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.