pan of many generations. But the parts of Darwin's theory that were the most
             difficult to test scientifically were the conjectures about the inheritability of traits or
             characteristics, simply because heredity was not understood yet. But at the turn of the
             century, the early work of Gregory Mendel came to be. Mendel had discovered that
             characteristics are transmitted across generations in units, known as genes. Then the
             discovery of mutations was discovered when they found that the inheritable changes in
             genes could occur spontaneously and randomly without watch to the environment. Since
             mutations were the only source of genetic idea, many geneticists believed that evolution
             was driven onward by mutational changes.
             Mutations, or gene changes, are a source of variation and have a strong influence on
             ...