Statistical Physics in Biology

In which areas of biology can statistical physics be applied? What is the problem of associating phenotype and genotype? Professor of Health Sciences and Technology and Physics at Massachusetts Institute of Technology, Leonid Mirny, tells how statistical approaches are applied across life sciences.

There is no unified statistical theory of biology, and I doubt there ever will be any. Nevertheless, I believe that statistical physics is very helpful in thinking about biological phenomena, primarily because biological phenomena are A) stochastic, so randomness plays a huge role and B) they’re lots of players in biological systems. These players can be many molecules in a body, this can be many cells in a human body, or this can be many organisms in a population. Again, the two underlying things are stochasticity and the large number of players.

The field of biology that really lives above all the complexity of molecular interactions is genetics. Genetics is interested in the emergence of new sorts of, say, mutations and then how these mutations spread in the population. For example, you have a population of white mice and then one of them becomes grey, and now you have grey mice which are able to better hide within their environment. So, the grey would spread in the population. That’s an evolutionary process and the field of biology that deals with this is genetics, or population genetics. So population genetics is generally interested in this kind of collective phenomena.

If you look at certain processes, like a developmental process: you had one cell, becomes two cells, four cells, then it acquires a sort of shape, and these cells form body parts. So, it’s a very reliable process, despite some underlined stochasticity. So statistical physical is certainly interested in this process. It may be reminiscent of some of the features, for example, of condensation of water, where initially very disordered system, each molecule is still sort of fluctuating and jiggling independently, though it will all end up being a snowflake, a very regular, very structured beautiful organization.