Early Hominin Evolution: Emergence of Our Lineage

Comprehensive vocabulary flashcards reviewing primate evolution epochs, hominoid taxonomy, early proto-hominins, bipedal anatomy, and australopithecine species based on the lecture notes.

What was the Eocene epoch?

56-33 million years ago; early primates resembled modern lemurs and lorises.

When did the earliest simians appear?

Around 37 million years ago in Africa; simians include monkeys and apes.

What was the Oligocene epoch?

33-23 million years ago; small, tree-dwelling primates with small brains and long snouts.

What does arboreal mean?

Living or spending most of the time in trees.

What does frugivore mean?

An animal that eats mainly fruit.

What two monkey groups split during the Oligocene?

New World monkeys (platyrrhines) and Old World monkeys (catarrhines).

What was the Miocene epoch?

23-5 million years ago; many ape species spread across Africa, Europe, and Asia.

What was Proconsul?

An early ape-like primate from Africa, dated around 25-23 million years ago.

What is a hominoid?

A member of the group containing all apes and humans.

What is a hominin?

A human or one of our recent evolutionary ancestors.

What is a proto-hominin?

One of the earliest members of the human evolutionary lineage, around 7-5 mya.

When did human and chimp lineages diverge?

DNA evidence suggests around 6.3-5.4 million years ago.

What are the three earliest hominin genera?

Sahelanthropus, Orrorin, and Ardipithecus.

Where are many early hominin fossils found?

East African Rift Valley, especially around Kenya and Ethiopia.

Why are many fossils found in East Africa?

Fossils were well preserved and are easier to discover there.

What is Sahelanthropus tchadensis?

An early possible hominin from Chad, dated 7-6 mya, with a small brain.

What is Toumai?

The nickname of the partial Sahelanthropus tchadensis skull.

What was Sahelanthropus's brain size?

About 350 cc, similar to a modern chimpanzee.

Why might Sahelanthropus have walked upright?

Its foramen magnum position suggests possible bipedalism, but evidence is uncertain.

What is the foramen magnum?

The opening underneath the skull where the spinal cord connects to the brain.

What was the first major hominin development?

Bipedalism, or walking on two legs.

What is bipedalism?

Using two legs instead of four for movement.

What is facultative bipedalism?

Being capable of walking on two legs, but not doing so all the time.

What is habitual bipedalism?

Walking on two legs most of the time.

What is obligate bipedalism?

Using two legs as the only normal form of locomotion.

What is mosaic evolution?

Different body features evolve at different rates rather than all at once.

What is Orrorin tugenensis?

An early hominin from Kenya, dated 6-5.8 mya, possibly capable of walking upright.

What do Orrorin's curved finger bones suggest?

It retained adaptations for climbing trees.

What does Orrorin's femur suggest?

Its thighbone shape suggests some ability to walk on two legs.

What is Ardipithecus kadabba?

An early hominin from about 5.6 mya with primitive teeth; ancestral to A. ramidus.

What is Ardipithecus ramidus?

An early hominin from about 4.5 mya with a small brain and facultative bipedalism.

What was Ardipithecus ramidus's brain size?

About 300-350 cc, similar to a chimpanzee.

What does sexual dimorphism mean?

Physical differences between males and females of the same species.

How did warmer climates affect African habitats?

More moisture allowed forests to expand.

How did colder climates affect African habitats?

Less moisture allowed open savannas to expand.

Why might bipedalism have evolved?

Possible benefits include carrying food, traveling, seeing danger, and cooling the body.

What is thermoregulation?

Controlling body temperature; one proposed advantage of upright walking.

What is Australopithecus?

An early hominin genus with small brains, large teeth, and regular upright walking.

When did Australopithecus live?

Approximately 4.2-1 million years ago, according to the lecture.

Where were Australopithecus fossils found?

Eastern and southern Africa.

What is Australopithecus anamensis?

An early bipedal hominin from 4.2-3.9 mya, found in Kenya and Ethiopia.

What was A. anamensis's brain size?

About 370 cc, with a long, narrow braincase.

How do we know A. anamensis walked upright?

Its knee and ankle bones show adaptations for supporting weight on two legs.

What is Australopithecus afarensis?

An early hominin from 3.9-2.9 mya that walked upright and could also climb trees.

Who was Lucy?

A famous, roughly 40%-complete Australopithecus afarensis fossil discovered in 1974.

Where were A. afarensis fossils discovered?

Hadar in Ethiopia and Laetoli in Tanzania.

What was A. afarensis's brain size?

About 375-500 cc, much smaller than a modern human brain.

What is a sectorial premolar?

A lower premolar shaped to shear against the upper canine tooth.

What are the Laetoli footprints?

Fossil footprints from about 3.7 mya showing early hominins walking on two legs.

Could Australopithecus afarensis climb trees?

Yes. Its shoulder structure and curved fingers suggest climbing ability.

Why might A. afarensis have climbed trees?

For protection, food, and nesting.

What evolved first: bipedalism or large brains?

Bipedalism evolved first; early hominins still had small, chimp-sized brains.