Monday, September 18, 2006

The incomparable Chuck...

Darwin - yeah, the evolution guy! Not much given to reading biographies, I had so long missed out on knowing more about Charles Darwin. Of course, Darwin and his theory of evolution doesn't have to wait for my introduction in a humble blog. My discovery of Darwin, the man and the tireless scientist, began recently. I started with a Wikipedia entry on Charles Darwin, and read on and on, going through the linkouts. I marvelled anew at the importance of his contribution to modern biology, as well as his continued dedication to science post The Origin of Species.

Darwin had taken up work on habits of worms. According to contemporary accounts, around 1881, he devoted himself "to worm experiments which included Darwin shining different colours of lights at them at night, his sons playing different musical instruments to them, different scents and kinds of food. Other stimuli were ignored, but a bright white light or a touch of breath would make them bolt "like rabbits" into their burrows. They appeared to "enjoy the pleasure of eating" showing "eagerness for certain kinds of food", sexual passion was "strong enough to overcome... their dread of light", and he saw "a trace of social feeling" in their way of "crawling over each other's bodies". Experiments showed that they dragged leaves into their burrows narrow end first, having somehow got a "notion, however rude, of the shape of an object", maybe by "touching it in many places" with a sense like "a man... born blind and deaf" and a rudimentary intelligence."

As we know, Science progresses on the premises of continuous observation and evaluation of its principles. Therefore, theories are often challenged by fresh experimentation and observation. Recently, Kelly Dorgan, a PhD student at the University of Maine, has challenged a century old theory, propounded by Darwin, about how worms move. The Popular Science magazine, in a recent issue, reports that "the work has quickly established her as an authority on the world underground."

According to the PopSci article, Darwin did not believe that the ground could yield on all sides to a worm nosing through soil. He thought that worms swallowed a path through the earth, which scientists later considered an extraordinarily inefficient means of movement. But since worms are very difficult to observe, biologists did not have a good idea about the mechanics of this motion. Dorgan's patient work has shed definitive light on this problem.

Using a method known as photoelastic stress analysis, which employs an elaborate setup of polarized light and camera filters to measure the stress placed on an object, and a seawater-gelatin mixture that had the physical properties of marine sediment, Dorgan put in a worm and filmed it burrowing. By studying the stress fields around the worms, she discovered that they actually launch their mouths inside out like a wedge to pry open the mud. Then they ease into the space opened by the crack. To keep moving, they just keep leveraging the crack. In engineering terms, this is known as crack propagation, and Dorgan’s studies suggest that it costs the worms much less energy than having to ingest every inch of mud in their path. Her finding has changed scientists’ understanding of the entire underground ecosystem: apparently, burrowers such as clams, sea urchins and even growing root tips are really living levers.

Kelly Dorgan, 26, is one of the Brilliant 10 awardees of 2006 by the Popular Science magazine.

To finish with a little bit more on my discovery of Darwin: I first met Charles Darwin in my junior high-school biology class, the man with the long white beard. While discussing the evolutionary theory, I remember, the teacher had written down the full name of his 1859 book On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life (usually referred to as The Origin of Species). He had discussed Darwin's journey on the Beagle; the Darwinian mechanism of evolution comprising the inheritable traits, occurrence of random variation, survival of the fittest and propagation of the species; and a comparison with Lamarck's theory, using the neck length of giraffes as an example. Even at that time, our young minds were impressed with the idea of evolution, and later on in higher classes, we gradually learned how natural selection was combined with Mendelian inheritance and genetics, to form the foundation of modern biology.

As I mentioned above, following his work on the evolutionary theory, [Quoting from Wikipedia] he conducted an innovative study of how (an orchid's) beautiful flowers served to control insect pollination and ensure cross fertilisation; he continued to write on origin of species, publishing in 1871 the two-volume The Descent of Man, and Selection in Relation to Sex, where he introduced in full his concept of sexual selection to explain the evolution of human culture, the differences between the human sexes, and the differentiation of human races, as well as the beautiful (and seemingly non-adaptive) plumage of birds. A year later Darwin published his last major work, The Expression of the Emotions in Man and Animals, which focused on the evolution of human psychology and its continuity with to the behaviour of animals. He developed his ideas that the human mind and cultures were developed by natural and sexual selection, an approach which has been revived in the last two decades with the emergence of evolutionary psychology. His evolution-related experiments and investigations culminated in five books on plants, and then his last book returned to the effect worms have on soil levels.

Until next time, folks! Adios.


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