A new study has found that the expansion of the black rat, accused of spreading the Black Death, is related to historical events that changed the world, in the Roman and medieval periods.
A new analysis of ancient DNA has shed light on how the black rat, accused of spreading the Black Deathspread across Europe, revealing that the rodent colonized the continent twice, in the Roman and medieval periods.
The study, led by the University of York together with the University of Oxford and the Max Planck Institutes for the Science of Human History (Jena) and Evolutionary Anthropology (Leipzig), is the first ancient genetic analysis of the rodent species, also known as the ship rat.
The black rat (rattus rattus) is one of three species of rodent, along with the house mouse (Mus musculus) and the brown rat (Rattus norvegicus), which have been distributed globally as a result of their ability to live around human dwellings, taking advantage of their food sources and means of transportation.
Black rats were widespread throughout Europe until at least the 18th century, before their population massively declined, most likely as a result of competition with the newly arrived brown rat, the now dominant rat species in temperate Europe.
By analyzing DNA from ancient black rat remains found at archaeological sites spanning the 1st to 17th centuries in Europe and North Africa, researchers have built a new understanding of how rat populations dispersed following flows. and ebbs of human commerce, urbanism and empires.
The study shows that the black rat colonized Europe at least twice, once during the first centuries of Roman expansion throughout Europe, the Balkans, the Middle East and North Africa.
The second wave occurred in the medieval period, coinciding with archaeological evidence of a decline or even disappearance of rats during the early medieval period, which ran from the late 5th or early 6th century to the 10th century.
According to the authors, these movements were related to the breakdown of the Roman economic system, although climate change and plague of justinian of the sixth century, may also have played a role. When cities and large-scale trade re-emerged in the medieval period, so did a new wave of black rats.
Repeated colonization of Europe
“We have long known that the spread of rats is related to human events, and we suspected that Roman expansion brought them into northern Europe,” said David Orton, from the Department of Archeology at the University of York, in a statement.
Black rats disappeared in Britain after the Roman period, when there was less urbanization and less trade, and only returned in the Viking Age, when trade and cities also returned.
This research confirms that the black rat was probably introduced to the eastern Mediterranean by a land route through Southwest Asia, although a sea route through the Indian Ocean and the Red Sea cannot be excluded.
He also identifies two waves of rat introductions in temperate Europe. The first probably accompanied the Roman expansion to the north, and the second took place during the medieval period, which declined with the collapse of the Roman Empire.
According to the authors, the study could also provide information on human movement on the continents.
“This study is a great showcase of how the genetic background of human commensal species such as the black rat, animals that thrive around human settlements, may reflect human historical or economic events. There is a lot we can learn from these often neglected little animals,” says lead author He Yu, a researcher at the Max Planck Institute for Evolutionary Anthropology.
Our results reveal how the black rat can act as an ideal proxy for interpreting the history of human movement and cultural change, the researchers conclude in their paper.
Palaeogenomic analysis of black rat (Rattus rattus) reveals multiple European introductions associated with human economic history. He Yu et al. Nature Communications, Volume 13, Article number: 2399 (2022).