Back Anonymous no more: combining genetics with genealogy to identify the dead in unmarked graves

Anonymous no more: combining genetics with genealogy to identify the dead in unmarked graves

A method developed by a team of Quebec researchers may make it possible to identify thousands of individuals whose remains lie in unmarked graves in historical cemeteries through the province. The Genomics Core Facility at UPF, specialist in analyzing historical DNA, participated in the srudy extracting DNA from the remains and analyzing them to reveal their genetic markers.

26.02.2020

Imatge inicial

In Quebec, gravestones did not come into common use until the second half of the 19th century, so historical cemeteries contain many unmarked graves. Inspired by colleagues at UPF, a team of researchers in genetics, archaeology and demography from three Quebec universities (Université de Montréal, Université du Québec à Chicoutimi and Université du Québec à Trois-Rivières) conducted a study in which they combined genealogical information from BALSAC (a Quebec database that is the only one of its kind in the world) with genetic information from more than 960 modern Quebecers in order to access the genetic profile of Quebec’s historical population. The results, published in the American Journal of Physical Anthropology, suggest the capabilities that this method may offer in the near future.

The BALSAC database contains the genealogical relationships linking five million individuals, the vast majority of whom married in Quebec, over the past four centuries. The first author of this study is Tommy Harding, a postdoctoral researcher at Université de Montréal who specializes in DNA sequencing. BALSAC, he said, “is a fabulous database for researchers, because both the quantity and the quality of the data that it contains are truly exceptional. The parish records meticulously kept by Catholic priests have been very well preserved so that today, thanks to advances in technology, it is possible to use this data to identify the bones from unmarked graves."

Using the Y chromosome and mitochondrial DNA

This study was directed by Damian Labuda, an expert in genetic structure and diversity. “Genetics,” he said, “has of course been used many times to identify the remains of historical figures, such as the members of the Romanov Russian imperial family who were killed by the Bolsheviks and buried in a common grave.

They combined genealogical information with genetic information from more than 960 modern Quebecers in order to access the genetic profile of Quebec’s historical population.

“What is different about our research team’s genetic method,” Labuda added, “is that we use the information contained in two genetic markers that are transmitted to children by only one parent: the Y chromosome, which is passed from fathers to their sons, and mitochondrial DNA, which is passed from mothers both to their daughters and to their sons. These two genetic molecules are inherited with few modifications (that is, mutations), so that individuals today have the same, or almost the same, DNA sequence as their ancestors who lived more than 10 generations earlier.”  

Making old bones tell their tales

Harding explaine: “To empirically test our method’s identification potential, we selected six unidentified male skeletons that had been exhumed over the years at four historical cemeteries in Quebec”. They sent these bones to the Genomics Core Facility at UPF, where the reserchers Ferran Casals and Roger Anglada extracted DNA from these remains and analyzed them to reveal their mitochondrial and Y chromosome genetic markers. Their team is specialist in analyzing historical DNA and they have been conducting genetic analyses from the remains of the Spanish Civil War graves for quite a while. Carles Lalueza-Fox from the Institute for Evolutionary Biology (IBE: CSIC-UPF), who is a specialist in the study of much older samples, has also taken part in the study in Barcelona.

The Quebec researchers then compared the genetic markers from these historical remains with the same genetic markers from over 960 modern Quebecers who had volunteered to be genotyped in an earlier research project and whose genealogy had been established using population data from the BALSAC database. Through this process, the researchers were able to deduce the genetic profiles of approximately 1.7 million individuals from historical Quebec.

This study is especially important for a territory like Québec, where genetic data can be crossed with genealogies, thanks to the extensive collection by the Catholic Church of information on weddings, baptisms, and deads. 

“However,” Harding acknowledged, “only 12 per cent of the men married before 1850 who are included in the BALSAC database shared a mitochondrial profile and a Y chromosome with the 960 Quebecers from the modern sample. Because of this limited genetic coverage, none of the men among these 12 per cent had the same genetic profile as any of the unidentified remains.” But if we could increase the number of genotyped modern individuals considerably – by hundreds of thousands – then we could identify up to 87 per cent of the men married before 1850.”

Casals states that "this study is especially important for a territory like Québec, where genetic data can be crossed with genealogies, thanks to the extensive collection by the Catholic Church of information on weddings, baptisms, and deads. Such a study here could not have much impact because we do not have detailed genealogical information at our disposal, which is the key resource.''

Harding also believes that this method has potential applications in public health. “Studying the genetic baggage of the founders of the French-Canadian population can help us not only to calibrate other methods, such as the reconstruction of historical genomes using bioinformatic models, but also to advance knowledge of the epidemiology of genetic diseases by identifying the historical sources of their genetic determinants, thus opening the door to easier screening for some of these diseases,” he concludes. 

Read more at the University of Montreal website

Reference article:

T. Harding, E. Milot, C.  Moreau, J.-F. Lefebvre, J.-S. Bournival, H. Vézina, C. Laprise C. Lalueza-Fox, R. Anglada, B. Loewen, F. Casals, I. Ribot, and D. Labuda, “Historical human remains identification through maternal and paternal genetic signatures in a founder population with extensive genealogical record”, American Journal of Physical Anthropology, 16 February 2020. DOI: 10.1002/ajpa.24024.

Funding:

This study was funded by the Fonds de recherche du Québec — Santé (through its applied genetic medicine research network), the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherche du Québec — Société et Culture and the European Regional Development Fund—Ministerio de Economia y Competitividad (Spain).

 

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