Time Space & Chg Human Soc (D)
Time Space & Chg Human Soc (D) ISS 220
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This 4 page Class Notes was uploaded by Buster Heller on Saturday September 19, 2015. The Class Notes belongs to ISS 220 at Michigan State University taught by William Lovis in Fall. Since its upload, it has received 33 views. For similar materials see /class/207749/iss-220-michigan-state-university in Integrative Studies Social Sci at Michigan State University.
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Date Created: 09/19/15
Chapter 10 The evolution and nature of Modern humanity 1 The major models in an ongoing debate a The recent African Model RAO i The hypothesis that Homo sapiens evolved recently as a separate species in Africa and then spread to replace more archaic populations ii View that modern Homo sapiens is a separate species that branched from preexisting archaic Homo species in Africa around 200000 to 15000ya This new species then spread over the old world iii Sometimes called the replacement model iv If this model is correct 1 There must be traits that all Homo sapiens share that are not found in premoderns and traits found in premoderns that are lacking in modern humans b The multiregional evolution model MRE i The hypothesis that Homo sapiens is about 2 million years old and that modern human traits evolved in geographically diverse locations and then spread through the species ii Still agrees that HSapiens arose in Africa iii A successful advantageous adaptive feature arose they were dispersed across the species through gene flow Ideas and technologies spread and were exchanged as well 1 Physical features we associate with modern humans appeared everywhere but may have been manifested in different environments iv lf correct 1 We should no clear evidence that modern Hsapiens is a separate species from the so called premodern groups 2 There should be no biologically meaningful definition of modernity 3 Populations with transitional sets of traits should be found in many locations 4 Should be evidence of interbreeding 2 The evidence a The fossil record i Modern traits did not all arise in one location but in many and that they spread throughout the species through gene flow to be expressed differently in different geographical locations ii There is a sufficient variation among humans and excludes all other proposed species A physical definition of modernity thus seems to be in the eye of the beholder based on one s interpretation and choice of populations and characteristics 1 In regards to this debate the fossil record is ambiguous It can clearly be interpreted to support either point of view iv It is hard to translate physical features into species classification b The cultural evidence C i Africa 2 The artifacts recovered at some through certainly not all early modern human sites in Africa do show some sophisticated technology than contemporary tool assemblages in Europe and Asia associated with premodern humans Three sites located in Katanda Democratic republic of Congo provide further evidence that more sophisticated tool making appeared earlier in Africa then in either Europe or Asia Outside of Africa 1 The stone tools of the earlier Neandertals of Europe and Southwest Asia simply does not look very different from the Toolkits of the early moderns of Africa and Southwest Asia a Toolkits A group of tools often found in spatial association at an archaeological site that were used together to perform a particular task b Aurignacian the toolmaking tradition of the anatomically modern Homo sapiens of the European Upper Paleolithic Frank Harrold a Chatelperronian The stone tool industry associated with the late Neandertals in Europe found it was the most sophisticated tool making method iquot Became so advanced after coming into contact with the techniques from Asia No good evidence in most areas for the wholesale replacement of s primitive tool technology practiced by premodern humans by an advanced practiced by modern humans Genetic Evidence Genetic lines of inquiry have usually been interpreted to support the recent African origin model 1 1 2 Living humans exhibit very little genetic variation Less than that seen within ape species There are three basic types of DNA that are used in this regard Nuclear DNA a The genetic material in the nucleus of a cell b Noncoding useful because it appears to be selectively neutral c May provide a more accurate record of the genetic history of two or more divergent lineages Mitochondrial DNA mtDNA m The genetic material found in the cell s mitochondria rather than in the cell s nucleus b Mitochondria at the energy factories within the cells of plants and animals c Posses their own distinct DNA d Accumulates mutations at a rate five to ten times faster than nuclear DNA and there is evidence that the mutation rate is fairly constant e lnherited only through the female lines 3 Ychromosome DNA a Is inherited only from the father s side and passed on only by males 4 The genetic difference among populations tell us how many mutations have taken place since they were a single population a If we can estimate the mutation rate for a given type of DNA we can turn these data into molecular clock b Adds dates to the family free 5 The world s people tend to cluster into two genetic groups those from subSaharan Africa and those from everywhere else 0 Africa is genetically diverse than the rest of the world put together DNA is not a very stable molecule l a Most famous ancient DNA samples have come from four Neandertal specimens i Short sequences of 379 base pairs of mtDNA 1 Base pair a Any pair of the four bases in the DNA molecule These pairings are the basis of the genetic code for the synthesis of proteins When compared with the same sequence in modern humans there was more than three times the number of differences between the Neandertal and the moderns than between two groups of moderns 1 The investigators conclude from this that the Neandertals made no contribution to modern human mtDNA and that our two lines diverged 690000 to 55000ya 8 DNA was extracted from the bone of an ancient anatomically modern human found at the Stetten site in Germany a More similar to the DNA of living people than it was the Neanderthal DNA of the same period 9 The evolutionary history of a origin of a separate modern human species then all genetic systems should have similar histories which in this case they don t d Evolutionary theory i Christopher Stringer 1 The gaps between groups were too large for genes to move around as MRE requires 2 Too many geographic barriers We must consider the evidence of possible hybridization between archaic and moderns iquot Another relevant aspect of evolutionary theory involves the process of speciation iv Our central adaptive theme is our big brains and the resultant behaviors 3 Mostly out of Africa An Alternative model a The hypothesis that Hsapiens is about 2million years old as a species but that most of the genetic variation and phenotypic features of modern humans have an African origin b While most of the ancestors of modern humans are from Africa not all are c A network of gene flow maintained that species identity across all geographical regions i For the most part seems to have originated in Africa d Were at least two major expansions out of Africa first being in Herectus times suggested as the origin of modern Hsapiens 4 Biological diversity In modern humans a Anatomically modern h sapiens inhabit a wide geographical range i Such widespread populations must have a degree of isolation from one another ii Human populations add to their reproductive isolation through cultural rules of endogamy 1 Marriage restricted to those within the same social group iii Modern humans display a large number of polymorphism 1 A trait showing variation within a species as a result of genetic variation 2 The explanation for human polymorphisms lies in the processes of evolution acting on populations as they spread out into their incredible variety of environments 5 Natural selection and human variation a To determine the role of natural selection in bringing about the variable expressions of a trait one must first try to link those expressions to particular environmental circumstances b Culture allows us to adapt to new environmental conditions much more quickly than natural selection can evolve adaptations i Biological fitness is relative to the environment in which a trait is found ii If some infectious disease is cured then any genes is selected for or against may now vary at random through genetic drift c The variation in blood type
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