What do you mean by a lie?
- Haeckel’s Embryos: Images, Evolution and Fraud by Nick Hopwood
Chicago, 388 pp, £31.50, May 2015, ISBN 978 0 226 04694 5
Some generalisations about the natural world are easy to recall because they are expressed in apothegms – concise, rhetorically marked-out sayings that stick in the mind and come easily to the tongue. Whatever goes up must come down; for every action, there’s an equal and opposite reaction; all life from pre-existing life; all cells from pre-existing cells; the angle of incidence is equal to the angle of reflection; energy can neither be created nor destroyed.
Then there are scientific principles whose mnemonic power, meanings and implications for future inquiry come in part not from words but from images – two-dimensional pictures or three-dimensional models. Consider the relationship between the Tree of Life and 19th-century understandings of species change; the Great Chain of Being and medieval ideas of plenitude; or Leonardo’s Vitruvian Man and Renaissance notions of microcosm and macrocosm. The orrery was an 18th-century mechanical model of the solar system that showed, at a glance and without equations, how the motions of one celestial body related to those of others. The ‘Rutherford atom’ – electrons orbiting a central nucleus – summons up both a theory of atomic structure and the powers of nuclear energy. The periodic table made visible ideas of the connection between atomic weight and the periodicity of chemical properties. Watson and Crick took one look at the first jerry-rigged workshop model of double-helical DNA and they saw how the structure might account for both genetic coding and genetic function.
There are only a few scientific principles that enjoy both advantages – the sticky-linguistic and the sticky-visual. Even if you aren’t a biologist, there’s a chance you will have heard the saying ‘ontogeny recapitulates phylogeny’: the claim that the growth and development of an individual from conception to maturity repeats the evolutionary history of the species, that embryological development passes through the adult forms of species in its evolutionary lineage. The human embryo, for example, starts out looking like an invertebrate, then like a fish, then takes on generic mammalian characteristics, then an ape-like appearance, and only finally comes to resemble a human being. If you Google the phrase ‘ontogeny recapitulates phylogeny’, or its shorthand form ‘the biogenetic law’, you will probably be told four things: that its author was the biologist Ernst Haeckel (1834-1919); that it was introduced as a key feature of German Darwinism; that it is now discredited or in need of serious qualification; and that its articulation in the 1860s and 1870s was surrounded with controversy and accusations of serious bad behaviour. Then it’s likely you’ll be shown a version of a picture produced by Haeckel which makes the biogenetic law visible and which impresses its meaning more vividly than language could ever do. As Nick Hopwood shows, this picture persists in present-day scientific discussions despite of – and in many cases because of – its being faulty or even fraudulent.
The original version of the most famous of Haeckel’s embryo pictures was a woodcut spread across two pages of a book from 1868 grandly titled Natürliche Schöpfungsgeschichte (translated as The History of Creation). But the version that eventually became most iconic, and most controversial, appeared in a book from 1874 called Anthropogenie (translated as The Evolution of Man). This was a grid, containing 24 woodcut images of embryos at progressive stages of development. This grid was continually reworked and elaborated throughout Haeckel’s publishing career, and there were many related images, so there is no single stable representation but a series, more or less thickly populated with examples from different species, with more or less detail, produced using various technologies – Haeckel’s drawings were given to others to be turned into wood-block and copper engravings and lithographs. They were accompanied by different textual glosses but they were all enlisted in the same basic scientific and philosophical cause. Hopwood’s book is a richly illustrated and staggeringly detailed story of how Haeckel’s embryo pictures came to be, how they were mobilised as resources in scientific and ideological causes, how versions of the grid picture were copied, recopied and modified, how their accuracy was vigorously disputed by some and defended by others, and how they continue to circulate – still relevant and still contentious – today.
The juxtaposition of embryos in graphic space can be a visual argument for their succession in time and for the causal relations between them. Hopwood notes that graphic series were not common in scientific imagery before this – perhaps the best-known instance is T.H. Huxley’s much copied and often spoofed 1863 series of five skeletons, lined up and increasing in height, from the gibbon at the left, through orangutan, chimp and gorilla, to the human being at the right. A double series, like Haeckel’s grid, was rarer still. The two modes of juxtaposition in the grid represent two scales of time and the biological relationships between organisms in each scale. The top row – from left to right – shows early embryos of eight different species: fish, salamander, turtle, chicken, pig, cow, rabbit and human being. The columns, from top to bottom, depict the embryological development of individuals of each species (their ontogeny), where you are meant to understand that the embryos shown are representative of how development goes for the species, not just for any individual chicken or cow. The columns chart developmental time: stages in the days-to-months scale in which an organism goes from fertilised egg to birth or hatching. The rows show embryos from different species at ‘equivalent’ developmental stages, though in one species this might be days after fertilisation and in another months. The rows also call on existing understandings of the timescales of life on earth – many thousands to millions of years – and of the historical relationship between species. The presumption is that we already possess, as a matter of course, some of the conceptual meaning of the left-to-right series – for example, that fish and reptiles are ‘lower’ forms than mammals like pigs and rabbits, and that human beings, at the far right, are the ‘highest’ form. The image is just ink on paper, but it is multiply dynamic, conceptually complex, culturally resonant and ideologically loaded.
The full text of this book review is only available to subscribers of the London Review of Books.