Thousands of years before ancient people in Central Eurasia learned to farm, hunter-gatherer groups in the subarctic were building some of the first permanent, fortified settlements, challenging the notion that agriculture was a prerequisite for societies to 'settle down'.
Researchers now think they have dated the earliest known fortifications in the icy north, if not the world, near a curve of the Amnya River in Western Siberia.
The Amnya archaeological sites were officially unearthed from 1987 onwards, but recent radiocarbon dating has found the main pit house at Amnya Site I and its fortifications date back 8,000 years or so.
The ancient building (circled in red in the illustration below) is now just a wide depression in the ground, but it was once protected by a ditch and possibly also another pit house. Radiocarbon dating suggests it was built in the final century of the seventh millennium BCE.
Later, in the sixth millennium BCE, another two ditches at the back of the site were built. Along with several more buildings, banks, and fences, these features represent a period where the site was more consistently occupied.
The Amnya II site was also built 50 meters to the east around this time (depicted in green in the diagram above).
According to an international team of archaeologists, led by researchers at the Free University of Berlin, both sites challenge the traditional notion of what hunter-gatherer groups were capable of.
It was clearly not just farming communities in the Stone Age that built permanent, fortified settlements.
"Our new palaeobotanical and stratigraphical examinations reveal that inhabitants of Western Siberia led a sophisticated lifestyle based on the abundant resources of the taiga environment," says the archaeologist Tanja Schreiber from the Institute of Prehistoric Archaeology in Berlin.
The West Siberian taiga is a sometimes swampy, coniferous forest habitat present in the subarctic. Around 6,000 BCE, the taiga near Amnya would have hosted herds of elk and reindeer, while the river would have been swimming in fish, like pike and salmonids.
In such fruitful places, even mobile foraging groups would have had good reason to protect their supplies from opportunistic raiders or hungry neighbors.
While it's not wholly clear what the Amnya fortifications were protecting (or why), researchers suspect the site contained surplus food, probably fish oil, fish, and meat, smoked and stored to keep.
"They don't have to grow or raise resources," Piezonka told Science Magazine's Andrew Curry. "The surrounding environment provides them seasonally. It's like harvesting nature."
The remains of intricately decorated pottery found at the site are likely to be vessels in which the food had been kept.
It's unclear if the buildings at the Amnya sites were inhabited or defended all year round. But for at least for some of the seasons, this seems to have been the settling place of a hunter-gatherer group in western Siberia.
Several other Stone Age forts have been found in this region of the world, but none are as old as the Amnya I site. In Europe, comparable sites don't show up until centuries later and only after the dawn of agriculture.
"The building of fortifications by forager groups has been observed sporadically elsewhere around the world in various – mainly coastal – regions from later prehistory onwards, but the very early onset of this phenomenon in inland western Siberia is unparalleled," write the international team of archaeologists.
Traditionally, archaeologists have assumed that foraging communities were not yet societally or politically 'complex' enough to build monumental, permanent structures that needed to be maintained or defended.
Yet ongoing research at the Amnya promontory and other archaeological sites around the world suggest that cultivating crops and rearing animals aren't the only incentives for such activity.
Göbekli Tepe, for instance, is a massive stone assembly in present-day Turkey constructed around 11,000 years ago. It was built before the advent of agriculture and is considered to be the oldest known megalith in the world. It seems hunter-gatherers gathered at this site to bid farewell to their dead or to stage sacred ceremonies.
Similarly, at the Amnya site in Siberia, archaeologists have found 'kholmy' mounds, which are described as "large-scale ritual structures in the landscape".
Researchers suspect that a shift in climate roughly 8,000 years ago created the stage for an abundance of seasonal resources in western Siberia, prompting an influx of human migrants.
The development of fishing and hunting strategies, or the advancement of food storage may have then led to a surplus of food, which needed to be defended.
It's also possible that the crowding of various hunter-gatherer groups in one region promoted a culture of raiding.
"Management of these surpluses then led to changes in the socio-political structuring of populations and the emergence not only of wealth inequality and exclusive property rights, but also of increased community cohesion, for example through collective work on, and use of, monumental constructions," suggest the researchers.
More work at the Amnya site is currently underway, and archaeologists are making sure to keep their minds open. The traditional notion of hunter-gatherer that persists in many academic texts may soon need some serious revision.
The study was published in Antiquity.