Shadows on the Cave Wall: a new theory of evolution – Keith Skene ***

Anyone claiming to have a new theory of evolution had better have good credentials, field experience, and a thorough knowledge of biology. Otherwise they are probably a crackpot. Keith Skene has these qualities, and Shadows on the Cave Wall is not the work of a crackpot. Indeed, for breadth, thoughtfulness, and a kind of happy-go-lucky charm, the book is a real treasure. But its aspirations – to replace evolution by natural selection with a new theory grounded in physics – are well beyond its powers of persuasion.

Skene’s key idea is that the long- and short-term dynamics of living things can be best understood in terms of the flow of energy into, out of, and within different levels of biological organisation. The levels of organisation that interest Skene are proteins, individuals, populations, communities, and biomes. Notably absent from this list are genes and species, which Skene rejects along with evolution by natural selection.

Drawing on Plato’s metaphor of the cave, Skene argues that energy is the “sun” that lies behind all of the biological activity we see in the world, while everything from the gene to the biosphere are merely “shadows on the cave wall”, the outward effects of energy. It may seem that Skene’s focus on physics is reductionist. Banish the thought. By focusing on physics, Skene does not mean that biological phenomena are simply consequences of atom-level laws. He means that they are driven by the macroscopic laws of thermodynamics. Once we have seen this, he argues, we can see that no level of organisation – proteins no more than populations – is more “basic” than the others.

The payoff for this theory, says Skene, is closure on some key issues in evolutionary biology, including altruism, life on other planets, and the social behaviour of animals. But the “most radical implication” of the theory is a new way to save the environment from human exploitation – a path to salvation that, as Skene puts it, “has nothing to do with carbon.”

It turns out that the solution is not as new or radical as the 250-page build-up suggests. Skene points out that the problem underlying climate change is our excessive reliance on energy, especially in the food sector. He describes the environmental damage caused by artificial fertilisers and lists some ways to minimise this damage – from eating less meat to planting a border of nutrient-loving plants around crop fields. Not everyone would agree with these ideas, but no-one would call them ground-breaking.

For this reader, Skene’s energy-based theory also ended in anticlimax. Few people would deny that biological processes obey the laws of thermodynamics (otherwise they would be shoddy laws). So the big question is whether Skene can use those laws can enrich our knowledge of biological phenomena. Skene undoubtedly gives rich accounts of biological phenomena, notably an account of how different levels of organisation interact with one another. But it is unclear just how much these accounts owe to the Skene’s overarching energy theory. For example, one does not need Skene’s theory of energy to understand why an excess of nutrients in an ecosystem can harm the community. At other times, Skene seems to use “energy” to refer simply to the common notion of biological resources, as in: “it is the resource distribution that determines how many organisms can live in a given area, and, therefore, what kind of social group can form.”

Fortunately, many of the ideas in the book do not rely on the energy theory to be interesting. For example, Skene draws together a range of objections to orthodox evolution by natural selection: the fact that most organisms through history have acquired new genes not by random mutation but by horizontal gene transfer (HGT, the absorption of genes from other organisms); the notion that empty niches, rather than competition for an occupied niche, is the main driver of speciation; and others. The case against Darwinian evolution could certainly be more tightly argued. It is not clear, for example, whether HGT provides a real alternative to natural selection, or just a new source of genetic variation upon which natural selection can act. And there is not enough room in one volume for Skene to do justice to his other arguments, or (just as importantly) to address objections to those arguments.

Shadows is best read not as an argument but as an adventure, a fast-paced ride through key ideas in evolution and ecology. Skene has an unusual style, mixing anecdotes and chirpy asides with earnest contemplation of the big questions. Here he is describing a species of wildebeest that breeds only in December and January: “if a wildebeest set up a greetings card shop, the business would only run for a very limited time: extremely seasonal employment when Christmas cards and birthday cards would be for sale for only one month of the year!” The effect is bizarre but disarming.

On the whole, the Shadows experience is less like reading a book than watching a lecture by a keen and knowledgeable, but slightly eccentric, professor: personal, chaotic, insightful, and unfailingly fun.

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Review by Michael Bycroft