Virginia Hughes in Nature:
Biologists first observed this 'transgenerational epigenetic inheritance' in plants. Tomatoes, for example, pass along chemical markings that control an important ripening gene2. But, over the past few years, evidence has been accumulating that the phenomenon occurs in rodents and humans as well. The subject remains controversial, in part because it harks back to the discredited theories of Jean-Baptiste Lamarck, a nineteenth-century French biologist who proposed that organisms pass down acquired traits to future generations. To many modern biologists, that's “scary-sounding”, says Oliver Rando, a molecular biologist at the University of Massachusetts Medical School in Worcester, whose work suggests that such inheritance does indeed happen in animals3. If it is true, he says, “Why hasn't this been obvious to all the brilliant researchers in the past hundred years of genetics?”.
One reason why many remain sceptical is that the mechanism by which such inheritance might work is mysterious. Explaining it will require a deep dive into reproductive biology to demonstrate how the relevant signals might be formed in the germ line, the cells that develop into sperm and eggs and carry on, at a minimum, a person's genetic legacy.
A mother might pass on effects of environmental exposures to a fetus during pregnancy. So, to study the phenomenon of transgenerational epigenetics cleanly, biologists are focusing on fathers, and have been looking at how sperm might gain and lose epigenetic marks. “In the past two to three years there's been a lot of new information,” says Michelle Lane, a reproductive biologist at the University of Adelaide in Australia. But proposals for how it all works are themselves embryonic. “It's a huge black box,” Lane says.