On 11/22/2013 2:26 PM, Malcolm McClure wrote: > > Have you seen an accessible reference where these paradoxes are > discussed in detail, with helpful diagrams that show the bias > introduced by bottlenecks, early death and girling? A few references, there are also academic papers and theses on these subjects not linked here but easily located...look in google scholar and other searches of academic and scientific journals: https://www.google.com/search?q=genetic+drift&tbm=isch&tbo=u&source=univ&sa=X&ei=erSPUuatMbLksAT4woCABw&sqi=2&ved=0CFoQsAQ&biw=882&bih=544 http://en.wikipedia.org/wiki/Genetic_drift http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml http://en.wikipedia.org/wiki/Population_bottleneck http://www.nature.com/scitable/definition/population-bottleneck-300 http://www.sciencedaily.com/articles/g/genetic_drift.htm > Is it all down to pure chance? Monte Carlo simulation of such a system > would surely result in an infinite number of unprovable hypotheses. I suppose one could equate all human survival as a game of chance:-D). Regarding analysis and assessment of population genetics and genetic genealogy in general, hypotheses are generally formed because of observations. What we are observing are the Y haplotypes and SNPs from living (and/or recently departed) people today. The Y of today is because of the survival of our Y ancestors; however wide sections of populations may and have gone extinct due to all kinds of things from cataclysmic disasters, resulting plagues, climate change even those which may have not been terribly severe as in ice ages but produced wide spread crop failure, loss of wild life and livestock, and resulted in serious plagues which then extended for many years there after--some these have produced population bottlenecks. Lineages go extinct due to accidents, war, famine, sickness and disease (in some cases genetic conditions), and girling out. We may observe only what is present to observe. Those who have gone extinct before us we may not observe except as with the archeological and anthropological finds as discovered and what remains observed--for the Y we can only hope in these circumstances that it is not so degraded that it may be extracted and analyzed. In terms of genetic genealogy, we may know firmly what our confirmed (not best guess) paper trails tell us; beyond that the trails are a combination of observable Ydna from today of survivors. > > If as you correctly point out, modern modes are meaningless, and > taking account of reverse mutation, it follows that we cannot > establish the actual profile of that remote 'ultimate' ancestral > haplotype/SNP without disinterring his actual remains and analysing > his Y profile. I hope that I did not infer that what we do is meaningless, as I do not believe that it is meaningless. On the contrary; but much of what we believe that we know is theoretical and these theories evolve from observations as well as knowledge of the historical. For instance, dinosaurs do not live among us as far as we know. They went extinct long ago; birds along with some creatures of the deep, reptiles and amphibians are believed to be evolutionary remnants from a time during which the dinosaurs roamed. Humanity is assessed to share genetics w/chimpanzees, Neanderthal, Denisovans etc. Chimpanzee species are yet among us, although they too have evolved; but as far as we know Neanderthal and Denisovans are not. > Such a discovery is akin to finding a needle in a haystack, > considering all the tumuli, tamlaghts and battlefields of the ancient > world. > > Further thoughts about this would be welcome. > > M. We may not figure it all out. But we can enjoy the process. Susan