April 02, 2013

More asymmetric migration (Sundqvist et al. 2013)

A day after the paper by Peter and Slatkin, a new paper has appeared on the arXiv dealing with the problem of detecting directionaliy in human migration patterns. This seems to be purely methodological, so no new insights on human history to report.

arXiv:1304.0118 [q-bio.PE]

A new approach to estimate directional genetic differentiation and asymmetric migration patterns

Lisa Sundqvist, Martin Zackrisson, David Kleinhans

In the field of population genetics measures of genetic differentiation are widely used to gather information on the structure and the amount of gene flow between populations. These indirect measures are based on a number of simplifying assumptions, for instance equal population size and symmetric migration. Structured populations with asymmetric migration patterns, frequently occur in nature and information about directional gene flow would here be of great interest. Nevertheless current measures of genetic differentiation cannot be used in such systems without violating the assumptions. To get information on asymmetric migration patterns from genetic data rather complex models using maximum likelihood or Bayesian approaches generally need to be applied. In such models a large number of parameters are estimated simultaneously and this involves complex optimization algorithms. We here introduce a new approach that intends to fill the gap between the complex approaches and the symmetric measures of genetic differentiation. Our approach makes it possible to calculate a directional component of genetic differentiation at low computational effort using any of the classical measures of genetic differentiation. The approach is based on defining a pool of migrants for any pair of populations and calculating measures for genetic differentiation between the populations and the respective pools. The directional measures of genetic differentiation can further be used to calculate asymmetric migration. The procedure is demonstrated with a simulated data set with known migration pattern. A comparison of the estimation results with the migration pattern used for simulation suggests, that our method captures relevant properties of migration patterns even at low migration frequencies and with few marker loci.


1 comment:

  1. Hi, Dienekes!

    This has to do with migration and genomics...have you seen this?

    Ancient Europeans Mysteriously Vanished 4,500 Years Ago

    The genetic lineage of Europe mysteriously transformed about 4,500 years ago, new research suggests.

    The findings, detailed today (April 23) in the journal Nature Communications, were drawn from several skeletons unearthed in central Europe that were up to 7,500 years old.

    "What is intriguing is that the genetic markers of this first pan-European culture, which was clearly very successful, were then suddenly replaced around 4,500 years ago, and we don't know why," said study co-author Alan Cooper, of the University of Adelaide Australian Center for Ancient DNA, in a statement. "Something major happened, and the hunt is now on to find out what that was."

    The new study also confirms that people sweeping out from Turkey colonized Europe, likely as a part of the agricultural revolution, reaching Germany about 7,500 years ago.

    For decades, researchers have wondered whether people, or just ideas, spread from the Middle East during the agricultural revolution that occurred after the Mesolithic period...



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