Lecture 21: Human Evolution, Australopithecines & Bipedalism

What is the key idea about human evolution?

Human evolution is branching, not a straight line.

What are the dates for Ardipithecus?

5.8-4.4 million years ago.

Where was Ardipithecus ramidus discovered?

Aramis, Ethiopia (Middle Awash).

What type of environment did Ardipithecus inhabit?

Woodland environment, not savanna.

What is the significance of the Ardipithecus foot structure?

It had a divergent hallux indicating tree climbing and no rigid arch.

What does the term 'mosaic evolution' refer to in Ardipithecus?

It refers to the combination of bipedal traits and climbing adaptations.

What are the key traits of Australopithecines?

Habitual bipeds, small-bodied, pronounced sexual dimorphism, and retained arboreal adaptations.

What is the time range for Australopithecus species?

4.2-2.0 million years ago.

Which Australopithecus species is considered the most important?

Australopithecus afarensis.

What is the significance of the fossil known as 'Lucy'?

Lucy is a 3.2 million-year-old Australopithecus afarensis specimen that is ~40% complete.

What adaptations indicate A. afarensis was a biped?

Bicondylar angle in the femur and a shorter, broader pelvis.

What are the Laetoli footprints, and what do they indicate?

Discovered by Mary Leakey, they are ~3.6 million years old and show evidence of habitual bipedalism.

What distinguishes human and chimp skulls?

Humans have an anterior foramen magnum, while chimps have a posterior foramen magnum.

How do the spines of humans and chimps differ?

Humans have an S-shaped spine, while chimps have a C-shaped spine.

What is a key difference in pelvis structure between humans and chimps?

Humans have a short, bowl-shaped pelvis, while chimps have a long, narrow pelvis.

What skeletal trait distinguishes human femurs from chimp femurs?

Humans have a bicondylar angle, while chimps have a straight femur.

What is the difference in foot structure between humans and chimps?

Humans have an adducted hallux with an arch, while chimps have a divergent hallux with no arch.

What does 'committed biped, but not obligate terrestrial' mean regarding A. afarensis?

It indicates that A. afarensis was primarily bipedal but still retained climbing abilities.

What does the term 'early bipedality' refer to in Australopithecines?

It refers to the initial adaptations for walking on two legs seen in these species.

What does 'retained climbing traits' mean for Australopithecines?

It means they still had physical features that allowed them to climb trees.

What is the importance of the A. afarensis species in human evolution?

It is considered transitional, showing both bipedal and climbing adaptations.

Why is Ardipithecus considered important in the study of human evolution?

It provides insights into early bipedalism and ecological adaptations.

What evidence do the Laetoli footprints provide about A. afarensis?

They demonstrate that A. afarensis was a habitual biped with a human-like stride.