Nature 2009 February

Darwin’s legacy – if eaten, beetles can leave a bitter taste in the mouth

A cold start to the year with Chesham and Benson in Oxfordshire sharing the National honours on the night of 6th January. With snow on the ground, temperatures fell to minus 11°C. Locally, I recorded –11.8°C that night. The outlook for the rest of the winter season is for slightly warmer and dryer conditions than typical for this time of year.

February 12th marks the 200th anniversary of Charles Darwin’s birth. He was one of the foremost scientists of the 19th century, who demonstrated how all species of life evolved from common ancestors by the process he called natural selection: a discovery that continues to have a profound impact on scientific thinking to this day. Although this is what he is principally remembered for, his inquisitive mind not only addressed this fundamental question but he also resolved, or at least laid the groundwork for, answers to many other big questions of the day.

So this Nature Notes picks up on just a few of the less celebrated of Darwin’s discoveries as an observer of nature and his largely unrecognised contribution to agriculture, market gardening and animal husbandry. His nature writing is descriptive, at times poetic, and elsewhere highly amusing. One or two quotes are picked out and included below but his complete works are available online at www.darwin-online.org.uk.

Charles Darwin initially trained to be a Doctor in Edinburgh but found himself not suited to following his father as a country GP, having observed the gruesome autopsy of young girl. This experience also conditioned his lifelong thinking as an anti-vivisectionist who resisted the new fashion of experimenting with live animals. In desperation, his father encouraged him to resume his studies at Cambridge with the aim of becoming a parson. However, instead of theological studies he soon became distracted by his exploits in riding, shooting and fishing.

Luckily for science, this extra-curricular activity led to him submitting letters of his discoveries to learned journals which brought him into contact with, and to the notice of, the most renowned naturalists of the day. This led to an invitation to be the ‘gentleman naturalist’ to accompany Captain Fitzroy on board the survey ship Beagle in 1831. After a five-year voyage of exploration and discovery to South America, including the Galapagos Islands, Australia and South Africa, Darwin returned with thousands of specimens and many new ideas. He took over 20 years to summon up the courage to publish “On the Origin of the Species”. The book immediately met with hostility from the established church, however his ideas survived this onslaught and were reinforced by the work of the scientists who followed him. Although his travels provided numerous exotic species, he equally relied upon numerous observations and studies of everyday British wildlife. Here are just a few.

On the earthworm, Darwin elegantly remarked “… it may be doubted if there are any other animals which have played such an important part in the history of the world as these lowly organized creatures”. He carried out experiments (in the billiard room of his family home in Downe, Kent), and calculated how materials strewn on the surface found their way deep down in the topsoil. He calculated that, over 10 years, the top two inches would have all been through the gut of worms. We take this subterranean activity for granted today but until Darwin investigated this most essential aspect of soil fertility, it was not understood.

Ever wondered how plants attach themselves to and climb up almost anything so effectively? So did Darwin. Although several had studied this plant behaviour previously, there was no clear understanding of how this occurred and, more importantly, how the different methods of climbing evolved. Darwin studied over a hundred different species grown from seed (including growing hops in his bedroom). His research enabled horticulturalists and market gardeners to develop new varieties of climbing plants: be they clematis, hops or runner beans.

There were many occasions when Darwin was challenged to explain the variety and wonder of the natural world. One such related to wild orchids and how species such as the bee and fly orchids mimic insects in the design of their flowers or as Darwin described them “… the wonderful contrivances of the orchid”. During a visit to Torquay in 1861 he noticed how wild orchids were distributed on the cliff side. Consequently, he had an orchid house built and demonstrated how only cross-pollinated orchids produced fertile seeds and the more successful an orchid at attracting insects, the more likely its inherited characteristics would survive. Darwin predicted this effect was down to the transference of genetic material, although it took another 50 years for Darwin’s theory to be proved and the principles of genetics to be developed. Unlike today, breeding of both domestic and exotic fowl and game birds were of popular interest. So it was typical of Darwin’s curiosity with nature in general that he experimented with the breeding of a wide range of varieties. He examined the features of racing pigeons and the colouration of male birds. At times the whole house stank of boiling bones as Darwin sought to determine differences in bone structure of birds bred for racing.

In his latter years Darwin turned his mind to the mysteries of plant movement. He was able to demonstrate that it was not a single entity that controlled plant movement but rather the reaction of a small number of cells just behind the growing tip of the shoot or root which reacted in one way to gravity and in the direct opposite to light. In relation to the root or ‘radicle’ Darwin, in dismissing many of the previous speculations, was close to resolving the mystery when he commented, “It is hardly an exaggeration to say that the tip of the radicle – having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals”. Once again it took until the 1930s for the final solution to emerge, but it was Darwin’s pioneering work that laid the groundwork for today’s market gardening industry.

To finish, an anecdote from his student days at Cambridge. Darwin describes the perils of being swept along by a beetlecollecting craze, which was fashionable at the time among young gentlemen. “No pursuit at Cambridge was followed with nearly so much eagerness or gave me so much pleasure as collecting beetles. It was the mere passion for collecting, for I did not dissect them and rarely compared their external characters with published descriptions, but got them named anyhow. I will give a proof of my zeal: one day, on tearing off some old bark, I saw two rare beetles and seized one in each hand; then I saw a third and new kind, which I could not bear to lose, so that I popped the one which I held in my right hand into my mouth. Alas it ejected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, as well as the third one.” Itself, an evolutionary tale of sorts, I guess.