4/2/2014 1 Course Business Midterm #2 next week! • Lecture – Modern Primates – Primate Social & Mating systems – Paleoanthropology – Primate Evolution – Geologic Record & Paleo Climate – Bipedalism – Australopithecines • Lab – Phylogeny – Primates – Primate Behavior – Paleoanthroplogy – Australopith Postcrania • Textbook – Ch. 6 - 11 Chronometric Dating Discrepancies From lecture • K-Ar – 500,000 to 4.5 billion • Ar-Ar – 500,000 to 4.5 billion • Thermoluminescence – 5,000 to 500,000 • DON’T USE THESE AGE RANGES!!! From lab • K-Ar – 10,000 to 4.5 billion • Ar-Ar – 10,000 to 4.5 billion • Thermoluminescence – 100 to 500,000 • USE THESE AGE RANGES!!!4/2/2014 2 What is an ape? Miocene: “Age of the Apes” 3 No tail Short trunk Long forelimb Mobile joints Upright posture Large brain4/2/2014 3 5 Old World Monkeys (Outgroup) Gibbons Orangutans Gorillas Chimpanzees Humans ~ 25 to 30 Ma Proconsul (23-15 Ma): primitive hominoid 64/2/2014 4 7 Old World Monkeys (Outgroup) Gibbons Orangutans Gorillas Chimpanzees Humans Proconsul? Some of the Miocene Apes… 84/2/2014 5 Dryopithecus (12-9.5 Ma) • Best known of the Eurasian Miocene hominoids • Exhibits suspensory adaptations similar to modern apes • Probably ancestral to living great apes 9 Dryopithecus (12-9.5 Ma) 104/2/2014 6 Sivapithecus (12.5-8.5 Ma) • Many specimens from India and Pakistan • Probably ancestral to orangutans • Pronograde? 11 Ouranopithecus (~9.0 Ma) • Known from Greece • Similar cranium to African apes 124/2/2014 7 Ouranopithecus: ancestor of apes and Humans? • No known fossil gorillas and only a few fossil chimpanzee teeth 13 Any Questions? 144/2/2014 8 Terminology • Hominoid = past and present apes • Hominid = past and present great apes • Hominin = past and present bipedal apes • Australopith = hominins in the genera Paranthropus (robust) and Australopithecus (gracile) • Human = members of Homo sapiens 15 Which of the human traits would we expect to find in our earliest ancestor? 16 Gorilla Pan Homo4/2/2014 9 ALA #7 (Part II of ALA #6): In other words, which feature(s) truly distinguishes humans from the other apes? 17 Gorilla Pan Homo ??? Canine Reduction and Bipedality 184/2/2014 10 Canine Reduction: Gigantopithecus • 7.0-0.5 Ma (possibly 9.0-0.1 Ma) • Largest primate that ever lived • Known only from teeth and mandibles • Nepal, China, India, and Vietnam 19 Canine Reduction: ‘Ramapithecus’ • Found in Siwaliks, Lufeng, Fort Ternan, Maboko (Asia and Africa) • Most experts consider it to be Sivapithecus 204/2/2014 11 Canine Reduction: Ouranopithecus • 10-9 Ma, Greece • Reduced sexual dimorphism • Reduced canines • Thought to be the ancestor the African Apes 21 Canine reduction is a hallmark of the human lineage, but it is also found among other, closely related taxa that are probably not on the human lineage. 224/2/2014 12 Bipedalism – non primates 23 Extant primate bipeds? 244/2/2014 13 What is unique about hominins = habitual bipedalism! And it occurs before brain size expansion… 25 264/2/2014 14 Pronograde Orthograde 27 Foramen Magnum • Humans: center of the base of the skull • Chimps: more posterior than a human 284/2/2014 15 Vertebrae • Size and function vary with locomotion – Quadrupeds: all vertebrae are about the same size – Bipeds: much larger vertebrae at the base of spine (weight bearing) 29 Vertebrae increase in size from neck to pelvis4/2/2014 16 Vertebrae • Size and function vary with locomotion – Quadrupeds: C-shaped spine – Bipeds: S-shaped spine (puts center of gravity over pelvis rather than out in front of the body) 31 Pelvis • Orientation and size of pelvis reflects gluteal muscle function – Chimp: long, tall iliac blades in the coronal plane – Human: short, broad iliac blades oriented toward the sagittal plane 324/2/2014 17 33 Gluteal Muscles • Chimp pelvis (long iliac blade, coronal orientation) – Gluteals help move legs equally in all directions (hip extensors) • Human pelvis (short iliac, sagittal orientation) – Gluteals act as abductors on the hip (stabilize) 344/2/2014 18 35 364/2/2014 19 Femur • Robusticity—VERY robust in humans (weight bearing) • High bicondylar angle = a valgus knee 37 Valgus angle Human Chimp 384/2/2014 20 Broad femoro-tibial (knee) joint 39 Chimpanzee “Lucy” Modern Human Foot • Adducted hallux (big toe) • Robust hallux • Presence of arches 404/2/2014 21 Ankle restricted to flexion-extension 41 Long metatarsals and hallux 424/2/2014 22 Short pedal phalanges and non-opposable hallux 43 444/2/2014 23 Constructing the Bipedal Body Plan • Mosaic evolution • Each small change was beneficial • No overall blueprint for bipedalism • Bipedialism, it’s got some issues too 45 Mosaic evolution: different traits evolve at different rates 464/2/2014 24 Any Questions? 47 Why bipedalism?? 484/2/2014 25 Ecological Influence: Savanna hypothesis • Opening of the forest into grassland 5-8 mya required that hominins travel further between fruit trees • Visibility! 49 Evidence against savanna hypothesis • However, woodland fauna may have been associated with Ardipithecus ramidus and Orrorin tugenensis (both probable bipeds) 504/2/2014 26 Dietary Influence: Take advantage of food resources • Bipedal posture allows efficient harvesting of fruit from trees. – When apes or Old World monkeys are bipedal it is often to grab food from branches 51 Tool Use and Carrying • Darwin: Bipedalism led to tool use, which led to smaller canines • Bipedalism evolved to allow carrying of tools and hunting of grassland game • But…early Hominins were habitual bipeds and not associated with tool use – Chimpanzees use tools also 524/2/2014 27 Energetic Efficiency: Bipedalism dissipates heat • Reduction in body surface exposed to sun • When sun is directly overhead, heat load of bipeds is 60% less than quadrupeds. • Faster and cooler winds are higher above ground loss of body hair? • BUT in the forest there would’ve been more shade. 53 Energetic Efficiency: Less oxygen consumption compared to knuckle-walking 544/2/2014 28 55 Locomotion of the Last Common Ancestor? Questions? 564/2/2014 29 Early Hominin Evolution 57 Topics • An adaptive radiation of hominins – The first hominins – The Australopiths • Paranthropus • Australopithecus • Social
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