Why I’m sceptical about the idea of genetically inherited trauma

Ewan Birney in The Guardian:

ScreenHunter_1383 Sep. 23 17.37Recently, the Guardian published a story based on a scientific paper that claimed the stress experienced by Holocaust survivors somehow was detectable in their children through a process known as epigenetics. The paper was riddled with flaws: the scientists studied blood, which is a mixture of cell types, meaning there are any number of causes for the changes reported. The scientists only looked at a tiny subset of genes. They had an absurdly small sample size of 32 people, a tiny eight-person control group, who didn’t really look like good controls, and produced a contorted argument for why their data supported their original hypothesis. The paper probably shouldn’t have made it through to the scientific literature, and it certainly shouldn’t have made it to your Saturday breakfast reading. I don’t believe it and I’ll outline some reasons why below.

The scientific paper and newspaper story point to a rising interest in epigenetics. This is a seductive but rather slippery word that has come to mean a variety of things in relation to how molecular structures close to DNA work, in particular modification of DNA bases by methylation. It is certainly exciting, and has become a leading mechanism to explain how the environment communicates with our genes. But it’s also easy to oversimplify, and has been set up by some people as an inaccurate alternative to genetics.

Coined before the discovery of DNA as the source of genetic information, the word “epigenetics” is now used in two way. Firstly, it can mean the ways in which modification or packaging of DNA results in the transmission of information within a group of cells. This is a well-established, evidence-based theory. However the second usage refers to the ways in which the modification or packaging of DNA might result in the transmission of information from one generation of people to the next, a theory for which there is not currently much evidence and which is therefore not well-established.
More here.