Sunday, August 17, 2008

Evolution and Darwin

'The Chairman' on the CRABS Curry Ride 2008 asked me 'had anything been done about Evolution after Darwin'. I mentioned Mendel and structure of DNA (forgetting DNA database). I'm reading The Origin of Species (HASSERS Amazon bookstore) and I'm frankly overwelmed with the huge number of observations backing up his ideas that Darwin includes in his book published in 1859.

Edward Baker at defence of reason linked to this article, reminding us that scientific theories, even those as extensively researched as Darwins', are usually incomplete.

Descent with modification was an incomplete theory based on decades of meticulous observation and endless questioning ... and it changed the world, explains Tim Radford

Charles Darwin hardly ever used the word "evolution". He chose the phrase "descent with modification". He did not coin the term "survival of the fittest". He did not suggest that evolution was a form of progress.

For him, an amoeba in a puddle of water was just as suited to its environment as a duck on a lake or a preacher in a pulpit.

He had, at the time, no idea of how living things passed their characteristics from one generation to the next, or how any modifications could happen. He was not the only prophet of evolutionary theory, but he is the one whose name will be forever linked with it, and that was because Darwin backed up a great, but incomplete idea, with a huge body of highly detailed evidence. Some of it was gathered on his voyage around the world on HMS Beagle, but

most of it was assembled painstakingly through decades of observation, note-taking and inquiry, quietly at home in his study and garden at Down House in Kent. There were no "eureka moments", dramatic pronouncements or a search for the limelight.

He probably first began to wonder about descent with modification in about 1838. He spent the next two decades simply thinking about creatures and how they varied. He wrote thousands of letters, to gardeners, foresters, naturalists, geologists, explorers, curators and keepers, asking questions, and then asking supplementary questions.
He wondered about why coral atolls formed and what strange specimens pigeon fanciers could breed, the enormous variation in the domestic dog, the effect of earthworms on the ground in which they lived, and the life cycle of the barnacle. (In 1859, the year of Origin of Species, he received the Geological Society's highest honour, for his work on barnacles and his study of the geology of the Andes.) He only consented to publication because a letter from Alfred Russel Wallace, exploring in the Malay archipelago, proposed an almost identical idea.
Darwin, a man with a conscience, insisted on a joint paper, to be presented to the Linnaean Society, so that two people could share the honour of one of the most important scientific discoveries ever made. However, only one is remembered.

Misunderstood theory

Darwin's achievement changed human history, and human attitudes to the natural world, but his achievement was incomplete.
He convinced the thinking world, according to the 20th-century scientist Stephen Jay Gould, that evolution occurred, but he didn't convince many people that it had happened because of natural selection "and even today, though it forms the core of our evolutionary theory, it is widely misunderstood, misquoted and misapplied," Gould says.

Darwin knew that descent with modification had something to do with inheritance but he knew nothing about the arithmetic of inheritance or the genetic substance that transmitted it. Gregor Mendel's 1866 study of garden peas, which was to become the foundation of modern genetics, was published in German, in a Moravian journal, and was not widely known until the beginning of the 20th century. DNA was identified during the second world war, but its role in the replication of life and the transmission of traits was not known until 1953. Both pieces of research confirmed the Darwinian argument that all life had descended, with modifications, from a common ancestry, and that natural conditions tend to favour useful variations at the expense of handicaps.

If detailed scientific confirmation appeared so long after Darwin's death, why did so many people accept his logic at the time? Because so many things - anatomical likenesses, skeletal similarities (the domestic dog, the farmyard animal and the garden vegetable, to name a few) - made it obvious that there had been some changes in species over time. Half a dozen great scientists, including Darwin's grandfather Erasmus, had already proposed some form of evolution. What Darwin did was assemble, with a mass of evidence and close reasoning, the best argument for believing that it had happened by the action of natural selection on random mutation. When he first read this argument, his friend and supporter Thomas Henry Huxley is supposed to have clapped his head and said: "How extremely stupid of me not to have thought of that!"

Why does Darwin's theory matter now? Because it is the basis of modern biology and much medical research; because it provides a tool with which to understand the natural world; because it offers a deeper, if imperfect, understanding of our behaviour, about where we came from and where we might be going. The philosopher Daniel Dennett once called it "the single best idea anybody ever had".

1 comment:

  1. Nice post.

    I found "Origin" surprisingly accessible and readable - but then it was a generally popular best seller at the time of publication and was intended for the lay auidence.