Presentation on theme: "Unique characteristics of the Human Species. Adaptations for Erect Stance: Position of Foramen Magnum (base of skull not back) Double curvature of spine."— Presentation transcript:
Adaptations for Erect Stance: Position of Foramen Magnum (base of skull not back) Double curvature of spine (S-shaped), lumbar vertebrae wedge shaped Reduction in Jaw size & protrusion Broad, bowl-shaped & short (top to bottom) pelvis (holds abdominal organs) Hip sockets wide apart- femur points in towards knee joint (stability when walking + straight walk)- carrying angle
Adaptations for Erect Stance: (cont.) Hip joint directly below trunk (straight even weight distribution) Due to carrying angle, knee joint has a stronger ‘hinge’ on the outer part to support weight Non-prehensile feet/non opposable big toe Transverse (only humans) + Longitudinal (front to back) arch in foot (good for striding gait) Longer legs than arms: lower centre of gravity
Stance & locomotion Support against gravity: Muscle tone (partial contraction of skeletal muscles) Sense/Stretch receptors Postural reflexes maintain balance Striding gait: Walking where hip & knee are fully extended (other apes have bent knees and hips) Foot/ground contact from heel to big toe across transverse arch. Trunk rotates about around pelvis, compensates by swinging arms. Due to carrying angle central axis during walking is kept close. (little/ no swinging hips)
Brain / Head Relatively large brains (900cm 3 to 2200cm 3 ) Ave 1350cm 3 Apes Ave 400 cm 3 - 500 cm 3 Cerebrum: Largest section of brain (Left & Right hemispheres) Outer portion of Cerebrum: Cerebral Cortex (area of greatest development) Covered by convolutions (increases SA by 50%)
Brain / Head (cont.) Proportion of Frontal lobe SA increased by 14% (area for higher order functioning – thinking, reasoning, planning, processing) from ape to human Larger proportion of cranium used to house brain Shortened snout No prominent brow ridge More prominent nose Decreased jaw size Decreased teeth size
Dentition Less prognathism (forward jutting jaw) smaller teeth Large decrease in size of Canines Minor decrease in size of molars Non interlocking canines, no diastema Dental Arcade (jaw shape): Parabolic, not U-shaped
Effect of the environment on hominin evolution. Hominin: (tribe) consists of humans and extinct ancestors Likely a woodland/forest environment Early hominis were ape-like (arms/limbs arboreal lifestyle) Between 5-6 million BP temp began to drop, forests shrank and were isolated by areas of grasslands Forests continued to thin and trees spread out arboreal lifestyle less beneficial, natural selection may have favored hominis which were better at bipedal locomotion.
Effect of the environment on hominin evolution. Advantages of erect stance: Increased range of vision (predators/prey) Increased size deters predators Hands free for other uses (carry food, tools etc) Higher reach (fruit picking etc) Improved body cooling
Australopithecines Approx 3.6 – 1.4 million BP Home bases, no fire use but tool use appears common. (Oldowan (pebble) tools choppers, scrapers, flakes, chisels) Tools dated back to 2.5 million BP Likely left Africa (2 million BP) to Egypt middle East Asia (?) Evolved to become taller, larger brained & more able hunters
Early Homo 1.8 – 1.75 million BP (Homo habilis) Walked upright with robust hands May have walked bipedally during day and slept in trees. Larger brain (to provide high energy meat diet would be necessary) Meat diet animal caught/killed, scavenged (more developed reasoning/cunning) (bones of animals consumed have cut marks stone (tools) and teeth) Based on modern day hunter-gatherers: Male hunted meat Female gathers fruit/veg Children remained in home base Food sharing between members of social group Increase in spoken communication (bulge in speech producing area in brain/ larynx capable of speech)
Homo erectus 1.4 million – 250 000 BP Europe / Africa (400 000 BP) Likely modifying environment to suit themselves (environments was less of a selective factor) Use of fire, building of shelters, sophisticated tools (stone and bone) Skillful hunter: planned slaughter of game Slaughter of baboons (Kenya) Required organization, logical thought and communication Fire used to drive elephants into swamp (Spain) Use of fire, stone and bone tools Use of fire: scare predators, warmth, light, hunting, cooking Possibly have a relatively complex spoken language
Homo neanderthalensis approx 350 000 – 125 000 BP Europe, end of Ice Age More advanced tool making cutting, gouging, scraping piercing Flake tools allow cloth making Burying of the dead belief in after life (ceremonial burials)
Homo sapiens Approx 200 000 – 0 BP Environment is no longer a major factor in human evolution as humans adapt environment to themselves rather than adapting themselves.