Hugo de Vries | Biography

De Vries was born on February 16, 1848. He grew up in Haarlem, an area in the Netherlands rich with plant life. During vacations from school, he would roam the countryside picking up more plants for his growing collection. By the time de Vries entered the University of Leiden in 1866, he was already an expert on plants of the Netherlands and turned to other related areas of study. One of those areas was evolutionary theory--an interest brought on by Charles Darwin's book The Origin of Species. De Vries thought a major flaw in Darwin's work was that Darwin could not identify what caused evolution, the changes in organisms. De Vries set out to develop his own theory.

In 1886, while de Vries was out for a walk, he came upon a field of flowering plants called evening primrose. He noticed that some of the specimens differed widely. He took samples back to his lab to find out why they differed. De Vries began experimenting to pinpoint the source of the changes. He felt that the key to understanding plant heredity was breeding different types of plants and studying their offspring over several generations. Using the evening primrose, he made many such crosses and discovered that periodically a dramatically different variety appeared that would occasionally reappear in later generations. Based on these findings, de Vries postulated that hereditary characteristics were independent units--they could not be "blended" like two liquids. He asserted that each characteristic is expressed physically, and he called that physical representation a pangene.

In this first book, de Vries presented a theory remarkably similar to the modern theory of heredity: pangenes grow and divide into two new pangenes; a set of pangenes are passed to offspring; a pangene can be active or latent; some characteristics may be represented by more than one pangene. Unknown to de Vries, these findings had already been documented by Gregor Mendel, an Austrian monk, over thirty-four years prior to de Vries's studies. During the late 1800s, de Vries devoted himself to the study of heredity and variation. When he came across the forgotten works of Mendel in 1900 (Karl Erich Correns [1864-1933] and Erich Tschermak von Seysenegg [1871-1962] independently uncovered Mendel's work around the same time), he used it to supplement his own work. De Vries demonstrated Mendel's segregation laws in over twenty species, whereas Mendel had studied only two species.

The rediscovery of Mendel's laws created quite a stir among scientists, and many flocked to the field to investigate. But de Vries felt something was missing. Mendel's laws of segregation explained how existing characteristics were redistributed to create variations, but not how new species originated. Harking back to his primrose experiments, de Vries termed the new varieties mutations. De Vries theorized that evolution occurred in sudden jumps due to these mutations, not in gradual increments as suggested by Darwin. He believed a species produced mutants over relatively short time periods throughout its evolutionary life, and only the useful or "progressive" characteristics contributed to the evolution of the species. He documented this theory in his Die Mutationstheorie (The Mutation Theory), completed in 1903.

De Vries died on May 21, 1935. Since de Vries's day, the term mutation has been adopted by geneticists to describe spontaneous changes in genetic material. Interestingly enough, it was later discovered that the new varieties of primrose observed by de Vries were not due to actual changes in the genes but to a different number of chromosomes in the plant. Despite this fact, de Vries's research has contributed much to genetics and evolutionary theory.