In the millennia that followed the last Ice Age, early humans began making their way into the inland mountains of southern Norway as ancient glaciers receded, revealing new portions of the landscape.
However, the landscape in this region made it impossible for fish to make their way upstream into high mountain lakes, impeded by waterfalls and other barriers. Somehow, fish appeared in these upland bodies of water anyway—so how did they get there?
The natural answer to this ancient question is that humans must have carried fish from regions further downstream, populating these ancient and once-lifeless lakes with an abundant food source. The question archaeologists have been unable to answer is when, precisely, these ancient transplants of wildlife took place.
Now, archaeologists with the University of Oslo believe they have finally solved this longstanding riddle, with the discovery of the remains of 7,000-year-old fish traps that reveal the likely period during which early Mesolithic inhabitants of the region engaged in some of its earliest fish farming.
The discovery not only offers archaeological evidence for when fish were likely first introduced into the region, but also reveals that agriculture was not the only means of nature management that these early Norwegians engaged in.
“For more than 100 years, it has been known that the fish inhabiting watercourses in the Norwegian mountains are descended from specimens translocated by humans,” says Axel Mjærum, a researcher at the University of Oslo and the lead author of a new study detailing the findings.
“However, until now, it has remained unclear when people first began transporting fish upstream into lakes and rivers that originally lacked natural fish,” he adds.
A 7000-Year-Old Discovery Leads to a Breakthrough
Offering a rare opportunity to unravel some of this mystery, the discovery of ancient fish traps constructed from wood, the remnants of which were discovered in southern Norway’s Lake Tesse, provided a unique look at the period during which fish transport and harvesting likely began.
Radiocarbon dating of the wood from the traps reveals that Salmo trutta, the region’s brown trout species, were relocated to the lake during the Mesolithic period.
Growing to considerable sizes, this species of trout was an ideal, high-protein food source that could readily be harvested from the lake once a thriving population had been established.
Although agriculture would later become a major source of food for these ancient Scandinavians, the period during which the fish traps are dated to predates farming in the region, which supports the idea that these people were hunter-gatherers, and also fishermen.
Environmental Management in Ancient Scandinavia
More broadly, the findings by Mjærum and his colleagues reveal the degree to which these Mesolithic Scandinavians were managing their food supply through direct control of the natural environment, setting the pace for several more millennia of food production.
Even today, brown trout are among the many fish species sportsmen harvest—the descendants of the very same fish originally carried to southern mountain Norwegian lakes thousands of years ago.
Mjærum says that the ancient Mesolithic Norwegian’s “release of brown trout into previously fishless lakes in the Norwegian mountains around 5000 B.C. is a very clear example of humans’ general capacity to reshape entire ecosystems, even before the introduction of farming.”
The study, “The introduction of fish to the Scandinavian mountains by hunter-fisher-gatherers 5000 BC,” appeared in the journal Antiquity.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.