Nature of a FossilBones 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 fossilsEpochs 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 PlateTectonicsCenozoic Era-North America andEurope wereconnected to oneanother during Paleoceneand Eocene. This explainsthe geographicaldistribution of earlyprimates. -Africa was an islandcontinent prior to 19mya. About 19 mya,Africa contactedSouthwest Asia. Thisexplains the geographicaldistribution of apes during theMiocene. 1*Problem IssuesHow did lemurs colonize Madagascar?-Madagascar was an island before the emergence of primates-The theory is that lemurs colonized Madagascar by crossing theMozambique 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 TechniquesRelative 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 concentrationChronometric (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 stableAr-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 material-Carbon -14 Dating- 14C is radioactive isotope of 12C; half-life of 14C is 5730 years2Discovery 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 projectTaung child, 1924-Raymond Dartridiculed and thought of as a faulty reconstruction-Ape like brain size, human like teethPaleocene: 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 -Anatomies that suggest Paleocene species may be primates:-Anatomy of molar teeth-Middle earEocene: 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 withone another in Eocene (by Greenland). 3-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 Omomyids.-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 toothcombDarwinius, 47 myalet down of a fossilOligocene: 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 polygynyMiocene: 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 Arabianplate 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. 4Authors’ Classifications-African taxa-23-14 mya (Proconsul)-European taxa-16-11 mya (Dryopithecus)-Asian taxa-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 diversityamong hominoids and, correspondingly, an increase in molar size enamel thickness and robust mandible.GSP 15000ancestor of orangutanGigantopithecus8 mya to 500,000 ya; AsiaAll early hominin fossil sites from Late Miocene and Pliocene are in