early scientists of evolution did not explain how the major changes that created new species of organisms began. The work of botanists in the 1 first helped explain the question of evolutionary development. Hugo de Vries studied genetic families in a flower called the evening primrose. He noticed that sometimes traits would appear in new plants that were not there before. The trait could not be found anywhere in the parents of the plant. De Vries believed that it began because of a sudden change of a specific gene. Genes are biological codes for inherited traits. They are passed from parents to offspring. They determine things such as hair color, paw size, or wingspan. De Vries believed that a change of this code introduces new characteristics. In addition, these characteristics can then be passed to future offspring. He called such hereditary changes mutations.