The Early Primate Fossil Record and the Origins of the Hominins Chapter 12

Early Primate Evolution The earliest mammals evolved during the Mesozoic era (252 to 66 mya) At the end, great forests evolved with flowering trees that would later provide protection and food for early primates The beginning of the Cenozoic era (65 mya to present) Paleocene epoch (66 to 56 mya) The dinosaurs and many other forms of life were extinct and mammals began their adaptive radiation Eocene epoch (56 to 33 mya) Most of the modern orders of mammals had appeared More than 200 species are known

The Plesiadapiformes Possibly the earliest primates Small, arboreal quadrupeds Placental mammals Long snout, small brain, and claws, and lack both a postorbital bar and a grasping big toe. Many primatologists believe the plesiadapiformes were not direct ancestors of later primates Two genera of plesiadapiformes are Purgatorius and Plesiadapis

The Eocene Primates Two groups of early primates Display distinctive primate features Wide geographical distribution Extinction for most by the end of the Eocene Adapidae Resemble the modern lemurs and lorises Date back as far as 47 mya Darwinius masillae from Germany Omomyidae Resemble the living tarsiers Found on all non-arctic continents

Anthropoid Evolution The Oligocene epoch (33 to 23 mya) Early Oligocene First anthropoids arose in Africa and Asia The suborder Anthropoidea includes the living monkeys, apes and humans End of the Oligocene South America and Africa are totally split Monkeys may have reached South America by “rafting” Ancestry of New and Old World monkeys separate after 35 mya

Fayum Fayum of Egypt The Parapithecidae The Late Eocene and Early Oligocene Primates families Parapithecidae and Propliopithecidae The Parapithecidae Apidium Small, squirrel-like Fruit and seed eating Clinging and leaping Aegyptopithecus Largest of Fayum anthropoids(13-18 lbs) Short-limbed, slow-moving Bridges the gap between Eocene fossils and succeeding Miocene (23 to 5 mya) hominoids May represent a group of primates ancestral to both the cercopithecoids and the hominoids

New World Monkeys Probably derived from early African anthropoids that traveled across the Atlantic Ocean on natural raft Earliest ceboids Branisella Late Oligocene (~26 mya) of present day Bolivia Evolution of the ceboids into their present subfamilies took place by the Middle Miocene

Old World Monkeys The cercopithecoids were relatively scarce in the Miocene More common, especially in Africa, by the Pliocene epoch (5 to 2.5 mya) Family Victoriapithecidae Two genera: Prohylobates and Victoriapithecus Divivded into he Cercopithecinae and the Colobinae by the end of the Miocene (5 mya)

Hominoidea The earliest hominoids appear in the fossil record in the early Miocene fossil beds of east Africa and Saudi Arabia Most disappeared by around 8 mya Proconsul (23 to 25 mya) of Eastern Africa Most successful of the early hominoids Ape-like teeth with Monkey-like body Possibly the last common ancestor of both the Old World Monkeys and Apes Gigantopitechcus (9 mya to 100,000 ya) of East Asia Largest primate to ever live Lived for millions of years Survived long enough to live alongside some of the genus Homo Sasquatch?

More Miocene Hominids Pierolapithecus (13 mya) of Spain Discovered in 2004 Possible last ancestor of all great apes, but perhaps not orangs Sivapithecus (12 to 8.5 mya ) of India and Pakistan Large varied group with three species One is likely the ancestor of the modern orangutan chimpanzee (l), Sivapithecus (m), and a modern orangutan (r) Both Sivapithecus and the orangutan exhibit a dished face, broad cheekbones, and projecting upper jaw and incisors

Sahelanthropus tchadensis Discovered in 2001 in modern-day Chad Not East African Rift Valley Dated to at least 6 mya Small, chimp-sized braincase Human-like, vertical face Huge brow ridge Foramen magnum Suggests some bipedalism Hominin status questioned Lived very close to the human-chimp split

Orrorin tugenensis Discovered in 2001 Dated to 5.5 to 6 mya Present day Kenya Chimp-like creature with bipedal ability Questionable hominin status Lived before Ardipithecus More accepted as “hominin”

Ardipithecus Dated to 4.5 mya Two Species ramidus kadabba Pelvis shows derived characteristics Imperfect capacity for bipedal locomotion Transitional pelvis Divergent big toe Woodland environment