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Thread: Population Size and Genetic Diversity

  1. #1
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    Population Size and Genetic Diversity

    Many people often overlook the relationship between population size and genetic variation, whenever people speculate the origins of particular haplogroup or ethnogenesis of a population from nuclear DNA. They sometimes use modern populations to reconstruct the past, while not taking into account that some populations with high genetic diversity are often less likely to experience any factors that would result in a loss of genetic diversity. You see, whenever a population numbers are reduced either through war, genocide, famine, natural disaster, etc. the total genetic variability in that population decreases drastically. Given how often my ethnic group was subject massacres, genocide, war and famine. I sometimes wonder how genetically diverse Assyrians would be had none of that happened.

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    Great topic and discussion point.

    The most accurate way of determining this could be through aDNA and the following steps;
    - Collecting many (50+) samples belonging to high quality ancient remains dating to the likely period of a modern ethnic group's formation (in the case of modern Assyrians, ~500 B.C.?)
    - Confirming these remains are ancestral to the modern population using relative IBD segment sharing (i.e. a northern Mesopotamian farmer sharing significantly more segments with Assyrians than Kurds, Turks, Armenians etc.)
    - Pooling these samples into a single group and considering these as the "pre-modern" population
    - Applying algorithms taking "natural" population genetic trends over time into consideration

    Outside of aDNA, I'm not sure if there are any statistical approaches population geneticists could use to create artificial reconstructions of what a given population's genetic diversity should be if the bottlenecks hadn't happened.

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    Quote Originally Posted by DMXX View Post
    Outside of aDNA, I'm not sure if there are any statistical approaches population geneticists could use to create artificial reconstructions of what a given population's genetic diversity should be if the bottlenecks hadn't happened.
    You can estimate effective population size from linkage disequilibrium.

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    Quote Originally Posted by Megalophias View Post
    You can estimate effective population size from linkage disequilibrium.
    You're right, I completely forgot about effective population size (Ne) simulations. Thanks for the reminder. That works as a conventional estimator of what Zeph is interested in.

    Those interested in what that entails can check these Holsinger lab lecture notes out.

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  9. #5
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    This is something I've wondered about. If a population from a low population density region moves to a high population density region then might not the later higher effective population lead to higher diversity over time so the newer population ends up seeming older?

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