Lifestyle in the sperm: there is growing evidence that epigenetic marks can be inherited. But what is the nature of the information they store and over how many generations do they prevail?

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More than 200 years ago, Jean‐Baptiste Lamarck (1744–1829) proposed a theory for the major question in biology: How do organisms change over time to adapt to their environment and create new species? Lamarck reasoned that if an organism changes to better adapt to its environment, these changes would be passed on to its offspring, and this would explain changes over generations. He was eventually refuted, however, by Charles Darwin's theory of evolution by natural selection, and Gregor Mendel's genetics, which explained how random mutations, not adaptive changes, generate diversity. The discovery of the structure of DNA, which mechanistically explained inheritance and mutations, finally moved Lamarck's theory to the huge pile of disproven scientific hypotheses. Recent research has re‐opened a debate about Lamarck, however, as so‐called epigenetic inheritance—based on reports that stress, nutrition, toxins, and infections not only affect an individual's behavior, body weight, and health and defense system, but also that of its offspring—goes some way to rehabilitating his theory. “A Revolution in Evolution: A Return to Lamarck?” wrote Gregg Henriques, Professor of Psychology at James Madison University, in December last year on the blog of Psychology Today (http://www.psychologytoday.com/), while Science magazine asked whether the discovery that epigenetic changes can be inherited is “evolutionary heresy” [1]. In reality, epigenetics does not really challenge our basic model of evolutionary inheritance, founded on the work of Darwin and Mendel, but it does add some important features to the model, and research into epigenetics and whether such epigenetic marks are heritable is expanding rapidly. Generally, epigenetics is the study of heritable changes in gene regulation that are not a result of changes to the underlying DNA sequence. Mechanisms that produce such changes include chemical modifications to the DNA, such as DNA methylation, or to proteins associated with the DNA (such as histone …