EARLY HOMININS

Characterised by THREE main features: (bdb)

• LARGE brain relative to their body size
• advanced dentition with rotary chewing
• adaptations to bipedal locomotion

The hominin and African ape lineage split about 6-8 million years ago.

6-7 million years ago: Sahelanthropus

6 million years ago: Orrorin

4.4 million years ago: Ardipithecus

3.9 -1.2 million years ago: Australopithecus / Paranthropus

3.5 million years ago: Kenyanthropus

2 million years ago - present: Homo

• Formation of the East African Rift Valley about 6-8 million years ago
• Conditions became drier and more open
• The forest became replaced with Savannah

THUS

Humans are apes adapted to an open habitat BUT many early hominids are at least partially arboreal.

• 6 - 7 million years ago
• had an extremely large, robust supraorbital torus (brow ridge)
• the cranium was similar to that of a gorilla
• its hominin status was defined by its "smaller canines with apical wear" (M. Brunet, 2002)
• many others suggest a closer relationship to gorillas or chimpanzees

• 5.6 - 6.2 million years ago
• also known as "the millenium man" as it was discovered in 2000
• its hominin status was defined by its femur, in particular its muscle attachment on the femoral neck
• many have argued that it is an agile climber but walked on 2 legs on the ground
• howevr, many are still not convinced by this e.g. B. Senut et al (2001)

• 4.4 million years ago
• its toe bone shows that it may have walked bipedally
• its teeth also suggest hominin status with projecting canines and hominin-like wear patterns which suggest rotary chewing
• long powerfully muscled arms
• no knuckle-walking features
• no hindlimb material

The GRACILE hominins are:

1) Australopithecus anamensis (3.9 - 4 mya)

2) Australopithecus afarensis (2.8 - 3.4 mya)

3) Australopithecus bahrelghazeli (3 - 3.5 mya)

The ROBUST hominins are:

1) Australopithecus africanus (3.2 mya)

2) Australopithecus gahri (2.5 mya)

3) Australopithecus Paranthropus aethiopicus (2.6 - 2.2 mya)

4) Australopithecus Paranthropus boisei (2.3 - 1.2 mya)

5) Australopithecus Paranthropus robustus (2.1 - 1.2 mya)