Mutation Theory of Hugo de Vries: Evolution by Mutations

The mutation theory of evolution was proposed by the Dutch botanist Hugo de Vries in 1901, based on his studies of the evening primrose, Oenothera lamarckiana. He argued that evolution occurs not by tiny gradual changes, but by sudden, large, heritable changes called mutations, which can create new species in a single step.

This theory matters because it introduced mutation as a central concept in biology. Although its claim of instant speciation was too strong, mutations are now known to be the ultimate source of all genetic variation on which selection acts.

Key Concepts

• Mutation: a sudden, random and heritable change in the genetic material (DNA), also called a saltation when large.
• Continuous versus discontinuous variation: Darwins small, fluctuating differences versus de Vries large, stable jumps.
• Mutant form: an individual showing a new trait produced by mutation; de Vries observed forms of primrose differing in size, leaf shape and chromosome number.
• Directionless change: mutations arise randomly, favourable or harmful, and selection later decides their fate.

How It Works

De Vries grew thousands of evening primrose plants and found that most offspring resembled the parents, but a small number appeared suddenly with distinctly new traits, and these mutants bred true. From this he concluded that new species arise by a single mutational leap, not by slow accumulation. He proposed that mutations occur from time to time in all organisms, producing variation in jumps; natural selection then preserves useful mutants and eliminates harmful ones, but the creative step is the mutation itself. Later work showed that many of his primrose mutants were actually due to unusual chromosome behaviour and rearrangements in that plant, not typical single-gene mutations, and that most mutations have small effects. Modern biology therefore combines both views: mutation supplies variation, large and small, and selection and drift shape it gradually or sometimes rapidly.

Worked Example

Use de Vries style counting with simple numbers. Imagine growing 10,000 evening primrose plants from one parent stock, as he did on a large scale over years. Suppose 15 plants show a clearly new, stable form, such as much larger leaves and flowers, and their seeds produce the same form. The mutation frequency in this sample is 15 divided by 10,000, which equals 0.0015, or 0.15 percent. Step by step this shows two of de Vries points at once: mutations are rare (only 15 in 10,000), yet they appear suddenly and completely in one generation, without intermediates. If one such mutant also had extra chromosomes, as some primrose forms did, its offspring could be partly isolated from the parent species, illustrating how he thought a new species could begin at once. Modern geneticists would then test whether the trait is a gene mutation or a chromosomal change before accepting it as a new species.

Common Misconceptions

• Mutations are not always large or visible; most are tiny DNA changes, many with no effect at all.
• Mutations are not produced because the organism needs them; they occur randomly, and the environment only selects among them.
• De Vries did not disprove natural selection; he gave it a source of variation, though he overstated how often one mutation makes a whole new species.

Real-World Applications

Mutation breeding uses radiation or chemicals to create useful plant mutants, producing varieties such as high-yield and disease-resistant crops released worldwide. In medicine, recognising mutations explains genetic disorders and cancer, and mutation rates in viruses guide vaccine updates every season.

De Vries showed that sudden heritable mutations create new forms in one step. Refined by genetics, mutation now stands as the raw material of evolution, with selection shaping what mutations create.