Undoubtedly, winter is difficult for most life forms on Earth. The ground goes dormant, and animals who have foraged during the transition season become less active. Domesticated pets and livestock must be protected from frostbite and starvation. Many species go into complete hibernation. For those that don’t it is survival of the fittest, with humans being especially ill equipped to weather cold seasons.
The human race is suited for temperate climates. Our naked skin finds temperatures under 77˚ F to be cold, at which point the body will start going through physiological changes. Mortality rates go up in the winter, along with cases Seasonal Affective Disorder (SAD). Traditional societies came to all but a halt in the coldest months while modern society finds winter inconvenient and economically untenable. Artificial lighting extends daytime hours and heated environments allow us to continue to work our scheduled shifts. Exacerbating the human trend of overcoming and conquering nature, people have stopped allowing themselves to rest during winter. The result is a population completely out of sync with our Circadian rhythms.
Hibernation and the Parasympathetic Nervous System
There is a natural tendency to conserve energy when the winter months roll around. Researchers are beginning to suspect that it is part of our evolutionary heritage to go into hibernation mode during winter time. Less exposure to daylight causes increased melatonin production which in turn creates an increased need for sleep. Sufferers of SAD show additional changes in the parasympathetic nervous system that mimic the beginning stages of mammalian hibernation. The overall effects on the autonomic nervous system is to conserve energy by slowing down metabolism while simultaneously increasing calorie intake. Additional changes include slower heart rate, decreased sex drive, and an increased need for sleep. The adaption of a lower sex drive enhances infant survival, as babies conceived in winter would be born in Autumn, a time when food is beginning to get scarce again.
Winter and the Origin of Man
Human use of fire is dated to about 400,000 years ago. Yet some of the oldest human remains are nearly 1 million years old, indicating that there was a period of time when people had to survive extreme cold without fire. This was achieved primarily by sheltering in place and relying on the physical heat of our comrades to keep warm.
Adaptation to heat is very ancient in hominids but our ability to endure cold is evolutionarily more recent. Some of our ability to withstand cold climates comes from Neanderthal DNA which lives on in European descendants. These traits include skin changes, as well as increased body hair and body mass. Key mutations in mitochondrial DNA (mtDNA) allowed energy from calories to be used to heat the body rather than for work. These changes synthesize ATP (adenosine triphosphate) in order to maintain body temperature. ATP is a chemical form of energy that repairs tissues and generates energy for external applications. In order to survive cold winters, early humans had to reallocate energy normally used for work and redistribute it to staying warm and surviving.
Populations genetically predisposed to cold also have a need for high fat, high calorie diets. In the absence of these conditions, calories are redirected from heat exchange to formation of free radicals, increasing the propensity for disease. Similarly, those genetically adapted to tropical climates tend to obesity when consuming calorie rich European diets.
Overwintering in Traditional Cultures
In the early 1900’s, before the advent of technological warmth and light, there is evidence of cultural hibernation. Documentation from France after the Revolution shows that the whole countryside stopped working and holed up for the entire winter. Russian villagers also slept away the winter, waking daily to eat, drink, and take turns stoking the fire. The inhabitants of these cultures would gradually resume their activities as the weather warmed up. With up to 20% of the population suffering from some form of SAD as well as the acknowledgement of general widespread preparatory behaviors in humans during winter, it seems that we might be technologically at odds with our evolutionary heritage.
The Solution to Weathering Modern Winters
Despite a predisposition to slow way down and institute hibernation behaviors, humans are pushed even harder in the winter. Fighting inclement weather to shuttle back and forth from work and school, not to mention extensive holiday preparations for many, often makes the days feel even harder. Decreased light exacerbates the situation, increasing melatonin production and the need to sleep. Solutions that don’t challenge the status quo include light therapy, changes in diet, and vitamin D supplements. While these are useful suggestions, they indicate a drive to further trick the body to work against it’s natural impulse.
An alternative would be to slow down significantly during winter. Even if a hibernation state was possible for people, most folks would balk at the idea of sleeping away an entire season. It goes against everything we have been taught about work ethic, drive, and the ability to consume at all costs. However, it doesn’t take a stretch of imagination to recognize that people are biologically tied to nature and that respecting our atavistic responses to the season is an important part of general well being. It might be wise to allow ourselves the freedom to indulge in every season, from the productivity of high summer, to the lethargy of mid winter. We are, after all, creatures of the Earth.
Find more articles by Traci Knight at http://iriesatya.com/
sources:
http://www.eurekalert.org/pub_releases/2010-08/econ-crt082610.php
http://www.dailymail.co.uk/health/article-94678/Tired-hungry-sad-Relax-youre-hibernating.html
http://johnhawks.net/weblog/reviews/neandertals/neandertal_dna/ruiz-pesini_selection_mtdna_2004.html
