Human Variation
In the cold, the body has two homeostasis responses to the cold by increasing heat production or heat retention. Heat retention requires less work from the body so this is normally the quickest and earliest response. Heat retention is energy that the body retains from food. Unfortunately, during the winter or in colder climates food is usually scarce. If the body is not receiving enough heat the body will go into increased heat production. Examples of this would be shivering, which is only short term. Vasoconstriction is another short term response that minimizes heat loss. Vasoconstriction narrows blood vessels to constrict blood flow from the skin. Therefore reducing the amount of heat lost at the surface of the surface of the body. Using the environmental stress I discussed above, shivering would be considered a short term adaptation for humans under cold stress. Shivering does not require genetic change ...