Archeao Genetics
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Archeao Genetics

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Archeao Genetics Archeao Genetics Document Transcript

  • Genetic Ancestry, Linguistic Ancestry and Mathematical Ancestry M N Vahia Tata Institute of Fundamental Research Ancestry 1 Ancestry 2 Archeao Genetics Methodology • There are two major signals in our genes that are carried • Mitochondrial (mt) genomes are pieces of DNA of about few forward in original format, except for occasional chance thousands of base pairs. mutations. – Mitochondrial DNA that comes from the Mother only. • Sequence analysis allows one to segregate human mt- – Y chromosome that comes from father only. genomes into various genotypes. • Genetic corrective mechanisms’ do not operate on them very • Analysis of these patterns in ethnic groups is a powerful tool to effectively since these are unique pieces with contribution from one parent only. understanding the past. • THIS PERMITS MAPPING OF MATERNAL AND PATERNAL • Human Y Chromosome with approximately 60 million base pair LINEAGE INTO ANTIQUITY. are also analysed in the same way . • This permits mapping of lineage in space (migration) and time (ancestry). Ancestry 3 Ancestry 4 mtDNA (mutation) Haplotype frequency Agharia Ambalkarer Bagli UP Bram WB Bra Chamar Gaud Irula Iyengar Iyer Kota Kurumba Lodha Mahishya Munda Muria Muslim Pallar Rajput Santhal Tanti Tripuri Vanniyar Malayan Chinese Vietnamese Mal. Aboriginies Malays Taiwanese Korean Sabah aborig. Intensity colour code Ancestry 5 Ancestry 6 1
  • Y chromosome studies ~40,000 BP Ancestry 7 Ancestry 8 Phylogeographic studies, Underhill et al. 2001 To investigate the origin of paternal lineages of Indian populations, 936 Y chromosomes, representing 32 tribal and 45 caste groups from all four major linguistic groups of India, were analyzed for 38 single-nucleotide polymorphic markers. Ancestry 10 Ancestry 11 Ancestry 12 Ancestry 13 2
  • Ancestry 14 Ancestry 15 Ancestry 16 Ancestry 17 Summary of results • Recent external contribution has been low. General distribution of each type of mutation and the distribution • Data suggest common ancestry between India amongst the tribal and central Asia. population (inserts) • There is some diffusion of some Indian-specific lineages northward. • Most communities in South Asia have local origin and there is no evidence of major influx from elsewhere. Proc. National Academy of Science (USA), 2006 Ancestry 18 Ancestry 19 3
  • Human arrivals in India Austro Asians Results from Archaeo Genetics 60,000 to 40,000 BC Indo Europeans Indo Tibetans • Comparison with the Euro-Asian population shows: – First group came in 50,000 BC. – Second group came in 40,000 BC. – Much less than 10% mixing in the last 10,000 years – NO major addition around 5,000 years (with 10% accuracy) (B J Rao and M N Vahia, 2006) Ancestry 20 Ancestry 21 Austro Asians Indo Europeans Indo Tibetans Archaeo Linguistics Major population groups in India till 2000 BC Ancestry 22 Ancestry 23 • Like human genes, languages also have seeds • Extensive work has been done in this area and they also evolve. in comparing words, grammar and • This allows us to study both, the migration and linguistic styles. evolution of language. • Since language evolution is much faster, the clocks work well over shorter periods. • We do not discuss this aspect of the • Comparison with contemporaneous documents studies of ancient India (because I am not and linguistic genetics reveal differences and competent to do it!) similarities between cultures. Ancestry 24 Ancestry 25 4
  • Genetics of Languages West European Languages Separated 4000 yrs BC Gray R. D., Atkinson Q. Central European Languages D., 2003, Nature, 426, 43 Separated 4,500 years BC Language of Caucuses Genealogical Ancestry Separated ~5,000 years BC INDIAN LANGUAGES Separated 2,500 years BC Afghan Languages East European languages AncestryGreek separated 8,000 yrs BC 26 Ancestry 27 universal common ancestor for a population of ‘n’ people. • I have two parents, who in turn had 2 parents • We need to go back only a few generations to we find an each (4 grand parents). So for every n persons, ancestor that is common to any two people. there should be 2n ancestors! The population explosion is not in future but in the past! • The expected time back to this most common recent ancestor is log2(n), where n is the population size. • The flaw in the argument is that as we trace back, the ancestors start to merge. • if you insist only on matrilineal or patrilineal side then the common relative will be n generation back for a population of n people. • So, when did we all have the same ancestor – or who was the most recent common ancestor, or • The calculations can be made more realistic by taking into an even more interestingly, an initial ancestor? account the population mixing rates, the non random mating rates, life expectancy etc. Ancestry 28 Ancestry 29 Results According to these calculations (Douglas L. T. Rohde, Steve Olson & Joseph T. Population Chang, Nature, 431, 562, 2004) group • Most Recent Common Ancestor of all present-day humans lived just “family” about 1500 BC. However, this may be different for different groups. You will have a MRCA with all human beings no more than 50 generations ago. 5300 BC • The Initial Ancestor comes out to be about 5,300 BC. That is all INCREASING living human being today have a common set of initial ancestors (IA) TIME going back to 7,300 years ago, about 240 generation ago! That is, there is a set of ancestors 240 generations ago, who are the Most ancestors of ALL HUMAN BEINGS. recent common • So from the human beings living 7,300 years ago, they are Ancestor. 1500 BC ancestors of all humans alive today, or no humans alive today! Initial Ancestor Ancestry 30 Ancestry 31 5
  • Comparison with genetic data Summary • Genetic data says we are separated by 60,000 years while genealogy says We therefore end up with two different results referring to we had all had common ancestors less than 7,000 years ago! two completely different kind of ancestry • The number of genealogical Initial ancestors is very large. Set 1: – Genetically: the sub-continental human groups separate around • Being a ancestor of all humanity does not imply that the individuals make any significant genetic contribution to the population. 40,000 years ago. – Archaeologically first humans populate the Indian sub-continent • You derive very little of the exact genes of your ancestor! They passed on 60,000 years ago. the ancestral genes to you, but their specific characteristics, are washed out in gene shuffling. So genetics still allows trace of ‘race’, provided a majority Set 2: of your ancestors came from the same race but not to individual ancestors! – Genealogically humans have a common ancestor from ~ 5,500 BC • You do not look like your great – great – great – great grandfather. By sixth – Linguistically our language separated from the European generation or so, the genetic shuffling is severe enough to remove genetic traces of the ancestors! languages 5,000 BC ago. Ancestry 32 Ancestry 33 Conclusion • Genetically human beings in the Indian Sub-continent have been evolving in genetically isolated manner. • However, the population and growth of population as well as language and cultures is very heavily influenced by global as well as local trends. Phew! • So you may not look anything like your great – great – great – great grandfather, but you still speak a language close to what he spoke! Ancestry 34 Ancestry 35 Acknowledgements • I want to acknowledge all the known and unknown Web sources that I have used in the lecture. • My special thanks to WIKIPEDIA which provided some valuable information. • I want to thank my friends Sudha Bhujle, Kavita Gangal, Hrishikesh Joglekar, Parag Mahajani, Aniket Sule. I have stolen ideas and images from all of them! • I want to particularly thank Dr. Jamkhedkar who has been my constant source of inspiration on this subjects. • I want to express my apology to all those whom I may have forgotten to thank. Ancestry 36 6