(Distributed by New York Times Special Features)
To the Norse men and women living in Iceland in the 10th century, an island called Greenland must have sounded like Eden.
At the time, the North Atlantic was in the throes of a warm spell, and parts of southern Greenland were actually green and fertile, at least by Icelandic standards.
Enticed by the promise of truly greener pastures, a group of Norse Icelanders established two settlements on Greenland —the Eastern, as archaeologists call it, on the southern tip of the island; and the Western, along the southwest coast near the modern capital of Nuuk.
The settlers built farms and large stone churches, raised animals, hunted seals and walrus, traded with Europe and struggled to survive.
Survive they did, for centuries, even as the temperatures chilled at the end of the 13th century with the onset of a prolonged European cooling trend often called the little ice age.
Then, mysteriously, the Norse Greenlanders—some 5,000 to 6,000 strong at their peak—disappeared.
The Western Settlement succumbed first, sometime in the mid-1300s; Eastern settlers hung on longer, until the mid-15th century.
Almost ever since the settlers' demise, historians and archaeologists have speculated about what happened to them: Were they killed by invaders from arctic Canada? Were they carried off by Basque pirates? Or did they starve to death in the bitter cold?
Now a diverse body of research is shedding new light on those final desperate years.
Pirates and war weren't the agents of doom, according to the emerging view. Rather, an unlikely combination of changing climate and ethnocentrism probably brought down the Norse colonies in Greenland.
The Norse colonists couldn't have had a better start. Both the Eastern and Western settlements were ideally placed—located on inner fjords miles from the sea, nestled up against the ice sheet and sheltered from fierce winds.
A persistent high-pressure zone over the ice cap made for warm summers on the fjords by deflecting coastal storms out to sea.
From archaeological excavations, researchers know that the Greenlanders subsisted on a diet of harp and harbor seal (and sometimes caribou), which were hunted in the summer on the outer fjords near the ocean, along with food from cows, sheep and goats.
The domestic animals pastured year-round along the inner fjords that produced grasses during the brief summer growing season.
Despite their closeness to the sea, the Greenlanders, for unknown reasons, apparently didn't fish.
A model of that economy, created by archaeologist Thomas McGovern of the City University of New York and his colleagues, indicates that the summer growth of fodder for those domestic animals—and, in turn, the survival of the Greenlanders—was critically linked to climate change.
``The model showed that the kind of climate change that would be most damaging would not be the once-every-500-years very bad year,'' McGovern says, or even a recordbreaking cold winter. ``The most difficult thing for them to cope with would be a string of especially cold summers.''
That conclusion is supported by the findings of Lisa Barlow, a paleoclimatologist at the University of Colorado in Boulder who has analyzed cores from the Greenland ice sheet.
To measure temperature change, Barlow looked at the ratio of deuterium (a heavy isotope of hydrogen) to normal hydrogen in sections of the ice core covering the last 700 years.
Oceanborne water molecules made up of normal hydrogen evaporate at slightly lower temperatures than do water molecules made with the heavier deuterium.
But as the temperature goes up, more heavy hydrogen evaporates, eventually precipitating out over Greenland.
Barlow managed to trace the fluctuations of the two forms of hydrogen and found that the 14th century suffered four periods with summer temperatures cooler than average.
The longest cold spell lasted for about 20 grim years, from 1343 to 1362, give or take a year—the same period during which the Western Settlement is believed to have collapsed.
(In one historical account, a seafaring Norwegian priest finds the Western Settlement eerily abandoned sometime before 1361.)
``In a cool summer the settlement is not going to get as much grass growth as it needs to get through the winter,'' Barlow says. ``If that consistently happened for a number of years, then they probably reached a breaking point. When you are dealing with a colony that was living at a subsistence level anyway, it wouldn't take much to put them over the edge.''
Did the Norse in the Western Settlement all die, or could some have evacuated?
``It would be nice to think that there were survivors'' who fled to the Eastern Settlement or perhaps to Europe, McGovern says. ``But the problem is that there is absolutely no evidence of that. In many parts of Europe at that time you could have a few boatloads of people show up and disappear into the population, but I think a formal abandonment of the Greenland colony would have been sufficiently newsworthy that it would have ended up in the annals of Iceland and the continent.''
And yet it seems that the Europeans were totally unaware of the fate of the Greenland settlements.
In the late 13th and early 14th centuries, vast amounts of sea ice began to clog navigational lanes, making travel to and from Greenland difficult even during the summer.
``As late as the 1600s the pope was still appointing bishops to Greenland, who of course never left Rome,'' McGovern says. ``As far as he was concerned, Greenland was then still a functioning part of Christendom.''
McGovern suspects a bleaker fate.
``As far as we can tell, they starved to death.''
Excavations have turned up many expensive portable items, such as crucifixes, that would probably have been removed by the settlers in an evacuation.
And had the colony's population gradually diminished, McGovern says, the wood in many of the farms—a valuable commodity in a place with few trees—would have been scavenged by the remaining settlers. Such was not the case.
``At least one of the farms we've examined shows evidence of a tough winter,'' McGovern says. ``We find the bones of a number of cows—about the same number that lived in the barn—and mixed in with them are a bunch of ptarmigan feet, also famine food. Mixed in with that are the bones of one of the big hunting dogs.''
Cut marks on the bones suggest the dogs were butchered. Even the cow hooves were eaten.
``It looks as though they ate the cows and then ate the dogs. It looks like hard times.''
Other evidence supports this grim scenario. Entomologist Peter Skidmore of the University of Sheffield in England uncovered an orderly succession of fossil flies in a Western Settlement farmhouse.
In the lower layers he found warm-temperature houseflies; in the layers above, cold-tolerant, indoor carrion eaters that might have moved in when the homestead could no longer be kept warm; and in the final layer, outdoor flies. At that point, the roof of the farmhouse had probably caved in.
This was no Jamestown: the Norse toughed it out for generations under steadily worsening conditions.
The Greenlanders became more isolated from Europe. Yet they apparently clung steadfastly to a European way of life, shunning contact with the Thule Inuit peoples who began immigrating to the island from northern Canada in A.D. 1100.
``There is indication on the Thule side of interest in the Norse and their technology. Inuit excavations contain quite a lot of material,'' McGovern says.
The Norse, on the other hand, suspiciously avoided contact with the Thule. ``You don't have this kind of barrier between cultures for so long without someone working very hard to maintain it.''
The Norse could have learned from the Thule. After all, there was food to be had, even in winter—under the ice.
``What has kept the Inuit communities alive through the winters, all through history, has been hunting through the ice or at the ice edge for ring seals,'' McGovern says. ``They have developed this complex hunting technology—harpoons and all sorts of other gadgets—that allows them to do this successfully.''
But the Norse never learned to use harpoons, and their animal-bone collections are strikingly absent of ring seals.
``Out of several thousand bones, there are two or three ring seal bones,'' McGovern says.
``They didn't adopt harpoons, they didn't adopt skin clothing and they didn't adopt skin boats,'' McGovern says. ``The extinction of the Norse in Greenland, aided certainly as it was by climatic change, possibly could have been avoided if they had picked up more of those arctic adaptations from the Inuit. You could argue that these folks managed to maintain ethnic purity at the expense of survival.''
(Kathy A. Svitil is an associate editor at Discover magazine.)