The various meanings of "understand" in science

Status: Finished
Confidence: Possible

On a mailing list, I wrote,

James Watson and Francis Crick are still spoken of in reverend tones, despite the fact that they contributed nothing, engaged in theft, set back biology by fifty years, and then spent the next few decades slandering everyone they stole from or that they thought might challenge their stranglehold.

Someone responded,

I know that W*C were a couple of pirates, but “set back biology 50 years”? Could you expand on that?

Here is my explanation:

Let me begin by talking about the word understand,” and then I promise to make my thesis precise. A field of science is defined by its meaning of “understand.” When a physicist says he understands a phenomenon, he means he has identified its relevant physical quantities and has a mathematical model that predicts the relationship among their values in all cases he can do experiments on. When a chemist says he understands a reaction, he means he knows how the change in physical properties, and the speed of that change, derive from the chemical constituents and the flow electrons, energy, and entropy. These two meanings are complementary.

Each meaning of “understand” also implies a notion of what is interesting. The elemental composition of a substance is incidental to a physicist. He wants to know why it shatters the way it does. For the chemist, shatter patterns might be a useful experimental tool, but are secondary to composition.

Biology has three natural subfields based upon different meanings of “understand”: genetics, natural history, and physiology.

A geneticist would understand curly versus straight coats for dogs if he knew under what conditions he could produce curly versus straight coats with a certain probability by breeding dogs with curly or straight coats and other, known characteristics and family histories. This meaning of “understand” makes unusual or intriguing patterns of heredity interesting, such as corn’s separate breeding types that let you grow strains mixed in the same field but have no interbreeding.

Natural history includes ecology, evolution, and archaeology. Understanding means being able to trace out the course of events, in both specific and typical cases. The exact path of evolution of the vertebrate eye; the dynamics of predator populations with seasons and prey populations; the life cycle of the malaria parasite as it cycles among mammals or birds and mosquitos: these would all be an understanding in natural history. Unusual patterns of evolution, ecology, or symbiosis, such as ring species, constitute the interesting material for this understanding.

Physiology treats the organism as a moving, functioning thing. This is where we find biophysics and biochemistry. How does the force a muscle can exert vary with how fast it must exert it? How do signals propagate in neurons? This meaning of “understand” is closest to that of physics and chemistry, yet quite distinct: the object of interest is not the physical laws or the flow of atoms and entropy, it’s the organism. The underlying chemistry and physics is usually known. In many ways, it’s like engineering, but in reverse, trying to understand rather than build. Physiologists get excited about things like the mantis shrimp’s ability to punch things at supersonic speeds or the immunological profiles induced by probiotic bacteria in hosts.

Each of these meanings of “understand” enriches the others. For example, the patterns that develop during the transition from an egg to an animal appeal to both the physiologist and the natural historian. Take any boundary – physiology/chemistry, genetics/psychology, natural history/physics – and think for thirty seconds and you’ll dream up neat problems that invoke and play upon both meanings of understand.

After that long winded introduction, I can state my thesis: molecular biology as set forth by Watson and Crick defined “understand” so as to isolate itself from all these other meanings, and it has taken the community roughly 50 years (taking Crick’s pronouncement of the fundamental dogma of molecular biology in 1958 as the starting point) to begin recovering from it.

The strict program of molecular biology begins with the statement “one gene, one protein,” that is, each trait a geneticist would breed and each causal agent in a physiologist’s models, corresponds to one protein encoded in DNA in an organism. Understanding in this program means identifying that protein and the stretch of DNA that encodes it.

Now, this is errant nonsense, and everyone realized that very quickly, so it became “one gene, a list of proteins.” And things like regulatory sites and RNAs were important, so it ended up being “one gene, a list of stretches of DNA.” To this day, the goal of a molecular biologist is to assembly a list of stretches of DNA. When a new, high throughput technique is developed, they all demand that the computer scientists, mathematicians, and statisticians figure out how to analyze all this data so as to produce a list of stretches of DNA. If you go to a molecular biology graduate program and listen to student research proposals, they nearly all propose years of labor to produce a list of stretches of DNA. Those that don’t often get reprimanded by the professors, who encourage them to figure out how to get a list of stretches of DNA.

To most people, this meaning of “understand” seems intuitively inferior to the ones we discussed earlier. Why? It’s no more arbitrary than a mathematical relation among selected variables. Where it fails is in its relation to other meanings of “understand”. It enriches no other field, nor is it enriched by any other field.

Along with slandering anyone who disagreed with them, Watson and Crick were the driving forces behind this program’s rise to dominance. There followed several generations of biologists who grew up only knowing this meaning of “understand.”

Why 50 years? Because I think there’s some cause for optimism today: