CHAPTER 15 .docx

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Esteban Parra

CHAPTER 15 – Recent microevolution of human populations - looking at the microevolution that occurred within our species recent evolutionary past as our ancestors moved out of Africa – - global patterns of variation: skin colour - local changes: genetic impact of historical events in Ireland There has been an influence on populations due to gene flow and genetic drift - there as also be different traits due to the influence of natural selection - Genetics and population history - questions about population history look at origin of populations - also looks at the relationship between historical events and genetic outcomes - populations in terms of common ancestry and gene flow = are expected to make populations more similar genticially to each other *it is believed that they influence ALL genes and DNA SEQUENCES to the same extent – (exception is: mitochondrial DNA (only transmitted by mother) and the Y chromosome polymorphism – transmitted by males only) - other instances don’t have the same impact throughout the genome - genetic drift – can make alleles in 2 alleles in closely related populations different of similar just by chance * natural selection has the same effect The origin of native Americans - after Christopher Columbus exploration – was when the New World (Americas) became discovered – Indies was initially described as a term for Asia – the people found here became known as “Indians” - from the bibilical perspective – native Americans were = lost tribes of Israel - - humans first evolved in Africa - then spread throughout the old world (Africa, asia, Europe, Australia) – then into new world - no early species of humans lived in the new world – - some argued that asia was the place of origin of native Americans – and that they crossed the Bering Land Bridge to come to the Americas - during glaciations when sea levels fell, it exposed a strip of land from asia to north America that connected both – its predicted that people used this land bridge to migrate - there is a connection between asia and the new world (even if the mechanism of how they travelled is unclear - when did humans move into the new world? About 15,000 – 20, 000 years ago (around Clovis stone culture time) Genetic evidence for an asian origin - physical traits like “shovel-shaped incisors” seem to show a genetic connection between Asians and Native Americans which isn’t present too much in other populations - analysis of genetic markers also shows the similarity between both groups - native Americans are more similar to Asians than any other geographic groups – but also evidence shows that the first immigrants to new world were from northeast asia - also, mitochondrial DNA which belongs to 5 different haplogroups (a,b,c,d,x) – four of the groups (a,b,c,d) are found in northeast Asians – and are rare in other groups X haplogroup is found in northeast asia and parts of Europe – thus perhaps there was migration between both How many migrations? - everyone agrees that there was an asian origin of native Americans - but how many migrations? - from DNA
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