ABSTRACT
Ultraviolet radiation (UVR) is a primordial and ubiquitous genotoxin. During the earliest stages of molecular evolution as the dynamics of DNA chemistry were being formulated, the surface of the planet was bombarded by extremely high levels of UVR. Any DNA exposed to sunlight during or soon after the genesis of life would require rapid and accurate repair of UVR damage for continued survival and procreation. Hence, it is probable that mechanisms of DNA repair evolved early in the Earth’s history and, in fact, may have coevolved with DNA replication and transcription. Today, the amount of UV-B radiation reaching the earth’s surface increased due to industrialization and chlorofluorocarbon pollution of the upper atmosphere. The consequences of stratospheric deozonation and increased UV-B exposure to the human population are difficult to predict, but research over the past 40 years suggests that accelerated rates of skin cancer and aging as well as deterioration of the natural environment and major food crops are probable outcomes.
