Myth 18 - That Darwin’s Theory Would Have Become More Widely Accepted Immediately Had He Read Mendel’s 1866 Paper

Summary

Conventional wisdom has it that Darwin’s theory of natural selection needed Mendel’s theory of inheritance to become workable, and relatedly, that had Darwin read Mendel’s 1866 paper on his experiments with crossbred peas, the necessary fix would have come around 1870 rather than decades later. This chapter shows that, on closer inspection, neither of these propositions should be accepted. From Darwin’s perspective, when it came to inheritance, his theory depended only on an undoubted fact: that offspring on the whole inherit their parents’ characters. Even when a character gets transmitted in a diluted form, due to blending, the struggle for existence ensures, as Darwin saw it, that such dilution is minimal, since only organisms that vary in similarly advantageous directions will live long enough to reproduce. Against the idea that Darwin would have instantly embraced Mendel’s paper as putting inheritance on a new, theory-saving basis, thus saving evolutionary biology from decades of sterile debate, the chapter emphasizes three points: first, the similarity between Mendel’s results and ones that Darwin was already familiar with from his own snapdragon crosses; second, the differences between Mendel’s results and ones reported in 1866 by Darwin’s pea expert, Thomas Laxton; and third, Mendel’s criticisms of Darwin on whether, as Darwin believed, variation under domestication is much greater in extent than variation in the wild.