Charles Robert Darwin (1809-1882) was born the fifth of six children into a wealthy Shropshire gentry family. His father, the hugely portly Robert Darwin, was a successful physician and son of the famous poet and naturalist, Erasmus Darwin. Charles Darwin's mother died when he was eight years old. Darwin, watched over by his elder sisters and maidservants, grew up amidst wealth, comfort and country sports.
In October 1825 he went to Edinburgh University to study medicine with a view to becoming a physician, like his father. While in Edinburgh, Darwin investigated marine invertebrates with the guidance of Robert Grant. Darwin did not like the study of medicine and so his father decided that the church was a respectable alternative.
The advantage to becoming a country parson, as Darwin saw it, would be the freedom to pursue his growing interest in natural history. To become ordained he must first get a B. A. degree from an English university.
On 15 October 1827 he was admitted to Christ's College, Cambridge. He did not come into residence in Cambridge until January 1828. Darwin was never a model student, but he did become a passionate amateur naturalist. He began avidly collecting beetles along with keen fellow students. Darwin became the devoted follower of Professor of botany J. S. Henslow. In 1831, he was taught the rudiments of field geology by Professor Adam Sedgwick during a tour of north Wales.

Henslow was able to pass on to Darwin the opportunity of travelling on a survey ship, HMS Beagle, as naturalist and commander Robert FitzRoy's gentleman companion. The round-the-world journey lasted five years. Darwin spent most of these years investigating the geology and studying animals and plants of the lands he visited, especially South America, the Galapagos islands, and pacific oceanic islands. He recorded many of his specimens and observations immediately in field notebooks. His telegraphic pocket notes were later used in writing up more formal notes, such as his animal notes. Later he recorded his experiences in a diary which became the basis of his famous book Journal of researches (1839) now known as Voyage of the Beagle. Darwin was particularly influenced by the works of men of science like astronomer Sir John Herschel, traveller Alexander von Humboldt and geologist Charles Lyell. Lyell's new book, Principles of Geology (1830-3), profoundly influenced Darwin. Lyell offered not just a new geology but a new way of understanding nature. Lyell showed how tiny, slow, gradual and cumulative change over immense periods of time could produce large changes. Darwin had the opportunity to witness all of these forces, such as erosion, earthquakes and volcanoes, during the Beagle voyage and he became convinced that Lyell's views were correct. Darwin made several very important discoveries about the geology of South America, volcanic islands and the origins of coral reefs by building on Lyell's ideas.

During the trip, Darwin also collected organisms of all sorts which he recorded in his specimen lists and zoology notes. These formed the basis of the five volume series he edited and superintended after returning home, The zoology of the voyage of H.M.S. Beagle (1838-43). Darwin also unearthed many fossil creatures in South America. He wondered why the fossils resembled the present inhabitants of that continent more than any other species. Where had the new species come from? In fact, why was the world covered with so many different kinds of living things? Why were some very similar to one another and others vastly different? If species were somehow created to fit their environments, as was then believed, why were jungle species different in Asia, Africa and South America despite the similarity of climate?
Later in London, experts, such as the ornithologist John Gould, were able to tell him how many of the species of plants and animals he had collected in the Galapagos Islands were unique species, found nowhere else. Clearly they resembled species from South America, 600 miles away. It seemed to Darwin as if stray migrants from South America had come to the Galapagos, after the islands rose from the sea as volcanoes, and then changed over time in isolation on the islands.

Darwin began to speculate on how new species could arise by natural observable causes. His idiosyncratic eclecticism led him to investigate some unconventional evidence. He made countless inquiries of English pouteranimal breeders, both farmers and hobbyists like pigeon fanciers, trying to understand how they made distinct breeds of plants and animals. Gradually Darwin concluded that organisms were infinitely variable. One conventional view of the time was that species had been created where they are now found, in  accordance with the environment. Few men of science then held to the view that there had been only a single species creation event. The fossil evidence seemed to show very many creations had occurred in different geological eras.
Darwin was familiar with the evolutionary speculations proposed earlier by his grandfather Erasmus and by the great french zoologist Jean-Baptiste Lamarck. But already Darwin's theorizing had extended in new directions. He was thinking of the history of life not as a number of independent lineages somehow impelled to progress upwards from monads to monkeys. Instead Darwin saw all life as a single genealogical tree, branching and rebranching. Thus similarities between different kinds of living things would be expected from their joint ancestry or common descent. Darwin's speculations and early theorizing were recorded, between 1836 and 1844, in a series of notebooks similar to those he kept during the Beagle voyage.

In September 1838, Darwin read Thomas Malthus's Essay on the Principle of Population (1798). Malthus argued that human geometrical population growth, unless somehow checked, would necessarily outstrip food production. The focus of this argument inspired Darwin. He realised that an enormous proportion of living things are always destroyed before they can reproduce. This must be true because every species would otherwise breed enough to fill the earth in a few hundred generations. Instead populations remain roughly stable year after year. The only way this can be so is that most offspring (from pollen, to seeds and eggs) do not survive long enough to reproduce.
Darwin, already concentrating on how new varieties of life might be formed, suddenly realised that the key was whatever made a difference between those that survive to reproduce and those that do not. He came to call this open-ended collection of causes 'natural selection' because it was analogous to breeders choosing which individuals to breed from and thus changing a breed markedly over time.

Darwin did not know precisely how inheritance worked-genes and DNA were totally unknown. Nevertheless he appreciated the crucial fact that inheritance mattered. Offspring resemble their parents and only the survivors would pass on their form and abilities. Their characteristics would persist and multiply whilst characteristics of those that did not live long enough to reproduce would decrease. Darwin first thought in terms of populations of diverse heritable things with no essence-not representatives of ideal types as many earlier thinkers had done. From his observations and experiments with domesticated and wild plants and animals he could find no limits to the extent organic forms could vary and change through generations. Thus the existing species in the world were related not along a ‘chain of being' or separated into artificially separate species categories but were all related on a genealogical family tree through ‘descent with modification'.
Darwin also identified another means by which some individuals would have descendants and others would not. He later called this sexual selection. This theory explained why the male sex in many species produce colourful displays or specialised body parts to attract females or to compete against other males. Those males who defeat other males, or are selected for breeding by females leave more offspring and so subsequent generations resemble them more than those who succeed less often.

Darwin married his cousin Emma Wedgwood in 1839. They had 10 children, two sadly dying in infancy, and daughter Annie dying at the age of 10. In 1842, the Darwins moved to Down House in the village of Downe, Kent. Darwin's many acute and innovative books and articles forged a great reputation as a geologist, zoologist and scientific traveller. His eight years grueling work on barnacles, published 1851-4 enhanced his reputation as an authority on taxonomy as well as geology and the distribution of flora and fauna as in his earlier works. Nevertheless there is no reason to allege, as is so often done, that Darwin needed to supplement his reputation or skills before he could publish his species theory.
Darwin conducted breeding experiments with animals and plants and corresponded and read widely for many years to refine and substantiate his theory of evolution. In 1842 he prepared an essay outlining his theory. This was greatly expanded in another essay written in 1844. After completing his work on barnacles Darwin immediately turned to his theory to explain species. He was more than half way through a great work on the subject when he was interrupted in 1858 by a letter from an English naturalist and collector, Alfred Russel Wallace. Wallace was then collecting in South East Asia. In an essay enclosed Wallace described his ideas ‘'On the Tendency of Varieties to Depart Indefinitely From the Original Type'. Darwin was struck by the similarity. He sent the letter on to Lyell and it was decided, with J. D. Hooker, to avoid competition for priority, to publicise abstracts by both men as soon as possible. The papers were read, in the absence of Darwin and Wallace, at a meeting of the Linnean Society of London in 1858 and later published in their Proceedings. Darwin worked on creating an ‘abstract' of his work-in-progress on natural selection. This abstract became one of the most famous books ever written On the Origin of Species (24 november 1859).

Although Darwin convinced most of the scientific community that descent with modification, or evolution, was true, many rejected natural selection as the primary mechanism. Darwin was not the first to propose that life evolves. A glance at his ‘'An historical sketch of the progress of opinion on the origin of species' shows that Darwin made no pretence to have originated or discovered evolution or descent with modification. However, Darwin's understanding of branching descent was more accurate, refined and convincing than his predecessors.
Darwin, as an unquestionably respectable authority in elite science, publicly threw his weight on the side of evolution, and soon young allies like Hooker, T. H. Huxley, and John Tyndall publicly threw their own weight towards the same position. Darwin's name is so linked with evolution because he was the high-status insider who made evolution acceptable, even respectable. In the two decades after the publication of Origin the great majority of the scientific community came to accept that Darwin was right about the evolution of life. But natural selection was often not accepted. Natural selection's canonisation had to wait until the modern synthesis of Darwinism with Mendelian genetics in the 1930s.
Darwin's theory of genealogical evolution (as opposed to earlier theories by Lamarck or Vestiges which entailed independent lineages unfolding sequentially because of an innate tendency towards progress) made sense of a host of diverse kinds of evidence such as the succession of fossil forms in the geological record, geographical distribution of life (biogeography), recapitulative appearances in embryology, homologies like the hand of a man and the wing of a bat, vestigial organs, nesting taxonomic relationships observed throughout the world and so forth.

The reactions to Darwin's evolutionary theories were varied and pronounced. In zoology, taxonomy, botany, palaeontology, philosophy, anthropology, psychology, literature and religion Darwin's work engendered profound reactions-many of which are still ongoing. Most disturbing of all, however, were the implications for the cherished uniqueness of man. Although Darwin refrained from discussing the derivation of any particular species, including man, in the Origin except for his famous sentence: ‘Much light will be thrown on the origin of man and his history' many people who read the book could think only about what this genealogical view of life meant for human beings. This is a subject Darwin later took up in The Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872). In these brilliantly original and seminal works Darwin showed that there is no difference of kind between man and other animals, but only of degree. Rather than an unbridgeable gulf, Darwin showed there is a gradation of change not only between man and other animals, but between all organic forms which is a consequence of the gradual change continuously and cumulatively operating over time.

Darwin's extraordinary achievements are not restricted to his early scientific works and his evolutionary works. His keen observation, imagination, curiosity and determination allowed him to make strikingly prescient contributions to ecology, botany and a dozen of what would later be distinct disciplines. Darwin was very impressed by the inter-relatedness of different species, climate and environment. He proposed new solutions to how organisms spread across the globe.
In his final book published the year before his death, The formation of vegetable mould through the action of worms (1881) Darwin again made an important contribution, and, as was characteristic of him, which revealed the amazing complexity and importance of a natural process of gradual accumulation, which no one seemed to have grasped before, and that had all along been under our feet.
Charles Darwin was a kind, good-humoured, pleasant man, unassuming and profoundly modest. He suffered from ill health much of his adult life. He nevertheless remained driven to understand nature and to remain part of the elite scientific world he respected and admired. Darwin died in April 1882 and is buried in Westminster Abbey near Isaac Newton.