Hugo de Vries (1848–1935) was a Dutch botanist and geneticist who introduced experimental methods to the study of evolution and heredity. He is a foundational figure in early 20th-century biology, known for independently confirming Gregor Mendel’s principles of inheritance and developing the theory of mutation as a driving force for evolutionary change. De Vries’s work helped shift biological thought toward a more mechanistic and quantitative understanding of how traits are passed down and how new forms of life originate.
The Independent Rediscovery of Inheritance Laws
De Vries spent years investigating heredity, culminating in 1900 with the independent rediscovery of Gregor Mendel’s work. Working separately, De Vries, German botanist Carl Correns, and Austrian agronomist Erich von Tschermak all published findings confirming the principles of segregation and independent assortment. This event was significant because it provided quantitative, predictable laws for the inheritance of traits, which had been lacking in evolutionary theory.
His rediscovery was built upon his earlier theoretical work, outlined in his 1889 book, Intracellular Pangenesis. In this work, De Vries hypothesized that hereditary characteristics were carried by discrete, material particles, which he termed “pangenes.” These pangenes were thought to reside in the nucleus of every cell and determine specific traits. The experimental results confirming Mendelian ratios validated his conceptualization of inheritance as involving distinct, non-blending units. This particulate theory of inheritance replaced the older idea of “blending inheritance” and laid the groundwork for modern genetics.
Developing the Theory of Mutation
De Vries’s focus on discrete hereditary units led him to study how these units could change. His theory was based on years of observations and hybridization experiments involving the Evening Primrose, Oenothera lamarckiana, starting in 1886. He noticed that among the thousands of plants he cultivated, a small number of offspring would spontaneously appear with strikingly different characteristics, such as changes in leaf shape or plant height.
Crucially, these new forms bred true, passing the new traits to their progeny and establishing them as distinct varieties. De Vries termed these heritable alterations “mutations” and proposed them as the source of new species. He published his findings in his 1901–1903 work, Die Mutationstheorie (The Mutation Theory). He suggested that evolution proceeds not through the slow, gradual accumulation of small changes, as Charles Darwin had proposed, but through rapid, single-step transformations. This concept of sudden, large evolutionary leaps is known as saltation, which De Vries believed was the mechanism by which new species originated abruptly.
De Vries’s Definition Versus Modern Genetic Mutation
While De Vries introduced the term “mutation,” its scientific meaning has evolved significantly. The changes De Vries observed in the Evening Primrose were later clarified by geneticists to be the result of a different biological phenomenon. The sudden changes in Oenothera were primarily caused by large-scale chromosomal anomalies, such as polyploidy (extra sets of chromosomes) or complex chromosomal rearrangements. These were not small changes within a gene sequence, but structural alterations affecting the plant’s entire genetic architecture.
Modern genetics, established by Thomas Hunt Morgan and his students, redefined mutation as a small, random change in the nucleotide sequence of DNA. These modern “point mutations” result in subtle changes to a gene’s function and provide the incremental variation upon which natural selection acts. De Vries’s historical definition of mutation as a large, discontinuous jump contrasts with the current understanding of mutation as a small, sequence-level alteration. His term for the phenomenon endured, even though the biological cause he observed was due to aberrations in chromosome number and structure.
Lasting Influence on Evolutionary Thought
De Vries’s work provided a mechanistic basis for the source of variation, addressing a weakness in Darwin’s original theory of natural selection. Although his specific interpretation of the Oenothera changes was later revised, his emphasis on mutation as the source of new heritable traits became widely accepted. By introducing the concept of sudden, discrete changes, his work helped integrate the newly confirmed Mendelian laws of inheritance with Darwinian evolution.
The concept of discrete hereditary units, which De Vries called pangenes, eventually led to the coining of the term “gene” by Wilhelm Johannsen. This nomenclature, combined with the recognition of mutation as the engine of genetic novelty, was instrumental in founding the discipline of genetics. Ultimately, the fusion of Mendelian genetics and Darwinian selection, which De Vries’s work helped initiate, led to the foundation of the Modern Evolutionary Synthesis in the 1930s.