[LINK] "Black Death Left a Mark on Human Genome"
Science's Elizabeth Pennisi wrote about a fascinating study that, by comparing the genes of ethnic Romanians with Roma residents of that country, determined that the black death had left an imprint on European populations absent elsewhere.
The Black Death didn’t just wipe out millions of Europeans during the 14th century. It left a mark on the human genome, favoring those who carried certain immune system genes, according to a new study. Those changes may help explain why Europeans respond differently from other people to some diseases and have different susceptibilities to autoimmune disorders.
Geneticists know that human populations evolve in the face of disease. Certain versions of our genes help us fight infections better than others, and people who carry those genes tend to have more children than those who don’t. So the beneficial genetic versions persist, while other versions tend to disappear as those carrying them die. This weeding-out of all but the best genes is called positive selection. But researchers have trouble pinpointing positively selected genes in humans, as many genes vary from one individual to the next.
Enter Mihai Netea, an immunologist at Radboud University Nijmegen Medical Centre in the Netherlands. He realized that in his home country, Romania, the existence of two very distinct ethnic groups provided an opportunity to see the hand of natural selection in the human genome. A thousand years ago, the Rroma people-commonly known as gypsies-migrated into Europe from north India. But they intermarried little with European Romanians and thus have very distinct genetic backgrounds. Yet, by living in the same place, both of these groups experienced the same conditions, including the Black Plague, which did not reach northern India. So the researchers sought genes favored by natural selection by seeking similarities in the Rroma and European Romanians that are not found in North Indians.
Netea; evolutionary biologist Jaume Bertranpetit of Pompeu Fabra University in Barcelona, Spain; and their colleagues looked for differences at more than 196,000 places in the genomes of 100 Romanians of European descent and 100 Rroma. For comparison, the researchers also cataloged these differences in 500 individuals who lived in northwestern India, where the Rroma came from. Then they analyzed which genes had changed the most to see which were most favored by selection.
Genetically, the Rroma are still quite similar to the northwestern Indians, even though they have lived side by side with the Romanians for a millennium, the team found. But there were 20 genes in the Rroma and the Romanians that had changes that were not seen in the Indians’ versions of those genes, Netea and his colleagues report online today in the Proceedings of the National Academy of Sciences. These genes “were positively selected for in the Romanians and in the gypsies but not in the Indians,” Netea explains. “It’s a very strong signal.”
The Black Death didn’t just wipe out millions of Europeans during the 14th century. It left a mark on the human genome, favoring those who carried certain immune system genes, according to a new study. Those changes may help explain why Europeans respond differently from other people to some diseases and have different susceptibilities to autoimmune disorders.
Geneticists know that human populations evolve in the face of disease. Certain versions of our genes help us fight infections better than others, and people who carry those genes tend to have more children than those who don’t. So the beneficial genetic versions persist, while other versions tend to disappear as those carrying them die. This weeding-out of all but the best genes is called positive selection. But researchers have trouble pinpointing positively selected genes in humans, as many genes vary from one individual to the next.
Enter Mihai Netea, an immunologist at Radboud University Nijmegen Medical Centre in the Netherlands. He realized that in his home country, Romania, the existence of two very distinct ethnic groups provided an opportunity to see the hand of natural selection in the human genome. A thousand years ago, the Rroma people-commonly known as gypsies-migrated into Europe from north India. But they intermarried little with European Romanians and thus have very distinct genetic backgrounds. Yet, by living in the same place, both of these groups experienced the same conditions, including the Black Plague, which did not reach northern India. So the researchers sought genes favored by natural selection by seeking similarities in the Rroma and European Romanians that are not found in North Indians.
Netea; evolutionary biologist Jaume Bertranpetit of Pompeu Fabra University in Barcelona, Spain; and their colleagues looked for differences at more than 196,000 places in the genomes of 100 Romanians of European descent and 100 Rroma. For comparison, the researchers also cataloged these differences in 500 individuals who lived in northwestern India, where the Rroma came from. Then they analyzed which genes had changed the most to see which were most favored by selection.
Genetically, the Rroma are still quite similar to the northwestern Indians, even though they have lived side by side with the Romanians for a millennium, the team found. But there were 20 genes in the Rroma and the Romanians that had changes that were not seen in the Indians’ versions of those genes, Netea and his colleagues report online today in the Proceedings of the National Academy of Sciences. These genes “were positively selected for in the Romanians and in the gypsies but not in the Indians,” Netea explains. “It’s a very strong signal.”