Two weeks ago, Pooja Swali from the Crick Institute announced the discovery of Yersinia pestis, the bacterium that causes plague, in the dental pulp of three people who died about 4,000 years ago – two in Somerset and the other in Cumbria. This finding is astonishing in its own right because it pushes back the earliest evidence of plague in England by several millennia. But the discovery may also help to solve one of our greatest prehistoric mysteries: why did the people who introduced farming to the British Isles suddenly vanish shortly after they built Stonehenge some five millennia ago?
Before last month’s announcement, the oldest evidence of plague in Britain came from a 1,500-year-old skeleton interred at an Anglo-Saxon burial site near Cambridge. That victim died during the plague of Justinian, which spread throughout the eastern Roman empire and beyond in the middle of the sixth century. While scientists have identified plague DNA in human remains across Europe and Asia dating to between 5,000 and 2,500 years ago, until last week, we couldn’t be sure that this prehistoric pandemic reached these isles. It’s now clear that it did.
We know that more recent plague pandemics have affected society in ways that are still evident. The Black Death, which killed more than half the British population in the mid-14th century, triggered a struggle between lords and serfs that led to the collapse of feudalism and the emergence of capitalism. Eight hundred years earlier, the plague of Justinian had halted the eastern Roman empire’s efforts to reconquer its lost western provinces. Eventually, the nation states of western Europe emerged from this political vacuum. Similarly, it is likely that the consequences of the prehistoric plague that killed Britons in Somerset and Cumbria were so profound that they can still be seen and heard today.
Where Britons are really from is a complicated story. The oldest complete human skeleton found in the British Isles belongs to 10,000-year-old Cheddar Man. When scientists extracted and analysed his DNA a few years ago, they realised that he wasn’t your stereotypical fair-haired, pale-skinned “English rose”. Cheddar Man had dark brown skin, black hair and blue-green eyes. He wasn’t an anomaly: this is how the first Britons looked.
About 6,000 years ago, Cheddar Man’s foraging kinfolk were replaced by an olive-skinned, dark-haired population who originated in modern-day Turkey and migrated slowly across Europe, bringing agriculture with them. They would have looked similar to modern-day southern Europeans, who have inherited a large proportion of their DNA from these Neolithic farmers. We can even hazard an educated guess as to what language they spoke. As the Basque people have a high proportion of neolithic farmer ancestry and their language is not related to any other, Euskara is likely to be the last surviving descendant of this prehistoric tongue.
It was these Anatolian immigrants who constructed that icon of Britishness, Stonehenge, between about 5,000 and 4,500 years ago. But not long afterwards, they vanished and were replaced by another genetically distinct population group who were taller and fairer. The newcomers were nomadic pastoralists from the Eurasian steppe, where they used cutting-edge technology – horses and wagons – to raise herds of animals. About 5,000 years ago, these steppe herders began to migrate westwards through northern Europe, reaching the British Isles half a millennium later. The Amesbury Archer was one of the new immigrants. His 4,300-year-old grave was discovered by archaeologists at a site slated for a new housing scheme a couple of miles from Stonehenge in 2002.
Violence may have played a role in the replacement of the Stonehenge builders from Anatolia: 90% of the steppe herders involved in the great westward migration were males, and domesticated horses and metal weapons would have provided them with a distinct advantage in conflict. But even taking all this into account, it is almost impossible to explain how a small group of nomadic herders was able to replace a large, well-established farming society.
The US geneticist David Reich suggests that the most similar historical parallel is the European colonisation of the Americas in the 16th century. Tiny numbers of Spanish conquistadors armed with guns and steel managed to vanquish vast and sophisticated empires. These seemingly miraculous victories were, of course, only possible because Old World germs – first smallpox, then others – raced ahead of the Spanish and devastated the enemy.
Similarly, it is possible that a prehistoric plague pandemic cleared the way for the steppe herders to migrate across northern Europe. Evidence points to a catastrophic demographic crash about 5,000 years ago. The population fell by as much as 60% and remained at that level for centuries. We can’t be sure that plague was responsible but it is the best explanation we currently have.
The implications of all this are extraordinary. The new migrants brought the latest technology – not just horses and wagons, but also Bell Beaker pottery and metal tools – that marked the end of the neolithic and the start of the bronze age. But their impact is much longer-lasting.
Although immigrants have continued to enrich the gene pool in the intervening years, the influx of steppe herders in the third millennium BC was the last transformative movement of people into Europe. Their DNA is the largest source of ancestry in northern Europe, accounting for slightly less than half of the genome of the British Isles.
Steppe herders are also the most likely source of Indo-European languages, which includes English but also German, French, Spanish, Greek, Russian, Farsi and Hindi, spoken by about half of the world’s population. In the distant past, proto-Indo-European was spoken by a small group of people, who then spread out across Europe and central and south Asia, taking their language with them. All Indo-European languages share similar vocabulary, including words related to wagons. Steppe herders introduced wagons to Europe and their DNA is found in significant proportions among people who speak Indo-European languages.
All this should be a reality check for notions of where people are “really” from, and how we measure who is entitled to settle where in the world. The white British population are certainly not the indigenous people of the British Isles. They are the descendants of immigrants who arrived on boats. And it is likely that they were only able to settle here because the humble Yersinia pestis bacterium cleared the way for them.
Jonathan Kennedy teaches politics and global health at Queen Mary University of London, and is the author of Pathogenesis: How Germs Made History