Guide I, Charles Darwin: Being the Journal of His Visitation to Earth in the Year 2009

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Submissions for this list (which is still being updated even though is over) The [Dutch] Beagle project - reconstructing Darwin's 5-year long voyage on HMS 31 May Charles Darwin and the Origin of Species A small display at the . Experience Darwin's world as never before with a visit to Down House - his.
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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.

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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.

The Genius of Charles Darwin (Full) - Richard Dawkins

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.


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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?

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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. The genes inserted into such host cells worked at first, "but then suddenly they were silenced, and that was it, generation after generation," says Eva Jablonka, an evolutionary biologist at Tel Aviv University in Israel. Researchers figured out that the host cells were tagging the foreign genes with an "off switch" that made the genes inoperable.

The new gene was passed to an animal's offspring, but so was the off switch—that is, the parent's experience influenced its offspring's inheritance. All sorts of changes in cellular machinery have shown up that have nothing to do with the sequence of DNA but still have profound, and heritable, impacts for generations to come. For example, malnourished rats give birth to undersized pups that, even if well fed, grow up to give birth to undersized pups. Which means, among other things, that poor old Lamarck was right—at least some acquired traits can be passed down.

Darwin included the concept of soft inheritance in Origin , mentioning "variability from the indirect and direct action of the external conditions of life, and from use and disuse," for example. It has been said that Darwin himself was not a particularly strict Darwinian, meaning that his work allowed for a wider variety of mechanisms than many of his 20th-century followers would accept.

Origin barely touched upon the most contentious evolutionary issue: If all life has evolved from "lower forms," does that include people? Darwin finally addressed the issue in The Descent of Man, and Selection in Relation to Sex , published in , explaining he had been studying human evolution for years, but "with the determination not to publish, as I thought that I should thus only add to the prejudices against my views. They shared Disraeli's discomfort at being descended from apes and complained that evolution pushed a divine creator to the side.

Disbelief in human descent may have been a justifiable comfort in Darwin's time, when few fossils of human ancestors had been discovered, but the evidence no longer allows it. Darwin, in Origin , admitted that the lack of "intermediate varieties" in the geological record was "the most obvious and gravest objection which can be urged against my theory.

The objection certainly applied to the paucity of ancestral human fossils in Darwin's time.

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Years of painstaking work by paleontologists, however, have filled in many of the important gaps. There are many more extinct species to be discovered, but the term "missing link" has for the most part become as outdated as the idea of special creation for each species. Anthropologists once depicted human evolution as a version of the classic "March of Progress" image—a straight line from a crouching proto-ape, through successive stages of knuckle draggers and culminating in upright modern human beings. There are now hundreds of known fossils, stretching back six to seven million years and representing about two dozen species.

Some were our ancestors and others distant cousins. Remarkably, our modern human forebears shared parts of Europe and western Asia with the Neanderthal species as recently as 30, years ago, and they may have also overlapped with two other long-gone ancient humans, Homo floresiensis and Homo erectus , in Southeast Asia.

The Voyages of Charles Darwin

Darwin himself was confident that the deep past would be revealed. Asked about gaps in Darwin's knowledge, Francisco Ayala, a biologist at the University of California at Irvine, laughs. Continue or Give a Gift. Privacy Policy , Terms of Use Sign up. SmartNews History.


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