Human Variation & Race

Human Variation & Race

Cold

Cold temperatures place physiological stresses on the body, the healthier and fit you are, the more easily your body can cope with these stresses. Cold is an environmental stress that negatively affects human survival by interfering with homeostasis. The core temperature of the human body is 37 degrees Celsius. Any deviation from this standard can cause serious problems. When the body temperature begins to drop, the body temperature will be too low.

Sudden severe cold stimulation is an injury to the organism. In very cold conditions, the blood vessels in the body will keep contracting, and all the blood will be gathered together, which can protect the internal organs of the body, so that the internal organs of the body can last a little longer, and people will not die so quickly. However, this can only last for a short time. Most obviously, skin (and muscles, and tissue) freezes solid. And the longer human beings are exposed in the extreme coldness, the more likely it is that the damage becomes widespread, to the point of possibly requiring amputation, even if they do manage to find medical attention.

Short-term Adaptation

Most of us definitely have experienced this adaptation, yet we barely notice them. The short-term adaptation includes shivering, goosebumps. The reaction of having goosebumps is a kind of stress response in the human body. Under the stimulation of a cold environment, muscles will twitch and produce heat to maintain body temperature, and there will be tremors. The skin sensory organ transmits a signal to the brain when it feels cold. The signal returned by the brain is to shrink the pores to reduce heat loss, and goose bumps appear. This can be reduced if it is adapted to a cold environment.

Facultative Adaptation

A facultative adaptation for human beings in response to the cold is vasoconstriction. When temperatures hit 50 degrees, human beings' blood vessels narrow to reduce blood flow near the body's surface. Sometimes the blood vessels dilate and burst, which causes redness.

Developmental Adaptation

Carl Bergmann found a negative correlation between body weight and environmental climate, as well as height (surface area) and heat loss rate, thereby creating Bergmann's law. In addition, Joel Allen pointed out the relationship between body surface area and heat loss rate - creating Allen's rules. People living in cold climates are often genetically shorter, people living in cold climates are often genetically shorter, having high body quality, and short length of appendages that help to generate and retain more calories.

Cultural Adaption

Cultural adaptation adopted by human beings to deal with cold is highly diversified, including cloths, house, diet with fat, fire, etc. For Inuit people will hunt polar beer to help them to get through the coldness because the polar bear contains rich fat. Their diets largely increase the basal metabolic rate which results in production of extra body heat. In modern and advanced city, people use central air systems to deal with coldness.

Human Variation & Environmental Clines 

The term cline is proposed by evolutionary biologist Julian Huxley in 1983 to describe the pattern of biological variation. The biggest benefit that we can get from the study of the variation of the adaptations from the perspective of the environmental clines is that we can obtain the professional knowledge about how human bodies response and adapt to extreme environment from short-term to long-term. Moreover, this methodology is highly inspiring for human beings to deal with the potential environmental challenge. For example, people will inevitably the consequences of climate change, that is to say, human beings are more possibly exposed to extreme environmental conditions. This learning perspective enables human beings to study the adapting mechanism to such environmental changes by figuring out the adaptation models at different levels.

Human Variation & Race

Race is rather a social concept than a biological concept, which surely cannot be used to explain the scientific situation about the genetic adaptations. How human beings' appearance can be affected by the study on the environmental influences. For example, the primitive ancestors left Africa and headed to other continents, when they entered the different environmental conditions (e.g. different different levels of UV rays), they began to adapt to local environment by creating less melanin through natural selection. Inuit people maintain medium to dark skin although they have are less exposed to UV lays than others who live near the equator. This is because they rely on fish to obtain enough vitamin D, which makes them maintain high level of melanin. Therefore, the concept of race cannot effectively address this situation.