In many parts of the world, where manufactured drugs are not available, people use plants alone to treat illness. Since we have identified only a tiny fraction of all the organisms on Earth, we can be certain that many new sources of medicine remain to be discovered. The genes found in the cells of every organism determine the unique characteristics of each living thing. Through a process called genetic engineering, scientists have learned to transfer genes from one organism to another to produce different traits. Scientists used this process in the early 1990's, for example, to develop a variety of cotton that is naturally resistant to pests.
Genetic research has countless applications in agriculture as well as medicine and other fields.
This research depends, however, on the continued existence of a variety of genetic material among living things. The loss of species also brings about the elimination of the valuable information found in their genes. The potential of living things as a useful source of information is not limited to genetics. Every area of knowledge has benefitted from the study of living things. Anthropologists have learned about prehistoric human beings by studying our closest living relatives, the apes.