Evolution and its Relevance to Temperature
Why is it so hard for humans to regulate their body temperature based on the environment? The majority of the human evolutionary process was spent in the African Savanna—an area of warm and dry climate. Thus, most of the human species at the time acclimated to this region's temperature with furless bodies, long appendages, and large density of eccrine glands. These are key morphological and physiological adaptations that remained even centuries later. However, eventual migration to northern regions of the globe resulted in demands to withstand colder temperatures, something which the human body wasn’t capable of physically adapting to. As a result, major cold-adapted behavioral and technological strategies (insulated shelters, fire, collaborative work, etc.) were required to survive. Nevertheless, even in today’s modern world, human tolerance to the cold remains limited and extremely dependent on the severity of the conditions (wind, humidity, contact with cold surface, etc.) as well as genetics.
Cold Defense Mechanisms
Even with the many adaptations of the human species, a greater part of the measures taken against harsh weather are reliant on natural physiological and metabolic responses, as well as morphological adaptations (an attempt to reduce heat loss and increase heat productivity). Due to a large dependency on genetic traits acquired through natural selection, as well as different morphology and body compositions (skin characteristics, body shape, narrowing blood vessels), these responses/adaptations are highly diverse amongst individuals. For example, although body fat (white adipose tissue) is believed to be a primary determinant of cold protection/tolerance, there has been little evidence that demonstrates it adequately mimics the insulative layer of blubber seen in Arctic marine mammals. Instead, body fat (which increases volume-to-surface ratios) contributes more to the total amount of heat lost, which therefore changes the amount of heat that must be produced rather than effectively reducing heat transfer. However, with deeper analyzations, it has become accepted that individuals who tend to have a large mass/volume as well as low surface body area with high body fat percentage are able to preserve the most heat in particular conditions such as cold water (even if body fat is not as efficient as blubber), rather than small individuals with high surface-area-to volume ratios.
Conclusion
While humans have developed basic physiological defenses against the cold, their ability to tolerate extremely cold temperatures remains limited. Individual differences in body composition and genetics further influence cold tolerance, underscoring the need for personalized strategies and continued research to improve resilience to harsh environments.
References
Haman, François, et al. “Human Vulnerability and Variability in the Cold: Establishing Individual Risks for Cold Weather Injuries.” Temperature (Austin, Tex.), U.S. National Library of Medicine, 29 May 2022, pmc.ncbi.nlm.nih.gov/articles/PMC9467591/.
Person. “Metabolic Syndrome Linked to Cold Tolerance.” UChicago Medicine, UChicago Medicine, www.uchicagomedicine.org/forefront/news/metabolic-syndrome-linked-to-cold-tolerance. Accessed 10 Nov. 2024.
Comments