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Flowing glaciers tend to grind up any human remains within them (Image: Stuart Franklin/Magnum Photos)

High mountains and latitudes were once thought far too bleak for ancient humans, but as icy patches melt they are revealing a rich world of human history

THE summer of 2003 was the hottest in Europe for 500 years. On the remote Schnidejoch pass, 2750 metres above sea level in the Swiss Alps, an ice patch shrank by half its volume, leaving a wooden object high and dry. When hiker Ursula Leuenberger came across it, she realised it had no business there, so far above the tree line, so she picked it up and handed it over to the local archaeological service. It turned out to be part of a Neolithic arrow quiver, almost 5000 years old.

Since then, archaeologists have found more than 800 artefacts in the vicinity of the pass. Schnidejoch links the Simmental valley to the north with the economically important Rh么ne valley further south, and the discoveries indicated that humans have used it for at least 6000 years: in the Middle Ages and Roman period, through the Iron and Bronze Ages, and back to the Neolithic. That was a big surprise. 鈥淭here are several large volumes on prehistory in Switzerland, and they completely exclude the Alpine regions,鈥� says , Switzerland. People were not thought to have been at home in the mountains until much more recently.

The Schnidejoch discoveries have prompted a shift in the way archaeologists look at high places. With archaeological material flowing out of melting ice on several continents, not only at high altitudes but also at high latitudes, that shift is picking up speed. Glacier archaeology, as the field is called, has been referred to as the silver lining in the cloud of global warming. Like underwater archaeology, it is exposing a dimension of humanity鈥檚 past that had been almost entirely neglected; one that has the potential to profoundly influence our understanding of our ancestors.

But it is a race against time. As soon as organic material melts out of the preserving ice and is exposed to the elements again, it starts to decay. 鈥淚t鈥檚 like this glimpse into a freezer that鈥檚 been left open for a couple of weeks,鈥� says at the University of Colorado, Boulder. 鈥淵ou might find a few jars of fruit that are still viable, but the rest is gone.鈥� The sheer amount of material now in this precarious condition 鈥� Swiss glaciers, for example, have lost a third of their volume since 1860 鈥� means that archaeologists simply cannot reach it all in time, not least because it is often inaccessible outside the narrow window of summer at these altitudes. It鈥檚 a case of triage, says Lee.

The first inkling that mountains might have more to add to the human story came in 1991 with the discovery of a mummified body, 脰tzi, in the Alps between Austria and Italy. Glaciers regularly disgorge human remains but these tend to be just a few centuries old (see 鈥�Not so ancient history鈥�). Frozen for 5300 years, 脰tzi was exceptional. Unfortunately, he was also a one-off, and scientists could glean only so much from him about the society to which he belonged.

脰tzi鈥檚 extraordinary preservation did provide an important pointer to the nascent field of glacier archaeology, however. He died at the edge of a glacier, rather than in it, where his remains would probably have been torn apart by the inexorably moving river of ice. Researchers realised that if they were to find more evidence of our ancient past, they would need to direct their efforts towards static patches of ice rather than moving glaciers.

You might think that finding an ice patch harbouring hidden treasure would be like finding a needle in a haystack, but aerial imagery can make it fairly straightforward 鈥� once you know what kind of ice patch to look for. 鈥淚t should be flat, ideally in a small depression 鈥� a small frozen lake perhaps 鈥� about 2500 to 2700 metres above sea level, and north-facing so that it鈥檚 shady,鈥� says Hafner. Too high, and only the most adventurous ancient humans would have ventured there; too steep, and gravity would have made a glacier out of it.

Such sites are surprisingly rare in Switzerland. Having surveyed the whole of the Bernese Alps, where Schnidejoch is situated (see map), Hafner鈥檚 team has identified only four, all of which have produced prehistoric material. The situation is different in Scandinavia and North America, where suitable ice patches are common. There, the search has been narrowed with the help of digital geographic information systems that combine maps with other information including historical paths and climate. But even then, it takes an expert to pinpoint the most promising sites. 鈥淏ecause there are hundreds of ice patches in the mountains, you have to have an eye for which are archaeological, which are old,鈥� says Martin Callanan at the Norwegian University of Science and Technology in Trondheim.

The majority of the fruitful ice-patch sites found in North America and Scandinavia are associated with hunting. In 2010, high up in the Rocky Mountains near Yellowstone National Park, Lee鈥檚 group found part of the shaft of a spear made from a birch sapling. Carbon dating revealed it to be 10,000 years old, making it . Lee thinks it is a relic of a summer hunting expedition for bighorn sheep, and as old as the ice it lay in. Seven years of exploration of Yellowstone have produced eight prehistoric sites and a wealth of material. 鈥淲e鈥檙e clearly demonstrating this long-term presence of Native American people in the high country, in areas that the dominant European culture sometimes refer to as wilderness,鈥� says Lee.

, ranging from part of a 9000-year-old spear to a 19th century musket ball. Frozen scat or faeces indicate the presence of large herds of wild caribou or reindeer, animals that no longer roam in those parts (Arctic, vol 65, p 118). Similar finds have been made in Alaska. And last year when Natalia Slobodina of the University of Washington in Seattle carried out the first Asian ice patch survey in the Russian Far East, she found fragments of wood above the tree line that may also indicate ancient reindeer-hunting expeditions.

Peoples of northern Eurasia have probably been herding reindeer since the Bronze Age, but the species is still not considered fully domesticated. In North America, no form of livestock domestication took place until the 19th century. So most of these finds relate to the hunting of wild animals, which would have gone out onto ice patches to cool down, or to avoid insects. 鈥淚鈥檝e experienced it myself,鈥� says Lee. 鈥淵ou have bugs swarming around you, you walk a couple of metres out onto the ice patch, and the insects stop.鈥�

This summer, Callanan鈥檚 group produced headlines when they discovered a 6000-year-old Neolithic longbow and arrows in ice patches in the Oppdal mountains of central Norway, the oldest finds in Scandinavia to date (). Given the accumulating evidence, he considers hunting on ice patches to be a circumpolar phenomenon, and not always just for subsistence. Scandinavian museums contain many examples of highly ornate hair combs made from reindeer antlers by itinerant craftsmen who powerfully influenced fashions during the Middle Ages. Very little is known about them but Knut R酶ed at the Norwegian School of Veterinary Science in Oslo and Gitte Hansen at the University Museum of Bergen aim to change this. They have been comparing DNA from antlers found in ice patches with that in the debris of this comb production, retrieved from medieval urban workshops. They want to map out antler trade routes in the hope of understanding the movements of the mysterious comb-makers, who they interacted with, and hence, who they were.

Elevated hunting grounds

It鈥檚 early days, says R酶ed, but one thing is clear. 鈥淧articularly during the early medieval period, there was a very organised hunting system in the mountains.鈥� Large hunts involving hired hunters, butchers and porters were orchestrated from the towns. From one hunting station alone, an estimated 10,000 reindeer were killed in under 50 years. At the end of the Middle Ages, for reasons that are unclear, the intensity of the hunting fell off.

The finds at Schnidejoch pass also throw light on the societies that deposited them. They include a bow, arrows and part of a goatskin legging that probably all belonged to the same traveller. His remains have never been found. They are Neolithic, about 4500 years old, and DNA analysis of the goatskin reveals that the goat belonged to a genetic group that originated in the Near East and that was thought to have entered Europe much later, perhaps with the Romans in the 2nd century BC (). The implication is that goats were domesticated in the Alps about 2000 years earlier than was thought.

Tests on fragments of Neolithic leather found at Schnidejoch produced another surprise. They were impregnated with plant extracts whose origin was pine forests on the lower slopes, meaning that Stone Age people were already familiar with complex tanning techniques that were thought to have arrived much later, again, probably with the Romans (Journal of Archaeological Science, vol 37, p 1851). The Schnidejoch cache also provided evidence that 鈥渁lpage鈥� 鈥� the practice of taking herds up to alpine pastures for the summer months 鈥� began about 7000 years ago, three millennia earlier than was thought.

We don鈥檛 need glacier archaeology to tell us that humans have long ventured into high places. Low-lying sites attest to early contact between populations separated by mountain chains. In Europe, for example, settlements indicate that hunters from the south started penetrating the Alps from the end of the last ice age, 12,000 years ago. Traders soon followed. Coral and shell necklaces from Italy start turning up in Switzerland, Austria and Germany, 7000 years ago, along with cultivated plants that could only have come from the Mediterranean, such as dill, parsley and celery. Genetics confirms this story: , indicates that his forebears came from the Middle East via the Mediterranean. Indeed, mountains have been less of a barrier to the spread of human culture than bodies of water, according to Philippe Curdy at the Valais History Museum in Sion, Switzerland. 鈥淚deas passed easily,鈥� as attested by the fact that Swiss dialects often span mountain ridges, but stop at rivers, he says.

What glacier archaeology does reveal is the extent of human social and economic activities at icy extremes. 鈥淭he periphery is coming into focus,鈥� says Callanan. The picture that is emerging of life at high altitudes and latitudes indicates that these areas often fed trade lower down, as in the Scandinavian reindeer example, and were fed by it. People risked their lives to go to altitude because they had incentives to do so. 鈥淭hey knew the mountains very well,鈥� says Hafner, 鈥淎nd if it was economically interesting for them, they knew them even better.鈥�

Glacier archaeology also exposes the limits of human ingenuity and endurance. Although people have been crossing the Schnidejoch pass for more than 6000 years, they did not use it continuously. Today, there is a 400-metre drop from the pass to the glacier that sweeps beneath it, but in colder periods the glacier was higher, and swallowed the path as it descended from the pass. Artefacts found by Hafner and his team coincide only with the warmer periods, indicating that at times the route was too dangerous to use. Each hiatus was long enough to ensure that knowledge of the pass faded from local memory, which Hafner believes might explain its absence from prehistoric records.

鈥淕lacial archaeology exposes the limits of human ingenuity and endurance鈥�

In this respect, Schnidejoch provides a gauge of climate change too. The most recent archaeological artefact found there dates from the 11th century, shortly before the Little Ice Age set in. After that, there is nothing for almost 1000 years. The next items to turn up are pieces of equipment mislaid by modern mountaineers and skiers.

This article appeared in print under the headline 鈥淥ut of the freezer鈥�