It's not a secret that I love science and in particular, biology. I majored in biochemistry in college and have a master's in epidemiology and infectious disease. I have been reading "Microcosm: E. coli and the new science of life" by Carl Zimmer, and so I didn't expect to run across anything that reminded me of eating disorders.

But if there's one thing I love as much as biology, it's metaphors. Or, in this case, finding parallels and expectations in the most unusual of places.

Many of the complaints I've heard about the importance of biology in eating disorders has less to do about the evidence and more to do with the simple fact that people think it's deterministic and depressing. If it's biology, there's nothing we can do. We were destined to become ill, and we're always going to BE ill because it's in our genes. To me, however, biology gives me a road map out of my illness, however vague and imprecise it is (think Columbus and Magellan, not GPS). I can't escape my biology, but I can learn to live with it.

Another complaint is that if eating disorders are genetically-based, then why don't all members of a family have them. Because not everyone's genes will be turned on at the right time to create a disorder. Environment matters, and it matters a lot.

Which is where one of my latest reads comes in. The actual passage is a little long, but I've tried to edit out the parts that didn't add to the ultimate point I'm trying to make.

We are not merely the output of software written in a programming code of DNA. As we develop in the womb, our genes interact with signals from our mothers. The environment continues to influence those genes in unpredictable ways after birth. The food we eat, the air we breathe, the traumas and joys and boredom of childhood, and all the rest have an influence on which genes become active...

Surely E. coli must be all nature and no nurture. A colony descended from a single ancestor is just a billion genetically identical cousins, their behavior all run through the same genetic circuits. E. coli is just a single cell, after all, not a body made of a trillion cells that take years to develop. E. coli doesn't grow up going to private school or searching for food on a garbage dump. It doesn't wonder whether it might like snails for dinner. It's just a bag of molecules. If it is genetically identical to another E. coli, then the two of them will live identical lives.

This may all sound plausible, but it is far from the truth. A colony of genetically identical E. coli is, in fact, a mob of individuals. Under identical conditions, they will behave in different ways...

There's much to be learned about E. coli by thinking of it as a machine with circuitry that follows the fundamental rules of engineering. But only up to a point. Two Boeing 777s that are in equally good working order should behave in precisely the same way. Yet if they were like E. coli, one might turn south when the other turned north.

The difference between E. coli and the planes lies in the stuff from which they are made. Unlike wires and transistors, E. coli's molecules are floppy, twitchy, and unpredictable. They work in fits and starts. In a plane, electrons stream in a steady flow through its circuits, but the molecules in E. coli jostle and wander...[This jostling] can produce long-term differences between genetically identical bacteria...Two genetically identical E. coli can respond differently to the same level of lactose because they have different histories...

At the very least, E. coli's individuality should be a warning to those who would put human nature down to any sort of simple genetic determinism. Living things are more than just programs run by genetic software. Even in minuscule microbes, the same genes and the same genetic network can lead to different fates.

Considering that I spent several years studying E. coli in college, I find these things fascinating. If we consider something like bacteria to be "simple," or at least simpler, with significantly fewer genes and much smaller than even a single one of our cells, and they are markedly affected by their environments, imagine how the environment acts on us. In biology, nothing is simple and easy.