Human Variation and Race

The Dangers of Heat

            Living in hot climates like the desert or tropical rain forest can negatively affect humans. In the United States more people die from the heat than the cold.  It is more bearable to live in the desert than a tropical rain forest because of humidity. Hot temperatures and humidity make it very difficult to sweat and evaporate excess heat. When we sweat we lose precious salts and water that our bodies need. Heat stroke is a major problem for humans. It occurs after our core body temperature reaches 104°F or higher and if not treated it can cause brain, kidney, heart, and muscle damage that can result in death.  Heat stroke symptoms include high body temperature, lack of sweating, nausea, vomiting, flushed skin, rapid breathing, racing heart rate, headache, confusion, and muscle cramps or weakness. Two lesser heat related illnesses are heat cramps and heat exhaustion. Heat cramps are caused by exposure to high temperatures or physical exertion. Heat exhaustion occurs when the symptoms of heat stress are ignored and get worse. The symptoms of both illnesses are very similar to heat stroke.

            Humans have adapted in many ways to live in extreme heat. A short term adaptation humans have is the ability to sweat when overheated. There are millions of sweat glands on the human body. An example of a heat related facultative adaptation is the ability to produce more sweat. The average human who is not adapted to live in an extremely hot environment sweats about 1 liter per hour. People who live in hot climates like the American Southwest can lose about 2-3 liters per hour. It can take about six weeks for a person to adapt to live in hot climates and produce more sweat. An example of a developmental adaptation is body shape. People who live in hot climate like East Africans tend to have longer appendages. Having longer arms and legs increases the body’s surface area. A larger surface area allows more heat loss and keeps people cooler. The last example is cultural adaptation. Humans have the power to use tools to create whatever they want. Humans have created many ways to stay cool. My personal favorite invention is air conditioning. Air conditioning has allowed humans to live in super-hot climates and still stay cool by controlling the temperature of their environment.

Short-term adaptation of what the sweat gland looks like

 

Facultative adaptation of a man sweating

 

 

Developmental adaptation of longer limbs in East Africa

 

 

Cultural adaptation of a woman keeping cool with air conditioning

 

 

             Studying human evolution from an environmental perspective is very important. It shows us how humans evolved to similar climates in different ways. This information can be very useful to us. Knowing it takes about six weeks for the body to adapt and produce more sweat in hot climates is important. This information can be very useful to soldiers serving in hot countries like Iraq. They can train soldiers in the desert for at least six weeks before being deployed to adapt to the heat. Once they have adapted and produce more sweat they can stay cooler for longer when resources may not be available.

            I would use race to compare a specific group of people. There is more variation among members within the same race than outside their race. I could use this information to calculate the surface area of people in East Africa by measuring their arms and legs.This would allow me to calculate how much they sweat compared to people who live in cooler climates and have less surface area. It is much easier to use environmental influences to understand human adaptions. Using race involves categorizing people based on physical traits and has no genetic basis. No one characteristic or trait can be used to distinguish and entire race of people and it is a highly subjective process.