1 Nature of a Fossil Bones and teeth can be destroyed by physical chemical and biological forces Fossilization protection from forces of destruction death near water or in cave Sources of bias in fossil record Body size of species Where fossilization occurs Exposure and discovery of fossils Epochs of Cenozoic Era Paleocene 65 to 56 mya Eocene 56 to 33 mya Oligocene 33 to 23 mya Miocene 23 to 5 mya Pliocene 5 to 1 8 mya Pleistocene 1 8 mya to 10 000 ya Holocene 10 000 ya to present Theory of Plate Tectonics Cenozoic Era North America and Europe were connected to one another during Paleocene and Eocene This explains the geographical distribution of early primates Africa was an island continent prior to 19 mya About 19 mya Africa contacted Southwest Asia This explains the geographical distribution of apes during the Miocene 2 Problem Issues How did lemurs colonize Madagascar Madagascar was an island before the emergence of primates The theory is that lemurs colonized Madagascar by crossing the Mozambique Channel on floating masses of vegetation How did monkeys colonize South America South America was an island continent long before the emergence of primates and the Isthmus of Panama connected N and S America 5 mya The theory is that the ancestor of NW monkeys colonized S America by crossing either the Caribbean Sea or Atlantic Ocean on flotation of masses of vegetation Categories of Dating Techniques Relative Dating organize items in rank ordered sequence Stratigraphy sequence of sedimentary rock Principle of Superposition younger items are closer to the surface of the earth than older items Biostratigraphy temporal association of species Index species fossil species of known age is used to estimate age of another species Fluorine Analysis relative age of an item based on its fluorine concentration Chronometric Absolute Dating assignment of a specific age to an item based on the principle of radioactive decay Radioactive isotope of an element releases energy at a fixed rate Half life amount of time for a radioactive element to lose half of its energy Potassium argon Dating K Ar radioactive K decays into stable Ar material Use volcanic rocks extensively used in dating early hominin fossils in East Africa Half life of K is 1 25 billion years Argon argon Dating same as K argon dating but uses less Carbon 14 Dating 14C is radioactive isotope of 12C half life of 14C is 5730 years 3 Discovery ofPiltdown Specimen 1912 Charles Dawson Human like brain size ape like teeth Fluorine test applied to Piltdown had less fluorine than contemporaneous fossils Piltdown mandible had different fluorine content than Piltdown cranium Proved that the specimen was actually an orangutan Teeth were filed down to give it a different appearance Suspects of the Piltdown hoax Charles Dawson Arthur Conan Doyle wrote mystery novels Martin Hinton his trunk was found containing rodent skulls tried to get back at who denied him his research project Taung child 1924 Raymond Dart ridiculed and thought of as a faulty reconstruction Ape like brain size human like teeth Paleocene 65 56 mya Paleocene species Plesiadapiforms were primitive primates Differences between plesiadapiforms and modern primates Longer snout Eyes not positioned at front of skull No post orbital bar Smaller brain Specialized dentition Claws not nails Non prehensile hands and feet Anatomy of molar teeth Middle ear Anatomies that suggest Paleocene species may be primates Eocene 56 33 mya look like modern primates Eyes face forwardly Post orbital bar Short snout Prehensile hands and feet Nails Large cranial capacity compared to Paleocene species Fossils found in North America and Europe and in Asia and North Africa near the end of the Eocene North America and Europe were geographically connected with one another in Eocene by Greenland 4 Omomyids May explain similarity among species of North America and Europe Environmental context tropical and sub tropical climates Two major lineages of Eocene primates Adapids and Adapids may be ancestral to lemurs and lorises Omomyids may be ancestral to tarsiers and anthropoids Some species were diurnal whereas others were nocturnal according to their orbit size Locomotion quadrupedality and leaping Diet insectivory frugivory folivory Absence of toothcomb Darwinius 47 mya let down of a fossil Oligocene 33 23 mya Earliest definitive anthropoids are dated to the Oligocene Fossils found of Oligocene are mostly found in Fayum Egypt dating 33 to 35 mya Environment of Fayum site during Oligocene was a tropical forest Two lineages of anthropoids during the Oligocene Propliopithecines propliopithecus and aegyptopithecus Dental formula 2 1 2 3 same dental formula as modern catarrhines OW monkeys apes and humans May be ancestors of catarrhines Parapithecines parapithecus and apidium Dental formula 2 1 3 3 Three premolar teeth in each quadrant of mouth same dental formula as some modern platyrrhines NW monkeys May be ancestors of NW monkeys Body size 2 to 4 pounds for Apidium 13 to 18 pounds for aegyptopithecus Diet frugivory Social organization for Aegyptopithecus may have been polygyny Miocene 23 5 mya First hominoids and hominins In Early Miocene Africa was an island continent separated from Europe and Asia by Tethys Sea About 19 mya the Arabian plate partly separated from Africa and contacted SW Asia forming a migratory corridor Prior to this plate tectonic event hominoids were distributed in Africa Europe and Asia 5 Authors Classifications African taxa 23 14 mya Proconsul European taxa Asian taxa 16 11 mya Dryopithecus 15 5 mya Sivapithecus Diversity in dental size and enamel thickness Some taxa proconsulines have relatively small molars with thin enamel and gracile mandible proconsul and Dryopithecus Other taxa sivapithecines have relatively large molars with thick enamel and thick mandible Sivapithecus Before 19 mya Africa was a relatively continuous tropical forest After 19 mya tropical forests in OW became fragmented the environment was more mosaic woodlands and open country This change in environment led to selection for dietary diversity among hominoids and correspondingly an increase in molar size enamel thickness and robust mandible GSP 15000 ancestor of orangutan Gigantopithecus 8 mya to 500 000 ya Asia All early hominin fossil sites from Late Miocene and Pliocene are in Africa East and North Central Africa Open air sites Famous sites include Hadar Ethiopia Lake Turkana Kenya Olduvai Gorge Tanzania Republic of