Saturday, October 12, 2019

Bronze Age Families in Southern Germany

Over the course of the 1980s and 1990s much of Germany's Lech River Valley was overrun by the spreading suburbs of Augsburg. Under German law all of this construction was preceded by archaeological study. Among the sites discovered were several farmsteads or small settlements from the end of the Neolithic to the Bronze Age (c. 2750-1700 BC). Hundreds of graves from this period were dug, with varying degrees of preservation.

Now a team of scientists have extracted DNA from more than 100 of those skeletons, from six sites, and the results of the study were just published in Science. The study also included elemental analysis of the bones, to find out which people grew up locally and which might have been immigrants. In terms of the big questions of migration and language that have gotten so much attention in paleogenetics, the data fit the common pattern; they show a burst of steppes ancestry at the beginning of the period, mainly in the male line; on the other hand they show that the percentage of steppes ancestry declined over time. (Likely because of gene flow from other regions.)

The more interesting results come from the analysis of family relationships:
  • Each farmstead had one high-status lineage that was maintained over time in the male line. The women were outsiders, some from the same region and some from farther away.
  • There was one exception out of 39 possible events, a case where a daughter seems to have inherited the farm.
  • Lower status individuals showed less continuity over time and many of them were immigrants from outside the region. (And remember archaeologists never find enough burials to account for everyone, so many of the lowest status people may not be represented at all.)
  • Several high-status women were identified who were from outside the region and not related to anyone else at their farms; nobody knows what to make of these. If they came as brides, why didn't they have children?
Here's an amazing bit of science for you:
Three of the adult males are exceptional as they exhibit a shift of strontium isotope ratios from their first to their third molars, indicating a movement away from their birthplaces during adolescence, and a return as adults. A similar analysis of early and late developing molars in females suggests that their movements from outside the Lech valley occurred in adolescence or later, as evidenced by non-local isotope ratios in early and late forming teeth.
As with all cutting edge science this will need to be verified by future studies, but if the movements of adolescents can really be studied by comparing the composition of their teeth, what an incredible discovery.

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