The inheritance of acquired characteristics
Jean-Baptiste Lamarck gets a bad rap. The French naturalist proposed in the early 1800s that organisms could pass on traits they acquired during their lifetime. A giraffe stretches its neck to reach higher branches, and its offspring inherit longer necks. An animal stops using a limb, and future generations have smaller ones.
Darwin and Wallace came along with natural selection, and Lamarck became a punchline. The discovery of DNA seemed to close the case entirely: traits pass through genes, not through whatever the parent experienced.
Except it's not that simple.
Epigenetics has complicated the picture. Environmental factors can influence how genes are expressed, and some of these changes can be inherited. A parent's diet, stress levels, or chemical exposures can affect their children and even grandchildren, not by changing the DNA sequence, but by changing which genes get turned on or off.
It's not quite what Lamarck imagined. Stretching your neck won't give your kids longer necks. But experience can leave biological marks that outlast a single generation. Lamarck was wrong about the mechanism but not entirely wrong about the idea.
Science textbooks love a clean narrative: Lamarck was wrong, Darwin was right, case closed. Reality is messier.
Further reading:
- A.S. Packard, Lamarck, the Founder of Evolution (Project Gutenberg)
- Stephen Jay Gould, The Structure of Evolutionary Theory
- Eva Jablonka and Marion J. Lamb, Evolution in Four Dimensions (MIT Press)
