1. Mid-Pliocene Hominids (4-3 mya)
Australopithecines
History of discovery influenced understanding of hominid evolution
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
You WILL NOT need to know these species for the exam!

2. 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

3. Australopithecus africanus
Discovered: in Taung limestone quarry in South Africa by Raymond Dart
Age range: 3.0 – 2.2 mya
Features: slightly projecting lower face, large molars, small front teeth & canines, short face

4. Australopithecus africanus
Cranial capacity: 440 cc (avg.)
Type specimen: Taung Child (6 yo)
First Australopithecine EVER discovered

5. 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

6. 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)

7. 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)
Relatives not ancestors
Distinct features/adaptations = Separate genus? - Paranthropus

8. 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)

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

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

11. 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 but shortened pelvis
Funnel shaped rib cage

14. Important Notes on Aus. afarensis, cont.
Behaviorally,
Aus. Afarensis spent time in the trees AND on the ground
Centralized foramen magnum indicates obligate bipedalism
Latest discovery - Lucy’s baby (Selam, 3 yr. old child skeleton) shows early hominid bipedalism not the same as modern bipeds

15. Summary of Early Hominids
Australopithecine ancestors are very ape-like in appearance & behavior
Lots of variation for natural selection to work with (lots of selective pressures, esp. “climate shocks” operating”
Exhibit a mix of traits but establishing a set of evolutionary trends that will define our genus, Homo
Very challenging to determine relatives from ancestors
Are not what we would consider “human” (so are not assigned to our genus)