Darwin was far from the conventional image of a stern Victorian patriarch. He was a perceptive and loving father: he had ten children, and seven survived childhood.
The illnesses that struck his family with fatal effect were devastating to him. More usually, as the children crashed around the house, Darwin absorbed their lively spirit and was a playmate. He never saw himself as impressively academic, and his formal education had a discernible limp.
Yet he was always interested in nature and from the beginning flavoured his schooling with his own studies of science. By his late teens, he had expertise in botany, zoology and geology, a serious training in natural history which for years ran alongside his studies of the classics, medicine and divinity.
It was his own programme of learning, not his university degree, that got him a place on the scientific survey ship HMS Beagle for a five-year round-the-world trip. Once aboard, his relaxed and secure temperament helped him thrive in those cramped and stringent oceangoing conditions.
The Beagle voyage lasted five years, taking him to South America, Australia and all points between. Those years, to , were the making of Darwin: a raw mix of adventure, physical challenge and exciting intellectual and emotional discovery.
Darwin made a name for himself during that trip. People he admired noticed his astute scientific commentaries, which he posted back to England during the voyage. When he eventually returned to London, and began to sort and describe his specimens, he could activate a ready-made network of scientists, roping them in for their expert opinions and for their patronage.
Over and above all this, he came home with his own big idea: a vast project in mind, a more-or-less secret urge to explain how life on Earth had changed over time. Fourteen thousand letters exist in the archives, and are available online. There is much documentation besides this correspondence. A collector from a young age, he was always meticulous in his record keeping — his household accounts are preserved, for example, as are his books, with all their revealing marginalia.
It is the reason we know so much about the way he lived and worked. And it is an archive which proves that science cannot be split from personality, or from society. Darwin groaned when he wrote his books, and there are vivid descriptions of his toils. But on the Beagle voyage, with so many ideas pressing in, writing became an important part of his life.
He could not draw well and photography did not exist yet. Darwin thought that the unique species of the Galapagos could not have been specially created for each island, but must have evolved from similar ancestors carried from the mainland and washed up on the islands.
But how had this evolution occurred? Read more. It truly is amazing that Charles Darwin put together the pieces, and his ideas have changed human history and our perceptions of our place both in nature and the history of the world.
Your email address will not be published. This site uses Akismet to reduce spam. Learn how your comment data is processed. MENU Toggle navigation.
Photo by: Purwo Kuncoro. Jeff Zekas says:. January 1, at pm. Leave a Reply Cancel reply Your email address will not be published. New Videos Just Released! But understanding the process would have to wait for the work of Wallace in the mids. Wallace, working in an area with tens of thousands of islands, showed that a single butterfly species could slowly become many as it adapted to the specific conditions encountered on each island.
But that was something that Darwin held back a little. Darwin knew that plant and animal species could be sorted into groups by similarity, such that birds clustered into songbirds and raptors, say, with each group subdivided again and again down to dozens or hundreds of distinct species. He also saw that the individuals within any given species, despite many similarities, also differed from one another—and some of those differences were passed from parents to their offspring.
And Darwin observed that nature had a brutally efficient method of rewarding any variation that helped an individual live longer, breed faster or leave more progeny. The reward for being a slightly faster or more alert antelope? The lions would eat your slower neighbors first, granting you one more day in which to reproduce.
After many generations and a great deal of time, the whole population would run faster, and with many such changes over time eventually become a new species. Evolution, Darwin's "descent with modification through natural selection," would have occurred. But what was the source of variation and what was the mechanism for passing change from generation to generation? Darwin "didn't know anything about why organisms resemble their parents, or the basis of heritable variations in populations," says Niles Eldredge, a paleontologist at the American Museum of Natural History in New York City.
In Darwin's era, the man who did make progress on the real mechanism of inheritance was the Austrian monk Gregor Mendel. In his abbey garden in the late s and early s, Mendel bred pea plants and found that the transmission of traits such as flower color and seed texture followed observable rules. For instance, when plants with certain distinct traits were bred with each other, the hybrid offspring did not have a trait that was a blend of the two; the flowers might be purple or white, but never an intermediate violet.
This surprising result helped point the way toward the concept of "units" of inheritance—discrete elements of hereditary information. An offspring inherits a set of these genetic units from each parent. Since the early s, those units of inheritance have been known as genes. Mendel knew Darwin's work—his German copy of Origin was sprinkled with handwritten notes—but there's no evidence that Mendel realized that his units of inheritance carried the variation upon which Darwinian selection acted.
But what if he had? Today, comparative genomics—the analysis of whole sets of genetic information from different species—is confirming the core of Darwin's theory at the deepest level. Scientists can now track, DNA molecule by DNA molecule, exactly what mutations occurred, and how one species changed into another. Darwin himself made a stab at drawing a "tree of life," a diagram that traces the evolutionary relationships among species based on their similarities and differences.
There have been plenty of evolutionary surprises in recent years, things that Darwin never would have guessed. The number of genes a species has doesn't correlate with how complex it is, for example. With some 37, genes, rice has almost twice as many as humans, with 20, And genes aren't passed only from parent to offspring; they can also be passed between individuals, even individuals of different species.
This "horizontal transfer" of genetic material is pervasive in bacteria; it's how antibiotic resistance often spreads from one strain to another. Animals rarely acquire whole genes in this way, but our own DNA is packed with smaller bits of genetic material picked up from viruses during our evolutionary history, including many elements that regulate when genes are active or dormant.
Do these surprises challenge the central idea of Darwinian evolution? Truly one of the most remarkable traits of Darwinism itself is that it has withstood heavy scientific scrutiny for a century and a half and still manages to accommodate the latest ideas. Another growing field of biology is shedding further light on the origins of variation. Evolutionary developmental biology, or evo-devo, focuses on changes in the exquisitely choreographed process that causes a fertilized egg to mature.
Behind one series of such changes are the so-called homeotic genes, which dictate where legs or arms or eyes will form on a growing embryo. These central-control genes turned out to be almost identical even in animals as different as worms, flies and human beings. Many researchers now think that much of evolution works not so much through mutations, or random errors, in the major functional genes, but by tweaking the ways by which developmental genes control other genes.
These kinds of connections were at the heart of descent with modification. Carroll says he thinks Darwin would be thrilled with the evolutionary details scientists can now see—how, for example, changes in just a small number of regulatory genes can explain the evolution of insects, which have six legs, from their ancestors, which had even more. From there, it's a short step to solving some of the mysteries of speciation, working out the mechanics of exactly how one species becomes many, and how complexity and diversity can be built up out of very simple beginnings.
Perhaps the most surprising discovery in recent years has to do with one of Darwin's predecessors in evolutionary theory. Jean-Baptiste Lamarck, a French naturalist, developed his own theory of biological evolution in the early 19th century.
He suggested that acquired traits could be passed along to offspring—giraffes that stretched to reach leaves on tall trees would produce longer-necked offspring. This "soft inheritance" became known as Lamarckism and soon proved susceptible to parody: Would clipping the tail off a rat lead to tailless pups? Of course not, and in time soft inheritance was dismissed, and Lamarck became a textbook example of shoddy thinking. Then, in the early days of genetic engineering more than two decades ago, researchers inserted foreign genes into the DNA of lab animals and plants and noticed something strange.
0コメント