Please Stand Up?
Earliest representatives of our lineage lived at end of Miocene & beginning of Pliocene epoch
6 – 4.5 mya

4. Geological Context of Hominid Sites
South African Sites
Mostly limestone (no volcanic sediments)
Cave sites with bone accumulations
Dated with biostratigraphy & paleomagnetism
East African Sites
Volcanic ash/sediments
Can be dated by Argon/Argon (chronometric) dating, relative dating techniques (stratigraphy) &
paleomagnetism

5. First Adaptive Radiation
Late Miocene (6-7 mya)
Produces potential/possible LAST COMMON ANCESTORS
These are the earliest (possible) Hominids
Forest adapted

6. Sahelanthropus tchadensis
Found in central Africa, country of Chad
7 myo
Nearly complete cranium
Mix of human & ape-like traits
Small braincase: cc
Massively built, heavy browridges, crest in back, large muscle attachments
Reduced upper canine
Small, vertical face
Cannot determine bipedality
OLDEST possible hominid
Common ancestor?

7. Orrorin tugenensis aka “Millenium Man”
Discovered: in western Kenya
Age range: 6 mya
Remains: Fragmentary arm & thigh bones; lower jaws & teeth
Features: Limb bones larger than later hominid species
Cranial capacity: Not yet determined

8. 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

9. Second Adaptive Radiation
Early Pliocene (4-5 mya)
New species & new genus evolves
Dense forest environment
All exhibit bipedalism – established hominids
Represent a challenge to the established “Savanna Hypothesis”

10. Ardipithecus ramidus
Discovered: in Ethiopia by various research teams
Age range: mya
Features: most complete ancient hominid skeleton – bones of hand, feet, limbs, pelvis, most of skull & teeth; remains of males, females, juveniles

11. A. ramidus, cont. Ape-like traits
Grasping big toe (only biped w/ this feature)
Long arms, short legs
Small brain
Human-like traits:
Small canines
Small molars
Hand bones NOT adapted for knuckle-walking

12. 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 chimps
Arboreal AND Bipedal Adaptations