Trends in Hominid Evolution

Human bio unit 4

What is a hominid

The group consisting of all modern & extinct Great Apes (that is, modern humans, chimpanzees, gorillas & orang-utans plus all their immediate ancestors).

Relative size of cerebral cortex - Great Apes

1. Smaller cranial capacity

2. Sagittal crest

3. Sloping forehead

4. Posteriony located foramen magnum

5. Increased post-orbital constriction

6. Thicker cranium

7. Prominent brow ridges

8. Less rounded cranium

Relative size of cerebral cortex - Humans

1. Larger cranial capacity

2. No sagittal crest

3. Vertical forehead

4. Anteriorly located foramen magnum

5. Decreased post-orbital constriction

6. Thinner cranium

7. Reduced brow ridges

8. Rounded cranium

Mobility of the digits - Great Apes

1. Less opposable first digit

2. Opposable big toe

3. Less Precision grip

4. More Power grip

5. Shorter thumb relative to other digits

6. Curved fingers

Mobility of the digits - Humans

1. More opposable first digit

2. Non-opposable big toe

3. More Precision grip

4. Less Power grip

5. Longer thumb relative to other digits

6. Straight fingers

Locomotion - Great Apes

1. Quadrupedal

2. C shaped spinal curve

3. Less wedge shaped lumbar vertebrae

4. Thinner lower vertebrae

5. Longer, narrow pelvis

6. Lesser carrying angle

7. Longer arms than legs

8. Longitudinal arch only 9. Smaller heel bone

Locomotion - Humans

1. Bipedal

2. S shaped spinal curve

3. More wedge shaped lumbar vertebrae

4. Thicker lower vertebrae

5. Shorter, wider pelvis

6. Greater carrying angle

7. Shorter arms than legs

8. Longitudinal/transverse 9. Larger heel bone

Prognathism/ dentition - Great Ape

1. Sloping/prognathic face

2. Large jaw

3. No chin

4. Larger molars & canines

5. Diastema

6. U shape dental arcade

Prognathism/ denotation - Human

1. Flatter face

2. Small jaw

3. Definite chin

4. Smaller molars & canines

5. No diastema

6. Parabolic dental arcade

What does ‘pentadactyl’ mean

Primates have 5 digits on each limb

What does ‘opposability’ mean

First digit can be moved in such a way that it can touch each of the other digits

What is the adaptation of Foramen magnum

Located centrally in the base of the cranium

What is the adaptation of the jaw bone

Small and non-protruding, enabling the skull to balance on the vertebral column

What is the adaptation of the vertebral column

Lumbar vertebrae wedge-shaped, producing an 'S -shaped curve that brings the vertebral column directly under the centre of the skull

What is the adaptation of the pelvis

Broad; shallow from top to bottom. Provides support for the abdominal organs. Attachment of femurs is wide apart, contributing to the carrying angle

What is the adaptation of the femurs

Large head of the femur contributes to carrying angle

What is the adaptation of the knee joint

Outer 'hinge' larger and stronger, to take weight of body. Knee is able to be straightened

What is the adaptation of the legs

Longer than arms, contributing to a low centre of gravity. Carrying angle allows the weight of the body to be kept close to the central axis

What is the adaptation of the foot

Large heel bone and aligned big toe form a pedestal on which the body is supported. Foot has both longitudinal and transverse arches

What is the adaptation of muscle tone

Partial contraction of muscles to support the spine, hip, knee and ankle