science

Scientists try and identity occupants of unmarked graves in Canada

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Unmasking the dead: Scientists try and identity occupants of unmarked graves in Canada – and the technique could help repatriate the remains of World War veterans

  • Six 19th-century males were compared to historical and modern Canadians
  • The remains had been accidentally found and exhumed over several years   
  • The method combines genetic markers with detailed genealogy  
  • A comprehensive picture of both past and present gene pools can be created 
  • Scientists say a large enough database could help identify and repatriate Canadian veterans from the two world wars 

Scientists are developing a way to discover the identity of a dead person’s remains without any information as to who they are. 

The method combines analysis of their DNA trapped inside their bones and a genealogical record of relatives, ancestors and descendants. 

It was developed in Quebec and scientists say it could one day identify remains of Canadian soldiers who were buried overseas during the two world wars.

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Six skeletons had been exhumed accidentally due to building work and excavations and the remains were then used in an experiment.  They were compared to modern and historical genetic records

Six skeletons had been exhumed accidentally due to building work and excavations and the remains were then used in an experiment.  They were compared to modern and historical genetic records 

In Quebec, gravestones did not come into common use until the late 1800s and many people were buried in unmarked graves. 

Six skeletons from four Quebec cemeteries were studied had been exhumed accidentally due to building work and excavations and the remains were then used in an experiment. 

Two of these cemeteries were in Montreal while the two others were those of the former municipality of Pointe-aux-Trembles and the city of Sainte-Marie-de-Beauce. 

The Quebec researchers compared the genetic markers from these historical remains with the same genetic markers from over 960 modern Quebecers in a database called BALSAC. 

Through this process, the researchers were able to deduce the genetic profiles of approximately 1.7 million individuals from historical Quebec. 

However, only 12 per cent of the pre 1850 men in the BALSAC database matched the modern inhabitants. 

And none of the 12 per cent had the same genetic profile as any of the six unidentified remains. 

Dr Tommy Harding, a postdoctoral researcher at Université de Montréal who specialises in DNA sequencing says this is likely because the six men were not related maternally or paternally to any of the individuals in the modern sample.

‘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.’  

‘In addition to being used to identify historical remains here in Quebec so that they can be laid to rest again in marked graves, our method might be used to identify the remains of Canadian soldiers who died and were buried overseas during the two world wars.’

Both the Y-chromosome markers and the mitochondrial DNA markers rarely mutate, making them reliable for long-term ancestry studies (stock)

Both the Y-chromosome markers and the mitochondrial DNA markers rarely mutate, making them reliable for long-term ancestry studies (stock)

WHAT IS THE Y CHROMOSOME AND WHY IS IT DISAPPEARING?

The Y chromosome is one of two sex chromosomes found in humans – the other is the X chromosome.

It is the only chromosome in an organism that isn’t essential for life – women survive just fine without one, after all. 

In humans, the 22 other pairs of chromosomes – the autosomes – are identical. 

The Y chromosome spans more than 59 million building blocks of DNA and represents almost 2 percent of the total DNA in cells.

But the human Y-chromosome is still one of the smallest in the genome. 

It is carried by roughly half of a man’s sperm, and dictates whether a child will be male or female.  

Despite this, it carries very little other important information. 

And researchers think it is quickly disappearing. 

The number of genes on the Y has dropped from over 1,000 to roughly 50, a loss of more than 95 per cent. 

If the same rate of degeneration continues, the Y chromosome has just 4.6 million years left before it disappears completely. 

But the Y chromosome hasn’t always been so small.  

It was once the size of the X chromosome and contained all the same genes. 

The problem, however, is that  Y chromosomes are only ever found as a single copy, passed from fathers to their sons, rather than a pair

This means that genes on the Y chromosome cannot undergo something known as ‘genetic recombination’.

This is switch of genes that takes place in each generation which helps to eliminate damaging gene mutations.

 

BALSAC is a unique database founded in 1972 which is the only one of its kind in the world. 

The genealogical information stored inside features two key genetic markers – one for women and one for men. 

The Y-chromosome is passed down from father to son and is preserved in the Y-chromosome. Some genetic markers are preserved through the generations and are almost identical. 

A genetic marker of any male’s Y-chromosome will be an almost identical clone to the Y-chromosome of his paternal great-great grandfather for example. 

However, it will not reveal any insight into the maternal lineage. 

A similar phenomenon occurs between mother and daughter, with the mitochondrial DNA which is passed down the female generations. 

Both the Y-chromosome markers and the mitochondrial DNA markers rarely mutate, making them reliable for long-term ancestry studies. 

These were the focal point of research from Damian Labuda, an expert in genetic structure and diversity who is a professor in the Department of Pediatrics at Université de Montréal.  

The BALSAC database contains the genealogical relationships linking five million individuals. 

Work on developing this database began in 1972 and Dr Harding called it ‘truly exceptional’. 

‘[BALSAC] 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.’  



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