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Charles Darwin, a Hero
of Humankind, February 12, 1809, a monumental day in the evolution of humankind from ignorance and myth -to- a much deeper understanding of the place of homo sapiens and all life in a naturalistic world. The following excerpts briefly touch on the subjects in each article. For complete informa- tion, access each of the links listed below. - - - January 2009 http://tinyurl.com/Darwin-Turns-200 - - - Excerpts: This special web edition of Science News includes expanded versions of articles from the magazine's print edition plus two addi- tional features, all commemorating the 200th anniversary of the birth of Charles Darwin. - - - Darwin's Evolution http://www.sciencenews.org/view/feature/id/40014/title/Darwins_Evolution - - - Excerpts: Two centuries ago, modern biology's found- ing father was born in England. He became the most celebrated scientist of his time, deci- phering the records of life's history from creatures extinct and living and thereby ex- plaining the genesis of life's diversity. Charles Darwin was born into a world that today's scientists wouldn't recognize. When baby Darwin arrived on February 12, 1809, modern science was also in its infancy. o Dalton had just recently articulated the modern theory of the chemical atom, but nobody had any idea what atoms were really like. o Physicists had not yet heard of the conservation of energy or any other laws of thermodynamics. o Faraday hadn't yet shown how to make electri- city from magnetism, and no one had a clue about light's electromagnetic identity. o Geology was trapped in an ante-diluvian para- digm, psychology hadn't been invented yet and biology still seemed, in several key ways, to be infused with religion, resistant to the probes of experiment and reason. Then came Darwin. By the time he died in 1882, thermodynamics possessed two unbreakable laws, chemistry had been codified in Mendeleyev's peri- odic table, Maxwell had discovered the math merg- ing electricity and magnetism to explain light. Lyell had established uniformitarianism as the basis for geology, Wundt had created the first experimental psychology laboratory, and science had something substantial to say about how life itself got to be the way it was - thanks to Dar- win's perspicacious curiosity, intellectual rigor, personal perseverance and power of persuasion. ... Today Darwin's original idea survives, although it has spawned many mutated forms, with nuances and complexities that make evolutionary science a constantly advancing field of research. And Darwin's logic has been borrowed by other investigators in diverse disciplines: o Psychologists try to explain behavior based on what mental habits would have enhanced sur- vival as human ancestors were evolving. o Biomedical researchers grapple with evolution- ary principles in fighting microbial resistance to antibiotics. o Computer scientists mix and select segments of binary code to generate optimal computer programs. o Even in physics, the word "Darwinian" appears in papers on thermodynamics, quantum physics and black holes. Darwin would have been fascinated by such research and would no doubt have understood a lot of it, as so much of the underlying reasoning was his. Darwin would also have been happy with the many modifications and adaptations to his ideas found in modern reformulations of evolutionary theory: o Speciation isn't always gradual, change isn't always the result of selection, organisms are not the only units of selection, evolutionists now believe. o Darwin foresaw some of these views, and he would have embraced them all - as a man of science willing "to give up any hypothesis, how- ever much beloved ... as soon as facts are shown to be opposed to it," in his words. "If I know myself, I work from a sort of instinct to try to make out truth." And in the battle to wrest truth from nature, none fought better than Darwin. "He found a great truth," Huxley wrote in Darwin's obituary, "trodden under foot, reviled by bigots, and ridiculed by all the world; he lived long enough to see it, chiefly by his own efforts, irrefragably estab- lished in science, inseparably incorporated with the common thoughts of men." - - - Evolution's Evolution http://www.sciencenews.org/view/feature/id/39999/title/Evolutions_Evolution - - - Excerpts: Darwin's dangerous idea has adapted to modern biology. Just a decade after he published On the Origin of Species, Charles Darwin was already worrying about the evolution of his idea. In an 1869 letter to botanist Joseph Dalton Hooker, Darwin lamented: "If I lived twenty more years and was able to work, how I should have to modify the Origin, and how much the views on all points will have to be mod- ified! Well, it is a beginning, and that is something." Calling the Origin a mere "beginning" is like saying the Beatles were just a rock band or that Shakespeare wrote some decent plays. Darwin's gifts to science were radical. He not only proposed that all of Earth's diverse beings shared a common ancestry, but also described an elegant mechanism to explain how all that diverse life came to be. Darwin was a master of merging data from different disciplines, pain-stakingly drawing from zoology, botany, geology and paleontology to build a solid foundation for evolutionary biology. Today, 150 years later, scientists continue to grapple with ideas descended from that foundation. Still, Darwin's central tenets survive, fit enough to frame the questions posed by modern biology. ... - - - Molecular Evolution http://www.sciencenews.org/view/feature/id/40006/title/Molecular_Evolution - - - Investigating the genetic books of life reveals new details of 'descent with modification' and the forces driving it. Charles Darwin didn't know about genes and DNA. In fact, hardly anyone noticed when Gregor Mendel, a monk whose pea experiments eventually led to modern genetics, published his findings in an ob- scure journal a few years after Darwin's On the Origin of Species appeared in 1859. It would take nearly a century more before James Watson and Francis Crick deciphered the structure of DNA, the molecule that contains the manual for building an organism. Yet Darwin was still able to describe a mechanism - natural selection - for how evolution shapes life on Earth. That's like describing how a car works without knowing about the existence of internal combustion engines. But while Darwin achieved his insights without molecular help, biologists today are intimately familiar with the molecules responsible for the diverse array of plants, animals and other organ- isms that populate the planet. The study of genes has revealed evolution as essentially a high-stakes poker game in which organisms draw randomly from a deck of genetic choices. At stake is the chance to pass along genes to the next generation. Sometimes the hand is good enough to get ahead in the game, but some hands are losers, perhaps to the extent of extinction. By studying the winners, scientists are learning how the forces of evolution work on DNA, the biochemical repository of an organism's entire natural history. DNA records the mutations that helped some animals to survive ice ages while others perished, the nips and tucks that make animals more attrac- tive to mates, the big leaps that allowed plants to become domestic crops - they're all there, writ- ten out in a simple alphabet of four letters. Each organism has its own book of life, but it's not a just-so story. The genomes of living things are constantly undergoing editing and revision. And each individual has its own edition of its species's book, shaped by natural selection and the other, perhaps less-appreciated forces of genetic mutation, recombination and drift. ... Scientists are now beginning to learn how tweaks and major changes on the molecular level enable adaptation to environments. The picture is painted in DNA, but it's far from a completed masterpiece. Changing environments coupled with the forces of natural selection, mutation, recombination and drift are continually reworking the painting. Only time will tell how the landscape will morph - and its inhabitants with it. - - - Step-by-step Evolution http://tinyurl.com/StepbyStep-Evolution - - - Excerpt: Mining the gaps: The in-between fossils are the hard- est to find, but they tell the best stories. When Charles Darwin proposed the idea of evolution in On the Origin of Species, he wrote "if my theory be true, numberless intermediate varieties, linking most closely all the species of the same group together, must assuredly have existed." At the same time, he bemoaned the dearth of such transitional fossils as perhaps "the most obvious and gravest objection which can be urged against my theory." Surely it was serendipity when, just two years later, quarriers unearthed fossils of Archaeopteryx. This creature, now recognized by many scientists as the first known bird, has a mosaic of features that links it with the disparate groups of species on either side of it in the fossil record: While its teeth, tail and overall body shape are distinctly reptilian, its fea- thers have the same complex structure as the lift- generating feathers of modern birds. In other words, it is just one of the "numberless intermediate vari- eties" that Darwin predicted must have existed. "It was the right discovery at the right time," says Richard Fortey, a paleontologist at the Natural History Museum in London. Darwin blamed the lack of transitional fossils in part on the poorness of the paleontological record. It's a rare accumulation of fortuitous events when a creature is fossilized, its remains are preserved over millions of years and then those remains are discovered. ... Many of the gaps in the fossil record that remained unfilled in Darwin's time now throng with creatures, such as the ones used to chronicle the 48-million- year series of evolutionary changes between whales and their predecessors. And particular biomarkers - chemical fossils, if you will - in rocks more than 240 million years old have provided clues about the evolution of flowering plants. Paleontologists still randomly stumble across tran- sitional fossils these days, such as a creature found in Texas that falls in a 50-million-year gap in am- phibian evolution and helps pin down when the groups that include salamanders and frogs arose. As often as not, however, transitional fossils are found when researchers head into the field with a specific target in mind: By focusing on rocks deposited during an interval where gaps in the fossil record exist, scientists can boost the chances of making a critical discovery. That's how research- ers unearthed Tiktaalik, a 2.7-meter-long beast that plopped into a 9-million-year gap in the chronicle of vertebrates' transition from water to land. ... - - - Computing Evolution http://tinyurl.com/Compute-Evolution - - - Excerpt: Scientists sift through genetic data sets to better map twisting branches in the tree of life. Among its many prose-filled pages, Charles Dar- win's On the Origin of Species includes only one illustration. It's a diagram of short lines leading upward from the base - a few lines at the bottom branch out repeatedly as they extend up. Darwin meant for the image to depict what he dubbed the "tree of life." This figure embodied Darwin's vision for how the tremendous diversity of life on Earth arose. A few species - the base of the tree - mutate and evolve over time, sometimes branching to form new species. An ancient species of bird might colonize a chain of islands and slowly evolve narrower beaks or other features specialized for the birds' new habitats. Eventually, groups in different habitats become separ- ate species, and each species continues to evolve and adapt, perhaps branching again. In this way, the first fishlike land animals gave rise to the great diversity of amphibians, lizards, insects, rodents, marsupials, primates and birds. It was a sweeping vision of life, revealing it to be a giant family with a vast genealogy. Branches of the tree show the kinship among creatures and the history of change and adaptation. Darwin toiled for much of his life to understand the relationships among species, the branches of this immense tree, by gathering countless specimens and scrutinizing their similarities and differences - a longer neck, a brighter-colored shell. Expanding this tree has been the painstaking work of generations of naturalists, biologists, taxonomists and paleontolo- gists during the 150 years since Darwin published his seminal book. Now that slow slog has quickened to an all-out sprint. Rather than divining clues to an organism's evolution- ary history from observed traits, scientists are going straight to the genetic ledger sheet. Modern tools for rapidly reading species' DNA are laying bare those species' genetic inheritances, the patterns of genetic code shaped by eons of mutation and natural selection. And ever more powerful computers are churning through gigabytes and gigabytes of this genetic data to decipher which species are like sisters and which are only distant cousins. "We've really learned more about relationships [among species] in the last 10 years than we did in the previous 200 years," says Doug Soltis, an evolu- tionary biologist at the University of Florida in Gainesville. "This is definitely going to be viewed as a golden era in our study of biodiversity. And it's just now taking off." Already, large branches of the tree are being redrawn as scientists compare the DNA of dozens or hundreds of distantly related species. Within years, rather than decades, this computational excavation of life's past will achieve an important milestone in the history of science: a highly accurate map of the major branches in Darwin's tree of life. "It's Darwin come full circle," Soltis says. "Starting from his tree figure [in the Origin], we're now put- ting together a basic tree of life for a large portion of known species. It's just incredibly exciting." ... - - - A Most Private Evolution http://tinyurl.com/Private-Evolution - - - Excerpts: Dumb Designs for Sex: Evolutionary biology walks on the weird side. ... Trying to understand counterintuitive sexual parts and habits follows in the best of scientific traditions. As Charles Darwin worked up his ideas on evolution, he pondered male phenomena that looked useless, or even harmful, for surviving. Outsized horns on male beetles puzzled him, as did male birds with gorgeous plumage. Out of this consternation came his insight into a process he called sexual selection, which he distinguished from natural selection. There may be survival of the fittest, but there's also survival of the sexiest. Today the sex-related selection process doesn't get much attention outside scientific circles, but it's a powerful tool for making sense of downright peculiar stuff. Arnq- vist and other biologists are expanding Darwin's frame- work, exploring the counterintuitive aspects of sex from flirtation to family life. And theorists are discussing fe- male behavior that Darwin never recognized, or perhaps just didn't care to discuss in print. Not-so-natural selection When Darwin first put his full idea of natural selection into print, he knew it wasn't enough. In 1859, he argued in On the Origin of Species that org- anisms best adapted to their environment survive in greater numbers and leave more offspring than do their less fit neighbors. Thus more suitable traits gradually replace clunkier versions. Yet antlers on stags and tails on peacocks could hardly be adaptations to the environment. Both antlers and tails may be so familiar that it takes a minute to summon a sense of their absurdity. They're huge. They must drain energy to produce. There's no way they improve agility in locomotion or foraging. "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!" Darwin wrote in a letter to the botanist Asa Gray, albeit in a whimsical paragraph. Nauseated or not, Darwin was willing to step beyond survival of the fittest. He devoted a few pages in the Origin to introduce sex- ual selection as a sort of wild oats younger brother of natural selection. Sexual selection, as Darwin formu- lated it in the sixth edition of Origin, depends "not on the struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for possession of the other." [insert -- the degree to which it's a male struggle for females -or- a female struggle for males, -or- both, varies from species to species; in homo sapiens, the additional element of cultural evolution is in play, interlocked with evolutionary struggles on genetic, sexual, and memetic levels (see Richard Dawkins' discussion of the 'meme') -- end insert] ... - - - end excerpts - - -
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