In an exceptionally honest article published in 1950, Alan Turing stated that “The popular view that scientists proceed inexorably from well-established fact to well-established fact, never being influenced by any unproved conjecture, is quite mistaken. […] Conjectures are of great importance since they suggest useful lines of research” (http://www.jstor.org/discover/10.2307/2251299?uid=3738032&uid=2&uid=4&sid=21101959472393). Here I would like to tell you the story of two leaps in the dark which bridged physics and biology in order to shine some light onto important open problems in science. Ready to jump?
The relevance of interdisciplinary collaborations is now widely recognised. However, the case of physics and biology stands out when one thinks about the diverse nature of these two disciplines. Biology deals with gargantuan amounts of data and relies on a rich classification mostly drawn from empirical observations. By contrast, physicists the whole world round have been long dreaming of a unifying “theory of everything” which would explain every known physical phenomenon, linking each branch to one single trunk.
In fact, biologists and physicists looking for a common ground must face a number of challenging questions. What is the most appropriate physical theory to explain a given biological process? Once a conjecture is formed, is it possible to find evidence to support it?
While Aretha Franklin sang “Respect” and the Beatles answered that “All You Need Is Love”, 1967 was also the year of the first meeting with the rather self-explanatory title “Theoretical Physics and Biology”. There, physicist Herbert Fröhlich theoretically predicted the existence of biological coherence, a result which was to become an influential sparkle reaching as far as the field of cancer research.
What is coherence, and why should we care about it? Gather a group of people in a room and ask them to shout out loud – in a loop – a short sentence. What is likely to happen once the experiment begins is a confused superposition of voices, the message contained in the original sentence being hardly audible. Now add a few instructions: tell them to tap their feet in order to keep the rhythm, let them all face the same wall and make sure that they hold a specific note when they shout. While still being far from the ideal case, the message should become clearer: the vocal emission is now coherent – every contribution adds up to give rise to a louder, collective voice.
In this analogy the information to be transmitted is carried by acoustic waves; some biological systems seem to rely on electromagnetic radiation. Either way, the above example shows that coherence is powerful, but it depends on a number of conditions being simultaneously met: this in turn suggests that coherence is also fragile.
In 2007, an article published in Nature reported on the direct measurement of “energy transfer through quantum coherence in photosynthetic systems”, as announced in the title (http://www.nature.com/nature/journal/v446/n7137/pdf/nature05678.pdf). Further findings indicate the presence of coherent electromagnetic fields in other systems, from bacteria to cells. This evidence seems to support Fröhlich’s hypothesis, a prediction regarded as impossible in 1967 precisely because it referred to a biological environment.
Another line of research has been looking into the role that Fröhlich’s theory may play in cancer biology, namely as a factor contributing to the development of tumours. Indeed, if coherence is a biologically efficient way of processing information within molecular and gene regulatory networks in living organisms, then tumour cells may turn such mechanism to their favour. Interestingly, these studies go as far as investigating new therapies.
The physics of cancer is an uplifting example of a promising cooperative approach. However, any respectable partnership has its ups and its downs. The collaboration between physics and biology does suffer from bustling debates, and I suspect that mentioning the “hard problem of consciousness” is likely to cause a neuroscientist to frown. The story is easily told: in the nineties, Roger Penrose and Stuart Hameroff proposed that conscious cognition may derive from purely quantum mechanical effects which would take place in the microtubules of neurons. A few publications later, many researchers (from both sides) are still doubtful as to why a quantum-level explanation should be sought for in the first place: quantum laws must apply to animal and plant tissue too, yet this does not imply that a plant is conscious (http://www.sciencedirect.com/science/article/pii/S157106451200084X#). In the absence of any piece of evidence to support the Penrose-Hameroff conjecture, the hypothesis that consciousness stems from biological adaptation remains the most convincing one. Who knows what discoveries await us in the future?
These stories of interdisciplinary leaps tackle different problems and have been more or less successful to date. This highlights the complexity of many open questions in science; it also proves that opening up to a different discipline is a long, winding road which is nonetheless worth exploring. Eventually, these stories share a common message – dare (with sense, if you can)!
This article was written for a science writing prize; it wasn’t shortlisted, for which reason I thought that publishing it here would make no harm. I hope I was right!