THE PRIMATES Year 13 Biology Achievement standard 3.7

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 5 th 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

Evolution of Apes and Human (Hominoids)

Primate Skull Features Sagittal Crest Cranial Vault Brow Ridge Heavy Malar Diastema Protruding Muzzle Large Canines Massive 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

Physical differences between Apes and Humans – The Skull HUMANSAPES Occipital Condyle forwardOccipital 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 cm 3 Smaller Brains – 400 – 500cm 3 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 Skull

Physical differences between Apes and Humans – The teeth and jaw. HUMANSAPES 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 cuspsFirst premolar has one cusp and second has 2 cusps. No DiastemaDiastema 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 teeth and jaw.

Physical differences between Apes and Humans – The pelvis and backbone HUMANSAPES Backbone is S shapedBackbone 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 pelvis and backbone

Physical differences between Apes and Humans – The legs HUMANSAPES 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 HUMANSAPES 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 HUMANSAPES Chest is broard and narrow, flattened from front to back Chest is flattened at the sides Collar bone is longCollar bone is shorter than in humans Shoulder blades lie on backShoulder blades sit along the sides of the chest.

Bipedalism V’s Quadrupedalism Advantages and disadvantages of bipedal (upright) walking AdvantagesDisadvantages Can 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.