Book Review

Barnacles of the world unite

Darwin’s Island: the Galapagos in the garden of England

Steve Jones, Professor of Genetics at University College, London, is by his own admission more atheistic than Richard Dawkins. He told me not so long ago that, on a scale of one to 10, Dawkins had professed himself to be two points religious, whereas he, Jones, considers himself only 1.5 points religious. He was recently voted "Secularist of the Year". All the same, it is a huge relief to read a book about Darwin by an ardent atheist that neglects to attack God, creationism, intelligent design or religion.

Darwin visited and studied the flora and fauna of some 40 islands in his lifetime. Great Britain was both the first and the last. He spent more time studying the natural history of Kent than any of the jungles of the Amazon, or the rocky islets of the Galapagos. To celebrate the Darwin bicentenary, Jones has written a book that ranges from the Galapagos to the countryside around Downe House, Kent, where the great man spent 40 years of his life. Darwin wrote six million words there, and published 19 books and many hundreds of scientific papers. Much of his massive oeuvre is concerned not with theoretical polemic about evolution but with observations, experiments, and reportage of natural organisms, over which he cast his talent for making wonderfully imaginative connections. Not least of Darwin's works, forming the central plank of Jones' book, is the four-volume, 1,000-page study entitled Barnacles.

It is commonly believed that barnacles are a sort of snail because of their solid shells. In fact they are joint-limb animals not unlike crabs, spiders or flies. Their ancestors once roamed the oceans, but they now spend most of their lives within their shells stuck to

strategic vantage points on rocks and hulls of ships. Darwin became interested in barnacles when hunting for marine life while studying medicine at Edinburgh. Ten years later, on the coast of Chile, he found an unfamiliar soft-bodied marine creature similar to the British barnacle, but without its shell.

It led him to initiate a work of many years, categorising barnacles the world over. He was convinced that barnacles (and indeed all animals) came from a common ancestor that could be traced ever further back into the distant past. "Five years after his cirripede [barnacle] opus," Jones tells us, "that radical notion became the theme of The Origin of Species." Jones goes on: the study "has grown into the science of evolutionary developmental biology, which unites barnacles from across the world with each other, with crabs and lobsters and even with geese. It reveals the common foundations upon which all animals are built."

In this passionate, beautifully written book, Jones expands out from the humble barnacle to a wonderful circuit of natural observations. The British barnacle, for example, has a shutter, which opens to extend its legs at high tide and closes to keep in water when the creature is exposed to air. Its mouth has teeth like those of crabs and cockroaches. Some barnacle species excrete through the mouth, while others lose their eyes in adulthood through being tucked away in the dark.

Many have a kind of complex cement made of a protein that repels water. According to Jones, it is "the toughest known natural glue". There are two components: when mixed, "cross-links" are made between the molecules and the barnacle, making it virtually impossible to shift. In a typical factoidal flourish, Jones tells us that a ship uses 40 per cent more fuel when covered with barnacles than when its surface is smooth.

Jones' excitement about Darwin's barnacles derives ultimately from his academic specialisation, genetics, which continues to shed new light on the affinities between embryos of distant creatures. "DNA, like the bodies it builds," writes Jones, "is itself based on a series of variations on a structure theme. As egg becomes adult, complex organs - eyes, ears, hands and brains - are pieced together from elements that can clearly be distinguished only in the embryo." In early development many organisms strongly resemble each other more than in their adult maturity, since each, as Jones puts it, "shares a series of genes that lay down the basic body plan, from head to tail. Such genes are control switches in the journey from fertilisation to the grave."

The genes stored in the embryo's DNA guide the egg to maturity; but "errors" or mutations in the genes' instructions can result in differences of form that drive evolution: "Eyes transformed to legs in fruit flies, lambs with two heads or extra fingers in human babies - together with more persistent changes such as those that made birds form dinosaurs or barnacles form the ancestors of crabs."

Jones' book reads at times like a hymn to the beauty, subtlety and astonishing potential of the embryo and its extraordinary progress "from fertilisation to the grave". If this is true of the humble barnacle, how much more remarkable is the journey of the human being from embryo to neonate. Jones has not set out to engage in polemic about the ethics of human embryo research; but the sheer poetry of his writing on the epic journey that connects every single embryo to its post-natal maturity is, for this reader, a stunning contribution to our understanding of the dignity of human nature, from "fertilisation to the grave".

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