Per sanguinem nostrum by William S. Peters

Many of the changes that have occurred during the course of evolution are mysterious. It is an undirected process: the raw fodder for evolutionary change is what is present in the organisms alive and breeding now. Sometimes, it can be difficult to picture how it might happen. For example, four million years ago, the human chromosome 2 was formed from the fusion of two chromosomes that are still found as separate structures in the other great apes. Quite how this radical change was able to propagate is mysterious—there cannot have been any other ancestors around with the same macromutation available for breeding—yet propagate it did: we all have 46 chromosomes, whereas the other great apes have 48. The evolution of the two separate circulations seen in humans (and birds) from the single circulation of fish can be guessed at only from the comparative anatomy of extant vertebrates. Fish have a single ventricle, paired ventral aortae connected to a dorsal aorta via aortic arches (and gill capillaries). Looping of the heart tube led to the more complex three-chambered amphibian and reptilian hearts. Genetic change gradually led to septation and separation of the pulmonary and systemic circulations at least twice: in mammals and birds. Birds are, after all, reptiles of a sort and are descended from crocodilians (the only reptiles to have a four-chambered heart). Per sanguinem nostrum by William S. Peters is a most unusual book. It is beautifully produced, printed on handmade paper with illustrations from etched copper plates. It is a long time since this reviewer was provided with a pair of gloves for turning the pages of a book. The content is more unusual still. It seems to be a description of how the human circulation arose as a complex looping of the ‘primitive’ fish heart. It suggests that a major driver of change comes from changes in the magnetic properties of haemoglobin as it binds oxygen: the iron in haemoglobin is paramagnetic (as is molecular oxygen in its usual triplet configuration), but oxyhaemoglobin is diamagnetic. Quite how this change alters the structure of the circulation is not immediately clear and does not come overburdened with evidence. It seems that ‘a slip of oxygenated gill blood’ mysteriously ‘short circuits the dorsal aortic passage’, and the mixing of diamagnetic and paramagnetic streams of blood somehow sets in motion the evolution of the circulation. I confess that I was unable to follow the chain of argument: the language seems to strive towards the mystical and parapoetic (‘with environmental change as a catalyst, the higher entropy hybrid electron carrier circuit evolves towards a new parity’) and contains little in the way of straightforward exposition. It is difficult to believe that the magnetic properties of streams of blood matter much—the turbulence of flow through blood vessels means that the iron atoms in haemoglobin are scarcely going to be aligned and besides will only demonstrate magnetic properties in an external magnetic field. At several points, photons appear in the argument. I may have missed something, but as far as I know, the binding of oxygen to haemoglobin does not result in ‘photons firing out’, and quite what this has to do with the circulation is darkly mysterious. The book seems to have the idea that the circulation is as it is because birds and mammals are bipedal—yet the mammalian circulation evolved a long time before anyone started walking upright. Evolutionary change happens due to the accretion of mutations in DNA that result in reproductive advantage to their carriers. The two-looped circulatory system evolved gradually over millions of years in response to the need to extract oxygen from the air rather than from aqueous solution. We are left with a book that should be thought of as an art artefact rather than a scientific text. It mentions William Harvey (though describes his contribution as a ‘conceit’—I would have thought that his findings are a little more than that) and reads as one of his precursors. As I turned the pages, I thought I might encounter some proposals for turning base metal into gold. Per sanguinem nostrum is clearly a labour of love, and the result is a novel contribution to the cardiology literature. BOOK REVIEW