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Why didn’t Darwin discover Mendel’s laws?

The publication of Charles Darwin’s On the Origin of Species in 1859, the 150th anniversary of which we celebrate this year, was a landmark event in the history of biology and widely noted at the time. But when, 7 years later, Gregor Mendel published his findings on the laws of inheritance, they were widely ignored. Not until the 20th century did scientists realize that the two theories were entirely compatible and put them together in what we now call the modern evolutionary synthesis.

In a fascinating paper published online this week in the Journal of Biology, geneticist Jonathan Howard of the University of Cologne ponders why Darwin, who took it as a given that natural selection acted on traits that were passed from generation to generation, didn’t scoop Mendel when he had the chance. The answer, Howard suggests, is that Darwin was focused on very small, often infinitesimal variations in plants and animals, which he saw as the raw material on which natural selection could work. Yet, as Mendel brilliantly demonstrated, inheritance is actually based on the passing on of discrete units—what today we call genes—from one generation to another.

Howard points out that Darwin had many chances to understand inheritance, but his mind was focused elsewhere. For example, Howard writes, in The Different Forms of Flowers on Plants of the Same Species, published in 1877, “Darwin wrote an entire book on a perfect Mendelian character” with “numerically precise and well-established behavior, yet he failed to extract Mendelian insights from his work.”

The article is available free online at the Journal of Biology (registration required.)