Cold and heat adaptations in humans
Adaptations in humans can be physiological, genetic, or cultural, which allow people to live in a wide variety of climates.
[1] Sufficient stress from extreme external temperature may cause injury or death if it exceeds the ability of the body to thermoregulate.
[3][4] Humans have adapted to living in climates where hypothermia and hyperthermia were common primarily through culture and technology, such as the use of clothing and shelter.
[5] Modern humans emerged from Africa approximately 70,000 years ago during a period of unstable climate, leading to a variety of new traits among the population.
[7][8] This is supported in the variability selection hypothesis proposed by Richard Potts, which says that human adaptability came from environmental change over the long term.
[11] Individuals with larger bodies are better suited for colder climates because larger bodies produce more heat due to having more cells, and have a smaller surface area to volume ratio compared to smaller individuals, which reduces the proportional heat loss.
A study by Frederick Foster and Mark Collard found that Bergmann's rule can be applied to humans when the latitude and temperature between groups differ widely.
[14] Paleoanthropologist John F. Hoffecker found that both Bermann's and Allen's biogeographical rules were confirmed, with it being seen that in modern populations, there is a clear trend of shorter distal limb segments in colder environments.
Also, humans had physiological mechanisms that reduced the rate of metabolism and that modified the sensitivity of sweat glands to provide an adequate amount for cooldown without the individual becoming dehydrated.
Individuals with less fat and slightly lower body temperatures can more easily handle both humid and dry heat.
A 1960 study on the Alacaluf Indians shows that they have a resting metabolic rate 150 to 200 percent higher than the white controls used.
[18] Social adaptations enabled early modern humans to occupy environments with temperatures that were drastically different from that of Africa.
Selective use of clothing and technological inventions such as air conditioning allows humans to live in hot climates.
