What Alters Our Genes
Was a 'fraud' really a discovery?
For a time, it was the most famous fraud in biology. From 1906 to 1923, Austrian biologist Paul Kammerer reported remarkable results in experiments with the midwife toad. Highly unusual for an amphibian, Alytes obstetricans mates on land, not water, and the males incubate the eggs on their legs, also on land. But when Kammerer housed midwife toads in a hot, dry terrarium, they spent most of their time in a nearby basin of cool water: they mated there, and mom deposited the eggs there rather than having dad carry them. It was odd enough that so intrinsic (and eponymous) a behavior was so malleable. But Kammerer found something else.
Once the tadpoles grew up—and here is where eyebrows all over European science shot up—they mated and deposited their eggs in water. Dads no longer midwifed eggs, even when they did not live in desert conditions. By the fourth generation, Kammerer reported, male toads even had black "nuptial" pads, a trait water-mating toads have (to grasp a female) but midwife toads do not. Thus did Kammerer demonstrate the inheritance of acquired characteristics, the then- and still-discredited idea that a new behavioral trait (such as reproducing in water) or anatomical one (nuptial pads) can be environmentally induced and passed on to progeny, despite the progeny's never having been exposed to that environment.
Other scientists were dubious. This was before the discovery that DNA is the molecule of heredity, but basic Darwinian and Mendelian theory held that traits are inherited intact from mom and dad, and that the experiences a parent has cannot alter the genetic material in eggs and sperm. Indeed, one of Kammerer's critics found that India ink had been injected into a toad, creating faux nuptial pads; on Aug. 7, 1926, a paper in Nature suggested that Kammerer had committed fraud. Six weeks later, he committed suicide. Arthur Koestler made the saga the subject of his 1971 book, The Case of the Midwife Toad.
Despite attempts here and there to restore his reputation, Kammerer's name became synonymous with science fraud. But in a fascinating new analysis, biologist Alexander Vargas of the University of Chile reaches a far different conclusion: that Kammerer was in fact the discoverer of a phenome-non called epigenetics, in which genes are silenced by—and here I'm simplifying, but only a little—experience. "Rather than being a fraud," says Vargas, "Kammerer could be the true discoverer of non-Mendelian, epigenetic inheritance."
Epigenetics is a booming new field that studies how genes are turned on and off. At the molecular level, that can happen when a cluster of four atoms called a methyl group attaches to a gene, silencing it. What's so fascinating about epigenetics is that it may explain how the life we live can reach into our double helix and alter our traits. For instance, when rat moms lick and groom their pups, it removes DNA silencers from genes that, allowed to sing, cause the pups to become curious and sociable. Epigenetic mechanisms may also explain why identical twins, who inherit identical genes, have different traits, including genetic diseases: the different lives the twins lead cause some disease genes, including those linked to cancer and schizophrenia, to switch off.
It turns out that when eggs, including those of amphibians, spend time in water—as did those of Kammerer's midwife toads—the DNA within undergoes a wave of methylation, turning some genes on and others off. If one such set of genes carries instructions for living on land and midwifing eggs, then turning it off would cause the toad to revert to a classically amphibian way of life, reproducing in water, as Kammerer found. Genes for living on land seem to get "environmentally silenced in early embryos exposed to water," says Vargas, who combed through Kammerer's lab notes and whose analysis appears in the Journal of Experimental Zoology. "It has taken a painfully long time to properly acknowledge that environment can influence inheritance," he told me. "I think academia has discouraged experiments testing environmental modification of inheritance," because the inheritance of acquired characteristics—Lamarckism—drives the self-appointed evolution police crazy.
They might want to spend more time reading studies and less energy manning the barricades.