Topic 19 - Human Evolution.pptx

Topic 19 - Human Evolution.pptx - BIOL 3030 Evolution and...

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Unformatted text preview: BIOL 3030: Evolution and Systematics Topic 19: Human Evolution A Species of Hybrid Origin • Humans are a single species • But, its more complex • The high Tibetan plateau is a harsh environment • High altitude = low oxygen • Tibetans and Han Chinese are closely related as evidenced by similar genes across the genome • Except 1 – EPAS1 • A transcription factor active in low oxygen conditions A Species of Hybrid Origin • Indicative of selection • Does anybody else have the sequence • Yes – Denisovans – an extinct group of humans related to Neanderthals • Coexisted with modern humans to about 30,000 years ago Rows – individuals, only polymorphic sites shown, tan is primitive, red or green derived The Evolutionary History of Humans • Fossils, genetics, genomics, biogeography all point to human origins in Africa from other Primates • Sister to Pan (chimps and bonobos) • Then Gorilla, then Pongo (orangutans), then gibbons • All in Hominoidea (superfamily) What was this most similar to? A. Chimps and bonobos (Pan) B. humans C. both The Evolutionary History of Humans • Hominoids arose in East Africa ~20 MYA • Proconsul – clearly an ape, but lacked the limb mobility of brachiators The Evolutionary History of Humans • Then the trail goes cold • ~14 MYA fossils from Africa, Asia, and Europe • But sparse fossils until ~5 MYA • Probably East Africa, but could be Eurasian Hominins • Almost only morphology • DNA to about 50KYA • Some bits further back to 700KYA, but not as good • Do have whole genomes of Neanderthals and Denisovans (Siberia) • Recently sequenced a human thought to be just 300 generations from ancestor of the Eurasian clade (had longer stretches of Neanderthal) Multiple species present until 30KYA Interbreeding What makes a Hominin? • Not a large brain • Bipedalism and loss of shredding canines and other dental changes What makes a Hominin? • Early ones difficult – bad fossils and not much removed from the ancestor • Rise of hominins related to changes in ecology 6 MYA • Cooling temperatures shifted forest to savannah Sahelanthropus tchadensis Bipedalism • Why? Not sure • Energetic efficiency • Keep cool in savannahs (less body surface facing sun, more facing wind) • Frees up hands Foramen magnum ventral Pelvis Shorter and Broader Femur Elongated, Angled Inward Foot Arched for Walking, Hallux Aligned vs. Opposable, Digits Shorter Pollex Hallux Early Hominins • Small brains • Ardipithecus ramidus may have been partially arboreal Ardipithecus ramidus Archaic Hominins • Shared increasing number of physical and physiological characters with us • Bipedal • Lucy – 3.2 MYA Praeanthropus afarensis • Later ones like Australopithecus garbi (2.5-2 MYA) used stone tools Megadont Archaic Humans • Large attachment sites for chewing muscles – chewed low quality food • Deadend • Sytopic with other archaics and Homo Homo • ~2.3 MYA – H. habilis, H. rudolfensis, and H. naledi(?) – bridge gap, intermediate brain size, used tools • H. ergaster in Africa and H. erectus in Africa and Asia ~1.9 MYA • Resembled humans • May be same species as one another • 5-6 ft. tall, longer legs, larger brain than ancestors • Stone axes, fire, cooked food • Very successful – throughout Africa, Europe, and Asia – some regional differences • Cooking may have led to morphological change • More energy, less chewing Homo habilis Homo rudolfensis • Rounder cranium • Larger brain • Facial structure like ours (but lg. brow ridge) • More like modern humans • Hunted big game • More elaborate tools • Spears • Gave rise to modern humans ~200-130KYA The New Guys • Homo floresiensis – the Hobbits • Indonesian Island of Flores • 840-12 KYA • About 1 m tall with large, flat feet • But facial structure like Homo and advanced tool use • Probably descendent of H. erectus or even earlier lineages The New Guys • Homo naledi • Whole skeletons • Don’t know the age • About 1.5 m tall with brain no larger than Australopithecus • Highly dexterous hands, but human-like feet • Reduced jaw and teeth • Cranial structure like H. erectus Found in a cave, back passage, had to have been put there Homo sapiens • Multiregional vs. Out of Africa Hypotheses • Arose in Africa ~200,000-130,000 YA • Expanded out ~100,000 – 35,000 YA • ~50,000 YA – more advanced stone tools, more elaborate shelters, are and music, hunting larger game, ceremonial burial, long-distance trade and maybe speech Tool Use • Distinct phases • All beginning in Africa Out-of-Africa vs. Multiregional We weren’t alone, Neanderthals gone by 30,000YA Neanderthals • Had complex behaviors • Overlapped with European early humans • Stouter, heavier brow ridge, larger eyes • Helped sick and injured, hunted big game, buried dead, probably capable of speech • First studies with mtDNA – separate haplotypes • Then genomic DNA from bone fragments • Pääbo and colleagues reasoned that people that overlapped with Neanderthals would have their DNA if we interbred Denisovans • Only recognized in 2010 from genetic data • And a single finger bone and some teeth • Sister to Neanderthals and interbred • Some interbreeding with H. sapiens • May have had a wide distribution Eurasians and New Guineans with 1-4% Neanderthal DNA And its not all the same genes When did we interbreed? • Published Oct. 2014 • Femur from Siberia • Genome sequenced – H. sapiens • 45,000 YA • Same amount of Neanderthal DNA, but in bigger chunks • Neanderthal gene flow into those humans about 7-13 KY before it lived. Geographic location, morphology and dating. Ust’-Ishim Neanderthal & Denisovan fossils Q Fu et al. Nature 514, 445-449 (2014) doi:10.1038/nature13810 Genographic from National Geographic ($200) I joined National Geographic's Genographic Project to map the human journey and its scientists ran a cuttingedge test of my DNA. Here is what I learned about my ancient ancestry: My Dad I AM * I AM 2.8% NEANDERTHAL As humans were first migrating out of Africa more than 60,000 years ago, Neanderthals were still living in Eurasia. It seems our ancestors hit it off, leaving a small trace of these ancient relatives in my DNA. 42% Mediterranean 38% Northern European 18% Southwest Asian I AM 1 705,343 of PARTICIPANTS MY MAP MY MATERNAL LINEAGE BEGAN ABOUT 150,000 YEARS AGO. MY PATERNAL LINEAGE BEGAN AT LEAST 180,000 YEARS AGO. My maternal ancestors left Africa and settled around southeastern Europe. They then expanded north into the rest of Europe. They survived by hunting and finding wild food sources. In Europe, they met with those who were already there and formed new cultures that are reflected in the archaeological record. Thus, my cousins played an important role in the history of Europe. My paternal ancestors left Africa and moved north through western and Central Asia. They then turned west and crossed the grasslands of southern Russia into Europe. There, they eventually drove the Neanderthals to extinction, though they did interbreed with them. Living a huntergatherer lifestyle, my early ancestors set the stage for later European history. My paternal branch is RCTS11962 My maternal branch is U8a1a1b1 * and 1.3% Denisovan That's my story. What's your story? J oin this real-time scientific project now and help us tell the human story, while discovering more about yourself than you ever thought possible. Go to www.genographic.com www.facebook.com/genographic @genographic My Dad How are we all related? • Greatest genetic diversity in Africa • Mitochondrial DNA phylogeny • But, it is more complex The phylogenetic tree of 456 whole Y chromosome sequences and a map of sampling locations. Monika Karmin et al. Genome Res. 2015;25:459-466 © 2015 Karmin et al.; Published by Cold Spring Harbor Laboratory Press Black is people of mixed descent Genetic Structure • Examine snp’s (single nucleotide polymorphisms) or microsatellites • Structure – program assumes DNA comes from a specified set of populations (K) • Assigns individuals to populations Column – individual Row equals snp • • • • • • 650,000 snp’s 938 individuals Supports Out-of-Africa Geographically close groups are phylogenetically close Series of founder events Results in less genetic variation the further from Africa How and when we moved ...
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