Chapter 14 "One in Every Four" Summary

Cancer has existed for so long that we do not know when it was first recognized. There are naturally occurring substances that cause cancer, such as radiation and arsenic. Life adapted to these threats, which are relatively few, but human beings alone among the planet's creatures have the ability to create carcinogens, which cause cancer. Soot is one carcinogen. The industrial era has brought many more. Because life, including human life, adapts to environmental changes extremely slowly, the carcinogens that man has created relatively recently in the span of history can have drastic effects on humans, as well as other creatures. Only since 1775 has the connection between external agents and the existence of cancer been recognized, and it was not until the latter part of the nineteenth century that various cancers were traced...