Physicists are serial offenders when it comes to cross-disciplinary meddling. Whether it’s a theoretical cosmologist claiming to solve consciousness or a professor smugly claiming all other sciences are “soft”, physicists are too often quick to pass judgement on other fields. So, I’m a little worried about coming off that way when I criticize a bad habit in biology of referring to the “dark matter of the genome” or other similar phrases.
Dark matter is a mysterious thing, to be sure: it’s an unknown type of matter entirely transparent to light that constitutes about 80% of all mass in the Universe. However, that’s not to say we know nothing about it. The name “dark matter” may be a placeholder for our ignorance, but the concept is not. The problem with the “dark matter of the genome” or what have you is that it uses “dark matter” to mean something we see, but don’t know what it does. That’s almost the conceptual reverse of what it means in physics. After all, the “dark matter” in genes is still part of DNA
are still genes: still part of the code geneticists have learned to read, even if the function isn’t clear. Researchers can see it and map it, just like other genes. [Update: corrected for clarity and accuracy – see comment below.]
By contrast, we know dark matter is there because of its influence on galaxies and galaxy clusters. We see its presence in the cosmic microwave background and baryon acoustic oscillations. Though we don’t know its identity, dark matter seems to be a particle, and we can even make concrete statements about possible mass ranges. It’s not the same stuff as ordinary matter, and its very invisibility is part of what makes it complicated.
I’m no geneticist. Genetics is a closed book to me, and I haven’t needed to understand it beyond a cursory level. (High school biology inevitably never got much beyond Mendel and his peas, and a bit about Drosophilia.) That’s OK: I trust my geneticist colleagues, and I get the gist of what they write. If I ever needed to delve into it more deeply, I like to think I’m smart enough to learn. I don’t presume to tell biologists how to study their topic (the very idea is frightening anyway). However, I really would like to see an important concept in physics not be misapplied. From what I can glean, the “dark matter of the genome” is an important subject, one worthy of something better than what amounts to a really bad metaphor.