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Human ancestors in Africa likely had dark skin, which is produced by an abundance of the pigment eumelanin in skin cells. In the high ultraviolet (UV) environment of sub-Saharan Africa, darker skin offers protection from the damaging effects of UV radiation. Dr. Jablonski explains that the variation in skin color that evolved since human ancestors migrated out of Africa can be explained by the tradeoff between protection from UV and the need for some UV absorption for the production of vitamin D.
Invisible ultra-violet light energy is finding its way into an increasing variety of high-tech applications, such as disinfecting water of hazardous micro-organisms and in the development of paint that dries in seconds. The highly competitive field of computer chip lithography also has chemists and physicists working with ultra-violet light technology. New light technologies are being used to manufacture semiconductors, lenses, and many other technological components.
A mutagen is any agent (physical, chemical, or biological) capable of altering the structure of DNA within human cells. This program explores how some mutations are a natural process resulting from errors in the copying and repair of DNA and how some mutagens naturally exist in the world (e.g., UV radiation, cosmic rays, and some radioactive isotopes). Others are specific chemicals that have been synthesized for use in manufacturing or other industries. Mutagens may also arise during the metabolism of certain foods. In many cases mutagens may also lead to the development of cancers.