This is the second of a two-part review where I am revisiting the idea that evolution by natural selection is not a process that will always result in perfect adaptations. I first touched on this back in 2019 when reviewing Daniel S. Milo’s Good Enough which, as per its title, argued that evolution does not care for perfection: good enough to survive will do just nicely. Having previously reviewed Andy Dobson’s witty Flaws of Nature, I am now turning to Telmo Pievani’s Imperfection: A Natural History which offers an altogether more erudite take on the topic.

Imperfection: A Natural History, written by Telmo Pievani, published by MIT Press in October 2022 (hardback, 164 pages)

Pievani is an Italian evolutionary biologist and science philosopher, holding a full professorship in the philosophy of biological sciences at the University of Padua. Author of over 30 books in Italian, some of which have been translated into English and other languages, he is also a columnist and essayist for several newspapers and scientific magazines, and an active science communicator. Imperfection was originally published in Italian in 2019 as Imperfezione: Una Storia Naturale by Raffaello Cortina Editore. MIT Press published it in English in 2022, courtesy of the late Michael Gerard Kenyon, a professional translator in the fields of biology and medicine who lived in Italy for nearly four decades. Anthropologist Ian Tattersall provides a brief foreword. This book has been on my radar for some time, and the publication of Flaws of Nature was the push I needed to finally read it.

Whereas Dobson’s book argues that natural selection becomes more interesting by focusing on its flaws, Pievani words it even stronger: “Naturalists wanting to understand how evolution works must look for imperfections, for useless and vestigial traits” (p. 144). After an opening chapter on the cosmological imperfections that allowed there to be a universe in the first place, with matter that ended up concentrated in stars and planets, the remainder of the book focuses on the natural history part. A guiding principle is that hindsight is definitely not 20/20. In a strident section titled “Let’s Kill Hindsight”, Pievani writes that it “makes anomalies seem necessary and complete, and therefore perfect even though they are not” (p. 10), and that “Hindsight is a poison. Let’s get rid of it” (p. 12). Drawing on Roman poet and philosopher Lucretius’s notion of clinamen (turning points that are unpredictable regarding what preceded them and decisive for what is to follow), he reasons that evolution can be better understood by looking for such critical junctures and the countless alternatives that could have been.

“The beauty of […] constraints is that, rather than posing a problem for the theory of evolution, they provide “confirmation of the universal common descent of all living beings“.”

In seven chapters and a mere 150 pages, Imperfection is a quick, slick, yet erudite read that posits six laws of imperfection, with some of these ideas later also mentioned by Dobson.

1) Contingencies: Chance events such as genetic drift or a rapidly shifting climate can modify the rules of the game, changing traits from beneficial to burdensome. The Irish elk with its giant antlers had the energetically costly strategy of regrowing them every year. This is permissible in a stable environment but may well have become prohibitive during the rapid climatic changes at the end of the last Ice Age. Pievani adds a few caveats to be mindful of: “In the incessant tug-of-war between laws and chance, contingency can manifest itself to different degrees” (p. 8). Furthermore, “imperfection and contingency do not imply a supreme and unrepeatable improbability” (p. 14); sequences of historical events are not necessarily unique or somehow special.

2) Compromises: Traits often cannot attain perfection due to trade-offs between different selective pressures. Many sexually selected traits strike a compromise between survival and sex appeal. The peacock’s tail is a frequently cited example but Flaws of Nature discussed others, such as swordtail fish and stalk-eyed flies. Pievani puts it nicely: “Evolution represents an ongoing dilemma” (p. 43).

3) Constraints: Historical, physical, structural, and developmental constraints can all limit by how much traits can evolve. Since evolution cannot go back to the drawing board and start from scratch, we end up with e.g. the sinuses in our face having their drainage openings at the top rather than the bottom, leading to them constantly clogging with mucus. This configuration made sense for our quadrupedal ancestors, but not for bipedal primates. The beauty of these constraints is that, rather than posing a problem for the theory of evolution, they provide “confirmation of the universal common descent of all living beings” (p. 54).

4) Repurposing: Evolution’s tendency to repurpose existing traits means that imperfect structures are actually common. Also known as exaptations, this one was discussed at length in Some Assembly Required. Stephen Jay Gould wrote about the panda’s second thumb (a repurposing of the sesamoid bone in its hand) that it uses while feeding on bamboo. Pievani pithily concludes that “Nature does not make plans, it finds solutions” (pp. 61–62).

5) Excess: Pievani dedicates a whole chapter to junk DNA, what it does, and whether the concept has run its course. Introduced elements and gene duplications provide excess material that can mutate without much risk, and possibly acquire a useful new function in the process. An example discussed here is the protein osteocrin which is expressed in the bones of mice and plays a role in neocortex development in primates. Pievani summarizes this law thusly: “excess, if it can be tolerated, is a source of change because evolution involves the transformation of the possible” (p. 82).

6) Inertia: When environments change faster than organisms can, they start running behind and become imperfectly adapted. Humans, in particular, are starkly maladapted to the modern world they have created for themselves. Pievani concludes that “evolution is a constant struggle between the available material […] and the ever-changing environment around us” (p. 118). For “environment” you can also read “another organism”, resulting in the famous Red Queen hypothesis coined in 1973 by Leigh Van Valen which explains arms races in nature, whether between predators and prey, parasites and hosts, or plants and pollinators. Dobson discussed these as well in Flaws of Nature, adding the insight that selection pressures in such arms races are often unequal, meaning that one side always has the evolutionary advantage.

“Evolution’s tendency to repurpose existing traits means that imperfect structures are actually common. […] “Nature does not make plans, it finds solutions“.”

The presentation of these six laws uses quite a lot of examples from human biology (I recognized many from reviewing Human Errors). Our DNA and brains both resemble Rube Goldberg Machines that are so “unnecessarily complicated [that] neither would pass an engineering test” (p. 98). Pievani also discusses our many bodily imperfections and our numerous mental foibles that give rise to cognitive errors, biases, prejudices, sensory illusions, superstitions, etc.

Given Pievani’s particular interest in the philosophy of evolutionary biology, his writing betrays a well-educated background. He regularly quotes from works by other scholars, including (understandably) fellow Italians such as the aforementioned Lucretius, chemist Primo Levi, neurobiologist and senator Rita Levi-Montalcini, and geneticist Luigi Luca Cavalli-Sforza, but also evolutionary biologists such as Stephen Jay Gould and Theodosius Dobzhansky, and philosophers such as Michel de Montaigne, Bertrand Russell, and Peter Godfrey-Smith. Pievani also frequently returns to Darwin’s writings. He struggled to reconcile the fact that “nature is full of leftovers” (p. 47) with his reading of natural theology texts and the critics who objected that his theory failed to explain complex structures such as the human eye. Something I did not know was that his supporter Ernst Haeckel even suggested the term dysteleology for the study of nature’s many imperfections. And yet, despite all this high-brow source material, Imperfection remains incredibly readable with Pievani’s experience in science communication shining through. The chapters are helpfully divided into intriguingly titled subsections. This is one of those books that is hard to put down and full of well-formulated and insightful ideas.

By addressing evolutionary imperfections from different sides, Imperfection feels more full-bodied than Flaws of Nature, even as that book added its share of interesting observations not made here. As such, it is a very nice follow-up if you started simple and want to go deeper. Those with a background in evolutionary biology or an interest in the history of science should not be afraid to jump straight in at the proverbial deep end. This is the first of Pievani’s books that I have read and, for me, establishes him as a notable thinker and writer whose other works I will look out for. For this, however, I will have to continue to rely on the commendable work of publishers such as MIT Press who carefully select and translate the best non-English scientific literature for the monoglot masses.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Imperfection

Other recommended books mentioned in this review:

__________________________________________________________________

__________________________________________________________________

“Biology’s First Law: The Tendency for Diversity & Complexity to Increase in Evolutionary Systems“, written by Daniel W. McShea and Robert N. Brandon, published by the University of Chicago Press in August 2010 (paperback, 170 pages)

The authors dive right in with some definitions, and to discuss this book it will be helpful to repeat these. If you have an evolutionary system, and you assume variation and heredity, then diversity and complexity will on average increase, unless other forces, e.g. natural selection, constrain or override this tendency. The authors give two definitions and point out they do not consider the ZFEL a new discovery. Rather it is a recognition of, and unifying principle for a range of findings across biological disciplines. When not subject to selection, differences tend to accumulate, both within organisms (e.g. random mutations or gene duplications leading to pseudogenes) and between them (the increasing diversity and complexity of life over evolutionary history).

McShea and Brandon quickly move to clarify what they mean with diversity and complexity. Especially the latter has a colloquial usage indicating sophistication, functionality, etc. They are not interested in this and define “pure” complexity: the number of part types making up a structure, or the degree of differentiation between parts – nothing more. And this creates a hierarchical relationship between the two: diversity at one level makes for complexity the next level up. For example, a great diversity of cells makes for a complex organism.

An important and very interesting consequence of their line of thinking is that it invites a so-called gestalt shift: a change in what is considered background and what foreground. In their view, change is the constant, with natural selection acting more to reign in the creative maelstrom generated by the ZFEL. In their final chapter, they consider how this provides a satisfying answer to the challenge often raised by creationists: how do complex structures such as eyes arise? Biologists often respond by suggesting a series of intermediate steps, each a little bit better than the last one, each selected for, which risks descending into just-so stories. But if the ZFEL creates diversity and complexity in abundance, natural selection acts more by whittling down and constraining that which is useful, meaning intermediate steps are not strictly necessary (which is not to say they do not occur, see e.g. Evolution’s Witness: How Eyes Evolved).

“The ZFEL […] provides a satisfying answer to the challenge often raised by creationists: how do complex structures such as eyes arise?”

Biology’s First Law is a brief book and throws out an interesting if provocative idea. Although the topic is rather technical and abstract, the authors do a great job keeping the reader on board, repeating important caveats where necessary, and being explicit in what they mean. Even so, some of the examples and argumentation feel, well, a bit clunky.

My first thought a few pages in was: “isn’t this just entropy?” The second law of thermodynamics states that there is a natural tendency for systems to become increasingly disordered and chaotic with time, while maintaining order takes a constant input of energy and effort. This is why stuff breaks and falls apart. The authors are adamant that it is not, and, to their credit, marshall convincing arguments (though see Cosmic Evolution: The Rise of Complexity in Nature for an example that does use entropy as an explanation). What does not help their argument, though, is that the two analogies they repeatedly use in the book (a picket fence breaking down and the wind scattering leaves in a garden) are prime examples of entropy in action.

Second, in some places the writing starts to reek of ad-hoc explanations and special pleading. They suggest that if complexity and diversity do not increase, you just need to invoke a mechanism (genetic drift, an absorbing barrier, stabilising selection) to explain why not. And any such inhibiting mechanism would not challenge the ZFEL, say the authors. Take it away and the tendency for the ZFEL to increase diversity and complexity will resume. Basically, they take the ZFEL to always be true, which does not leave much room for falsification.

“Taking the ZFEL to be true is putting the cart in front of the horse – possibly a purposeful provocation to get people thinking. For now, it is a hypothesis. “

Third, given the starting points of several of their hypothetical examples, the outcomes are self-evident: a picket fence with identical pickets, a population of initially identical organisms, a wormlike animal with identical segments. These systems are at the extreme end of morphospace (the space of possible configurations) and can only develop in one direction. What about real-life systems, in all their messy glory? Wagner’s computational work and identification of astronomically large spaces of possibility are interesting in this context (see Arrival of the Fittest: Solving Evolution’s Greatest Puzzle).

Tying in with that, despite the author’s purported humility, calling their idea a law and drawing parallels to Newton’s first law is anything but. Taking the ZFEL to be true is putting the cart in front of the horse – possibly a purposeful provocation to get people thinking. For now, it is a hypothesis. To their credit, they outline what research needs to be done to falsify their idea and they provide some interesting evidence. Some of this is not supportive and they evade this by the epistemological escape hatch I mentioned above: just find an ad-hoc constraint to invoke.

Usually I review new books, but since this is a 2010 book we can ask: what has become of this idea? I have not done an exhaustive search, but there are two noteworthy follow-up papers I immediately found. Puzzles for ZFEL, McShea and Brandon’s Zero Force Evolutionary Law was published in 2012 in Biology & Philosophy (PDF here) and raises several points of criticism, different from mine and more thoroughly developed. A Quantitative Formulation of Biology’s First Law was published only last month in Evolution (PDF here) and is a modelling exercise for discrete and continuous traits.

Biology’s First Law is a very interesting, thought-provoking book and I think the authors are on to something, but this idea needs developing. Some of the examples and arguments here are self-evident or not very strong. And I’m not yet convinced that we need a name for this, calling it “stochastic processes” or “randomness” fits the bill just fine in my view.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Biology’s First Law paperback, hardback or ebook

Other recommended books mentioned in this review: