Unit 3: The hominid line (bipedalism & non honing chewing) ANTH 111

What are the defining characteristics of a hominin?

- honing vs. non honing chewing - bipedalism vs. quadrupedalism - small brain

How can you tell if a skeleton belongs to a hominin?

1. Bipedal Locomotion - walking on 2 feet 2. Nonhoning chewing - small canines - no diastema - nonhoning 1st bottom premolar

What are some disadvantages of bipedalism discussed in class? (Besides not being able to walk/climb quadrupedally)

1. Exposure to predators 2. Back injury 3. Circulatory system (blood- toes-- up) 4. Foot injury

Which of the fossils discussed this semester are hominins?

1. Pre-Australopithecines 2. Australopithecines 3. Homo

Identify/name the three possible earliest hominins, or pre-australopithecines.

1. Sahelanthropus 2. Orrorin 3. Ardipithecus

Name or describe multiple theories regarding why hominins began walking bipedally

1. Useful for carrying things - infants - food 2. Energy Efficient - more efficient (especially over knuckle walking) - dissipates heat 3. Stance is advantageous - feeding (fruits in trees, seeds in grasslands) - bipedal in trees - better view - deter predators

Which specific teeth make up the honing complex? Explain in detail.

Canines (sharp or not), 1st bottom premolar (honing or non)

Honing Chewing

Canines: large, sharp Diastema: gap for sharp canines 1st lower premolars: Honing, large cheek side cusps, small tongue side cusps (large cusp to teeth ratio difference)

Nonhoning Chewing

Canines: small, blunt Diastema: none 1st lower premolars: nonhoning, similar sized cheek and tongue cusps (same size ratio for cusp to tooth)

Who is Ardipithecus?

Most likely to be the first hominin

Why is the distinction between honing and nonhoning chewing important?

The distinction between the two is important because nonhoning chewing shows a change in diet that doesn't need sharp canines to break down food - new tools to make it easier, fire to cook food

Orrorin

What are some identifying characteristics of each? - Femur is bipedal - Nonhoning chewing In what part of Africa were they found? - East Africa (Kenya) Are they part of the hominin line? - Yes

Sahelanthropus

What are some identifying characteristics of each? - forward foramen magnum (bipedal) - small canine/ no diastema In what part of Africa were they found? - Central Africa (Chad) Are they part of the hominin line? - Yes

Ardipithecus

What are some identifying characteristics of each? - small canine (nonhoning/ but rest of teeth closer than ape) - bipedal pelvis In what part of Africa were they found? - East Africa (Ethiopia) Are they part of the hominin line? - Yes (most likely to be the first)

Is Ardi a hominin? Explain.

Yes, possibly first

What is a hominin?

humans and all our ancestors since our evolutionary line split from the last common ancestor with chimpanzees