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Lamarck and the Inheritance of Acquired Characters
When a field that uses “evolution” in the descent sense finds that what it passes on was not produced blindly, the word it reaches for is “Lamarckian”. The word names one idea, the inheritance of characters acquired in a lifetime, and one of the oldest disputes in the theory of descent.
Lamarck’s theory and the name
Jean-Baptiste Lamarck’s Philosophie zoologique (1809) made the inheritance of acquired characters the engine of the transformation of species: changed circumstances change needs, needs change habits, habits strengthen or weaken organs, and what is gained or lost is preserved in the offspring. The idea was not his. It had been assumed for some two thousand years before him, and what attached his name to it was the use he made of it. The first English application of “evolution” to species, in Lyell’s Principles of Geology (1832), is a hostile summary of Lamarck (see The word).
Darwin’s own use
The inheritance of acquired characters was not what divided Lamarck from Darwin. The Origin (1859) lists “use and disuse, combined with natural selection” among its laws of variation, and gives the inherited effects of habit a subordinate place beside natural selection. The Variation of Animals and Plants under Domestication (1868) supplied a mechanism in pangenesis: the cells of the body throw off particles, gemmules, which collect in the reproductive organs and carry the body’s modifications to the next generation. What Darwin rejected in Lamarck was the tendency to progression and the part he read as animals’ willing, not the heritable effects of use. Spencer held the inheritance of acquired characters more strongly still, and defended it against Weismann.
Weismann’s barrier
August Weismann made the question sharp. His germ-plasm theory, set out through the 1880s and in Das Keimplasma (1892), separated the hereditary material of the germ cells from the body that carries it: the body is built from the germ plasm, and nothing that happens to the body passes back. His experiment of cutting the tails of mice over five generations produced no offspring with shortened tails (1889).
The exchange that followed set the terms for a generation. Spencer and Weismann argued it out in 1893, and neither moved. George Romanes named the Weismannian position neo-Darwinism; Alpheus Packard named its opponents neo-Lamarckians. In the United States the palaeontologists Edward Drinker Cope and Alpheus Hyatt read directed trends in the fossil record as the work of use and effort, and through the decades that Julian Huxley later called the “eclipse of Darwinism” the inheritance of acquired characters was a leading alternative to selection. The integration of Mendelian genetics and the Modern Synthesis left it without a place: the gene was the unit of heredity, and genes did not record what the body had done.
Absorbing the appearance
Part of the Darwinian answer was to explain Lamarckian-looking results without Lamarckian inheritance. In 1896 James Mark Baldwin, and in the same year Lloyd Morgan and Henry Fairfield Osborn, proposed that behaviour learned in a lifetime can steer selection, so that inborn variations which reproduce the learned adaptation are favoured and the adaptation becomes hereditary without anything acquired being inherited. George Gaylord Simpson named it the Baldwin effect in 1953, the same year C. H. Waddington reported genetic assimilation: a response induced by heat shock in fruit flies appeared, after selection, without the shock.
Kammerer and Lysenko
The claim’s twentieth century had two cases remembered for more than their science. Paul Kammerer’s report that midwife toads acquired and passed on nuptial pads collapsed in 1926, when the pads on the surviving specimen proved to be India ink. In the Soviet Union Trofim Lysenko’s Michurinist biology, teaching that plants inherit characters acquired under changed conditions, was declared official doctrine in 1948, and genetics was suppressed until the mid-1960s.
Epigenetics
The word returned to biology with epigenetic inheritance, the passing on of states of gene expression, through DNA methylation and other marks, without change to the DNA sequence. Eva Jablonka and Marion Lamb’s Epigenetic Inheritance and Evolution: The Lamarckian Dimension (1995) and Evolution in Four Dimensions (2005) take the label on deliberately, with genetic, epigenetic, behavioural and symbolic inheritance as four systems. Whether such marks persist long enough to matter for evolution, or are reset each generation, is argued under After the synthesis.
The word in other homes
Outside biology “Lamarckian” is usually a placement a field makes of itself. Stephen Jay Gould, in “Shades of Lamarck” (1979, collected in The Panda’s Thumb, 1980), put it directly: “Human cultural evolution, in strong opposition to our biological history, is Lamarckian in character. What we learn in one generation, we transmit directly by teaching and writing.” Richard Nelson and Sidney Winter’s An Evolutionary Theory of Economic Change (1982) casts routines in the role of genes and states that “our theory is unabashedly Lamarckian: it contemplates both the ‘inheritance’ of acquired characteristics and the timely appearance of variation under the stimulus of adversity.” John Ziman’s Technological Innovation as an Evolutionary Process (2000) asks whether design makes invention Lamarckian rather than Darwinian, with Jablonka contributing the biological models, and Joel Mokyr’s chapter there finds the biological paradigm too limiting for technology because “in nature there is no feedback from the manifest entity to the underlying structure.”
Whether inheritance of this kind is decisive for how these fields should be modelled is argued under Cultural extensions of Darwinism.
See also: Evolution (the subject landing) · The word · The criterion · Lamarck · Darwin · Spencer · Integration with genetics · After the synthesis · Cultural extensions