Lecture 16 - Early Hominins (pt.2)

What time period did early hominins live in?

Late Miocene to early Pliocene (~7–4 million years ago)

What does “Ma” mean?

Million years ago

Which is the earliest known hominin in this set?

Sahelanthropus tchadensis

Key traits of Sahelanthropus tchadensis

Small canines, small brain, possible bipedalism

When did Orrorin tugenensis live?

~6 million years ago

What is the strongest evidence of bipedalism in Orrorin?

Femur structure indicates upright walking

Key trait of Orrorin teeth

Large, ape-like canines

When did Ardipithecus kadabba live?

~5.8–5.2 million years ago

Key trait of Ardipithecus kadabba

Medium canine size between apes and later hominins

When did Ardipithecus ramidus live?

~4.4 million years ago

Key traits of Ardipithecus ramidus

Bipedal, climbing traits, grasping big toe, small brain

What does Ardipithecus ramidus’ pelvis show?

Mix of bipedal and climbing adaptations

What is the overall evolutionary trend in early hominins?

Increasing bipedalism and decreasing canine size over time

What stays mostly the same in early hominins?

Small brain size

What is “mosaic evolution”?

Having a mix of primitive (ape-like) and derived (human-like) traits

What environmental changes influenced early hominins?

Cooler climate → less rainfall → fragmented forests

How might environmental change relate to bipedalism?

Forest fragmentation required movement between areas, encouraging upright walking

What type of habitat did Ardipithecus likely live in?

Closed, wooded environment

How do scientists determine ancient habitats?

By analyzing animal fossils (like antelopes) found at the same sites