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. Dalton had just recently articulated the modern theory of the chemical atom, but nobody had any idea what atoms were really like. Physicists had not yet heard of the conservation of energy or any other laws of thermodynamics. Faraday hadn’t yet shown how to make electricity from magnetism, and no one had a clue about light’s electromagnetic identity. Geology was trapped in an ante-diluvian paradigm, 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 periodic table, Maxwell had discovered the math merging 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 Darwin’s perspicacious curiosity, intellectual rigor, personal perseverance and power of persuasion.

Charles Darwin Two centuries ago, modern biology’s founding father was born in England. He became the most celebrated scientist of his time, deciphering the records of life’s history from creatures extinct and living and thereby explaining the genesis of life’s diversity. Reproduced with permission from John van Wyhe ed., The Complete Work of Charles Darwin Online (http://darwin-online.org.uk/) Today his view of evolution by natural selection forms the core of the scientific study of life, and his mode of thought has earned its own addition to the lexicon of both scientific and popular discourse. Darwinian logic pervades the sciences of life, from the spread of viruses to interactions between and within human cultures, and has infiltrated other arenas as diverse as quantum physics and computer science. Far from a relic in textbooks, Darwinism breathes vitality into biology on a broad spectrum of research frontiers, inviting reflections on the life of, and the science made possible by, Charles Darwin.

Superlatives are commonplace in accounts of Darwin’s life. “An intellect which had no superior, and with a character which was even nobler than the intellect,” wrote Thomas Henry Huxley, Darwin’s champion in the original evolution debates. More recently Stephen Jay Gould called Darwin “the Muhammad Ali of biology.” But all Ali did was fight. Darwin was more like Willie Mays — he could hit, hit with power, run, field and throw. Translated to science, Darwin could read, reason, experiment, theorize and write — all as well or better than any of his contemporaries. Several scientists before Darwin had expressed the idea of evolution, some even hinting about the role of selection. But none had the wherewithal to perceive the abundance of evidence for evolution, deduce its many nuances, explain its mechanism, foresee and counter the many objections, and articulate it so convincingly to the world.

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And even had Darwin never written a word about evolution, he would be remembered today as one of the 19th century’s premier botanists, a superb entomologist and prominent geologist. He was a leading authority on carnivorous plants and coral reefs, pigeons and bees, earthworms and orchids, beetles and barnacles (especially barnacles). And yet he was never educated to be a scientist and held no academic position. All he brought to the scientific table was his brain. What a brain.

Woe unto the beetles

In his youth, Darwin was an average student but an avid reader. He had an early interest in observing and collecting, mainly beetles and butterflies. (“Woe unto the beetles of South America, woe unto all tropical butterflies,” a friend wrote in advance of Darwin’s famous sea voyage.) When it came time for higher education, Darwin headed to Edinburgh, a few hundred kilometers north of his birthplace in Shrewsbury, England, to study medicine. Soon discovering that he couldn’t stand the sight of blood, Darwin headed back south to Cambridge, to prepare for the clergy, a profession in which blood wouldn’t be such a problem.

His heart was not in religion, though, and his Cambridge years exposed him to other intellectual pursuits — lectures on botany, for instance, fieldwork with geologist Adam Sedgwick and friendships cultivated with biologists like John Stevens Henslow. Darwin’s interest in science was most significantly stirred while reading books by the German savant Alexander von Humboldt and the English astronomer John Herschel, which imbued in him “a burning zeal to add even the most humble contribution to the noble structure of Natural Science,” Darwin wrote decades later.

Henslow was perhaps the first to see in Darwin the makings of an uncommon scientist, and recommended him to serve as naturalist on the exploration voyage of the Beagle. During that ship’s leisurely circumnavigation of the globe, Darwin spent five years observing the diversity of the planet’s life, its sundry geological formations and rich fossil record of life long gone. Darwin’s eye saw more than what met it. He remarked on the variations between fossils and living forms, on the similarities of animals separated by vast distances and on the subtle differences and relationships among organisms on the South American mainland and the nearby Galápagos Islands.

By the time the voyage ended in October 1836, Darwin had amassed a mental catalog of life’s diversities and subtleties never before held in one head. It gave him a lot to think about.

Sick at Down

Darwin’s dispatches to England during the Beagle trip made him a scientific celebrity by the time he returned, and he hobnobbed with the leading lights of London’s elite. But soon ill health drove him southeast of London to a rural home (known as Down House) near the town of Downe.

For the rest of his life, Darwinsuffered, almost daily, from a mystery illness something akin to repetitive food poisoning. Doctors of his day couldn’t help him; modern diagnosticians have speculated on a variety of disorders, ranging from lactose intolerance to Crohn’s disease.

Darwin’s barnacles Top: Feeding goose barnacles Bottom: Balanus tintinnabulum barnacles David Shale; Reproduced with permission from John van Wyhe, ed., The Complete Work of Charles Darwin Online (darwin-online.org.uk)

Whatever it was, Darwin’s illness, a curse to him, perhaps established the circumstances subserving his scientific success. Forced to live in the country, he had no job and few distractions. He could devote his time to investigating nature in his own way. He spent eight years studying every aspect of every species of barnacle, for instance. All that time he also read with a vengeance, compiling and indexing detailed notes from book after book. He read virtually all of every issue of the journal Nature, taking special delight in the physics and math articles that he admitted he could not understand. He read science and philosophy and history and even trashy novels (there should be a law, he said, against unhappy endings). When Darwin opined, he knew what he was talking about, and he knew what everybody else knew, too.

He knew so much that he could often see what others couldn’t, and he could also reason about things without wondering whether his suspicions would be supported by observations — he knew what observations had already been made. If they were insufficient, he made his own, growing orchids, breeding pigeons, spying on earthworms.

Of all his reading, the most signal was the 1798 essay on population by Thomas Malthus, which Darwin perused “for amusement” in 1838. About 15 months earlier, Darwin had begun a systematic investigation of “the species question,” an issue at biology’s foundation. Conventional wisdom held that species had been created individually and were immutable (in much the way that astronomers assumed the universe to be everlastingly static). Some thinkers, though (including Darwin’s grandfather, Erasmus), believed otherwise. While on the Beagle, Darwin began to suspect that immutability could not be correct (though he had been unimpressed by grandpa’s book, finding it to contain an excessively high ratio of speculation to fact). But the idea of natural selection had not yet entered the grandson’s mind.

Malthus helped. Population, unchecked, would grow uncontrollably and run out of resources, he wrote. Scarcity kept populations in check; not all who were born could survive to reproduce. Darwin recognized in this account the “struggle for existence” he had observed in all manner of plants and animals. “It at once struck me that under these circumstances favorable variations would tend to be preserved and unfavorable ones to be destroyed,” he wrote in his autobiography. “The result of this would be the formation of new species. Here, then, I had at least got a theory by which to work.”

By 1842 he had prepared a rough 35-page outline (in pencil) of his evolutionary ideas, expanded by 1844 to a 230-page manuscript. In a letter to his wife, he allowed that his theory would be “a considerable step in science,” if it ever were to be accepted “even by one competent judge.” He asked in that letter that she be sure to publish the manuscript if he died before getting around to it himself. He did show it to a couple of colleagues, but otherwise the most earthshaking ideas in the history of biological science remained unpublicized. Darwin was busy classifying barnacles.

By 1854 he had begun spending most of his time on the species question, and in 1856 the geologist Lyell warned him to publish soon, before another naturalist anticipated him. Sure enough, two years later Alfred Russel Wallace, working in Indonesia, arrived at nearly the same notion — that species developed over time as small variations accumulated, with favorable ones enhancing survival. For counsel and comment, Wallace sent his paper to — Darwin.

Dismayed, Darwin sought advice from Lyell. Wallace’s idea was sound, and deserved to be published. Could Darwin now dare publish himself, without appearing to be stealing Wallace’s discovery?

Lyell and Henslow brokered a compromise. Wallace’s paper would be read to the Linnean Society, and so would an extract of Darwin’s 1844 manuscript, at one session, with Lyell and Henslow vouching that they had indeed seen Darwin’s work years earlier. Wallace was acknowledged, but Darwin’s claim to priority was preserved.

That hardly mattered, though. It was Darwin’s artful reasoning and marshaling of the evidence that established evolution by natural selection, as propagated in his masterwork, On the Origin of Species. Published in 1859, it electrified the scientific and intellectual world, evoking the prejudicial condemnation that afflicts most great new insights, but also filling the open-minded with food for centuries’ worth of future biological thought.

A simple solution

Darwin’s notebooks Notebooks full of writings and sketches, including this tree of life, document Charles Darwin’s ideas and inspiration. Tama/Getty

For so momentous a problem, Darwin’s solution seems elegantly simple, although also so subtle that its exposition is often badly mangled. Offspring differ slightly from their parents and each other (descent with modification), making some “fitter” than others in the struggle for existence (survival of the fittest). Over periods of time unimaginably long, the small changes from generation to generation accumulate, mutating one species into others. On smaller scales, over shorter times, such accumulated changes can be seen in various breeds of dogs or pigeons or plants, often induced by the artificial selection of particular traits by human breeders. On evolutionary scales of millions of years, the selection driving the appearance of new species is natural.

Some scientists (such as Huxley) saw the truth in Darwin’s views immediately; others came to agree gradually. Many, of course, disagreed bitterly and attacked both Darwin and his book. But most of the “rebuttals” of evolution, even today, merely raise points that Darwin anticipated and countered. Gaps in the fossil record? To be expected, Darwin explained, because the geological record was so imperfect, as if only a few pages remained from only the most recent volume in the entire encyclopedia of the Earth’s history. Complexity of the eye? The slightest sensitivity to light would aid in survival, and more versatile, focused organs should develop over a long enough time.

Besides explaining the vagaries of life-forms that nature presented, Darwin’s work, in a sense, also made spectacularly successful predictions. One was the requirement for a mutable mechanism of heredity. Subsequent genetic research, from Mendel to Watson and Crick, produced just what Darwin ordered. The other was the need for a very old Earth, providing the eons of time necessary for natural selection’s choices to accumulate. Prominent physicists of the day contended the planet was much too young for that, but Darwin’s original intuition eventually proved accurate.

Darwin attributed his success to “love of science” and “unbounded patience” and “industry in observing and collecting facts.” He understood fully the importance of his work, but his humility permitted only understatement. “With such moderate abilities as I possess,” he wrote, “it is truly surprising that I should have influenced to a considerable extent the belief of scientific men on some important points.”

As a scientist, Darwin was both chronicler and synthesizer, experimentalist as well as theorist. His power to unearth biology’s secrets so successfully stemmed from his devotion to acquiring all the evidence and assessing it honestly. He compiled facts from all possible sources, arranging them to reveal the most logical general conclusions. He could explain all the subtle points of natural selection and its power by citing observations from the Beagle voyage, the writings of experts from around the world, or his own experiments in breeding pigeons, dissecting barnacles, tormenting ants. He could demonstrate how natural selection reconciles observations otherwise irreconcilable if species had been created separately and remained immutable.

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. Psychologists try to explain behavior based on what mental habits would have enhanced survival as human ancestors were evolving. Biomedical researchers grapple with evolutionary principles in fighting microbial resistance to antibiotics. Computer scientists mix and select segments of binary code to generate optimal computer programs. 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. Speciation isn’t always gradual, change isn’t always the result of selection, organisms are not the only units of selection, evolutionists now believe. Darwin foresaw some of these views, and he would have embraced them all — as a man of science willing “to give up any hypothesis, however 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 established in science, inseparably incorporated with the common thoughts of men.”