The devastation of the plague pandemic left such an incredible genetic mark on humanity that it's still affecting our health nearly 700 years later.

Up to half of people died when the Black Death swept through Europe in the mid-1300s.

A pioneering study analysing the DNA of centuries-old skeletons found mutations that helped people survive the plague. But those same mutations are linked to auto-immune diseases afflicting people today.

The Black Death is one of the most significant, deadliest and bleakest moments in human history. It is estimated that up to 200 million people died. Researchers suspected an event of such enormity must have shaped human evolution. They analysed DNA taken from the teeth of 206 ancient skeletons and were able to precisely date the human remains to before, during or after the Black Death.

The standout finding, published in the journal Nature, surrounded mutations in a gene called ERAP2. If you had the right mutations you were 40% more likely to survive the plague.

"That's huge, it's a huge effect, it's a surprise to find something like that in the human genome," according to Professor Luis Barreiro, from the University of Chicago.

The gene's job is to make the proteins that chop up invading microbes and show the fragments to the immune system, priming it more effectively to recognise and neutralise the foe. The gene comes in different versions - those that work well and those that do nothing - and you get a copy from each parent.

So the lucky ones, who were most likely to survive, inherited a high-functioning version from mum and dad. And the survivors had children and so passed those helpful mutations on so they suddenly became much more common.

You can read more in an article by James Gallagher published in the BBC News web site at: https://www.bbc.co.uk/news/health-63316538.