Helicobacter pylori in the Iceman

Science 8 January 2016:
Vol. 351 no. 6269 pp. 162-165

The 5300-year-old Helicobacter pylori genome of the Iceman
Frank Maixner1,*,†, Ben Krause-Kyora2,†, Dmitrij Turaev3,†, Alexander Herbig4,5, et al.

The stomach bacterium Helicobacter pylori is one of the most prevalent human pathogens. It has dispersed globally with its human host, resulting in a distinct phylogeographic pattern that can be used to reconstruct both recent and ancient human migrations. The extant European population of H. pylori is known to be a hybrid between Asian and African bacteria, but there exist different hypotheses about when and where the hybridization took place, reflecting the complex demographic history of Europeans. Here, we present a 5300-year-old H. pylori genome from a European Copper Age glacier mummy. The “Iceman” H. pylori is a nearly pure representative of the bacterial population of Asian origin that existed in Europe before hybridization, suggesting that the African population arrived in Europe within the past few thousand years.

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Migration from Sweden to Poland during the Early Bronze Age

Proof of human migration from Sweden to Poland during the Early Bronze Age

During the Early Bronze Age there was a very high level of territorial mobility of the Únětice culture in Silesia, a large community inhabiting the south western territories of Poland approximately 4 000 years ago. This is found in a new doctoral thesis from the University of Gothenburg which also conclusively confirms the first case of human long-distance overseas journey to Silesia from Scandinavia, probably from southern Sweden.

'Over 3800 years ago, a young male, possibly born in Skåne, made a journey of over 900 kilometers south, to Wroclaw in Poland. He died violently in Wroclaw, killed by Úněticean farmers, possibly due to romance with two local females, who were murdered together with him. This 'Bronze Age love story', with no happy end today is the first case of Swedish-Polish contacts in history ever', concludes archaeologist Dalia Pokutta, author of the thesis.

Here is the thesis, titled:  Population Dynamics, Diet and Migrations of the Únětice Culture in Poland.

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.

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