Mod. 4 Lectures 1-3
Mod. 4 Lectures 1-3 ASM 104
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Date Created: 10/01/15
MODULE 4 LECTURE 1 INTRODUCTION This lecture is about different types of evolution and how these relate to several hypotheses on the origin of primates MAIN IDEAS Modes of evolution Cladogenesis one species splits into two or more distinct species Anagenesis one species gradually transforms into a new species the original species may or may not continue to exist The stages in the transformation are called morphospecies referring to morphology or chronospecies referring to time Tempo of evolution Gradual phyletic gradualism happens very slowly over time Punctuated punctuated equilibrium happens quickly due to a disturbance sudden change in the environment Often followed by a period of equilibrium hence punctuated equilibriumquot Results in cladogenesis branching of species Macroevolution Evolution between species Major phenotypic changes The big picturequot ancient ancestry diversity of species extinction etc As opposed to microevolution which is change within a population amp observable during short periods of time Divergent evolution one species evolves into two or more different species Those species diverge over time meaning they each continue to evolve amp become more amp more different from each other Parallel evolution two distantly related species evolve similar traits The species share a common ancestor but not an immediate one amp are now in different groups but have independently evolved similar traits Convergent evolution unrelated species evolve similar traits Species without a common ancestor evolve similar traits called analogous structures Caused by the species having similar environments habitats amp similar roles within them How does this relate to primates They must have originated by diverging from an ancestral mammal which could have been something like a tree shrew a very primitive arboreal mammal Why did primates evolve the features that make them primates binocular vision grasping ability at nails etc Arboreal Theory 1913 Developed by paleontologists Grafton Elliot Smith and Frederick Wood Iones Suggested that primates developed all of these features because they were arboreal Grasping ability needed to hold onto branches Binocular vision needed depth perception to run amp leap in the trees Larger brains needed to process arboreal environment in 3D Reduced sense of smell shifting winds in the trees made smells less useful so a strong sense of smell was unnecessary Problems Other arboreal mammals do not have primate features amp are still well suited to their environment Ex squirrels are arboreal but have forwardfacing eyes claws amp no grasping ability Visual Predation Theory 1972 Proposed by biological anthropologist Matt Cartmill Thought primates evolved from small animals that lived in bushes amp ate insects Needed grasping ability amp depth perception to catch insects These features would also help these animals climb small branches in trees to catch more insect amp possibly access other food like fruit Cartmill concluded this by observing that other predatory animals usually optic convergence amp some amount of grasping ability although many have claws Parallax view apparent displacement of a close object as compared to what s farther away Ex if you hold up a finger with one eye closed then open that eye amp close the other one it appears to move Stereoscopic vision which is what animals with optic convergence have gets rid of this effect if you are using both eyes Problems Some early primates did not depend on insects amp ate plant matter including fruit amp owers Biological anthropologist Robert Sussman observed that fruit bats also have optic convergence but exclusively eat fruit not insects Robert Sussman s theory Angiosperms fruit bearing plants that appeared in the late Cretaceous period Primates appeared after this New availability of fruit amp owers in terminal branches led to the evolution of primates Refined vision needed to locate fruit amp owers in the trees Good sense of smell strepsirrhines needed to examine the fruit owers Grasping ability allowed maneuvering in small terminal branches CONCLUSION For primate traits to have evolved they must have a selective advantage and should also be found in other animals that use similar strategies for survival We know this is true because of researcher Tab Rasmussen s observations of Derby s woolly opossum a small tree possum that is NOT related to primates Arboreal climbing ability Relatively large brain amp eyes Small litters with long developmental period Eats fruit from terminal branches amp grabs insects from the air This is an example of convergent evolution amp also gives strong evidence for Robert Sussman s theory MODULE 4 LECTURE 2 INTRODUCTION This lecture gives a history of primate evolution covering the most major species KEY POINTS Crown group group that appears at the ends of a cladogram s branches Ex Strepsirrhini Epochs of the Tertiary Period Pleistocene Pliocene Miocene Oligocene Eocene Paleocene MAIN IDEAS Paleocene epoch 6556 million years ago Origin of angiosperms amp pollinating insects Placental mammals Have radiated into 35 different orders only 16 living Thought to have dispersed prior to the breakup of the supercontinent Pangaea as they ve been found on N America S America amp Asia Eocene epoch 5634 million years ago First identifiable primate fossils found in N America Eurasia amp Africa Lived in tropical rain forests Convergent orbits with postorbital bar divergent hallux first digit amp at nails shorter snouts than other mammals 2133 dental formula Over 200 species most belonged to superfamily Adapoidea or superfamily Omomyoidea but there were also very small tarsierlike primates found in Asia Adapoidea Small eyes probably diurnal Longsnout Large body small incisors large canines high cusps probably ate leaves amp fruit Auditory ring Omomyoidea Large eyes probably nocturnal Short snout Small body large incisors small canines high cusps probably ate insects Auditory tube Asian primates 10100 grams Fossils found in owl pellets Oligocene epoch 3423 million years ago Surface seawater cools causing habitats to shift tropical plants in the northern hemisphere move south Antarctic ice cap forms Fayum region in Sahara Desert near Cairo Discovery site of many important primate fossils including early strepsirrhines amp haplorrhines Was probably a swampy forest with monsoon season Review of haplorrhine characteristics Postorbital closure eye sockets Shorter snouts with weaker sense of smell Mandibular fusion Generalized teeth without toothcombs Three families of haplorrhines found in the Fayum region Parapithecidae Primitive dental formula 2133 Arboreal Stem catarrhinesquot have some but not all features of catarrhines Review of catarrhine characteristics 2123 dental formula loss of one premolar Different skull structure with fused frontal bones amp auditory tube Ischial tuberosities Propliopithecidae Generalized not bilophodont molars more like apes Postorbital closure Arboreal Oligopithecidae Auditory ring platyrrhine feature Dirunal Arboreal leaping quadruped Relation to Hominoidea amp Cercopithecoidea Old World Monkeys Most scientists think these groups share a common Catarrhine ancestor originating in AfroArabia Propliopithecidae amp Oligopithecidae found in Egypt amp Oman are the oldest stem catarrhines in the fossil record late Eocene to early Oligocene epochs 3530 million years ago 2010 discovery of Saadanius hijazensis in Saudi Arabia Close to the HominoideaCercopithecoidea clade splitting off 2928 millions years ago No synapomorphies derived traits of apes or old world monkeys meaning it is more evolved than the primates found in the Fayum Thought to have preceded the HominoideaCercopithecoidea split Earliest crown catarrhine not stem catarrhines are recognizable as Cercopithecoidea amp Hominoidea fossils only date back to 20 million years ago 510 million years after estimated date of splitting off Oldest known fossil ape amp oldest stem species of Cercopithecoidea discovered by Nancy Stevens Tanzania Rukwa section of East African Rift 252 million years old New World primates found in South America dating from 28 million years ago Oligocene Miocene amp Pleistocene epochs All have platyrrhine features Hypotheses for arrival origination in S America Evolved in S America Unlikely bc no Eocene epoch before Oligocene primates found there Rafted from N America were carried on large pieces of land that broke off at river mouths Unlikely bc currents weren t right Rafted from Africa Accepted theory right directions of currents groups of rodents amp birds w African roots appeared in S America at the same time Ancestor was likely similar to Parapithecidae one of the families found in the Fayum Ancestor of all living platyrrhines Miocene epoch 2255 million years ago Victoriapithecidae early monkey fossils that can t be differentiated into Colobinae and Cercopithecinae Early to middle Miocene Hominoidea loss of tail broader nose amp palate simple molars increased brain size Proconsul early African ape found in about 6 different sites 2017 million years ago Unknown if it had a tail YS pattern molars Dryopithecus most wellknown WestCentral European ape Climate uctuations increased temperatures evaporated Mediterranean Sea in Middle Miocene allowing migration to Europe The sea returned during late Miocene cooling period separating the continents MODULE 4 LECTURE 3 INTRODUCTION This lecture is on the context of human evolution information like age location etc of fossils MAIN IDEAS East African Rift Valley Site of almost all hominin fossil discoveries why Mantle plumes at tectonic plate boundaries Tanzanian Craton between African plate and Somalian subplate heat the crust leading to rifting amp formation of basins that are filled in by lakes amp rivers Lakes amp rivers provided good habitats Sediment carried in by water buries bones Volcanic activity provides material for dating the sites Stratigraphy Uniformitarianism strata layers of sediment were formed by the same natural processes that occur today Law of superposition oldest layers are on the bottom youngest are on the top Depositional indicators Particle grain size clay particles can t be felt or seen wo high magnification silt particles can be felt amp seen w low magnification sand easily seen amp felt gravel Can infer amount of energy used to carry sediment Ex a river system uvial may have gravel amp sand in the channel silt on the proximal oodplain amp clay on the distal oodplain since there is not enough energy farther from the channel to carry larger grains Ex lake system lacustrine will have larger grains near the edge where rivers enter amp finer grains in the middle except during storms or ooding in which more energy carries coarser grains farther into the lake Color Lake deposits often either highly organic or organic reduced due to anoxia lack of oxygen resulting in darkblack color if rich or green color if reduced Floodplain sediments are oxidized from oxygen exposure so often brown or red Laminated structure horizontal layers of deposition Better preserved in a lake Disturbed or destroyed on a oodplain by plants animals insects etc Crossbedded structure layers are tilted at an angle Sign of high energy wind or water Significance depositional indicators where fossils are found indicate what kind of habitat they lived in Geologic time scale Divisions from largest to smallest Eon Era Period Epoch Age Cenozoic Era Age of Mammals last 66 million years separated from Mesozoic Era by the dinosaur extinction Paleocene Epoch 6656 million years ago First primatelike animals including plesiadapiforms Eocene Epoch 5634 million years ago First primate fossils including lemurlike adapids amp tarsier like omomyids Oligocene Epoch3423 million years ago Antrhopoid monkeys amp apes primates become dominant Earliest fossil records of platyrrhines amp catarrhines Miocene Epoch 235 million years ago Apes become more diverse amp abundant Africa amp Eurasia First hominins Pliocene Epoch 5326 million years ago First fossil records of early hominins Ardipithecus ramidus Australopithecus afarensis Pleistocene Epoch 26 million12k years ago Radiation of Paranthropus amp Homo genus Holocene epoch last 12k years After last ice age Dating methods Radiometric absolute dating Relies on radioactive decay of unstable parent element to stable daughter element Halflife rate of decay Isotope atom w same of protons unique to a specific element but different of neutrons different mass Carbon isotopes 2 stable 1 unstable Carbon12 most abundant stable Carbon13 much less abundant stable Carbon14 most rare unstable Potassium argon KAr amp argonargon ArAr dating Mineral crystals formed by magma cooling in volcanic deposits East African Rift Valley Feldspar potassium4O decays into argon40 whichis trapped inside the crystal 125 billion years halflife can date volcanic deposits a few thousand years old or billions of years old Exposure dating cosmogenic luminescence OSL electron spin resonance ESR Caves Determines how long material has been exposed cosmogenic or buried OSL amp ESR Only accurate for last 500000 years Example of Karst topography landforms created by dissolution of bedrock by acidic water Acid dissolves surface along fractures enlarging them overtime Drainage system may form underground South African Pliocene cave sites many fossils fall or are washed dragged dropped or carried into caves Fossils are more buried amp protected but it s harder to tell when amp where they came from