The Path to Modern HumansPaleoanthropology Study the skeletal remains and material culture of early humans and their ancestors Paleoanthropologists are responsible for reconstructing human evolution using the fossil record. Their research is multidisciplinary and draws from physical anthropology, archaeology, paleontology, and geology.Human Origins We did NOT evolve from living apes – we share a common ancestor The common ancestor was more “apelike,” but not like our living apes These questions are inherently flawed: The Human Evolution Debate If we evolved from apes, why are there still apes? Why didnʼt they evolve into humans, too? “…fresh knowledge leads to recognition of the theory of evolution as more than just a hypothesis.” Pope John Paul II (1996) Slide Courtesy of Sarah A. BlankenshipWhat is a primate?? order: Primate suborder: anthropoids prosimians humans, apes, and monkeys lemurs, tarsiers, and other so-called pre monkeys primates share a number of common characteristics. Some important trends include: - hands and often feet that are dexterous and able to grasp with opposable thumbs - the replacement of claws with fingernails - reduced emphasis on olfaction and increased reliance on eyesight, with color vision - a locomotion that placed great emphasis on the use of the hind limbs and the common adoption of an erect trunk while, foraging, climbing, and exploring - the tendency for the evolutionary development of large brains (in terms of brain- to-body ratio) Slide Courtesy of Sarah A. Blankenshipanthropoids hominins pongids suborder: modern humans and our earlier ancestors closest living nonhuman primate relatives Humans and our closet nonhuman primate relatives evolved along parallel lines from a common ancestor. Slide Courtesy of Sarah A. Blankenship Image courtesy of http://www.guardian.co.uk/environment/gallery/2009/may/27/bonobos-congo-wildlife?picture=347974148Miocene Pliocene Pleistocene 5 mya 1.6 mya 24 mya Holocene 10 kya Oligocene Deep Geologic Time: The Cenozoic Era Slide Courtesy of Sarah A. BlankenshipThe Cenozoic Era The Paleocene epoch 65 – 50 mya (after mass extinction event) - mammals radiated to the environments vacated by the dinosaurs. - the early primates adapted to arboreal (forested) environments, feeding on plants and insects that thrived in these environments The Eocene Epoch 50-36 mya - global warming – spreading of tropical environments - primates diversified into the spreading tropical environments - primates show evolution of the nail, some development of grasping hands and feet, and improvement in vision over olfaction The Oligocene epoch 36-24 mya - global cooling commences - distinct anthropoids begin to leave prominent traces in the fossil record Slide Courtesy of Sarah A. BlankenshipThe Cenozoic Era The Miocene epoch – 24 mya – 5mya • Emergence of distinct lineages of Old World monkeys and apes (different superfamilies) • Ape species began to dwindle due to cooling environments (a major drop in temperature occurred between 14 and 11 mya) • Development of increasingly open environments • Ca. 5mya, ape species were few and more geographically restricted • It was from these later Miocene apes that early human ancestors (and ancestors of gorillas and chimps) emerged • Eventually branching off from our last shared common ancestor (probably chimpanzees) around 6-7 mya Slide Courtesy of Sarah A. BlankenshipThe Cenozoic Era The Miocene epoch – 24 mya – 5mya “coming down from the trees” 1. the difficulty of getting around in open country hominids adopted a bipedal posture around 4mya. Our ancestors became bipedal over a long period of time, perhaps as a result of pending more time feeding on food resources on the ground 2. the savanna had a lot of predators, making it hard for primates to sleep safely. Large hominids made home bases, where they sheltered from the hot sun and slept safely. 3. high-quality plant foods, abundant in the forests, were widely dispersed over the savanna. As part of human evolution, hominid ancestors expanded their food range to include more meat, perhaps during periods of plant scarcity. Slide Courtesy of Sarah A. BlankenshipSahelanthropus tchandensis n Toros-Menalla, Chad (Central Africa) n 7-6 MYA n Ancestral: – Braincase n Derived: – Facial Structure – Tooth Layout – Anterior Foramen Magnum Toumaï Ancestral traits: are primitive traits which appear in older species of the same lineage, but are retained to meet some evolutionary needs. Derived traits: are more human-like traits that changed from an ancestral state to meet some biological evolutionary needs “Hominin of the Sahel, of Chad”Ardipithecus ramidus n Ethiopia n 4.5 MYA n Ancestral Traits: – Skull shape – Dentition n Thought to be close to divergence from African apes ArdiThe Pliocene epoch ~ 5mya Most of the early fossil evidence for emergence of the human lineage (and the beginnings of the archaeological record) date from: The “gracile” Australopithecines (Latin for “southern ape”) genus of early hominids Australopithecus afarensis and Australopithecus africanus The Cenozoic Era Slide Courtesy of Sarah A. Blankenship Bipedal posture adopted circa 4 myaAustralopithecus afarensis n Hadar, Ethiopia; Laetoli, Tanzania; Koto Toro, Chad n 4-3 MYA n Example: – Lucy Illustration by John Sibbick TextImages Courtesy of http://www.anthro4n6.net/lucy/ Lucy Hadar - Afar Triangle , Ethiopia • Don Johanson (1970s) • 60% complete • Dated to about 3.18 MYA • K/Ar DatingPotassium-Argon (40K/40Ar) Dating!(Courtesy of exn.ca.cfm)!Measures the decomposition of K-40 to Argon gas (Ar-40) Archaeologists use Potassium-Argon dating to estimate the ages of our oldest human ancestors. 40K Half life of 1.3 BILLION years (See page 35 in your book)Volcanoes produce sedimentary deposits of lava and ash.!(Courtesy of earth.esa.int)!(Courtesy of bbc.co.uk)!Volcanic !deposits!are called!tuffs!Potassium-Argon dating of the tuffs allows us to estimate the age of fossils occurring above, within, and below the fossil-bearing strata (measures age of the volcanic event) 1 MYA!2 MYA!When volcanoes erupt and beds (tuffs) of lava develop,