When the plague swept Europe in 1665, no one could understand how the spread of the devastating disease. But after a tailor in the village of Eyam in the center of England died that September, people end up putting the two together. He had received a parcel fabric infested with fleas just four days before dying of bubonic plague. Within a month, five other villagers had died, and the local vicar convinced the city to voluntarily put in quarantine. It eventually became clear that he was smart, probably on rats that spread the plague so far and so fast.
But now it seems that the plague has not always infect fleas and disease may not have always spread so quickly and been so devastating. A new study of ancient DNA of teeth 101 skeletons Bronze Age found that seven people living there from 2800 to 5000 years in Europe and Asia have been infected Yersinia pestis , the bacterium that because the plague. But their strains of Y. pestis were missing a gene that allowed it to infect fleas, according to the study published today in Cell . This pushes the first evidence of plague nearly 3,300 years and offers a key indicator of how this disease has become so contagious. "It's really cool that they can locate the acquisition of key genes that enable the movement of this bacterium in fleas," says evolutionary geneticist Hendrik Poinar of McMaster University in Hamilton, Canada, who was not involved in the study.
plague caused the death and destruction in Europe at least since Roman times, the launch of three major pandemics that changed the course of history it plague of Justinian 541-544, which weakened the Byzantine Empire, the black Death, which killed nearly half the population of Europe between 1347 and 1351, and the Great plague of 1665, which lasted more 30. the ancient DNA researchers have shown in recent years that Y. pestis caused these three pandemics. But so far they have been unable to determine whether Y. pestis caused reported scourges there 2224 years in China and there are nearly 2500 years in Greece. they suspected that older versions of the plague are not as fast devastating spread, but they could not test this idea because they lacked samples earlier pathogens.
Now, an international team of researchers and archaeologists ancient DNA has solved the mystery almost by accident after sequencing the genomes of 101 skeletons from the Bronze Age in Europe and Asia. The team began by trying to identify the origins and early European migration. DNA samples have revealed that a group of pastoralists, the Yamnaya, swept Europe in the plains of Russia and Ukraine today somewhere between there 5000 and 4800 years, bringing their culture and, perhaps, the proto-Indo-European language with them. But the archaeologist Kristian Kristiansen from the University of Gothenburg in Sweden wondered if they also brought disease and suggested that researchers are testing the human DNA Bronze Age in Europe and Asia to the know.
The team, led by evolutionary biologist Eske Willerslev of the University of Copenhagen, screened 89 billion short DNA segments of teeth 101 people. Raw data included bacterial DNA in the teeth, generally considered "data on legacy waste," says Willerslev because it can contaminate human DNA samples. They detected Y. pestis people seven, ranging from the Bronze Age skeletons dating from 4800 years ago in Russia, Estonia and Poland, to an individual who lived Iron Age there are almost 3,000 years Armenia.
When they sequenced the complete genomes of Y. pestis DNA in these seven people, the team found that the bacterial genomes from the first samples lacked two genes that helped Y. pestis escape the immune systems of humans and chips during the black Death. In particular, the Y. pestis in the early Bronze Age individuals lacked a gene called Yersinia murine toxin , which protects the bacteria toxin in the gut fleas. So although these people the Bronze Age have suffered from the plague, they probably obtained from airborne droplets, contaminated food, or the transmission of bodily fluids rather than fleas that infested rodents, such as have done Europeans during the black Death and other pandemics.
using the same samples, the team also traced the evolution of Y. pestis and confirmed that it has evolved from a soil bacterium closely related to Yersinia pseudotuberculosis, a bacterium that causes scarletlike Far east fever in humans and is most often spread through food. Both bacterial lineages diverged there are about 55,000 years old. This date has large margins of error, but suggests that Y. pestis is much older than the estimates of thought-earlier suggested it originated there are only 3300 years. But researchers now realize that this was probably not before the end of the Bronze Age that bacteria have evolved from a less virulent species that have spread more like flu, tuberculosis or AIDS that bubonic plague, which is transmitted by flea bites on the skin.
"This suggests that it is a disease quite different in the Bronze Age than it was in medieval times," says Johannes Krause, a paleogeneticist the Institute Max Planck for science in human history in Jena, Germany, who was not involved in the study. Poinar agrees that the most exciting part of the paper is that it solves a longstanding mystery about how that bubonic plague was able to spread so rapidly in the Middle Ages He said:. ". The entire ecology flea rodent plague is what has led to major pandemics of bubonic form of the plague in Europe "
The plague was devastating the age of bronze too. the researchers believe that if the invading armies of the Russian steppe has the plague with them in Europe, although it is not spread by fleas it would have wiped out small bands of European farmers and made them vulnerable territory the invasion, much as the Spanish conquistadors infected Indians with smallpox. And the plague was just an arsenal of devastating diseases that have shaped the course of human history. "the most important message is we now can do it for all kinds of diseases, "said Willerslev.
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