A fascinating journey into the relatively new field of epigenetics, which “has a great deal to add to the overall understanding of the history of life, beginning with the origin of the first living species itself.”
According to this outstanding account by paleontologist and astrobiologist Ward (The Flooded Earth: Our Future in a World Without Ice Caps, 2010, etc.), epigenetics is the biological revolution du jour. The author explains that Jean-Baptiste Lamarck (1744-1829), a predecessor of Charles Darwin, believed that species evolved by passing on acquired characteristics. The oft-repeated example was a giraffe stretching to reach leaves in tall trees and giving birth to offspring with longer necks. However, Lamarck was marginalized by Darwin’s teaching that acquired traits are never inherited but that children vary slightly from their parents. When a variation provides a survival advantage, its possessor produces more offspring, and this “natural selection” slowly drives evolutionary change. Yet fossil evidence doesn’t support it. “New species,” writes Ward, “appear with what seems like too much rapidity to be explained by current theory.” Bacteria routinely pass genes to neighbors, including unrelated species. Does “horizontal gene transfer” occur in complex organisms? The answer came when studies showed stretches of bacterial and viral DNA in the human genome. Biologists also knew that stressful environmental conditions change gene function. They mistakenly assumed that these changes vanish when the organism produces sex cells for reproduction. It turns out that “major environmental changes during the life of an individual can cause heritable changes to that organism, that can then be passed on to the next generation.” This defines epigenetics: a better explanation for life’s history and the quick appearance of unique body plans after mass extinctions. Skilled in both science and writing, Ward walks readers through its history, mechanisms, and the current fierce debate over its role.
The best introduction so far to one of the most controversial elements of 21st-century evolutionary science.