Human Variation & Race Blog

Heat negatively impacts the survival of humans by disturbing homeostasis because it can be expensive and dangerous in terms of water and sodium loss. There are two types of heat – arid and humid. Arid exists in the southwestern United States, Middle East, and in some parts of Africa and are characterized by high temperatures, wind, and low water vapor. Humid heat is increased water vapor and is found in regions with a great deal of vegetation and precipitation which can be found in the eastern and southern U.S., parts of Europe, and in the tropics. Increased water vapor inhibits the evaporation of sweat, which makes it easier for humans to adapt to dry heat. People who exercise in the dry heat may sometimes not be aware they are sweating because it evaporates as soon as it reaches the surface of the skin so while the rapid evaporation can cause one to become dehydrated which is important to drink plenty of water in the dry heat, even if one is not thirsty.

Humans have adapted to the following stress: short term, facultative, developmental and cultural in the following way:

Short term -  Sweating is a response to a person who overheats in an attempt to cool you off. The optimum body temperature is 37 Celsius where “sweating is responsible for 70 percent to 80 percent of the body's heat regulation”, according to the MBF website.  

"A common misunderstanding was that our skin's pigmentation, melanin, served as a facultative layer to provide a beneficial glow after and following sun exposure. The tanning response is, in reality, a physiological repair mechanism to instant UV damage of the skin cells (epidermis/dermis). Further, it was contemplated whether UVB alone was responsible for the long-term mutations seen in the epidermis. It has since been established from carcinogenic models that UVA plays a synergistic and complementary role to UVB, whereby the wavelengths determine the ability to penetrate the skin layers."  http://www.clinuvel.com/scenesse/technology-updates/technology-update-i

fake or natural tan?

It is said that the closer one is to the equator, chances are those people will have darker pigmentation whereas people living farther away from the equator, will have lighter pigmentation. A perfect example of this would be people living in some parts of South America such as Ecuador (darker pigmentation) or parts of Europe such as Ireland (lighter pigmentation)

Irish boy

Ecuadorian woman

Rich or poor, people find a way to culturally adapt to their environment. In this case, heat, one would assume that they could try to maintain themselves cool or comfortable when the weather isn't pleasant, basically, nothing over 90 degrees (which in my opinion is TOO hot!). People find a way to make due with what they have and in the event a particular person is on a tight budget and can't afford such luxury as, an example, air conditioner, they would most likely open a window or dress in a manner that is cool for them. I can go on and on with many examples however I won't. The point I am trying to get across is, as I mentioned, rich or poor, they will adapt and make due with what they have and make it work for themselves.