Towards a Probabilistic Theory of Life

prisme12Prisme N°12 September 2008

Thomas Heams

Prisme N°12 September 2008 (551.8 KiB)



Biology has long been dominated by a deterministic approach. The existence of a genetic code, even a “genetic programme”, has often led to descriptions of biological processes resembling finely-regulated, precise events written in advance in our DNA. This approach has been very helpful in understanding the broad outlines of the processes at work within each cell. However, a large number of experimental arguments are challenging the deterministic approach in biology.

One of the surprises of recent years has been the discovery that gene expression is fundamentally random: the problem now is to describe and understand that. Here I present the molecular and topological causes that at least partly explain it. I shall show that it is a wide-spread, controllable phenomenon that can be transmitted from one gene to another and even from one cell generation to the next. It remains to be determined whether this random gene expression is a “background noise” or a biological parameter. I shall argue for the second hypothesis by seeking to explain how this elementary disorder can give rise to order. In doing so, I hope to play a part in bringing probability theory to the heart of the study of life. Lastly, I shall discuss the possibility of moving beyond the apparent antagonism between determinism and probabilism in biology.