There suddenly flashed upon me the idea of the survival of the fittest. All organisms tend to increase in geometric proportion. In spite of this tendency, the numbers of individuals of a given species remain more or less constant. Deduction 1 . Thus there is a struggle for existence.
All organisms vary considerably.
Deduction 2 . After the rediscovery of Mendelian genetics at the beginning of the twentieth century, a fourth fact and third deduction were added. The incorporation of modern genetics in the theory of natural selection is known as the Modern Synthesis. Some variation is inherited and will be available for transmission to later generations. Deduction 3 .