Evolution begins with a roll of the dice – a random mutation. This mutation has the potential to change the course of evolution and to determine the fate of a species. Its destiny, and the influence it has on living history, will sometimes depend on natural selection, but not always. John Tyler Bonner not only argues the importance of randomness but celebrates the part it plays in shaping our living world.
Bonner carefully navigates the reader through the important role that random processes play in evolution. This is not radical in itself. Most mutations will not affect their host one iota, and the unpredictable ebbs and flows of allele frequencies will determine their fate within a population over time.
This is where this book is incredibly useful, offering a fresh perspective for those interested (personally or academically) in evolution. Bonner steers advocates away from “ultra-Darwinism”, whereby every trait is assumed to have an adaptive function, and introduces them to other players in the evolutionary game. It is easy to misinterpret natural selection as omnipotent but to do so is to ignore other important influences in evolution, Bonner argues.
Next, Bonner makes the more provocative claim that, when it comes to natural selection, size matters. He argues that the strength of natural selection on an organism’s appearance will be dependent on size, because smaller organisms, in general, show a more selectively neutral morphology.
His rationale for this claim is that constraints imposed by more complex, interconnected developmental processes potentially restrict the role of randomness. For simple organisms, short developmental chains mean the consequence of most mutations will be obvious in the resultant offspring. However, in larger organisms mutations that occur early in development will most likely result in an unviable embryo, whereas those that occur late may become part of the mature organism but their effects will be subtler. From here, these mutations will be open to the scrutiny of natural selection.
Bonner is not hasty or harsh in his delivery, and is refreshingly honest about his battles with colleagues regarding his controversial ideas. His writing style is witty and engaging, and he comes across as a voice of experience. I imagine him as the kind of professor who makes self-doubting scientists (like me) frightened to open our mouths, in case we say something stupid and find ourselves at the receiving end of a pitying look of disappointment.
However, I am an experimental evolutionary biologist, and although his arguments are convincing, I find myself resorting to the playground taunt of “Oh yeah? Prove it!”. I cannot really argue against the evidence presented before me, but equally, in the absence of robust evidence, I cannot really unequivocally accept it either. Perhaps this quality can be considered a strength of the book: it will undoubtedly create lively debate, and Bonner throws down the gauntlet to other scientists to take on the challenge of finding experimental evidence to support, or refute, his claims. Not that I’m volunteering.
Randomness in Evolution is not just another book about why size matters. Bonner is not arrogant or haughty; he is refreshingly modest and humble in his reasoning. He gives the reader the freedom to decide based on his carefully selected arguments; it seems, without judgement or ridicule. As Bonner himself puts it, the evidence he presents is another just-so story like all the others – the only difference is that in his story, randomness is the protagonist and natural selection plays only a supporting role.