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Unformatted text preview: Chapter 26 II Chapter 26 II
Animal Evolution III– Primate Evolution..The Emergence of Humans Primate family tree Primate family tree Early Hominoids Early Anthropoids 6040mya 35mya 2515mya 105mya Earliest Primates Earliest Primates Primates evolved more than 60 million years ago during the Paleocene First primates resembled tree shrews – Long snouts – Poor daytime vision VARIOUS PRIMATE VARIOUS PRIMATE LINEAGES
Apes Monkeys Humans Tarsiers First Primates:Adaptations to an First Primates:Adaptations to an Arboreal Lifestyle Better daytime vision Shorter snout Larger brain Forwarddirected eyes Capacity for grasping motions FROM PRIMATES TO FROM PRIMATES TO HUMANS By 36mya Anthropoids had evolved. These tree dwellers were on or close to the lineage that led to the Monkeys, the Apes, and the Humans and human lineages “Anthropoids” include the monkey,ape, From Primates to Humans From Primates to Humans
“Uniquely” human traits evolved through modification of traits that evolved earlier, in ancestral forms Trends in Lineage Trends in Lineage Leading to Humans Less reliance on smell, more on vision Skeletal changes to allow bipedalism Modifications of hand allow fine movements (power/precision grip) Bowshaped jaw and smaller teeth Longer lifespan and period of dependency Hominoids Hominoids HOMINOIDS INCLUDE:Apes, humans, and extinct species of their lineages In biochemistry and body form, humans are closer to apes than to monkeys First appeared in Africa 2318 mya, then spread through Asia and Europe as the climate became cooler and drier HOMINIDS:
– Subgroup that includes humans and extinct humanlike species – First appeared 67mya The First Hominids The First Hominids Sahelanthropus tchadensis arose 67 million years ago Bipedal australopiths evolved during Miocene into Pliocene
A. anamensis A. afarensis A. africanus A. garhi A. boisei A. robustus Exact relationships are not known The Hominid Lineage Fig. 26-38, p.457 Africa appears to be the cradle of human Earliest Fossils Are African Earliest Fossils Are African evolution No human fossils older than 2 million years exist anywhere but Africa Homo erectus left Africa in waves from 2 million to 500,000 years ago Early Hominids Early Hominids Early hominids did not have a splayedout big toe Arch, big toe and heel give evidence of a biped 3.2million year old bones “Lucy” who walked upright 3.7 million year old fossilized footprints of a bipedal hominid Fig. 26-34a-c, p.455 1.91.6 million years ago Homo Habilis Homo Habilis May have been the first member of genus Lived in woodlands of eastern and southern Africa
Fig. 26-33,36p.455,456 Was known as the “Handyman” or tool user Homo erectus “bigtime walker” Homo erectus “bigtime walker” 2 million53,000? years ago Evolved in Africa Migrated into Europe and Asia Larger brain than H. habilis Creative toolmaker Built fires and used furs for clothing More social organization and communication skills Neanderthals Neanderthals Early humans that lived in Europe and Near East. 200,00030,000 years ago Massively built, with large brains Disappeared when H. sapiens appeared DNA evidence suggests that they did not contribute to modern European populations Homo sapiens Homo sapiens Modern man evolved by 100,000 years ago Compared to Homo erectus:
– Smaller teeth and jaws – Chin Smaller facial bones – Largervolume brain case Where Did H. sapiens Arise? Where Did Two hypotheses: Multiregional model, African emergence model Both attempt to address biochemical and fossil evidence MULTIREGIONAL MODEL AFRICAN EMERGENCE MODEL Argues that H. sapiens arose in subSaharan Africa H. sapiens migrated out of Africa and into regions where H. erectus had preceded them Only after leaving Africa did phenotypic differences arise Argues that H. erectus migrated to many locations by about 1 million years ago Geographically separated populations gave rise to phenotypically different races of H. sapiens in different locations Gene flow prevented races from becoming species MODERN HUMANS MODERN HUMANS 40,000 years ago–today, cultural evolution has outpaced biological evolution Cultural innovations help to adapt to the broad range of environmental challenges Stoneage to hightech technology coexist today, demonstrating the “PLASTICITY” of the human species ...
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