Transcript Document
Human Evolution and PREHISTORY Chapter 5: MACROEVOLUTION AND THE EARLY PRIMATES Link to the Canadian Association for Physical Anthropology COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Chapter Preview When did the first Primates Appear, and What Were They Like? When did the First Monkeys and Apes Appear, and What Were They Like? COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. LINEAR EVOLUTION A process of non-directional, variational change Changes can occur by chance and accumulate over time because they are advantageous; e.g. elephants becoming progressively hairier (chapter 3) Linear evolution may or may not produce a new species COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. The Nondirectedness of Evolution “Human brains and bodies did not evolve along a direct and inevitable ladder, but by a circuitous and tortuous route carved by adaptations evolved for different reasons, and fortunately suited to later needs” ….Stephen J. Gould COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. EARLY MAMMALS By 190 million years ago (mya) true mammals appear in the fossil record Today’s diverse forms of mammals (including the primates) are the products of an adaptive radiation at the end of the Cretaceous period, around 65 mya Mass extinction of many reptiles made available existing ecological niches, and new niches opened up as climate changed COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. RISE OF THE PRIMATES Adaptive Radiation The rapid increase in number of related species following a change in their environment Ecological Niche A species’ way of life in a particular environment, including all other species of plants and animals in that habitat COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. RISE OF THE PRIMATES By the end of the Cretaceous: Separation of the continents New and available ecological niches Mild climate supporting new vegetation, e.g. flowering plants Spread of tropical and subtropical forests COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. RISE OF THE PRIMATES Move to arboreal life Natural selection favoured flexible decision-making, depth perception, a strong grip and dexterous fingers Number of hypotheses to explain primate specialization, e.g. use of smaller branches for fruit foraging and insect predation COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Paleocene Primates Ancestry of primates is in the insectivore group of mammals Earliest known primate fossils are 10 teeth from a site in Morocco, about 60 million years old, and are very similar to those of a modern mouse lemur These fossils show that primates are going their separate evolutionary way by 60 mya Place of origin is unknown COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Paleocene Primates Carpolestes simpsoni, 56 mya, Wyoming Grasping ability Fruit-eating dentition Long arms suitable for tree life All good adaptations for arboreal foraging at ends of small branches COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Eocene Primates 55 to 34 mya Ancestors of lemurs, tarsiers and other haplorhines Some probably were ancestral to platyrrhines and catarrhines Found in Africa, North America, Europe and Asia where warm, wet conditions sustained extensive rainforest COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Eocene Primates Genus Adapis COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Eocene Primates – Climate change Sudden temperature drop in late Eocene, creating cooler and drier climates There was a marked reduction of environments to which the early primates were adapted, e.g. they became extinct in North America Precursors of monkeys and apes may have been able to take over some of these niches COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Evolutionary Timeline COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Oligocene Monkeys and Apes 34-23 mya Scarcity of fossils, mainly found in the Fayum Depression, Egypt (once tropical rainforest) Prominence and diversity of haplorhines showing monkeylike and apelike features, e.g. Aegyptopithecus Evidence of ancestors of true monkeys, resembling modernday platyrrhines Some of the platyrrines could have found their way to South America on “rafts” of floating vegetation COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Aegyptopithecus Oligocene catarrhine Apelike dentition Forward eye sockets, as in modern monkeys and apes Larger brain than any lemur or tarsier, past or present Its teeth suggest that it belongs in the ancestry of those Miocene forms that gave rise to both humans and today’s African apes Quadrupedal, monkey-like locomotion COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Miocene Apes 23-5 mya Proliferation of apes in forests throughout the Old World East Africa is particularly rich in fossils from early to middle Miocene COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Miocene Apes Genus Proconsul (Early Miocene) Represents an unspecialized tree-dwelling, fruiteating hominoid (the catarrhine superfamily to which apes and humans belong) COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Miocene Apes 16-5 mya (middle to late Miocene) Europe, Asia and Africa Teeth and jaws like Proconsul but more ape-like in overall appearance Some species surely were ancestral to later largebodied apes, including the hominids (the primate family containing African apes and humans) COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. ORIGINAL STUDY Will the Real Human Ancestor Please Stand Up? The wide variety of Miocene fossils have had many interpretations and generic and specific names, in an attempt to find the common ancestor of humans, chimpanzees and gorillas Molecular analysis of proteins in the 1970’s indicated a divergence for living hominoids of 5 mya, no earlier than 7 mya Fossil remains of the common ancestor have not been found, but molecular evidence points to Africa as the origin of humans COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Miocene Apes Potential hominid ancestors known from teeth, jaws, and more recently skull and limb bones, e.g. China, Greece, Hungary, Pakistan, Turkey Sivapithecus is orangutanlike Dryopithecus resembles African apes and early hominines COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Miocene Apes and Human Origins The ancestry of humans may be among late Miocene apes of Africa that show some resemblance to Sivapithecus. This is consistent with: Dental evidence molecular evidence that suggests that humans, bonobos, chimpanzees and gorillas could not have separated from a common stock more than 8 mya Forms like Sivapithecus were still on the scene after this split, and our own human ancestors were going their own separate evolutionary way by at least 4.4 million, if not 6 million, years ago. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Hominoid Adaptations and Late Miocene Climatic Change Climatic shift created mosaic environments, i.e. forest and open grassland Food could be obtained by foraging on the ground as well as in trees Late Miocene fossils typically are found in association with greater numbers of animals adapted to grassland Physical and behavioural changes were needed for survival on the open ground, e.g. bipedalism COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. EARLY APES AND HUMAN EVOLUTION The late Miocene apes were much too apelike to be considered hominines and were optional rather than obligatory bipeds However, anatomical and molecular evidence indicates the separation of apes and humans from the common evolutionary line some time near the end of the late Miocene Some late Miocene fossils do possess traits seen in humans COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. EARLY APES AND HUMAN EVOLUTION Some of the Miocene apes evolved into contemporary apes and remained in the forests and woodlands continuing to develop as arboreal apes, and ultimately, for some, a more terrestrial life These are the bonobos, chimpanzees, gorillas COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. EARLY PRIMATE EVOLUTION: AN OVERVIEW Initial diversification of strepsirhine and some haplorine forms as they adapted to life in the trees Haplorhines diversified into a large variety of monkeylike apes, from which developed true monkeys, true apes, and (later) humans Apes and monkeys competed in the forests Forests continued to shrink and ground-dwelling niches for primates opened up, particularly for baboons and humans COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. NEXT TIME: The Earliest Hominines COPYRIGHT © 2007 Nelson, a division of Thomson Canada Limited. ALL RIGHTS RESERVED.