Tuesday, January 16, 2018

Two Egyptian Mummies Sharing A 12th Dynasty Tomb Were Half Brothers

Despite previous evidence to the contrary, two mummies from almost four thousand years ago have been determined to be half-brothers based upon ancient DNA analysis. Science News provides an educated layman's level explanation:
The tomb dates to ancient Egypt’s 12th Dynasty, between 1985 B.C. and 1773 B.C. 
Coffin inscriptions mention a female, Khnum-Aa, as the mother of both men. And both mummies are described as sons of an unnamed local governor. It has always been unclear if those inscriptions refer to the same man, but discoverers decided the mummies were full brothers, because the two were buried next to each other and had the same mother. 
Over time, differences discovered in the men’s skull shapes and other skeletal features raised suspicions that the Two Brothers were not biologically related at all. And some researchers argued that the inscriptions indicating the men had the same mother were misleading. 
Adding to those doubts, a 2014 paper reported differences between the two mummies’ mitochondrial DNA, suggesting one or both had no biological link to Khnum-Aa. Mitochondrial DNA typically gets inherited from the mother.
But that study extracted ancient DNA from liver and intestinal samples using a method susceptible to contamination with modern human and bacterial DNA, Drosou’s team argues. In the new work, researchers isolated and assembled short pieces of mitochondrial and Y-chromosome DNA from both mummies’ teeth using the latest methods. The Y chromosome determines male sex and gets passed from father to son. This approach minimizes potential contamination from modern sources.
This discovery contributes to a mosaic of other evidence suggesting that succession to leadership positions in the early Egyptian kingdom may have been from mother to child, rather than from father to son. 
We resolve a longstanding question regarding the kinship of two high-status Egyptians from the 12th Dynasty, Nakht-Ankh and Khnum-Nakht, whose mummies were discovered in 1907 by Egyptian workmen directed by Flinders Petrie and Ernest Mackay. Although their coffin inscriptions indicate that Nakht-Ankh and Khnum-Nakht were brothers, when the mummies were unwrapped in 1908 the skeletal morphologies were found to be quite different, suggesting an absence of family relationship. We extracted ancient DNA from the teeth of the two mummies and, following hybridization capture of the mitochondrial and Y chromosome fractions, sequenced the DNA by a next generation method. Analysis of single nucleotide polymorphisms showed that both Nakht-Ankh and Khnum-Nakht belonged to mitochondrial haplotype M1a1, suggesting a maternal relationship. The Y chromosome sequences were less complete but showed variations between the two mummies, indicating that Nakht-Ankh and Khnum-Nakht had different fathers. Our study emphasizes the importance of kinship in ancient Egypt, and represents the first successful typing of both mitochondrial and Y chromosomal DNA in Egyptian mummies.
K. Drosou, C. Price and T. Brown. The kinship of two 12th Dynasty mummies revealed by ancient DNA sequencing. Journal of Archaeological Science: Reports. Vol. 17, February 2018, p. 793. doi:10.1016/j.jasrep.2017.12.025.

The new result contradicts a previously analysis from 2014 done using methods more prone to contamination. C. Matheson et al. Molecular confirmation of Schistosoma and family relationship in two ancient Egyptian mummies. In H. Gill-Frerking et al., editors, Yearbook of Mummy Studies Volume 2, p. 39.

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