I am the descendant of Vikings and Visigoths. This is evident from my fair skin and blue eyes, and shows up in an analysis of my DNA. My ancestors came from the North, and it would be surprising if their genes did not carry a few traits other than lack of pigmentation which were adaptive at high latitudes. The purpose of this essay is to explore one possible adaptation and how it might express itself in character traits associated with people from Northern Europe, and to some extent northeastern Asia.

Primates are basically tropical animals. The genera Homo and Macaca (rhesus monkeys and their allies) are the only representatives that penetrate much into the temperate zone, and only Homo sapiens thrives above the fortieth parallel. This is due largely to behavioral adaptations. The basic primate life strategy is adapted to uniformly warm temperatures, and, more importantly, to a lack of dramatic seasonal variation in food availability and daylight.

This contrasts with bears, for example. Some bears exhibit notable genetically programmed adaptations to seasonal climates near the Arctic Circle, which are lacking in tropical species. Even within a species like the American black bear (Ursus americanus) with a wide latitudinal range, boreal populations exhibit stable high latitude traits which are absent in Florida and Louisiana. Black bears in Canada hibernate. In Oregon (latitude 45 degrees) they den up and are much less active in the winter, and in Florida, where temperatures and day length do not fluctuate nearly as much on an annual basis, Activity Levels fluctuate correspondingly less.

It would be surprising if humans did not exhibit an innate change in activity level in response to fluctuating light levels, weak in the case of populations that have lived for countless generations in the tropics, strong in the case of populations that have lived for countless generations in the North Temperate Zone. Historically at least no area far south of the equator supported dense populations of humans (there is very little land below 45 degrees south latitude) and until recently the only densely populated areas north of 45 degrees were central and Northern Europe and the northeast coast of Asia, with smaller foci around Puget Sound, Lake Baikal, and the American Great Lakes.

Returning to my Viking ancestors, they lived and built up large populations around the Baltic sea during periods of relatively benign climate, migrated to the North of England during the Late Antique Little Ice Age (536-680 CE), again built up populations during the Medieval warm period and the 15th-16th centuries, and finally migrated to New England in the 17th century, always doing best economically at high latitudes.

Being able to adjust activity levels seasonally was a key to success in the north: one needed to be able to summon bursts of energy in the summer to store enough food for the winter merely to survive in Denmark in 400 CE, or Nottingham in 1300, or Connecticut in 1630. In the middle of winter people slept a great deal; total energy output on an annual basis was most probably comparable to that of people in warmer climates, and that particular adaptation conferred no notable advantage when Vikings ventured into low latitudes.

The Industrial Revolution and particularly the invention of efficient indoor artificial lighting changed all that. Throughout history, at least until about 1700, wealth, power and civilization developed in warmer climates where large populations and surplus resources accumulated – around the Mediterranean, in India and Southeast Asia, in Mexico and Peru. With artificial light and machines, high-latitude adapted individuals could maintain their high activity levels for longer periods of time, generating additional surplus wealth and power for themselves or for those who employed them. Tropical people lacking the light-response adaptation got the reputation for laziness and a lack of work ethic.

Taking advantage of high-latitude light response comes at a high price, particularly if an individual is caught in an endless cycle of enforced productivity, with the bulk of that productivity being siphoned off to benefit others. I believe that a certain amount of down time is necessary for optimum mental and physical health, and that we are born with an instinctive pattern of allocating that down time which is tied to our ancestry. North Europeans like myself are notoriously prone to bipolar “disorder” and seasonal affective “disorder.” Are these really disorders, or are our minds and bodies telling us that we are forcing ourselves into a pattern of summer productivity which is ultimately unsustainable? Is this making us sick in ways that an array of pharmaceuticals can mask without ultimately effecting a cure?

In the eighteenth century George Cheyne described what would now be called bipolar disorder as a distinctly English malady; at the time, and into the early 19th century, the competitive nature of English life during the commercial and early Industrial revolutions meant that England was also foremost in the mental pathologies attendant on pushing individuals past the limits of light adaptation. At the time the Scots were particularly noted for their industry and hard work, compared to people from the South of England or immigrants from Mediterranean countries.

Mental health professionals profess to be puzzled concerning why people experience mental breakdowns and severe depression just when they appear to be succeeding at some long term endeavor requiring almost superhuman effort. This happened to me as I was trying to springboard into a career after having completed a doctoral dissertation in biology, and I now think that it was because I had already exceeded what my mind and body could sustain for a long period of time – several years in this case – and that the effect was exacerbated by a “payoff” that was far less than what I had been led to expect.

Photo Credit

Photo is Wikimedia Creative Commons
See also Life on a Viking Farm for a good description of farming conditions in Scandinavia in the Middle Ages.