ISS 210 1st Edition Lecture 6 Outline of Last Lecture I Louis and Mary Leaky II Virtual Anthropology III Taphonomists and Deposition IV A Leopards Pray V Stratigraphy VI Vulcanic Tuffs VII Chronometrics VIII Trapped Charge Dating IX Species Where do you draw the line X Catastrophism XI Uniformitarianism XII Phyletic Gradualism XIII Punctuated Equilibrium XIV Allopatric Speciation XV Homosapiens Sapiens XVI Cladistics Vs Evolutionary Tree XVII The Disadvantages of Bipedalism XVIII Dentition and Skulls XIX Tooth Enamel Wear Patterns Outline of Current Lecture I The Piltdown fossil II Piltdown Skull III The Benefits to Bipedalism IV Bipedalism vs knuckle walking V The case for bipedalism VI Ardipithecus ramidus VII Ardi s Anatomy VIII Ardi s Environment IX Hominids in Africa X Map of Chad XI Sahelanthropus Tchadensis or Tourani XII The Human Evolution Story XIII Distinctive features Australopiths XIV A aferensis Teeth and Jaws XV A afarensis Lucy XVI XVII XVIII XIX XX XXI Pelvis and Femur Chimpanzee Australopitheorine and Human Laetoli Footprints Laetoli Footprint Thermal Image How made stone tools A garhi 2 5 mya Bouri Ethiopia Heavy Duty Scraper from Olduvai Gorge Current Lecture I II III IV V The Piltdown fossil Discovered in 1912 this skull with human and ape like features provide the missing link Someone hafted the jaw of an orangutan to a modern human cranium fit the model of the time Discredited in 1953 it ruined career and reputations Piltdown Skull Brain Bias Theory only a hominid with a large brain could walk bipedally Brain evolved to make tools Bipedalism evolved to carry tools Impact Discredited Dubois s 1891 Upright Ape man Made acceptance of Dart s 1924 Southern apes difficult The 1974 discovery of a small brained fully bipedal 3 2 million year old A afarensis Lucy ended the debate Scientists began looking for older fossils and began finding them further west The Benefits to Bipedalism Look larger and don t present a horizontal target to predators See farther when in tall grass Carry things about Better able to cool the body and brain Hairless and sweat glands Aftord humans incomparable stamina and the ability to remain active in the sun for long periods and travel long distances easily Bipedalism vs knuckle walking energy efficiency is determined by length of stride and amount of muscle activated in each stride Humans use only 25 of the energy apes use whether knuckle walking or walking upright The case for bipedalism Apart from a larger brain upright bipedalism is the other uniquely human trait Evidence of ancient experiments in bipedalism within a new ape niche part arboreal part terrestrial Tattersal suggests earliest ancestor preferred upright posture and maintined it on the ground Early species 3 4 mya pulled a seemingly random selection of possible dental facial and cranial traits Large hominid like or smale ape like ear openings Foramen VI Ardipithecus ramidus Found at Aramis in Ethiopia in 1994 and proposed as the root of the hominid line A bipedal chimpanzee with mix of ape and hominid features Narrow molar teeth with thin enamel coating are ape like Tiny chimpanzee like braincase has a forward shifted foramen magnum indicates it was Habitually upright Lived in densely wooded area VII Ardi s Anatomy Less muzzle and no dagger like canine teeth seen in chimpanzees Opposable big toe but toes in the line to allow walking Spine curved like humans pelvis shorter and broader than apes Flexible wrist that could bend backward Suggests that ancestors never knuckle walked forcing a rethink of what the last common ancestor walked like VIII Ardi s Environment Savannahs had nothing to do with walking upright Lived in a woodland area climbing fig and palm trees Ate a woodland not a grassland diet fruits nuts tubers with insects small mammals or bird eggs Size shape and distribution of enamel on teeth suggest a more omnivorous diet than chimps IX Hominids in Africa Environment and Evolution Plate tectonics raised the landscape of Eastern Africa creating the African rift valley from the Horn of Africa to Mozambique Moisture from the Atlantic was trapped in the west maintaining tropical forest where apes evolved The east was in the rain shadow and became dry with a mosaic of habitats in which hominids engaged Recent discovers show that hominids emerged in the west as well X Map of Chad Discovery of new fossils is a matter of looking in new places Hominid fossils are no longer an East SideStory Sanelanthropus tchadensis XI Sahelanthropus Tchadensis or Tourani 6 to 7 mya A mosaic of chimpanzee and hominid features If truly a hominid then hominids branched off from chimps before 6 mya XII XIII XIV XV XVI XVII XVIII XIX The Human Evolution Story Australopithecusmanesis 4 2 to 3 9 mya Found in Kenya in 1995 at Kanapoi and Allia Bay Possessed wide thick enameled molars Lived in riverine forest bordering on woodland and open areas A amanesis upper and lower tibia Distinctive features Australopiths Upright bipedal walkers but hardly human in other respects Diet grains roots tubers and scavenged meat Y5 cusped molars reduced canine diastema and a parabolic dental arcade Skull has chimp sized brain case and a large strongly projecting face Increased cranial capacity Australopiths described as bipedal apes A aferensis Teeth and Jaws Chewing teeth are big Jaws are of primitive proportion Enamel is thick as in later hominids Canine teeth are smaller and more stoute rooted than apes but larger and a bit more projecting than later humans A afarensis Lucy Broad pelvis and lower limb bones correlate with bipedal walking hyperadapted to bipedalism Longer arms with short upper arms shorter legs long curving hands and feet built for grasping narrow shoulders and rib cage that widened dramatically Bipedal A slow runner but good at climbing favoring an environment with trees for shelter Pelvis and Femur Chimpanzee Australopitheorine and Human For chimps walking on two feet is as energy efficient as knuckle walking Human bipedalism is more efficient than chimp bipedalism Indicates bipedalism was well established but with some physiological differences Laetoli Footprints An 80 foot track left 2 6 myr when two hominids walked through fresh volcanic ash Laetoli Footprint Thermal Image Comparison with modern human foot lower left indicates a divergent big toe How made stone tools Stone tools were once seen as the sole produce of Homo but there are now being attributed to the australopiths as well