Evolve 2
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Evolve 2 Presentation Transcript

  • 1. Out-of-Africa Theory: The Origin Of Modern Humans Presented By Adrian Padilla
  • 2. Background Information
    • First species of Homo, Homo habilis, evolved in Africa around 2 million years ago.
    • Later, a descendant of Homo habilis, Homo erectus evolved (along with other hominids), and spread out of Africa.
    • Homo erectus gave rise to Homo sapiens around 100,000 to 200,000 years ago.
  • 3. Two Main Theories
    • Out of Africa Theory (OOA) – suggests that Homo erectus evolved into Homo sapiens in Africa, and then ventured out of Africa and dispersed to all around the world.
    • Multi-regional Evolution Theory – suggests that Homo erectus ventured out of Africa and then evolved into modern man in several different locations through out the world.
  • 4.  
  • 5. Genetic Tools to Find the Answer
    • Fossil records
    • DNA sequencing
      • Mitochondrial DNA analysis (mtDNA)
        • Maternally inherited, therefore telling the story from the female side of human history
      • Y Chromosome analysis
        • Inherited down the paternal line, complementing the mtDNA
      • Microsatellite DNA analysis
        • Segments of tandemly repeated DNA with a short repeat length, usually 2-5 nucleotides
  • 6. Polymorphisms
    • Polymorphism - Existence of a gene in several allelic forms.
    • Polymorphic regions provide a very unique set of genetic markers for studying human origin and migratory patterns.
    • Used to construct a global evolutionary tree of modern man
  • 7. Mitochondrial DNA
    • Out-of-Africa hypothesis was first sketched out in 1987, based on mitochondrial DNA analysis
    • Suggested that modern man first appeared on the scene in eastern Africa about 150,000 years ago, and left between 35,000 and 89,000 years ago, eventually conquering the globe.
  • 8. Y Chromosomal DNA Study
    • Researchers looked at DNA samples from 12,000 male Y chromosomes in Asia.
    • Looking for 3 specific mutations on the Y chromosome known to have originated in Africa.
    • Researches found that every one of the 12,000 samples carried one of the three mutations or polymorphism
  • 9. Conclusion to the Y Chromosome Study
    • Little or no interbreeding of Homo erectus and Homo sapiens.
    • Individuals are descendants from Africa
    • Likely that the early African man emigrated to North Africa and made the leap to Asia and then to the rest of the world.
    • Indicates that modern humans of African origin completely replaced earlier populations in East Asia.
  • 10. More Y Chromosomal Studies
    • Samples were taken from men in 22 different geographical areas.
      • In countries that included Pakistan and India, Cambodia and Laos, Australia and New Guinea, America, Mali, Sudan, Ethiopia and Japan.
    • Researchers identified 167 polymorphic markers on the Y chromosome.
    • Markers were then assembled into 10 types, called haplogroups.
  • 11. Findings from Y Chromosomal Analysis
    • Assembled a phylogenetic tree showing a migration from eastern Africa into the Middle East, then southern and southeast Asia, then New Guinea and Australia, followed by Europe and Central Asia.
    • Some modern day men in Sudan, Ethiopia and southern Africa are the closest lineal descendants to the first Homo sapiens who left Africa
    • New Guinea and Australia were settled early in the process
    • Japan has remained in genetic isolation. Mutations are strikingly different from those of surrounding populations, they account by themselves as a specific haplogroup
    • Native Americans have a common ancestry with Eurasians and East Asians
  • 12. Microsatellite DNA Analysis
    • Researchers tried to find the estimated time of the deepest split of the human population.
    • Applied a genetic distance measurement to 30 microsatelite regions to construct a pylogenetic tree for 14 world-wid human populations
  • 13. What did they find?
    • In the tree obtained, the deepest root separated Africans from non-Africans.
    • Their calculations suggest the split ahppened an en estimated 115,000 to 156,000 years ago.
  • 14. mtDNA Analysis
    • Study on the complete mitochondrial genome.
    • 16,500 base pairs in each sequence
    • 53 people diverse from different geographical, racial, and linguistic backgrounds.
  • 15. Results
    • A tree rooted in Africa
    • Tree suggests that some Africans are closer to Europeans and Asians than to other Africans.
  • 16. Fossils
    • Archeologists find a fossil in Herto, Ethiopia dating about 160,000 years old
    • The oldest fossil found of Homo sapiens dates back 115,000, and is found in Israel.
    • Researches link the fossil found in Israel to the fossil in Herto, Ethiopia and other fossils found in Africa, based on physical characteristics of the skull.
  • 17.  
  • 18. Conclusion
    • DNA sequencing evidence shows that modern humans originated in Africa and migrated north out of African, then eventually to the rest of the world.
    • Oldest fossils of modern humans are found in Africa dating around 160,000 years old.