What is the main factor that determines human skin colour?
Q: What is the main factor that determines human skin colour?
A: The single most important substance deciding human skin colour is the pigment melanin.
Q: How does UV radiation affect skin pigmentation?
A: There is a direct relationship between UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that have more UVR also have darker-skinned populations, while areas that are far from the tropics and closer to the poles have lower concentration of UVR, and lighter-skinned populations.
Q: How did humans evolve to have lighter skin as they moved away from Africa?
A: Human populations have changed from dark-skinned to light-skinned as they left Africa about 100,000 years ago, and some have changed back to darker skin as they returned to higher UV zones. Natural skin colour can also darken as a result of tanning due to exposure to sunlight. The leading theory is that skin colour adapts to intense sunlight in order to provide partial protection against ultraviolet radiation which damages DNA of the skin cells and so produces mutations.
Q: Why do females usually have lighter skins than males?
A: Adult human females are usually lighter in skin pigmentation than males because females need more calcium during pregnancy and lactation. The body synthesizes vitamin D from the action of sunlight on the skin, which helps with calcium absorption; therefore, females evolved to have lighter skins so their bodies absorb more calcium.
Q: What are two possible reasons why white skins may be an advantage in colder climates?
A: Researchers suggest two reasons why white skins may be an advantage in colder climates; firstly, at a given temperature, a white skin radiates less heat than a black one; secondly, in weaker sunlight the body tends to produce less vitamin D - there is a hypothesis that selection for lighter skins was due to this need for higher vitamin D production when people moved north out of Africa.
Q: How has social significance varied regarding differences in human'sskin color across cultures over time?
A: The social significance of differences in human'sskin color has varied across cultures over time; it has been demonstrated with regard to social status and discrimination throughout history.
