The Black Death of the 14th century may be written into the DNA of survivors' descendants, new research finds.
The study reveals that Roma people (sometimes known as gypsies, although this is considered a derogatory term) and white Europeans share alterations to their genetic code that occurred after the Roma settled in Europe from northwest India 1,000 years ago. The plague of the 1300s, which killed at least 75 million people, is a likely candidate for forcing this evolutionary change.
"We show that there are some immune receptors that are clearly influenced by evolution in Europe and not in northwest India," said study leader Mihai Netea, a researcher in experimental internal medicine at Radboud University Nijmegen Medical Center in the Netherlands.
"India did not have the medieval plague, as Europe had," Netea told Live Science. "We have also demonstrated that these receptors are recognizing Yersinia pestis, which is the plague bacterium." [In Photos: 14th-Century Black Death Graves Discovered]
Searching for similarities
Netea and his colleagues made their discovery by scanning almost 200,000 single-nucleotide polymorphisms (SNPs), or short segments of DNA that vary among people. They tested people from Romania, as well as Roma people. For social and economic reasons, Netea said, the Roma have lived among Europeans since about A.D. 1000, without much interbreeding between the two groups. That gives researchers a rare opportunity to study two genetically distinct populations in one geographical region.
The researchers looked for genetic variations that appeared in both Europeans and Roma people. Then, they took that list and crossed off the genetic variations that also appeared in a population of northwest Indians, to rule out evolutionary change that originated outside Europe.
The result was a list of about 20 genes that show evidence of convergent evolution between Europeans and Roma -- meaning the two groups started out different but evolved to look more similar because of pressures in their environment.