Human variability

Human variability, or human variation, is the range of possible values for any characteristic - physical or mental - of human beings.

Variation is inherent in all species, and is necessary to ensure diversity within the species, and thus the species’ survival over time. There are conflicting views on the attitudes towards variability traits according to each society that is rooted in cultural taste or local traditions. The variations that are often evaluated differently are mental abilities, body shape, and skin color. These variations may come from genetics, in the form of heritable traits obtained from parents, or from the environment, a factor of both prenatal health and subsequent lifestyle choices. Humans are said to have a higher degree of variation than most other species, and an increased awareness of variation, which has a significant societal impact in the way humans interact with and evaluate others.

Human variability is attributed to a combination of environmental and genetic sources including:

For the genetic variables listed above, few of them are controlled by simple Mendelian inheritance. Most are polygenic or are determined by a complex combination of genetics and environment.

Many genetic differences (polymorphisms) have little effect on health or reproductive success but help to distinguish one population from another. It is helpful for researchers in the field of population genetics to study ancient migrations and relationships between population groups.

Other important factors of environmental factors include climate and disease. Climate has effects on determining what kinds of human variation is more adaptable to survive without much restrictions and hardships. For example, people, who live in the climate where there is a lot of exposure to sunlight, has a darker color of skin tone. With evolution favors protection of folate (folic acid) from UV radiation, they have darker skin tone with more melanin to make sure child development is smooth and success. On the other hand, people who lived farther away from the equator have a lighter skin tone. They have lighter skin tone because they need more exposure and absorbance of sunlight to make sure the body produce enough vitamin D for survival.

Blackfoot disease is a disease caused by environmental pollution and causes people to have black, charcoal-like skin in the lower limbs. This is caused by arsenic pollution in water and food source. This is an example of how disease can affect human variation. Another disease that can affect human variation is syphilis, a sexual transmitted disease. Syphilis does not affect human variation until the middle stage of the disease. It then starts to grow rashes all over the body, affecting people's human variation.

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