1. Early Hominins
Chapter 13

2. Bipedal Adaptation
Efficient bipedalism as the primary form of locomotion is seen only in hominins
Advantages of bipedalism:
Freed hands for carrying objects
Wider view of the surrounding countryside
Efficient means of covering long distances

3. Australopithicines (4.2–1.2 mya)
Most widely distributed and diverse early African hominins
Taxonomy:
Made up of two closely related genera
Australopithecus (gracile) and Paranthropus (robust)
Well established by 3 mya
Major features
All bipedal
Relatively small brains compared to Homo
Large teeth (particularly back), thick molar enamel

4. Australopithecus and Paranthropus
anamesnis ( mya)
bahrelghazalia (3.6 mya)
afarensis ( mya)
africanus (3-2 mya)
garhi (2.5 mya)
sediba ( mya)
Kenyanthropus platyops ( mya)
Paranthropus
aethiopicus ( mya)
boisei ( mya)
robustus (2-1 mya)
Dates are approximate, evolution is not instant!

5. Erect Bipeds
The postcranial skeletons of Australopithecus and Paranthropus are those of erect bipeds
Evidence includes:
Shape of the pelvis
Position of the foramen magnum
Presence of a lumbar curve
Way the femurs are angled in
Anatomy of the foot
Laetoli footprints
3.8 and 3.6 mya
A. Afarensis

6. Early South African Hominin Fossils
Taung quarry, SA
Raymond Dart
Taung Child
Discovered in 1925
Australopithecus africanus
Sterkfontein Valley, SA
A. africanus and Paranthropus robustus
A. africanus lived earlier than P. robustus

7. East African Hominin Fossils
Olduvai Gorge, Tanzania
Leakey family
P. boisei and early members of the genus Homo
Lake Turkana Basin, Kenya
P. boisei, P. aethiopicus, A. anamensis, and K.platyops
Hadar, Ethiopia
“Lucy”

8. Chadian Hominin Fossils
Australopithecus bahrelghazalia
Discovered in 1995 by Michel Brunet
Only hominin species found outside of south or east Africa
Suggests that the distribution of the early hominins may be greater than that suggested by the better-known south and east African sites

9. Australopithecus anamensis
Northern Kenya (Rift Valley) mya
Possible Ardipithecus descendent
Possible afarensis ancestor
Weighed about 110 lbs
Large ape-like canines
Large back teeth
Bipedal anatomy

10. Australopithecus afarensis
Kenya mya
Around 50 individuals discovered between two sites
Laetoli
Hadar
Lucy
Donald Johanson
40% complete
Valgus knee
Pelvic arc more similar to Homo than ape
Probable ancestor to all other australopithecines

11. Paranthropus

12. Early Hominin Dentition
Early Australopithecus show many non-hominin features
Many features of the dentition of A. afarensis are intermediate between that of modern humans and apes
Paranthropus evolved rather specialized dentition
Heavy grinding with the back teeth

13. The Early Hominin Brain and Skull
Cranial capacities
Australopithecus and Paranthropus vary from 400 to 530 cc
Skull structure
Reflects a small cranium associated with large dentition and powerful chewing muscles
Prognathism
Postorbital constriction
The forehead is low and flat
Australopithecus – presence of a temporal-nuchal crest suggests large temporalis muscle
Paranthropus - skulls are characterized by a small sagittal crest for attachment of the powerful temporalis muscle

14. The Hominin Brain Evolution of the human pelvis
Repositioning of the sacrum has created a complete bony ring through which the birth canal passes
The need to pass the large human brain through this opening has resulted in the human newborn having a brain less than 30 percent of its adult size
The brains of other animals are almost completely developed at birth
Thus the human infant is very dependent on others for an extended period

15. Australopithecine Tool Use
Earliest hominin tools
Probably made of perishable tools
Wood, bark, leaves, and fiber
The evidence for tool use in the archaeological record consists primarily of stone objects
Paranthropus robustus
Hand structure suggests capability of a precision grip and complex toolmaking
Australopithecus garhi
Garhi means surprise in Afar (Ethiopia)
First stone tool manufacturer
Dated at 2.6 mya
Possible direct ancestor to genus Homo

16. Australopithecus and Early Homo
By 2 mya
Early Homo is now a distinct population form late Australopithecus
Johanson and White
A. afarensis splits into two groups
One becomes reproductively isolated
Homo habilis
Earliest member of the genus
Co-existed with late Australopithecines