Nature of a Fossil Fossil evidence of pre existing species o Fossil can be tooth bone feather imprint o If conditions are favorable minerals replace substances in bone and fill in porous spaces converting the bone into a rock Bones and teeth can be destroyed by physical chemical and biological processes Fossilization protection from forces of destruction Sources of bias in fossil record o Body size of species o Where fossilization occurs o Exposure and discovery of fossils Cenozoic Era Epochs Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene Plate Tectonics Time Period 65 56mya 56 33mya 33 23mya 23 5 mya 5 1 8mya 1 8mya 10 000ya 10 000ya present Earth s outer shell is subdivided into several major plates and a number of minor plates Plates move relative to one another Movement of plates influences migratory routes climate and ecology Plate Tectonics and Primate Evolution Cenozoic Era North America and Europe were connected to one another during Paleocene and Eocene Explains geographical distribution of early primates Africa was an island continent prior to 19mya About 19mya Africa contacted southwest Asia Explains geographical distribution of apes during the Miocene o Madagascar was an island before the emergence of primates o Theory is that lemurs colonized Madagascar by crossing the Mozambique Channel on Colonization of Madagascar by Lemurs How did lemus colonize Madagascar floating of masses of vegetation Colonization of South America by Monkeys How did monkeys colonize South America o S America was an island continent long before the emergence of primates and the isthmus of Panama connected North and South America less than 5mya o Theory is that the ancestor of New World Monkeys colonized S America by crossing either the Caribbean Sea or Atlantic Ocean on floating masses of vegetation islands Categories of Dating Techniques Relative dating organize items in rank ordered sequence Chronometric dating assignment of a specific age to an item Examples of Relative Dating Techniques Stratigraphy sequence of sedimentary rock o Dating fossils based on their relative positions in the ground Biostratigraphy temporal association of species o Dating of a fossil based on its association with fossils of another species Index fossil index species Fluorine analysis relative age of a fossil based on its fluorine concentration site specific Fossil species of known age is used to estimate age of another species Discovery of Piltdown Specimen 1912 Charles Dawson Found fossils of what he thought were related to humans Reconstructed skull Arthur Smith Woodward Determined that increased brain size sets us apart from ancestors PILTDOWN SPECIMEN WAS FRADULENT o Fluorine test applied to Piltdown o Piltdown had less fluorine then contemporaneous fossils o Piltdown mandible bad different fluorine content than Piltdown mandible Suspects in Piltdown Hoax o Charles Dawson o Arthur Conan Doyle o Martin Hinton Taung Child 1924 Raymond Dart South Africa Face and part of cranium and outline of brain contours recovered Closely related to humans Chromometric Absolute Dating Based on principle of radioactive decay o Radioactive isotope of an element releases energy at a fixed rate half life o Half life amount of time for a radioactive element to lose half of its energy Examples of Chromometric Dating Potassium argon dating K Ar o Radioactive 40K decays into stable 40Ar o Used in volcanic rocks extensively used in dating early hominin fossils in East Africa o Half life of 40K is 1 25 billion years Argon Argon Dating Carbon 14 Dating o Same basic principle as K Ar dating but uses less materials o 14C is a radioactive isotope of 12C o Determine ratio of 14C 12C in items with carbon o Half life of 14C is 5 730 years Paleocene 65 56 mya Fossil primates found principally in North America and Europe Plesiadapiforms were Primitive Primates Differences between plesiadapiforms and modern primates o Longer snout o Eyes not positioned at front of skull o No post orbital bar o Smaller brain o Specialized dentition o Claws not nails o Non prehensile hands and feet Eocene 56 33 mya Primate look more human Anatomies o Eyes face forward o Post orbital bar o Short snout o Prehensile hands and feet o Nails o Large cranial capacity compared to Paleocene species Location of Fossils o Fossils found in N America Europe Asia and Africa o N America and Europe were geographically connected with one another in Eocene by Greenland May explain similarity among species of N America and Europe Environment of Eocene Primates o Tropical and sub tropical forests Taxonomy and Phylogeny o 2 lineages of Eocene primates adapids and omomyids Adapids may be ancestral to lemurs and lorises Omomyids may be ancestral to tarsiers and anthropoids Inferences about Eocene Primates o Some species were diurnal some were nocturnal o Locomotion quadrupedality and leaping o Diet insectivory frugivory folivory o Observation absence of toothcomb Oligocene 33 23 mya Earliest definitive anthropoids are dated to the Oligocene Fossil locations o Fayoum Egypt o Dates 33 35 mya Environment o Tropical forests Taxonomy of Oligocene Anthropoids o 2 lineages Propliopithecines Propliopithecus and Aegyptopithecus Dental formula 2 1 2 3 2 1 2 3 o Same as modern catarrhines apes old world monkeys Parapithecines Parapitheais and Apidium Dental formula 2 1 3 3 2 1 3 3 o Same dental formula as some modern platyrrhines new world humans monkeys Phylogeny of Oligocene Anthropoids based on dental formula o Propliopithecines may be ancestral of catarrhines Evolutionary divergence between old world monkeys and hominoids had not yet occurred o Parapithecines may be ancestral of new world monkeys Colonization of South America o If you accept the thesis that New World Monkeys rafted to S America on floating vegetation then there are anthropoids in Africa with the same dental formula as New World Monkeys parapithecines These African anthropoids predate earliest New World Monkeys by about 10 million years Locomotion Size and Diet o Propliothecines quadrupedality slow climber o Parapithecines quadrupedality runner and leaper o Body size 2 4lbs for Apidium 3 18lbs for Aegyptopithecus o Diet frugivory Time of Activity o Diurnal Social Organization o Aegyptopithecus polygyny Sexual dimorphism in canine tooth implies polygyny Miocene 1st hominoids 1st hominins Geographical distribution o In early Miocene Africa was and island continent separated from Europe and Asia by Tethys Sea