by Leslie E. Orgel

Growing evidence supports the idea that the emergence of catalytic RNA was a crucial early step. How that RNA came into being remains unknown.
LESLIE E. ORGEL is senior fellow and research professor at the Salk Institute for Biological Studies in San Diego, which he joined in 1965. He obtained his Ph.D. in chemistry from the University of Oxford in 1951 and subsequently became a reader in chemistry at the University of Cambridge. While at Cambridge, he contributed to the development of ligand- field theory. The National Aeronautics and Space Administration supports his extensive research on chemistry that may be relevant to the origin of life. Orgel is a fellow of the Royal Society and a member of the National Academy of Sciences.
When the earth formed some 4.6 billion years ago, it was a lifeless, inhospitable place. A billion years later it was teeming with organisms resembling blue-green algae. How did they get there? How, in short, did life begin? This long-standing question continues to generate fascinating conjectures and ingenious experiments, many of which center on the possibility that the advent of self-replicating RNA was a critical milestone on the road to life.
Before the mid-17th century, most people believed that God had created humankind and other higher organisms and that insects, frogs and other small creatures could arise spontaneously in mud or decaying matter. For the next two centuries, those ideas were subjected to increasingly severe criticism, and in the mid-19th century two important scientific advances set the stage for modern discussions of the origin of life.
In one advance Louis Pasteur discredited the concept of spontaneous generation. He offered proof that even bacteria and other microorganisms arise from parents resembling themselves. He thereby highlighted an intriguing question: How did the first generation of each species come into existence?
The second advance, the theory of natural selection, suggested an answer. According to this proposal, set forth by Charles Darwin and Alfred Russel Wallace, some of the differences between individuals in a population are heritable. When the environment changes, individuals bearing traits that provide the best adaptation to the new environment meet with the greatest reproductive success. Consequently, the next generation contains an increased percentage of well-adapted individuals displaying the helpful characteristics. In other words, environmental pressures select adaptive traits for perpetuation.
Repeated generation after generation, natural selection could thus lead to the evolution of complex organisms from simple ones. The theory therefore implied that all current life-forms could have evolved from a single, simple progenitor – an organism now referred to as life’s last common ancestor. (This life-form is said to be “last” not “first” because it is the nearest shared ancestor of all contemporary organisms; more distant ancestors must have appeared earlier.)
Darwin, bending somewhat to the religious biases of his time, posited in the final paragraph of The Origin of Species that “the Creator” originally breathed life “into a few forms or into one.” Then evolution rook over: “From so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.” In private correspondence, however, he suggested life could have arisen through chemistry, “in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. present.” For much of the 20th century, origin-of-life research has aimed to flesh out Darwin’s private hypothesis – to elucidate how, without supernatural intervention, spontaneous interaction of the relatively simple molecules dissolved in the lakes or oceans of the prebiotic world could have yielded life’s last common ancestor.
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An Interview with Andy Knoll

What are the origins of life? How did things go from non-living to living? From something that could not reproduce to something that could? One person who has exhaustively investigated this subject is paleontologist Andrew Knoll, a professor of biology at Harvard and author of Life on a Young Planet: The First Three Billion Years of Life. In this wide-ranging interview, Knoll explains, among other compelling ideas, why higher organisms like us are icing on the cake of life, how deeply living things and our planet are intertwined, and why it’s so devilishly difficult to figure out how life got started.
NOVA: When people think of life here on Earth, they think of animals and plants, but as you say in your book, that’s really not the history of life on our planet, is it?
Knoll: It’s fair to say when you go out and walk in the woods or on a beach, the most conspicuous forms of life you will see are plants and animals, and certainly there’s a huge diversity of those types of organisms, perhaps 10 million animal species and several hundred thousand plant species. But these are evolutionary latecomers. The history of animals that we’ve recorded from fossils is really only the last 15 percent or so of the recorded history of life on this planet. The deeper history of life and the greater diversity of life on this planet is microorganisms—bacteria, protozoans, algae. One way to put it is that animals might be evolution’s icing, but bacteria are really the cake.
NOVA: So we live in their world rather than the other way around?
Knoll: We definitely live in a bacterial world, and not just in the trivial sense that there’s lots of bacteria. If you look at the ecological circuitry of this planet, the ways in which materials like carbon or sulfur or phosphorous or nitrogen get cycled in ways that makes them available for our biology, the organisms that do the heavy lifting are bacteria. For every cycle of a biologically important element, bacteria are necessary; organisms like ourselves are optional.
NOVA: What is your definition of life?
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By Stefan Lovgren

Scientists have sequenced the genome of the chimpanzee and found that humans are 96 percent similar to the great ape species.
“Darwin wasn’t just provocative in saying that we descend from the apes—he didn’t go far enough,” said Frans de Waal, a primate scientist at Emory University in Atlanta, Georgia. “We are apes in every way, from our long arms and tailless bodies to our habits and temperament.”
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Only this site contains Darwin’s complete publications, 20,000 private papers, the largest Darwin bibliography, manuscript catalogue and hundreds of supplementary works: specimens, biographies, obituaries, reviews, reference works and much more.
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By R. G. Price

There is a growing effort among opponents of evolution to portray Charles Darwin as a racist, and evolutionary theory as morally reprehensible, even to claim that Darwinism “provided Hitler and the Nazis with a scientific justification for the policies they pursued once they came to power.”
These accusations are not merely from fringe radicals, but have indeed been made by elected officials and published in books by university professors, as we shall see.
Most disturbing, however, is the lack of significant rebuttal to these charges. Many people in fact, including some evolutionary biologists, find it easy to believe that perhaps Darwin was a racist, and perhaps evolutionary theory did contribute to Nazi ideology.
In 2001 African American State Representative Sharon Broome of Louisiana sponsored a resolution to condemn “Darwinist ideology” as racist and liken it to Nazism.
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By Adrian Desmond and James Moore

Global brands don’t come much bigger than Charles Darwin. He is the grizzled grandfather peering from book jackets and billboards, from textbooks and TV — the sage on greeting cards, postage stamps and commemorative coins. Darwin’s head on British £10 notes radiates imperturbability, mocking those who would doubt his science. Hallow him or hoot at him, Darwin cannot be ignored. Atheists trumpet his ‘atheism’, liberals his ‘liberalism’, scientists his Darwinism, and fundamentalists expend great energy denouncing the lot. All agree, however, that for better or worse Darwin’s epoch-making book On the Origin of Species transformed the way we see ourselves on the planet.
How did a modest member of Victorian England’s minor gentry become a twenty-first-century icon? Celebrities today are famous for being famous, but Darwin’s defenders have a different explanation.
To them Darwin changed the world because he was a tough-minded scientist doing good empirical science. As a young man, he exploited a great research opportunity aboard HMS Beagle. He was shrewd beyond his years, driven by a love of truth. Sailing around the world, he collected exotic facts and specimens — most notably on the Galapagos islands — and followed the evidence to its conclusion, to evolution. With infinite patience, through grave illness heroically borne, he came up with ‘the single best idea anyone has ever had’ and published it in 1859 in the Origin of Species. This was a ‘dangerous idea’ — evolution by ‘natural selection’ — an idea fatal to God and creationism equally, even if Darwin had candy-coated this evolutionary pill with creation-talk to make it more palatable. Evolution annihilated Adam; it put apes in our family tree, as Darwin explained in 1871 when he at last applied evolution to humans in The Descent of Man. Secluded on his country estate, publishing book after ground-breaking book, Darwin cut the figure of a detached, objective researcher, the model of the successful scientist. And so he won his crown.
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By Kate Wong

When Charles Darwin wrote On the Origin of Species, he pondered the evolution of organisms ranging from orchids to whales. Conspicuously missing from his magnum opus, however, was any substantive discussion of how humans might have arisen. He wrote only “light will be thrown on the origin of man and his history.” Scholars attribute Darwin’s relative silence on this matter to reluctance on his part to further nettle the Victorian establishment (and his pious wife), for whom the origin of all living things—especially humans—was God’s work.
Thomas Henry Huxley, the biologist otherwise known as “Darwin’s bulldog,” had no such reservations. In 1863 Huxley penned Evidence as to Man’s Place in Nature, in which he explicitly applied Darwin’s theory of evolution to humans, arguing that we had descended from apes. Eight years later Darwin himself, possibly encouraged by Huxley’s effort, wrote The Descent of Man. In it he declared the chimpanzee and gorilla our closest living relatives based on anatomical similarities and predicted that the earliest ancestors of humans would turn up in Africa, where our ape kin live today. At the time, only a handful of human fossils were known—all of them Neandertals from sites in western Europe.
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By Steve Mirsky

“If I were to give an award for the single best idea anyone ever had, I’d give it to Darwin.” So wrote philosopher Daniel Dennett in his 1995 book Darwin’s Dangerous Idea. “In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning and purpose with the realm of space and time, cause and effect, mechanism and physical law.”
Dennett’s musing really hits home to anyone who took introductory biology that did not include evolution: such a course is a giant survey of the different kinds of plants, animals and other organisms of our planet, tied together by a single principle–you needed to know it for the final. But evolution by natural selection ties all life together with process and chemistry. As the great biologist Theodosius Dobzhansky famously, and correctly, said, “Nothing in biology makes sense except in the light of evolution.”
The idea itself is fairly easy to grasp (which may be one reason why people who would never dream of finding fault with Einstein feel qualified to dispute Darwin): in populations of organisms, each individual is a bit different from every other; the differences may give that individual a bit of a survival advantage; that individual is more likely to pass on the traits that helped it survive; that trait becomes more widespread; rinse; repeat. In a few hundred million years, you can go from amoebae to elephants (and still have amoebae).
Of course, in the decades since the publication of Origin of Species, scientists have learned much more about the evolutionary process than Darwin could have dreamed of. Genes get duplicated; chromosomes get rearranged; viruses shuttle genetic information from one species directly to another; individual genes govern the activity of other genes. But Darwin got much of the overall picture right–a remarkable achievement for a man working with whole organisms, before the unraveling of heredity on the molecular level of DNA.
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By Bertrand Russell

The eminent theologian Dr. Thaddeus dreamt that he died and pursued his course toward heaven. His studies had prepared him and he had no difficulty in finding the way. He knocked at the door of heaven, and was met with a closer scrutiny than he expected. “I ask admission,” he said, “because I was a good man and devoted my life to the glory of God.” “Man?” said the janitor, “What is that? And how could such a funny creature as you do anything to promote the glory of God?” Dr. Thaddeus was astonished. “You surely cannot be ignorant of man. You must be aware that man is the supreme work of the Creator.” “As to that,” said the janitor, “I am sorry to hurt your feelings, but what you’re saying is news to me. I doubt if anybody up here has ever heard of this thing you call ‘man.’ However, since you seem distressed, you shall have a chance of consulting our librarian.”
The librarian, a globular being with a thousand eyes and one mouth, bent some of his eyes upon Dr. Thaddeus. “What is this?” he asked the janitor. “This,” replied the janitor, “says that it is a member of a species called ‘man,’ which lives in a place called ‘Earth.’ It has some odd notion that the Creator takes a special interest in this place and this species. I thought perhaps you could enlighten it.” “Well,” said the librarian kindly to the theologian, “perhaps you can tall me where this place is that you call ‘Earth.'” “Oh,” said the theologian, “it’s part of the Solar System.” “And what is the Solar System?” asked the librarian. “Oh,” said the theologian, somewhat disconcerted, “my province was Sacred Knowledge, but the question that you are asking belongs to profane knowledge. However, I have learnt enough from my astronomical friends to be able to tell you that the Solar System is part of the Milky Way.” “And what is the Milky Way?” asked the librarian. “Oh, the Milky Way is one of the Galaxies, of which, I am told, there are some hundred million.” “Well, well,” said the librarian, “you could hardly expect me to remember one out of so many. But I do remember to have heard the word galaxy’ before. In fact, I believe that one of our sub-librarians specializes in galaxies. Let us send for him and see whether he can help.”
After no very long time, the galactic sub-librarian made his appearance. In shape, he was a dodecahedron. It was clear that at one time his surface had been bright, but the dust of the shelves had rendered him dim and opaque. The librarian explained to him that Dr. Thaddeus, in endeavoring to account for his origin, had mentioned galaxies, and it was hoped that information could be obtained from the galactic section of the library. “Well,” said the sub-librarian, “I suppose it might become possible in time, but as there are a hundred million galaxies, and each has a volume to itself, it takes some time to find any particular volume. Which is it that this odd molecule desires?” “It is the one called ‘The Milky Way,'” Dr. Thaddeus falteringly replied. “All right,” said the sub- librarian, “I will find it if I can.”
Some three weeks later, he returned, explaining that the extraordinarily efficient card index in the galactic section of the library had enabled him to locate the galaxy as number QX 321,762.
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