Growing Apart, Together: Lessons from Salvelinus alpinus

An evolutionary phenomenon has been emerging from the depths of Þingvallavatn over the last 10,000 years. It can teach us much about Iceland’s cultural evolution.

Ask an Icelandic person about the importance of Þingvellir National Park, and they may say that it is Iceland’s cultural epicentre—that it is the site where Alþingi first formed in the year 930 to develop the societal institutions and standards by which Icelandic people would live, and that even today, the historic shrine holds significant records of human history, belief systems, and sagas. At its core, Þingvellir embodies cultural evolution shaped by geologic and biophysical change.

In terms of geologic processes, evolution, and cultural development, Þingvellir represents transitions. Within its bounds, two tectonic plates pull apart, forming a rift zone—a continuation of the spanning mid-Atlantic ridge across Iceland. Within the expanding rift, the structures and geology of Þingvallavatn are formed by sinking and expanding faults, as groundwater filters through porous basalt into the catchment and surrounding rift structures. At the end of the last Ice Age, Þingvallavatn became an isolated body of water when terrain shifted at its south shore. Today, it is the largest natural lake in Iceland and is 90% spring-fed with cold water rich in soluble minerals. In combination with long summer daylight hours, these characteristics are a recipe for abundant marine life despite its physical isolation. In fact, Þingvallavatn’s isolation makes it an ideal laboratory for studying the ways in which species grow and change without much influence on biodiversity from the outside world. Þingvallavatn’s size and depth means it contains several habitat types with little species competition or biodiversity. It is a perfect storm for a singular species to teach us about the possibilities of genetic variation.

Who are the key players in this natural laboratory? A surprisingly resilient species of fish: the humble Arctic char, Salvelinus alpinus. When Arctic char was first isolated in Þingvallavatn shortly after the retreat of the ice cover, it was likely a more uniform species in its appearance, diet, and ecological niche, or role of a species within a specific environment. Over time, genetic variation caused different physical characteristics to emerge, and the lack of competition allowed the Arctic char to live to its full potential in multiple habitats within the entire lake.

Arctic char is characterised by its resilience to variations in the way individuals look, eat, spawn, and behave in its environment. It also has an ecologically diverse life history, meaning its patterns of reproduction and survival are not uniform, which facilitates more variation and change within species traits. Its ability to thrive in different habitats in Þingvallavatn led to four distinct morphological variations: piscivorous, large benthic, planktivorous, and dwarf. These varying appearances have different preferred habitats; for example, the dwarf-char tends to stay at the bottom of the lake where food is abundant and there are structures to hide from predators. Meanwhile, the piscivorous-char has evolved a streamlined body structure to live as a fish-eating predator in the open water.

How is it that a singular species can settle in an isolated habitat, but evolve and survive in such different ways? How can a generally homogenous group live so close together under the same umbrella of history, but still find space for fundamental variations of identity? 

If the narrative feels familiar, look to Iceland’s anthropologic history. When humans arrived to this volcanic island around 874, settlement was the product of extensive migration, cooperation, and belief in the societal potential of rugged and unforgiving terrain. The geologically complex Þingvellir site was selected as the meeting site for a newly established Icelandic people to travel and assemble due to its flat pastures and accessibility. For some settlers in the north and east of Iceland, the journey to the assembly place took several days. But in this zone of geologic and biophysical transition, it was intentionally decided that human settlement in Iceland would grow and change under a set of shared values. 

Ecology is the study of the diverse, interconnected relationships between living things and their home; cultural ecology is the study of how humans socially adapt to a specific environment and the ways in which environmental change influences cultural change. How have Icelanders evolved differently within the same isolated physical boundaries? Minor north-south regional accents may be an example. Still, the linguistic homogeneity of Icelandic means it has impressively retained some of its character from the early Norse settlers. The modern day cultural distinction between city and country dwellers is an evident example of divergent social evolution, as well as political tributaries that may spur from generational or socioeconomic differences throughout the country. The divides that emerge from physical isolation often inform political discourse. Through common roots, Icelanders have socially evolved to fulfill different societal roles and lifestyles.

Many cultures worldwide recognize the environment as a mirror. Societal wellness is reflected in the way land is managed and stewarded. Conversely, when the land experiences trauma, the people who live on that land often too experience trauma. In the same way, when we examine our ecological surroundings alongside cultural evolution, parallels emerge. How will the evolving climate crisis affect culture over time? Climate change is an emerging threat to Arctic char, as warmer conditions in Icelandic lakes present metabolic and habitat challenges—declines in Arctic char have been observed in all parts of Iceland. Will some morphs fare better under changing environmental conditions? Who will survive, and who will be left behind? As the climate crisis continues to evolve and social challenges emerge in its midst, which Icelandic demographics will be most impacted?

Of course, the globalisation of media, economics, and communication has had a significant impact on how people interact with each other, develop shared language, and experience shifts in shared values. In this way, Icelandic culture is not evolving under the same isolated conditions as Arctic char, which is probably fortunate. Even so, there is history in the land and water of Þingvellir that encompasses cultural variations and binds people together, just as the Arctic char’s distinctive morphs are genetically categorised within the same species, even though they may look and behave differently. The ecological relationships are dynamic and evolving alongside anthropogenic change, direct reflections of ecological systems, culture, and future challenges.