Mod. 4 Lectures 4-9
Mod. 4 Lectures 4-9 ASM 104
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This 9 page Class Notes was uploaded by Gabrielle Hsu on Thursday October 1, 2015. The Class Notes belongs to ASM 104 at Arizona State University taught by Campisano in Fall 2015. Since its upload, it has received 44 views. For similar materials see Bones, Stones/Human Evolution in anthropology, evolution, sphr at Arizona State University.
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Date Created: 10/01/15
MODULE 4 LECTURE 4 INTRODUCTION This lecture is about paleoanthropology field work and data MAIN IDEAS Field site Hadar village in Addis Ababa capital of Ethiopia Nonhominin fossils Biostratigraphical markers animal fossils can be used to date deposits because they have known dates in the fossil record Taphonomy comes from Greek word meaning death Studies processes in which organisms become fossils Old age predation accidents disease catastrophes hunting Between death amp fossil discovery Decomposition Transportation by water or other animals Burial Other chemical biological amp physical processes Time averaging how long was the period of accumulation of fossils at a site What material researchers collect amp what they leave behind Ex Hadar site AL 333 discovery site of hundreds of hominid fossils Thought to have been attacked by carnivores Many hand amp foot bones found here bc carnivores carried away the larger bones w more meat Paleoecology study of relationship between extinct organisms amp their environment Can examine one species diet locomotion life span location cause of death age at death etc Or many species w goal of studying their habitats amp relationships between species Habitats provide context for species behavior ecological context for evolution amp ways of travel migration Comparative collection examples of bones to compare to fossils that are found MODULE 4 LECTURE 5 INTRODUCTION This lecture is about the hominid adaptation to bipedalism and why this was so important MAIN IDEAS Disadvantages decreased speedagility gt increased susceptibility to predators Physical features Foramen magnum opening in the skull where the spinal cord connects More centered in bipedal hominids so the head is balanced Less need for the large neck muscles that are present in apes whose foramen magnum is farther back Nuchal crest bony ridge across back of skull site of neck muscles attachments Barrelshaped rib cage wider front to back than side to side More defined curves in vertebral column especially lumbar curve lumbar lordosis Sacrum bone at the base of the spine that connects to the pelvis Tilted forward to support lumbar curve amp maintain center of gravity Aligns other pelvic bones to reduce need for muscle stabilization of torso Short wide curved iliac blades as opposed to tall narrow blades in apes Wider shape supports the abdominal organs since they rest above the pelvis in bipeds unlike quadrupeds Shorter distance from back of ilium to front hip socket makes balance amp walking more efficient Ischial tuberosity works w hamstrings amp sacrotuberous ligament to stabilize sacrum Gluteus medius attached differently used for stability as well as abduction Center of gravity closer to the hip joint instead of in front of the hip joint in apes requires less energy to stay upright More body mass in legs than arms amp torso Longer legs than arms rather than longer arms than legs more efficient walking Valgus knee shaft of femur angles inwards so it is closer to the center of gravity making it easier to stand upright Foot arch absorbs shock while walking Convergent big toe more efficient for walking than divergent hallux seen in apes Straight phalanges rather than the curved bones used for climbing Summary of adaptations for bipedalism Centered foramen magnum Increased spine curvature amp tilted sacrum Shorter wider pelvis More barrelshaped rib cage Valgus knee Convergent hallux Foot arch Hypotheses for evolution of bipedalism Provisioning model Lovejoy Males needed their hands free to carry food amp bring it back to mates amp offspring Problems This behavior is unlikely to have occurred in early bipeds seen today in few primates other than humans Thermoregulatory model Wheeler Bipedalism raises body surface higher from the ground amp makes it vertical This allows more heat dissipation amp minimizes direct sun Problems open grasslands that would make this necessary didn t appear until long after bipedalism Postural feeding hypothesis In uence of arboreal foodgathering postures suspension amp vertical climbing Problems chimpanzees are not bipedal Knuckle walking hypothesis Knuckle walking as intermediate stage between quadrupedalism amp bipedalism Problem what caused the switch to bipedalism Climbing mechanical model Combination of factors Suspensory apes may have been forced to become terrestrial amp didn t know how to use all four legs Branching event into knuckle walking amp bipedalism parallel evolution MODULE 4 LECTURE 6 INTRODUCTION This lecture discusses what a hominin is amp how it s different from a hominid Family Hominidae members are hominids humans amp great apes Subfamily Homininae members are hominines humans amp African great apes Tribe Hominini members are hominins bipedal members of Homininae Characteristics of early Hominini Bipedal Increased brain size Nonhoning premolars apes amp monkeys have premolars designed to sharpen the upper canines Sahelanthropus tchadensis dated 67 million years ago Sahel African region anthropus human tchadensis from Chad Skull found in Chad by paleoanthropologist Michele Brunet Previously lacustrine site in Sahara Desert Appears bipedal from position of foramen magnum but skull is deformed amp could actually be an ape Decreased honing premolar Orrorin tugenensis about 6 million years ago Orrorin original man tugenensis from Tugen Hills Tugen Hills area of Kenya East African Rift Thought to be bipedal but retains curved phalanges Smaller canine amp decreased honing premolar Forest habitat Ardipithecus kadabba 5852 million years ago Found in Middle Awash Ethiopia by Yohannes HaileSelassie Ardi ground pithecus ape kadbba original Smaller canine decreased honing premolar Long primitive phalanges Closed woodland habitat Ardipithecus ramidus 4844 million years ago Ardi ground pithecus ape ramidu root Even more reduced honing premolar Bipedal but retains divergent hallux Long arms amp fingers Climbed trees amp ate fruits amp leaves Closed woodland habitat MODULE 4 LECTURE 7 INTRODUCTION This lecture is about the Australopithecus genus KEY POINTS Lived in Africa about 4219 million years ago Terrestrial bipeds Six known species MAIN IDEAS Slight increase in brain size about 3040 bigger than chimpanzees Subnasal prognathism jaw protrudes in front of the face Larger thicker mandible with reduced honing premolar that eventually disappears but larger premolars amp molars than apes or humans Reduced lower canine that eventually disappears reduced canine diastema gap on upper jaw that leaves space for lower canine Australopithecus african us Australo southern pithecus ape africanus Africa Found by Raymond Dart s team in South African cave sites in early to mid 1900s Difficult to date bc sites had no volcanic deposits Dart knew it was a biped bc of the foramen magnum position this was poorly received bc other scientists were convinced brain size evolved before bipedalism Australopithecus afarensis Afar region of Ethiopia First found in Laetoli Tanzania 1973 Don Iohanson found valgus knee joint in Hadar Ethiopia 1974 discovery of Lucy one of the most complete hominin skeletons 1993 Israeli scientist Yoel Rak finds male Afarensis skull that has larger canines than female Male skeleton Kadanuumuu Big Man found at WoronsoMille site near Hadar also had larger body than females SelemDikika Child juvenile skull shows growth patterns early hominids had a much shorter juvenile period than modern humans Australopithecus anamensis Anam lake Found by Meave Leaky near Lake Turkana in Kenya Oldest Australopithecus 4236 million years ago Australopithecus garhi Garhi surprise Found by Dr Berhane Asfaw near Addis Abbaba Dated 25 million years ago Large teeth amp small brain May have used stone tools Australopithecus sediba Found in 2008 by Lee Berger in Malapa Cave near Pretoria South Africa Dated 19 million years ago Smaller teeth than other Australopithecus species Australopithecus dentition diet Large at molars with thicker enamel chimpanzees have thin enamel that leads to sharp edges when worn Suggests that they ate harder food like fruits amp nut as well as weak food like owers amp buds as opposed to tough food like stems seed pods or meat Carbon isotopes Certain grasses have a C4 pathway while trees shrubs amp some different grasses have a C3 pathway Hominin enamel carries an imprint of isotopes from what they ate while their teeth were developing Some marks on bones suggest Australopithecus afarensis may have used stone tools on meat but no tools have been found Phytoliths microscopic plant structures found between hominin teeth can be used to determine what kind of plant was eaten SUMMARY Australopithecus features Bipedal Slightly increased brain size Sexual dimorphism probably lived in groups w multiple males amp females Ate fruit nuts roots amp meat Paranthropus and Homo appear before Australopithecus became extinct about 19 million years ago MODULE 4 LECTURE 8 INTROUCTION This lecture is about the genus Paranthropus which follows Australopithecus KEY POINTS Lived in Africa 251 million years ago Three species found in Eastern amp Southern Africa MAIN IDEAS Zygomatic bones cheekbones are wider amp more anterior in relation to the jaw Face is higher on the braincase than Australopithecus Sloping frontal bone forehead Males have sagittal crest Dentition Very large jaw Molarization premolars look the same as molars Molars amp premolars are much larger amp farther forward very small canines amp incisors Sexual dimorphism Males are larger amp taller amp have sagittal crests Large temporal fossa space between zygomatic bones amp skull Postorbital constriction skull indents behind the eyes Paranthropus robustus Par beside anthropus human robustus robust Found in South Africa in 1930s by medical doctor Robert Broom Paranthropus boisei Boisei name of man who funded research Discovered in by Mary Leakey in 1959 Found only in East Africa Paranthropus aethiopicus Aithiopicus Ethiopia Dated about 25 million years ago Most primitive species Large jaw referred to as nutcracker menquot Very prominent sagittal amp nuchal crests Subnasal prognathism Large temporalis amp neck muscles Temporalis fanlike muscle on the side of the skull maintains the closed rest position of the mandible amp pulls it back while chewing This explains the sagittal crest which would anchor amp strengthen the temporalis Large neck muscles that attached to amp were strengthened by the nuchal crest Microwear examining teeth for scratches amp pits left by hard food Shows that P boisei only ate grasses so why did it need such a large jaw Bone digging sticks found with Paranthropusfossils Wear patterns suggest they were used to dig in termite mounds This still doesn t explain the huge jaw Many juvenile males found in cave sites Long juvenile growth period may have left groups until they could grow up amp challenge alpha males similar behavior found in some apes Susceptible to predation holes found in a skull that match leopard canines SUMMARY Went extinct around 14 million years ago no living descendants Scientists still don t really know why or why it had such large jaws MODULE 4 LECTURE 9 INTRODUCTION This lecture is about the genus Homo KEY POINTS Found in both East amp South Africa Two distinct species around 23 million years ago Homo habilis and Homo rudolfensis MAIN IDEAS Oldowan tool industry early stone tools discovered by paleoanthropologists Louis amp Mary Leaky in Olduvai Gorge site in Tanzania Who used these tools It couldn t have been Paranthropus because They were thought to have been used for meat amp Paranthropus wasn t a meateater Paranthropus wasn t ancestral to humans amp it was thought only an ancestor of humans could have produced tools Brain wasn t large enough Homo habilis Found in 1964 by the Leakeys Habilis handy thought to have created the Oldowan tools Larger cranium Rounder braincase w more prominent forehead Smaller face below braincase instead of in front of it orthognathic not prognathic Brow ridges Smaller teeth Similar body size to Australopithecus Feet specialized for terrestrial bipedalism Long arms amp hand bones that indicate climbing Homo rudolfensis Found in 1972 near Lake Turkana in Kenya by Richard Leakey Even larger cranium More prominent forehead with smaller brow ridges Larger atter face Kenyan thropus platyops Found in 2009 near Lake Turkana by Meave Leakey 35 million years ago 1 million years older than Homo species Until its discovery amp noted similarities to H rudolfensis H rudolfensis amp H habilis were argued to be the same species displaying sexual dimorphism We now know H rudolfensis is descended from K platyops amp H habilis is not