The inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged through use) are transmitted to offspring. It is often equated with the evolutionary theory of French naturalist Jean-Baptiste Lamarck; however, it was proposed even by Hippocrates and Aristotle. Near to Lamarck's time, the idea was commonly accepted. Comte de Buffon, before Lamarck, proposed ideas about evolution involving the concept, and even Charles Darwin, after Lamarck, developed his own theory of inheritance of acquired characters, pangenesis. The basic concept of inheritance of acquired characters was not widely rejected until the early 20th century.

Long after the triumph of the central dogma of molecular biology, which is often equated with the idea that the DNA of a cell alone determines its fate, it was the fact that the cell plasm of an egg cell, whose composition can influence the early stages of a developing embryo, is in part derived from the diploid cells of the parent, which will have a different genotype, that inspired researchers to look for examples where this is important. In a separate development, it was realised in quantitative genetics that models that included a maternal effect made more accurate predictions. Some maternal effects are acquired traits; namely, when the relevant parent's and offspring's trait are the same.

The original idea of inheritance of acquired characters has survived as a proverb, "use it or lose it".

In the 1920s, Harvard University researcher William McDougall, studied the abilities of rats to correctly solve mazes. He found that children of rats that had learned the maze were able to run it faster. The first rats would get it wrong 165 times before being able to run it perfectly each time, but after a few generations it was down to 20. McDougall attributed this to some sort of Lamarckian evolutionary process.

Genetic Disproof

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There are many formulations of the genetic disproof, but all have roughly the same structure as the following:

1. Acquired traits do not affect an organism's genome.
2. Only the genome is passed to the offspring.
3. Therefore, acquired traits cannot be passed to the offspring.

While this proof may be logically valid, it suffers from the material fallacy of begging the question, since no one who believes in inheritance of acquired characters would believe both assumptions.

See also

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• Epigenetics
• Germ plasm theory
• Lamarckism
• Morphogenetic field
• Pangenesis

History of ideas | History of biology | Evolutionary biology