Human Evolution

Primates

group of mammals including lemurs, monkeys, apes, and humans

Unique Feature of Primates - Eyes

Forward-facing eyes: binocular vision for depth

Unique Feature of Primates - Grasping Hands & Feet

Climbing and manipulation

Unique Feature of Primates - Flattened Nails

have flat nails

Unique Primate Features - Flexible Limb Structure

high degree of limb flexibility and a range of motion

in their joints.

Adaptations to Methods of Primate Locomotion

Brachiation, Quadrupedalism, Climbing, Bipedalism

What are Hominoids

all apes and hominins (including ancestral and modern apes)

Anatomical features and habits: The Apes

Brachiating, Some mainly ground dwelling and quadrupedal, Arms longer than legs

Flattened nose

Bony eye ridges

No tail

Hominins

modern and ancestral humans

Anatomical Features: Hominins

Bipedal, large cerebral cortex, reduced canines, prominent nose and chin, reduced eye ridges, body hair short, sensitive skin, complex social behaviour

Define biological evolution

change in inherited traits over successive generations in populations of organisms. These traits are subjected to selection pressures. The alleles are responsible for improved fitness will increase in the gene pool

What is the sagittal crest

attachment site for jaw muscles

What is the nuchal crest

attachment of neck muscles

What is the diastema

gap between teeth

Gorilla skull feature

Large saggital crest, low small cranial vault, brow ridge, heavy molar, diastema, protruding muzzle (prognathism), large incissors, large canines (defense), large molars (grinding vegetation), foramen magnum positioned rear, massive zyogmatic arch, nuchal crest

What is the foramen magnum

attachment point for the

skull and the spine through which the spinal cord

passes to the brain.

Foramen magnum - rear

opening close to the rear of the skull implies a

quadrupedal habit of locomotion: the head is held

upright by powerful neck muscles.

Foramen magnum - central

opening located more centrally on the skull, as is

found in modern humans, indicates a bipedal habit of

locomotion: the head balances on the spine and less

powerful neck muscles.

Advantages of S-shaped spine

accommodate the upright

walking posture.

Helps position the head over the centre of

the body

Acts as a shock absorber during bipedal

locomotion - enables more efficient

locomotion and conserves energy.

Human lower limbs have been highly modified for bipedal

locomotion:

legs are longer than arms

shorter and broader pelvis

inwardly-angled femur, creating larger valgus angle

strong knee joint

a platform foot

ape’s lower limbs feature:

a long pelvis

an outwardly-angled femur with smaller valgus angle

grasping toes

In modern humans - knee

knee joint is adapted to

bear weight through the

lateral condyles, which

are larger than the

medial condyles.

chimpanzees - knee

knee joint is adapted to

bear weight through the

medial condyles.

Adaptations to bipedalism - valgus angle of femur

brings knee underneath the centre of

gravity – allows for more efficient bipedal locomotion by

reducing sway – results in increasing stability- saves energy.

Adaptations to bipedalism - femur longer than arms

-leads to longer strides during bipedal

locomotion – makes bipedal locomotion more efficient by

allowing for greater distances to be covered per stride.

Adaptations to bipedalism - distal end of the femur / knee

buttressed (enlarged) - outer

condyle larger than the inner to support the additional weight

force of walking bipedally- increases efficiency.

Adaptations to bipedalism

carrying offspring/resources, seeingn over the grass and spotting predators, smaller surface area presented to the sun, greater airflow across the body thus assisting in cooling, low speed long distance efficient locomotion (bipedalism)

Advantages of Bipedalism - Foot

platform - toes are short, with big toe thrusting forwards, inner side of the foot is elevated into an arch to provide shock absorption

Advantages to Bipedalism - femur

longer and angled inwards from the hips so knees nearly touch, assists in positioning the upper body over the centre of gravity