Evolve 2


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Evolve 2

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