If you ever count the segments on a centipede, you’ll find there’s always an odd number of them. This isn’t because that’s what the genetic code of each species says must happen; it’s because the processes behind a centipede’s development constrain what is possible.
According to a growing number of researchers, the standard story of the influence of genes is overblown. So many other factors influence how we turn out as individuals and how we evolve as a species that the fundamentals of biology need a rewrite. “This is no storm in an academic tearoom,” a group of biologists wrote in the journal Nature in October. “It is a struggle for the very soul of the discipline.”
An organism’s environment is another complicating factor. Shape, for instance, is supposed to be genetically determined in fish. However, a trip to Lake Malawi has shown how shallow that idea can be. The lake’s cichlid fish are genetically unique, yet some species look a lot like those in the nearby Lake Tanganyika. Their big, pouting lips and protruding foreheads seem to be a result of environmental pressures and developmental pathways and not genetic instructions.
The shape of a sycamore leaf, too, is determined only in part by genetics. The chemistry of the soil the tree is growing in, even just its wetness, affects the outcome. And wetness matters to commodore butterflies: they emerge from the chrysalis orange in the dry season and blue in the rains.
So, life is complicated. Random mutations in DNA play a role but so do plenty of other factors. What’s fascinating is that even those random mutations are more complex than we thought: some may be driven by the most fundamental processes in the universe.
At the cutting edge of physics, researchers believe that quantum uncertainty, a kind of blur at the root of physical processes, brought the cosmos into being. Our advanced engineering tools exploit this uncertainty to make lasers, silicon chips and all the gadgets of the 21st century. And at the cutting edge of biology, the same phenomenon is being held partly responsible for driving evolutionary change.
That’s because some genetic mutations result from a seemingly innocuous misplacement of protons within the DNA molecule. Protons are one of the constituents of atomic nuclei and are able to exploit quantum phenomena such as uncertainty. They don’t have to be in just one place, for example; a single proton can exist in two different places on the molecule. Until, that is, the cell’s molecular machinery arrives to read the instructions encoded in the DNA. This action forces the proton into one place or the other, an action that will, in some outcomes, bring about mutations in the DNA’s structure.
The Surrey University geneticist Johnjoe McFadden was the first to suggest that biology may exploit this peculiarity of quantum physics. It may be, he says, one of many quantum tricks at work in the living world. He has outlined the possibilities in a new book, Life on the Edge, co-written with the theoretical physicist Jim al-Khalili. The pair believe that animal migrations, photosynthesis, the sense of smell and a slew of other everyday phenomena might be quantum at heart.
The idea of a quantum aspect to biology was first suggested by Erwin Schrödinger in his 1944 book What is Life? This inspired the physicist Francis Crick to move into biology and led to his 1953 discovery, with James Watson, of the structure of DNA. After that, few paid quantum biology much attention. However, with biologists facing uncertainty about what lies beneath their discipline, Schrödinger’s idea may be about to rise again.