Archaeologists crack the mystery of the Neolithic decline (2024)

Over 5,000 years ago, the human populations in Northern Europe collapsed. Large settlements were abandoned. Megalith construction evaporated.

Why the Scandinavian "Neolithic decline" happened is a mystery. Many assume some sort of crisis in their early stabs at farming. But another suspect has been the plague.

Now a study published Wednesday in Nature finds that an early form of plague was running riot at the time, Frederik Valeur Seersholm of the University of Copenhagen and colleagues deduced from testing 108 ancient bodies in eight graves and one stone cist from Neolithic Scandinavia, spanning a wide geographical area, for pathogens.

They found an ancestral form of plague bacteria, Yersinia pestis, in 17 percent of the bodies they checked.

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Losing a fifth of the population to a horrible disease sound awful, but short of population collapse, doesn't it?

The team explains that 17 percent doesn't necessarily reflect the true disease prevalence. For one thing it only represents the plague death rate in the "sampled" population in the graves they checked and given the paucity of bodies, it seems that not everybody received ritual burials; Mother Nature may have taken care of people who fell far from the homestead. Also, not everybody who got the disease will be preserved well enough to produce detectable signals of it 5,000 years after the evil day. In fact, few of them are likely to have been preserved well enough.

In other words, well over 17 percent of the population may have gotten this ancient version of the terrible sickness that would mutate into the flea-disseminated "Black Death" we know and fear from medieval times.

Ghost villages

The theory of the Neolithic decline in northern Europe arose when archaeologists detected large-scale abandonment of what had been flourishing settlements in prehistory.

Villages do appear and disappear – such is life – but this was at another scale. Before the downturn, Europe's trajectory had been one of rising population density as agriculture spread out of Turkey with migrating early farmers starting around 8,500 years ago. It came as a surprise that agricultural revolutions around western Europe that supported denser populations were swiftly followed by regional population collapses.

Since the postulated demographic decline in northern Europe coincided with the emergence of the Neolithic revolution, one theory was a crisis in agriculture. But no correlation was found between the regional booms and busts and climatic vagaries. A 2013 paper on the phenomenon could offer no theory for the Neolithic collapse beyond vaguely citing "endogenous causes."

Then with the discovery of ancient bodies with plague bacteria, for instance in Latvia from 5,000 years ago and Britain from 4,000 years ago, and more, the disease became a suspect.

Note that plague is a fast killer that doesn't leave lesions on the bones, as syphilis and leprosy can do, for instance. But it can be detected through genomic analyses that identify pestis genetic material in a long-dead person, if preserved well.

The new study deduces that in Scandinavia, an epidemic of plague erupted in three distinguishable waves during the Neolithic over a span of about 120 years.

The first two waves were relatively minor, as was the Latvian strain. But the third wave was wider, apparently much nastier and may have been the missing key to the Neolithic decline, the team suggests.

We men don't get about

The pros and cons of the Neolithic revolution that drove the agricultural revolution that led to industrial farming are hotly debated. Arguably, if we had never tamed the goat and the wheat, the sheep and the lentil, and if we hadn't wiped out the megafauna (we ate them), the planet would be in better condition. From this perspective, these profound changes in human trajectory were an own goal.

Be that as it may, when the shift from subsistence hunting and gathering to farming began, it created the conditions for increased human (and murine) population density, researchers believe. Thus bigger, more permanent settlements emerged. Megacities like Lagos and New York aren't the result of Og inventing a better spear.

We do note that people were leaving the caves and erecting houses before the Neolithic and agricultural revolutions, but moving on – agriculture began, we flourished, we procreated, we spread out and about 5,300 years ago something apparently went wrong.

The bottom line is the authors do not claim the Black Plague did it. They claim its ancestral form plausibly contributed to the Neolithic decline.

Their finds do not support the alternative theory, that cases of plague detected in ancient peoples by other studies were caused by sporadic zoonotic infection, meaning don't blame rats or their fleas. Early plague infections seem to have been human to human, it seems, in much the same way we give each other E. coli ("It usually spreads when people accidentally consume invisible amounts of human or animal feces" - U.C. Davis Health).

The study also shed light on the secrets of mortuary practice in prehistoric Scandinavia. While investigating the deaths of the 108, the archaeologists deduced that family members were buried together.

They also deduced that the Neolithic society in Scandinavia was patrilineal, and that four of the men had multiple wives. They found no instances of women with multiple husbands.

And they deduced that the men stayed at home, forming the core of the society. While female exogeny, moving afar to marry, has been suggested for prehistoric societies before – now the team found proof.

Though, it has to be said, she didn't move that far.

The heartbreak of Neolithic daughters

It bears adding that mortuary practices in Neolithic Scandinavia have been a matter of much contention. Were the megalithic tombs family affairs? Is it possible that they only buried their "elites," not everybody, since actually very few remains seem to be in the tombs? Were long-dead bodies sometimes replaced with fresh ones?

The new study, focusing on the eight grave sites and one cist, sheds light there too. The vast majority of the 108 bodies (dating to 5200–4900 years ago) descended from European hunter-gatherers and early farmers who spread out of Anatolia. A smaller, later group (4100–3000 years ago) also featured ancestry from the central Asian steppes. And it is clear that the males in the graves were related, while the women were not kin.

In one tomb the team identified no less than 38 members of one family over six generations. At the Frälsegården burial ground, the team discovered a patriarch and his three sons. They also found a woman buried there whose two brothers were buried 8 kilometers (4.9 miles) away at a megalithic site called Hjelmars Rör in Sweden.

She's the proof they cite for female exogeny. "At Frälsegården this female gave rise to a large family with seven grandchildren, indicating that she moved away from her family during her lifetime to start her own family in a new settlement," the team writes. She did move, eight kilometers.

They also point out that of all the dozens of people tested at Frälsegården, only eight were unrelated to anyone else buried there and six of those were female. They suspect the six were "foreign" brides, possibly from neighboring villages – the team admits the relocations were not vast.

No children from these women were found in the same tombs, which suggests that either they died childless or they had only daughters who moved away, and are sleeping for eternity in their husbands' tombs. Or their sons weren't buried ceremoniously, or at all. Who knows.

In another case, four siblings from a single generation were buried with their half-brother, but their half-sister was elsewhere inside the same tomb complex. The team suspects in short that being a man was key to burial location.

The purpose of moving away to marry is to prevent inbreeding, insofar as the ancients realized that was the purpose, but the team reports detecting evidence of inbreeding in two brothers whose parents were third-degree relatives.

So what have we? This study supports the plague as an agent of the Neolithic decline in northern Europe around 5,000 years ago, mainly in a third, more virulent wave. Male relatives were buried together while the women interred with them hailed from elsewhere, possibly not that far away though. The rate of plague may have been much higher than we can detect today – and it wasn't the same as the pestis variant transmitted by fleas today, but likely infection spread human to human. Rats can't take the blame for the Neolithic decline.