1. 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

2. 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

3. Mid-Pliocene Hominids (4-3 mya)
Australopithecines
Obligate bipedalism established
Climate & landscape changes acting as strong selective pressures
A lot of variation in species:
Aus. anamensis
Aus. bahrelgazali
Aus. Garhi
Kenyanthropus platyops

4. Adaptive Patterns of the Australopithecines
Small bodied (avg. height 4-5 ft.)
Small brains (approx. same as modern chimp)
Tool use similar to modern chimps
NOT stone tool makers
Foragers – gathered fruits, nuts, seeds, roots, tubers, insects
Mixed woodland/savannah environment
Small, nomadic social groups
Effects of genetic drift, mutation likely to be felt more strongly
Resulting in more rapid genetic divergence & eventual speciation

5. Australopithecus africanus
Discovered: in Taung limestone quarry in South Africa by Raymond Dart
Features: slightly projecting lower face, large molars, small front teeth & canines, short face

6. Australopithecus africanus
Age range: 3.0 – 2.2 mya
Type specimen: Taung Child (6 yo)
First Australopithecine EVER discovered
Cranial capacity: 440 cc (avg.)

7. Australopithecus robustus
Discovered: 1936 by Robert Broom in South Africa
Age range: mya
Features: robust features = sagittal crest, large teeth, thick & wide cheekbones, large face, large jaw, small brain
Diet of hard food items: nuts, seeds, tubers, roots, leaves
Cranial capacity: 530 cc

8. Australopithecus boisei
Discovered: by Mary Leakey in
Tanzania (East Africa)
Features: “Hyper-robust” – massive jaw, huge molars & big teeth w/wear, prominent sagittal crest
Cranial-dental features work as “grinding machine”; nicknamed “Nutcracker Man”; ate seeds, nuts, roots, tubers, leaves (NOT a tool maker---teeth are tools)

9. Australopithecus boisei
Age range: 2.3 – 1.2 mya
Cranial capacity: 530 cc
Note: Originally named “Zinjanthropus boisei”
Both A. robustus & A. boisei become extinct (an evolutionary dead end)

10. Australopithecus afarensis (aka “Lucy”)
Discovered: in Hadar,
Ethiopia (East Africa) by Don Johanson
Age range: 3.9 – 3 mya
Significance:
Antiquity - 1 my older than any
other hominid found at that time
40% complete – nearly all bones
represented
Established bipedalism in earliest
known hominid (w/small brain)

11. Australopithecus afarensis, cont. “The First Family”
Discovered: by Don Johanson in Hadar, Ethiopia, E.Africa
Features: Remains of 13 individuals (male, female, adults, juveniles)
Highly sexually dimorphic (males much bigger than females)
Significance: strong evidence of variation within the species & for Au. afarensis as a hominid

12. Aus. afarensis, cont. The Laetoli Footprints
Discovered: in Tanzania by Mary Leakey
Features: Prints reveal human-like stride; big toe in line with others; arch in foot
Age: 3.7 – 3.5 mya
Significance: Firmly establishes bipedality in earliest hominids

13. Important Notes on Aus. afarensis
Physical Features:
Ape-like face, jaw
Small brain
( cc)
Males w/sagittal crest
But…(unlike apes)
Reduced canine
Broader palate
From neck down:
Arms longer than legs
Curved finger & toe bones
Flexible ankle & shoulder joints
Wide pelvis, but shortened pelvis
Funnel shaped rib cage

16. Important Notes on Aus. afarensis, cont.
Behaviorally,
Aus. Afarensis spent time in the trees AND on the ground
Centralized foramen magnum indicates obligate bipedalism

17. Adaptive Patterns of Early African Hominids
Gracile australopiths
More omnivorous
More arboreal
Reflected in foot, ankle,
hand, wrist bones
A. afarensis, A. africanus

18. Adaptive Patterns of Early African Hominids
Robust australopiths
Diet of hard food items
Less arboreal
Due to food sources
Extinct 1 mya
A. robustus, A. boisei
Different Genus? Paranthropus

19. Second Adaptive Radiation
Early Pliocene (4-5 mya)
New species & new genus evolves
All exhibit bipedalism – established hominids

20. 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

21. A. ramidus, cont. Mix of ape & human traits: Small canines
Grasping big toe (only biped w/ this feature)
Long arms, short legs
Small brain
Hand bones NOT adapted for knuckle-walking
Small molars
Diet: omnivorous - plants, fruits, insects, nuts, seeds
Environment: lush woodlands, forests

22. Ardipithecus ramidus Significance: 1 my older than Lucy
Closest established hominid to Last Common Ancestor with chimps
Evidence of bipedalism arising in a more arboreal context than previously thought

23. Ardipithecus ramidus, cont.

24. Ardipithecus ramidus

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

26. 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
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

27. Sahelanthropus tchadensis
Found in central Africa, country of Chad
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?

28. Summary of Early Hominids
Australopithecine ancestors & relatives are very ape-like in appearance & behavior
Lots of variation for natural selection to work with
Exhibit a mix of traits but establishing a set of evolutionary trends that will define our genus, Homo
Are not what we would consider “human” (Thus, are not assigned to our genus)