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Evolution

Evolution. A “Human” Perspective. Human Evolution. Human evolution began about 60 million years ago with the earliest primates: mammals with long snouts, sharp teeth and large eyes who lived in trees and fed on insects. Three distinguishable traits evolved: Flattened molars to eat plants

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Evolution

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  1. Evolution A “Human” Perspective

  2. Human Evolution • Human evolution began about 60 million years ago with the earliest primates: mammals with long snouts, sharp teeth and large eyes who lived in trees and fed on insects. • Three distinguishable traits evolved: • Flattened molars to eat plants • Grasping hands with opposable thumbs • Forward directed eyes

  3. Primate Phylogeny • About 30 to 40 million years ago humans evolved into prosimian and anthropoid organisms • Prosimian  large eyes, nocturnal, long tail (lemur) • Anthropoid  diurnal, feed on fruits and leaves, enlarged brain, social groups and care for young (monkeys, apes and humans)

  4. Primate Phylogeny • About 25 to 30 million years ago the anthropoid lineage split into • Old World monkeys arboreal and ground dwelling, close together nostrils and tails are not prehensile • New World monkeys migrated to South America and evolved in isolation, exclusively arboreal, widely separated flared nostrils and prehensile tails • hominoids most are ground dwelling, longer front limbs than hind limbs and larger brain size relative to body size, no tails (gibbons, orangutans, gorillas, chimpanzees and humans) • Humans share a lot of traits with hominoids • Bipedal motion (wide pelvis & curved vertebral column), enlarged brain, complex language, construction and use of complex tools. Olive baboon Southern Muriqui or wooly spider monkey

  5. Emergence of Humans • Without fossil records Darwin linked apes to humans and that fossil records to prove it would be in Africa. • Hominid clade has many branching lineages and related species • Hominid humans and other extinct members of their lineage arising from the most recent common ancestor that humans share with apes. • Australopithecines  6 different species between 4.2 and 1.0 million years ago. Generally a group of extinct hominids closely related to humans.

  6. Emergence of Humans • As more fossils are found paleontologists attempt to put together phylogenetic tree for humans. • Homo genus  Africa, 2.4-1.6 million years ago • H. habilisH. erectus about 1.6 million years ago. H. erectus used stone tools and fire. Brain size around 750cm3 (1200cm3 today), a rounded head and smaller teeth…more like current human features. H. erectus moved out of Africa into Asia and Europe. • H. erectusH. neanderthalensis and H. sapiens about 600 000 years ago. • H. sapiens first appeared in Africa 130 000 years ago and H. neanderthalensis was already living in Europe and Asia

  7. Competing Theories • Multiregional Hypothesis anatomically modern humans evolved in parallel in a number of places (Africa, Europe, Asia). Gene flow accounts for them not becoming distinct species. • Regional genetic diversity arose due to regional selective pressures over about 1 million years. • Monogenesis HypothesisH. sapiens evolved only in Africa and then migrated displacing Neanderthal and other H. erectus populations. • Regional genetic diversity arose in humans with the past 80 000 to 100 000 years, that is, since H. sapiens left Africa. • Homo sapiens vs. Neanderthals

  8. Did we come from Africa? • If this is true then there should be the greatest amount of genetic diversity there within our genes. The research backs this up. On a highly variable region on chromosome 12 there were 24 different versions discovered: 21 from African populations, 3 in European populations and 2 in Asian and Australian populations. • Similar idea with Y chromosome variability  there is more variability in Y chromosomes from Africa.

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