Bio Anth Week 10 of Notes
Bio Anth Week 10 of Notes Anth 1001
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This 6 page Class Notes was uploaded by Jaimee Kidd on Wednesday March 23, 2016. The Class Notes belongs to Anth 1001 at George Washington University taught by Shannon C. McFarlin in Spring 2016. Since its upload, it has received 19 views. For similar materials see Biological Anthropology in anthropology, evolution, sphr at George Washington University.
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Date Created: 03/23/16
Primate Origins Continental Drift- • Earth’s crust is formed by continental plates that float and move on the plastic mantle • Position of continents has changed throughout time • (1) Position of the continents influence the movement and distribution of animal species, including primates • (2) Distribution of continents influence climate Recognizing early fossil primates • Petrosal Bulla • Highly Derived Hands and Feet ◦ Grasping hands and feet ◦ Flat nails instead of claws • Decreased reliance on smell ◦ Reduction of the snout • Increased reliance on vision ◦ Forward facing eyes ◦ Protected eyes (postorbital bar) Adaptive Origins of Primates • Hypothesis: ◦ Arboreal ▪ Primate characteristics such as grasping hands and feet, nails, and stereoscopic vision evolved as adaptations to the arboreal lifestyle of early primate ancestors ▪ BUT: Primate ancestors were already arboreal so arboreality alone is not enough to explain primate adaptations ▪ Many other extant arboreal mammals lack primate specializations ▪ Arboreality alone can’t fully explain distinctive primate traits- ▪ opossum, squirrel, raccoon, tree shrew ◦ Visual Predation ▪ Primate visual specializations and other distinctive primate traits, evolved as adaptations for stalking and grasping insect prey in the terminal branches of trees ▪ Reduction of olfaction would be a secondary result of the orbits coming together ▪ Attempts to link the visual specializations in viewing prey with depth perception in being accurate in targeting prey in an arboreal environment, in the terminal branches of trees ◦ Angiosperm Exploitation ▪ Primates co-evolved in concert with the adaptive radiation of flowering plants to exploit their products (fruits, flowers, nectar) and the insects that feed on them in a small branch setting ▪ This links the evolution of primates in the beginning of the cenozoic area with the appearance of angiosperms or flower breeding plants ▪ Environment that was much warmer than is it today, thought to have been a period of recovery from the comet impact killing off much of the plant life before it, before that period the prominent plant were gymnosperms that are exposed seeds such as pine trees with their pine cones ▪ around this time that flowering plants appeared (angiosperms) ▪ with these, insects that act as pollinators also appeared ▪ In other words, all of a sudden on the landscape you have new resources to be exploited —> the flowers, the fruits, the insects ▪ This hypothesis thus proposes that primates would have coevolved to exploit these newly found resources ▪ Visual adaptation according the this was based on the necessary ability to distinguish between colorful fruits and flowers as well as the insects within the canopy • Consensus view incorporates ideas from the visual predation model and the angiosperm exploitation model • Consistent with fossil evidence showing that earliest primates were nocturnal and had adaptations for insectivore and fruit-eating Evolution of Primates: Family Tree • Paleocene (65-55 million years ago/mya) ◦ Earliest record of primates in fossil record from the paleocene comes from Plesiadapiformes ▪ Primitive, they retain a number of ancestral mammalian traits ▪ Some plesiadaapiformes possessed some, but not all, derived primate traits ▪ Not clear if they fall within or just outside of the primate evolutionary tree • Eocene (55-34 mya) ◦ First Primates of “Modern Aspect" ◦ Adapoids ▪ Elongated snout ▪ Many were diurnal (small orbits) ▪ Lack derived features of strepsirhines of haplorrhines ▪ Probably ancestral to strepsirrhines ◦ Omomyoids ▪ Short snout ▪ Large orbits suggest nocturnality ▪ Small, primarily insectivorous ▪ Possible relationship with haplorrhines • Oligocene (24-35 mya) ◦ First evidence of anthropoid primates ◦ Marked cooling and drying grand at the end of the Eocene ◦ Extinction of certain species and evolution of new ones ◦ Geographic distribution of early fossil anthropoids ◦ Found in the Fayum (in Egypt)- very rich fossil depository ▪ at least fourteen different species of anthropoids were found here ◦ Genus Apidium ▪ Small bodied arboreal quadrupedal ▪ Small brain ▪ Diurnal ▪ 18.104.22.168 dental formula —> indicative of its evolutionary position before NW monkeys divergence ◦ The arrival of the New World Monkeys in South America ▪ (1) Ancestors of NW monkeys originated in Africa and rafted across the Atlantic Ocean ▪ (2) Ancestors of NW monkeys can be North American primates (but no fossils support this hypothesis) ◦ Genus Aegyptopithecus ▪ Medium sized, arboreal ▪ Diurnal ▪ Frugivorous ▪ Small Brain ▪ Derived Catarrhine dental formula ▪ Loss of the 2nd premolar, for a dental formula of 22.214.171.124 ▪ Postdates divergence of New World monkeys and shares affinities with Old World monkeys • Miocene (25-5 mya) ◦ Earliest encounter with apes ◦ Extant Apes ▪ Locomotion underneath branches (large size) —> corresponding post cranial adaptations ▪ Apes swing below branches ▪ No tail, long flexible arms, more vertical posture, larger brains ◦ Ape Localities- today apes show a more limited geographic distribution ▪ All diversity we saw in the miocene has been limited to 4 main species today because of limited geographic locations ◦ Ape Diversity ▪ Approximately 100 ape species during the Miocene ▪ In Europe, Asia, and Africa ▪ Examples of some of these species: ▪ Early African Morotopithecus and Proconsul ▪ 20 Million years ago, Uganda, Kenya, Namibia ▪ Good evidence that this group originated in Africa because the earliest Miocene forms were found in Africa ▪ Derived Hominoid Features: ▪ Larger relative brain size ▪ Shorter snout compared to Aegyptopithecus ▪ Y-5 Molars ▪ A lot of scientists like to call Miocenes Dentist apes because a lot of what links them together is their dental makeup ▪ lacked a tail ▪ The post cranial skeleton indicates Proconsul was quadrupedal and lacked derived features for suspensory locomotion ▪ Good candidates to represent the last common ancestor of apes and humans ▪ Asian forms, Sivapithecus ▪ Late Miocene: 12-18 million years ago ▪ Many features of the skull suggest a close evolutionary relationship with orangutans ▪ Post cranium suggests quadrupedal locomotion ▪ Hominoid Diversity: Gigantopithecus ▪ 9 mya- 100,000 years ago Nepal, China, India, Vietnam ▪ Largest primate that has ever existed: 10 ft ▪ Coexisted with H. erectus for some time ◦ Evolutionary History of the Apes ▪ Many different species, with unclear evolutionary relationships ▪ Sivapithecus or similar forms likely ancestors of orangutans ▪ Some European and Asian species might be ancestral to African apes ◦ Decline of Miocene Hominoids ▪ Climate changes in the late Miocene (cooler and dryer climate) ▪ Too slow generation time and developmental period to deal with these climatic changes ▪ With significant climate changes between the birth of apes, because of the slow developmental time it is much more difficult to deal with these climatic influences ▪ The same climatic conditions favored the evolution of the earliest ancestors of the human lineage Becoming Human What Makes a Hominin? • Major evolutionary novelties of humans Habitual upright walking (bipedalism) Characteristics of the dentition Elaboration of material culture Significant increase in brain size Long developmental period and long lifespan • Mosaic Evolution- different traits evolve at different points in time Dentition • 126.96.36.199 dental formula (same as in all Catarrhines) • Y-5 lower molar pattern • Canine reduction ◦ Canine size and shape is associated with behavioral differences in apes ◦ Reduction of sexual dimorphism—>less male-male competition—>different social interactions ◦ Canine-3rd Premolar (CP3) honing complex of apes Upper jaw has a gap by canine for lower canine- called the diastema The rubbing of the rubber and lower canine actually sharpens the upper canine • Apes have U-shaped dental arcade while humans have a parabolic dental arcade ◦ front part of ape dental arcade is wider, while course is more curved ◦ this also characterizes the lower jaw • Apes also have large canines, and broad incisors while humans have smaller teeth • Chimpanzees have more facial prognathism ◦ Humans have less facial prognathism and a smaller, shorter mandible Muscles of Mastication • Temporalis- action of closing the jaw • Masseter- originates on the cheekbones and inserts on the lower jaw, when this contracts they are responsible for the bite forces that can cut through foods • Areas where these muscles attach are more robust and flaring on apes than they are on humans Anatomy of Bipedalism • Not the only animals to do this but of the few animals to do this habitually • Defining characteristic of humans • Suspensory Locomotion and Vertical Climbing ◦ Increased mobility of extremities ◦ Shoulder blade located on back ◦ Forelimbs elongated compared to hind limbs ◦ Long and curved fingers for grasping branches • Knuckle Walking ◦ Wrist joints are stabilized • African apes have long upper limbs 9inherited from an ancestor with suspensory locomotion) • Dorsal positions of the shoulder blade • Humans have inherited these adaptions as well • Bipedal Locomotion- What anatomical modifications are needed to become a habitual biped? ◦ Center of Gravity ▪ Fixed point, through which body weight is transmitted or balanced ▪ When humans stand, the COG is situated directly in the midline ▪ Only minimal muscle activity is needed to maintain standing posture ◦ Foramen magnum position ▪ Foramen magnum is positioned directly underneath the skull in humans— pull through which your spinal cord passes ◦ Body proportions ▪ Intermembral Index = (forelimb / hindlimb) X 100% ▪ Chimpanzee ~ 110% ▪ Humans ~ 70% ◦ Vertebral Column ▪ Cervical (neck) and lumbar (lower back) curvatures to maintain center of gravity over the pelvis ▪ Larger size of the lumbar vertebrae to support body weight ◦ Pelvis Shape ▪ Humans have a wider, basin-shaped pelvis with short, broad, curved iliac blades ▪ Apes is much longer and not as wide, less curved iliac blades, laterally flared ▪ Iliac Blades repositions the gluteal muscles on humans creating improved lateral stability during swing phase of bipedal walking ▪ abduction- bringing your leg out to the side ▪ repositioning of gluteal muscles allows for abduction in humans which is important because they allow for us to counteract instability of falling over when we are on one leg ▪ method to lateral stabilize the pelvis so that we don’t fall over when we are on one leg when we are taking steps ◦ Knee ▪ Valgus angle of the knee ▪ When humans walk, the foot falls directly below the center of gravity ▪ Femur is oriented at an angle ◦ Foot ▪ Big toe is not opposed to the other four digits, and is enlarged in size ▪ Enlarged heel (calcaneus) ▪ Development of arches
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