Jim Kozubek in Nautilus:
Johann Wolfgang von Goethe, the 18th-century poet and philosopher, believed life was hardwired with archetypes, or models, which instructed its development. Yet he was fascinated with how life could, at the same time, be so malleable. One day, while meditating on a leaf, the poet had what you might call a proto-evolutionary thought: Plants were never created “and then locked into the given form” but have instead been given, he later wrote, a “felicitous mobility and plasticity that allows them to grow and adapt themselves to many different conditions in many different places.” A rediscovery of principles of genetic inheritance in the early 20th century showed that organisms could not learn or acquire heritable traits by interacting with their environment, but they did not yet explain how life could undergo such shapeshifting tricks—the plasticity that fascinated Goethe.
A polymathic and pioneering British biologist proposed such a mechanism for how organisms could adapt to their environment, upending the early field of evolutionary biology. For this, Conrad Hal Waddington became recognized as the last Renaissance biologist. This largely had to do with his idea of an “epigenetic landscape”—a metaphor he coined in 1940 to illustrate a theory for how organisms might regulate which of their genes get expressed in response to environmental cues or pressures, leading them down different developmental pathways. It turned out he was onto something: Just a few years after coining the term, it was found that methyl groups—a small molecule made of carbon and hydrogen—could attach to DNA, or to the proteins that house it, and alter gene expression. Changing how a gene is expressed can have drastic consequences: Every cell in our body has the same genes but looks and functions differently only due to the epigenetics that controls when and how genes get turned on. In 2002, one development biologist wondered whether Waddington’s provocative “ideas are relevant tools for understanding the biological problems of today.”