Post on 14-Dec-2015
Terms Arboreal – Tree-dwelling Binocular Vision – ability to see 3D, depth
perception and colour Prehensile – ability to grasp (hands, feet, tail) Quadrapedalism – walking on all four limbs Brachiation – use of arms to suspend body during
feeding and to move the body by arm-swinging Bipedalism – walking on two legs (habitual) Hominid – Humans and their ancestors Hominoid – Group containing humans and apes
Primate Groups Prosimians
Arboreal or tree living Grasping hands and feet Long, mobile limbs Quadrapedal Binocular vision Upright sitting position Nails instead of claws Use scent marking to
communicate – wet nose
Primate Groups New World Monkeys
(Americas) Prehensile or grasping tail – used
as a 5th limb Quadrapedal Arboreal or tree living Nostrils wide apart E.g. spider monkey
Primate Groups Old world monkeys (Africa
and Asia) Tail not prehensile Quadrapedal Some are ground living Nostrils close together – reduced
sense of smell E.g. Baboon
Primate Groups Great Apes
Some brachiating Mostly ground dwelling Quadrapedal Flattened nose Bony eye ridges E.g. Gibbon, Gorilla, chimp,
Orangutan
Primate Groups Hominids
Bipedal Reduced canines and outer teeth Large cerebral cortex (forebrain) Eye ridges reduced, chin and nose
protrude Very sensitive skin Reduced body hair Very complex social behaviour
Primate Skull Features
Sagittal Crest Cranial Vault
Brow Ridge
Heavy Malar
Diastema
Protruding Muzzle
Large CaninesMassive Molars
Massive Jaw
Foramen Magnum
Zygomatic Arch
Nuchal Crest
General Ape Characteristics
No tail Y-5 Pattern on teeth.
Quadrupedal Semi or fully-erect posture Arms long in comparison with hind limbs Rib cage flattened from front to back Larger brains Upper lip free from gums Powerful canine teeth and large incisors
Differences between Humans and Apes Main physical differences between
quadrupedalism and bipedalism The Skull Teeth and Jaw The legs The feet The chest
Physical differences between Apes and Humans – The Skull
HUMANS APES
Occipital Condyle forward Occipital Condyle far back
Foramen Magnum positioned underneath skull
Foramen Magnum positioned towards the back
Area of attachment for neck (nuchal) muscles is small
Area for attachment for neck (nuchal) muscles is large. Apes also have large sagittal crest for attachment on heavy chewing muscles
Large Brains – 1400 cm3 Smaller Brains – 400 – 500cm3
Modern human has chin and nose that sticks out
Apes have no chin and a flat nose
Face is flat with forehead rising up from the eyes. Some early human had wide cheek bones called Zygomatic Arch.
Forehead slopes back from the eyes, large brow ridges. Apes are prognathic – lower face and jaw project in front of upper parts of face.
Physical differences between Apes and Humans – The teeth and jaw.
HUMANS APES
Both males and females have small incisors and canines that do not project further than any of the other teeth
Apes have large incisors and canines.
Both premolars have 2 cusps First premolar has one cusp and second has 2 cusps.
No Diastema Diastema in lower jaw where canines fit.
Palate is arched and teeth shaped like a rounded ‘V’
Palate is flat and teeth shaped like a ‘U’ with parallel sides
Physical differences between Apes and Humans – The pelvis and backbone
HUMANS APES
Backbone is S shaped Backbone is arched
Pelvis is broad, shallow from top to bottom and bowl-shaped
Pelvis is narrow and elongated
Centre of gravity is just behind the lower back above the legs
Centre of gravity is in the middle of the spine.
Have large gluteus maximus muscles to support femur and pelvis
Small gluteus maximus and support body with arms instead.
Physical differences between Apes and Humans – The legs
HUMANS APES
Head of femur is far apart and knee ends close together forming an angle (valgus angle)
Head of femur and knee ends in a vertical line – no angle
Outer condyle is larger than inner one in the knee joint
Inner condyle is larger than outer one in the knee joint.
Legs are longer than arms
Arms are longer than legs
Physical differences between Apes and Humans – The feet
HUMANS APES
Foot has short toes. The big toe is longer and lies close alongside the other toes.
Gap between the big toe and the rest and the big toe is shorter than the rest
Weight is taken on the outside of the foot. Inner side is elevated into an arch.
Apes have flat feet.
Physical differences between Apes and Humans – The chest
HUMANS APES
Chest is broard and narrow, flattened from front to back
Chest is flattened at the sides
Collar bone is long Collar bone is shorter than in humans
Shoulder blades lie on back Shoulder blades sit along the sides of the chest.
Bipedalism V’s Quadrupedalism
Advantages and disadvantages of bipedal (upright) walking
Advantages DisadvantagesCan see further
Free hands
Can carry babies etc
Can throw stones and wield sticks
Can keep cooler by less sun falling on the body and more wind off the ground
Look larger and more menacing
Greater display of sexual organs to members of opposite sex
Back-aches
Painful birth
Takes a long time to learn to walk
Varicose veins
Why walk upright?
In Early Africa, Apes lived in a continuous forest and as a result were adapted for an arboreal life.
Climate changed (drier) and forest retreated leaving large areas of grassland.
Divergent evolution occurred – some remaining in the trees and some developing bipedalism as an adaptation for moving between the patches of forest.