Centuries later, the Black Death still has a big impact on our immune systems, study shows

Our Medieval ancestors left us with a biological legacy: Genes that may have helped them survive the Black Death make us more susceptible to certain diseases today. It's a prime example of the way germs shape us over time, scientists said in a new study published Wednesday in the journal Nature. "Our genome today is a reflection of our whole evolutionary history" as we adapt to different germs, said Luis Barreiro, a senior author of the research. Some, like those behind the bubonic plague, have had a big impact on our immune systems. The Black Death in the 14th century was the single deadliest event in recorded history, spreading throughout Europe, the Middle East and northern Africa and wiping out up to 30% to 50% of the population. Barreiro and his colleagues at the University of Chicago, McMaster University in Ontario and the Pasteur Institute in Paris examined ancient DNA samples from the bones of more than 200 people from London and Denmark who died over about 100 years that stret