Sequencing Sumeria

A study published on September 11 of this year through the Public Library of Science draws a genetic connection between ancient Mesopotamia and the Indian Subcontinent. Researchers used ancient DNA analysis to identify the genetic origins of the remains tested. These remains were collected at two different sites, modern-day Tell Ashara and Tell Masaikh (or ancient Terqa and Kar-Assurnasirpal), in what is now Syria. The remains were dated to between 2500 BC and 500 AD (or BCE and CE, if you prefer), placing them between the Early Bronze Age and the Late Roman Period.

Ancient DNA analysis differs from modern DNA analysis largely in the samples used. Modern DNA techniques benefit from generally utilizing samples taken explicitly for the purpose of genetic testing, or at least samples which are viable for analysis. Ancient DNA though, is often degraded or damaged, and only obtainable in small amounts from decayed human remains, thus limiting the depth of analysis.

The researchers sequenced the mitochondrial DNA (mtDNA) of the remains (two male and one female) and identified each individual’s haplotype. A haplotype is a combination of alleles at specific locations on a chromosome, or in this case, in the mitochondrial genome. Within this framework, individuals are categorized by the alleles they carry at specific locations throughout the genome. Since mtDNA is passed only through the mother, there is much less genetic recombination of the genome and so mitochondrial DNA can provide a more direct avenue to establishing genetic history.

The mtDNA haplotypes identified in the ancient Mesopotamian samples that were tested (derived from the teeth of skeletal remain unearthed at archaeological digs) corresponded to haplotypes present in both modern and ancient India and Tibet (but that are now absent in Syria). This suggests that these individuals were either immigrants from the Indian subcontinent or descended from immigrants. The samples tested came from slightly different eras and came from both male and female individuals, both of which point to a long-standing population in the area, as opposed to incidental migration.

This new finding fits into a larger historical context with regards to Sumerian civilization. The remains from Terqa date to only slightly before the ancient city’s founding, indicating that these distant migrants could have been involved in its initial formation. The origins of the Sumerian civilization and its peoples are still a matter of debate among historians of the era, meaning that immigrants such as these could have been part of an initial movement which helped to establish the ancient dynasty which included the reign of King Gilgamesh (yes, that Gilgamesh). Similarities between the Tibeto-Burman languages and the Sumerian language have often been suggested as support that the civilization’s roots laid east, in areas such as Tibet or India, and these findings certainly lend weight to that possibility. While these results are hardly conclusive in proving who founded Sumer and helped give birth to its legacy, they certainly do help to diversify the population we know lived there, helping to create a more detailed and rich history of the region.

Original article: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073682

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