Tuesday, July 07, 2015

Biography of Charles Darwin | The theory of Evolution

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His scientific voyage around the world led him to formulate the theory of evolution, which collided head-on with the concepts of the time.
The scientific revolution of the Renaissance established a new astronomy where land ceased to be the center of creation; his defense earned Galileo an inquisitorial process. When, in the 19th century, the British naturalist Charles Darwin formulated on a scientific basis the modern theory of evolution in his work the origin of species (1859), also more angry reactions came from the ecclesiastical estates: the evolutionary model questioning the divine origin of life and of man. Once again (and therein lies the historical significance of the work of Darwin), scientific advances undermined convictions firmly rooted, kicking off a change of mentality of magnitude comparable to the Copernican revolution.

Charles Darwin
Charles Robert Darwin was born in Shrewsbury on February 12, 1809. He was the second son of Robert Waring Darwin, physician of Fame in the town, and Susannah Wedgwood, daughter of a famous Potter from Staffordshire, Josiah Wedgwood, promoter of the construction of a canal to unite the region with coastlines and a member of the Royal Society. His paternal grandfather, Erasmus Darwin, was a well-known physician and important naturalist, author of a long poem in heroic couplets presented an allegory of the Linnaean of sexual plants classification system, which was a literary success of the moment; Moreover, their theories about the inheritance of acquired characters were intended to fall into disrepute by work, precisely, of his grandson.
In addition to his brother, five years older, Charles had three sisters also older and one younger sister. After the death of his mother in 1817, his education took place at a local school; in his old age, I would remind his experience there as the worst thing that could happen to their intellectual development. Since childhood he gave signs of a taste for natural history which he considered innate and, in particular, a great hobby of collecting things (shells, stamps, coins or minerals), the kind of passion that leads one to become a systematic naturalist, an expert, or a miser».

Vocation and education

In October 1825 Darwin entered the University of Edinburgh to study medicine by decision of his father, he always remembered with affection and admiration, and psychoanalytic connotations not without respect; the Darwin hypochondriasis in adulthood would always combine distrust doctors with unlimited faith in instinct and methods of treatment of his father.
The young Charles, however, did not get interested in the race; disgust for surgical operations and the inability of teachers to attract its attention, it came to joining the growing conviction that the inheritance of his father would allow a comfortable subsistence without exercising a profession as the doctor. So, at the end of two years, his father, ready to prevent it from turning into an idle son of family, suggested an ecclesiastical career. After solve own scruples about their faith, Darwin warmly accepted the idea to become a rural clergyman, and in early 1828, after cooled his classical training, entered the Christ College Cambridge completo.
In Cambridge, as before in Edinburgh and at school, Darwin lost time in what refers to the study, often neglected to satisfy his passion for hunting and riding activities occasionally culminating in dinner with friends at which Darwin retained a (possibly exaggerated) memory as of real debauchery. However, his indolence was heated by the acquisition of two separate tastes in painting and music, which he was surprised later, given their absolute lack of musical ear and his inability to the drawing (a "bad irremediable» which, together with his practical ignorance of dissection, represented a disadvantage for their later works).

Charles Darwin (portrait of George Richmond, 1840)
More that academic studies he was obliged to pursue, Darwin extracted out in Cambridge of his voluntary attendance at classes of the botanist and entomologist John Henslow, whose friendship was "an invaluable benefit" and that had a direct intervention on two events that determined their future: the expedition to Wales and, above all, the voyage of the Beagle. At the end of his studies in April 1831, the Reverend Henslow convinced him that you develop in geology, matter by which classes received in Edinburgh had made him conceive true dislike, and introduced him to Adam Sedgwick, founder of the Cambrian system, who just started his studies about the same on an expedition to North Wales in April of that same year in the company of Darwin (thirty years later Henslow was forced to defend the common disciple to violent criticism directed by Sedgwick to evolutionary ideas).
But the decisive importance of the figure of the Reverend in the life of Darwin is measured above all by the fact that it was Henslow who provided Darwin the opportunity of embarking as a naturalist with Captain Robert Fitzroy and accompany him on the trip that it was proposed to on board the Beagle around the world. At first his father objected to the project, stating that it would only change opinion if «someone with common sense» was able to consider advisable to travel.
That someone was his uncle (and future father-in-law) Josiah Wedgwood, who interceded on behalf of his young nephew participate in the expedition; Meanwhile, the purpose of travel had been consolidated in Darwin from months earlier, when the reading of the works of the German naturalist Alejandro Humboldt aroused in him an immediate desire to visit Tenerife and began to learn Spanish and to learn about ticket prices.

The expedition of the Beagle

On December 27, 1831, the Beagle sailed from Davenport with Darwin aboard, ready to start that he called his "second life" after two months of grim waiting in Plymouth, while the ship was repaired the damage caused in its previous trip, and once the galerna deflect two attempts of starting. During that time, Darwin underwent 'palpitations and pains in the heart' of origin more than probably nervous, as perhaps also should it later be their frequent prostrations. Without knowing it, Darwin had run the risk of being rejected by Robert Fitzroy, since the captain, a convinced supporter of the fisiognomicas of the Swiss priest Johann Caspar Lavater theories, estimated initially that the nose of the naturalist did not reveal the energy and determination for the company.
The aim of the expedition led by Captain Fitzroy was the completion of the survey of Patagonia and Tierra del Fuego territories, the outline of the coasts of Chile, Peru and some Pacific Islands and carrying out a string of chronometric measurements around the world. The journey, of almost five years, led Darwin along the coasts of South America, to then return last year visiting the Galapagos, Tahiti, New Zealand, Australia, Mauritius and South Africa.

The voyage of the Beagle
During that period the mood of Darwin underwent a profound transformation. The old passion for the hunt survived the first two years with full force, and it was he who was responsible for firing shots at the birds and animals that went to swell their collections; gradually, however, this task was being entrusted to his servant as his attention was more and more absorbed by the scientific aspects of its activity.
The study of geology was, initially, the factor that most helped to convert the trip in the real formation of Darwin as a researcher, since with it came inexcusably in game the need of reasoning. Darwin took with him the first volume of principles of geology of Charles Lyell, author of the so-called theory of the current causes and that would be their partner in the exhibition of evolutionism; Since the recognition of the first geological terrain that visited (the island of Santiago, Cape Verde), Darwin became convinced of the superiority of the approach advocated by Lyell.
In Santiago he had for the first time the idea that the white rocks that watched had been produced by the melted lava of ancient volcanic eruptions, which, to slipping to the bottom of the sea, would have dragged crushed shells and corals communicating Rocky consistency. Towards the end of the voyage, Darwin was reported that Adam Sedgwick had expressed the view that the young man would become an important scientist; his father the successful outcome was the result of reading by the Reverend Henslow, to the Philosophical Society of Cambridge, of some of the letters sent by Darwin.

The Beagle in Tierra del Fuego
Among the scientific achievements of Darwin during the trip, the first to see the light (1842) would be the theory on the formation of coral reefs by growth at the edges and on top of islands that were slowly sinking. Along with this hypothesis and the establishment of the geological structure of some islands such as Santa Elena, it is necessary to emphasize the discovery of the existence of a certain similarity between the fauna and the flora of the Galapagos Islands with the of South America, as well as differences between a same animal or plant specimens collected in the different islands What made him suspect that the theory of the stability of the species could be put into question. It was the theoretical elaboration of those observations which, years later, resulted in its statement of the evolutionary thesis.

The fruits of a journey

Darwin returned to England on 2 October 1836; the change in those years must have been as remarkable as his father, «the sharpest observer which has seen natural skeptical and that was far from belief in phrenology», ruled to return it to see that the shape of his head had changed completely. His health had also be altered; towards the end of the trip you dizzy easier that in its early days, and in the autumn of 1834, had been ill for a month. He has speculated on the possibility that, in March 1835, he contracted a latent infection called Chagas disease as a result of the bite of an insect.
Anyway, from their arrival until the beginning of 1839, Darwin lived the most active months of his life, despite losses of time which you occasionally feel unwilling. He worked in the drafting of his journal of the voyage (published in 1839) and in the drafting of two texts presenting geological and Zoological observations. Based in London since March 1837, devoted himself to "do a bit of society", acting as Honorary Secretary of the Geological Society and making contact with Charles Lyell.

Charles Darwin (detail of a portrait of John Collier, 1881)
In July of that year he began to write his first notebook about their new points of view about the "transmutation of species', which were imposing to him reflect about their own observations on the classification, the affinities and the instincts of animals, and also as a result of an exhaustive study of how much information she could collect concerning the transformations experienced by species of plants and pets due to the intervention of breeders and horticulturists.
His research, carried out on the basis of "authentic baconianos principles", soon convinced him that the selection was the key to human success in obtaining useful improvements in the races of plants and animals. The possibility that this same selection acted on the organisms living in a natural state became it apparent when in October 1838 he read Thomas Malthus's essay on the principle of population "as a hobby".
Willing as he was, by its prolonged observations on the habits of animals and plants, to perceive the universal presence of the struggle for existence, it occurred instantly that, in these circumstances, favourable variations would tend to preserve, while the unfavourable would disappear, resulting in the formation of new species. Darwin estimated that «finally, she got a theory to work with»; However, anxious to avoid prejudice, he decided to abstain for a while «write even more concise outline of the same». Pleasure private of a very brief summary (thirty-five pages written in pencil), which extended up to two hundred thirty pages in the summer of the year 1844 was allowed in June 1842.
Darwin had contracted marriage on 29 January 1839 with his cousin Emma Wedgwood. They resided in London until September of 1842, when the family settled in Down, in the County of Kent, looking for a way of life that is better adapted to frequent periods of disease, since the return from your trip, constantly afflicted to Darwin. Moreover, the years of London were, so that social life is concerned, the prelude to an almost total withdrawal in Down, where he lived until the end of his days. On December 27, 1839 was born the first son of the marriage, and Darwin started with a series of observations, which were extended over the years, on the expression of the emotions in man and animals. Had ten children, six men and four women, born between 1839 and 1856, including two girls and a boy died in childhood.

Emma Wedgwood
During the first years of their stay in Down, Darwin completed the writing of his works on geological topics and also dealt with a new edition of his travel diary, which initially had appeared as part of the work published by Fitzroy on his expeditions; in autobiographical notes written in 1876 (revealingly titled Recollections of the Development of my Mind and Character), Darwin acknowledged that "the success of this my first literary offspring always inflames my vanity more than in any other of my books".
From 1846 to 1854, Darwin was occupied in writing their monographs on the cirripodos, which had been interested during your stay on the coasts of Chile to find copies of a type which posed problems of classification. Those years of work served to turn it into a true naturalist according to the demands of their time, adding to the learning acquired during the trip the theoretical training needed to address the problem of the relationships between natural history and taxonomy. In addition, his studies on barnacles reported a solid reputation among specialists, being awarded in November 1853 by the Royal Society, of which Darwin was a member since 1839.

The theory of evolution

In early 1856, Charles Lyell advised to Darwin to work in the full development of their ideas about the evolution of species. Darwin then undertook the drafting of a work that, still being conceived on a scale three or four times higher than the then it was to be effectively published text, represented, in his opinion, a mere summary of the material collected in this regard.
But when he was in the middle of the work, their plans went to ruin by an event that precipitated the events: in the summer of 1858 was a manuscript that contained a brief but explicit exposition of a theory of evolution by natural selection, which coincided exactly with their own points of view. The text, sent from the island of Ternate, in the Moluccas, was the work of Alfred Russel Wallace, a naturalist from 1854 was in the Malay Archipelago and that already in 1856 Darwin had sent an article about the emergence of new species that became widely identified.
In his new job, Wallace talked, like Darwin, "fight for existence", an idea which, interestingly, also had come her inspired by the reading of Malthus. Darwin put Lyell in the history of the issue and informed him their hesitancy about how proceeding with respect to the publication of their own theories, coming to express their intention to destroy their own writing rather than appear as a usurper of the rights of Wallace to the priority.
The incident ended in a Solomonic way thanks to the intervention of Lyell and the botanist Joseph Dalton Hooker, future director of the Kew Gardens created by his father and one of the main defenders of the evolutionary theories of Darwin, with whom he joined a close friendship since 1843. Following the advice of both, Darwin summed up his manuscript, which was presented by Lyell and Hooker to the Linnean Society on 1 July 1858, along with the work of Wallace and an excerpt from a letter sent by Darwin on 5 September 1857 the American botanist Asa Gray, which contained an outline of his theory.
Alfred Wallace not never called into question the correctness of the procedure; later, in 1887, he expressed his appreciation for the way in which all had developed, claiming that he had no «love work, experiment and so preeminent detail in Darwin, without which any thing that I would have been able to write would not never convinced anyone».

The origin of the species

After the episode, Darwin was forced to shelve their hesitations so their ideas advertising referred, and addressed the task of reducing the scale of the work that was at hand to send as soon as possible to the press; "thirteen months and ten days of hard labour" was finally written the book on the origin of species by means of natural selection or the preservation of favored in the struggle for life races, long title is almost the enunciation of his thesis and frequently abbreviated as the origin of species. The first 1,250 copies were sold the same day of its emergence, on November 24, 1859.
The theological implications of the work, which attributed to natural selection powers hitherto reserved for the divine, were the cause of that immediately began to form a fierce opposition, headed by paleontologist Richard Owen, who twenty years earlier had welcomed enthusiastically the collections of fossils brought by their trip Darwin.
In a memorable meeting of the British Association for the Advancement of Science, which took place in Oxford on 30 June 1860, Bishop Samuel Wilberforce, as a spokesman for the party of Owen, ridiculed with brilliant eloquence the evolutionary thesis, causing a strong retort by the zoologist Thomas Henry Huxley, who was the main defender against religious opposition to the thesis of Darwin earning the nickname of your bulldog. Wilberforce asked whether Huxley to him would have been indifferent to know that his grandfather had been a monkey, the immediate response was, according to the testimony of Lyell: «Would be in the same situation as the Honourable».

Darwin in an image taken to 1874
Darwin stayed away from direct intervention in the public controversy until 1871, when his work was published the origin of man, and selection in relation to sex, where he showed his arguments in favor of the thesis that man had appeared on the Earth by only natural means. Three years earlier had released its study on the variation in animals and plants by the effects of artificial selection, where he tried to formulate a theory on the origin of life in general ("pangenesis"), which turned out to be the poorest of his contributions to biology.
In 1872, with the expression of the emotions in man and animals, seminal what later it would be the modern study of the behavior, work Darwin ended their concerns by theoretical problems and devoted the last ten years of his life to research in the field of Botany. At the end of 1881, he began to suffer from serious heart problems, and died from a heart attack on April 19, 1882.


Timeline of Charles Darwin


1809Born in Shrewsbury.
1825He entered the University of Edinburgh to study medicine.
1828It starts the career of theology at Cambridge.
1830The botanist John Henslow awakens the interest of Darwin by the natural history.
1831-1836Travel with the Beagle as a naturalist for a voyage of exploration.
1837He moved to London.
1839It publishes a naturalist around the world trip in the H.M.S. Beagle.
1842First draft of the theory of evolution. It settles down.
1858Joint submission to the Linnear Society, the theory of selection of A. R. Wallace and Darwin.
1859He published The Origin of Species (the origin of the species).
1862It publishes about the intervention of the insects in the fertilisation of orchids.
1871Public The Descent of Man and Selection in Realtion to Sex (the human offspring and sexual selection).
1877First translation into Spanish of the origin of species.
1881He published on the influence of worms in the formation of the topsoil.
1882Dies down.

Charles Darwin and the theory of evolution

Until the 17TH century, naturalists claimed that the different animal and plant species had been created independently and since then remained immutable, without undergoing any change. The theory of evolution, according to which human beings suffer alterations with the passage of time and come from other ancestral forms, is relatively recent. Although the British naturalist Charles Darwin is considered the father of the current theory of evolution, the concept was not new at the time. In the middle of the 18th century, for example, the evolutionary hypothesis proposed by the French mathematician Pierre-Louis Maupertius (1698-1759) and the French encyclopedist Denis Diderot (1713-1784) contained ideas that, a century later, would be part of Darwin's theory.

Charles Darwin
The French zoologist John Baptist de Lamarck was the first to make clear, in his Zoological philosophy (1809), the idea that all species could change over the course of time and end up becoming a new species. Lamarck, all living beings evolve inevitably towards greater perfection and complexity, and the reason for such changes is the natural environment. The environment changes alter the needs of living organisms; because of the environment, is reduced or intensifying the use of certain organs or parts of the body, causing changes in size or shape.
To develop the concept that are new bodies in response to the needs of the struggle with the medium, the French naturalist deduced that their size and importance was associated with the law of "use and non-use". Lamarck also argued that adaptations to the environment, once set, were propagated to successive generations, or acquired characters inheriting. According to this notion, the giraffes would have acquired their long necks to go gradually stretching (each generation a little more) to reach the leaves of difficult access to other animals.
The lamarquista theory explained the adaptation of many plants and animals to the environment, but was mainly speculative and lacked empirical support; modern genetics discredit it totally to demonstrate that characters who can purchase an individual (such as the lengthening of the neck by the constant effort) are not inherited. Despite this, is recognizes the value his work pioneer, by first apply the adaptability of the organisms.
The shortcomings of the failed attempt of Lamarck underscore the strength and consistency of the Darwinian model. Charles Darwin's contribution to scientific knowledge was two-fold: provide the evidence to demonstrate that evolution had occurred, while he formulated a theory of natural selection, to explain the mechanism of evolution. The publication of Darwin, in 1859, of the origin of species is a milestone not only in the history of biology, but also in the human thought, since this book, providing a demonstration positive evolutionary doctrine, would exert a considerable influence on the development of philosophy, and altered deeply rooted conceptions about life and man.
Darwin embarked as a naturalist on the expedition of the Beagle, a scientific ship that traveled the world between 1831 and 1836. In his trip Darwin met lots of interesting observations, established fruitful analogies and meditated on major issues, such as the adaptation of living beings, the diversity of species and their mutual relations and the struggle for existence. Upon his return, Darwin was devoted to write his travel diary; It announced also several works of geology, especially on the formation of coral and volcanic islands. Twenty-three years after his return to England, he published the origin of species. Then, he wrote numerous books, some of which would be an extension of this work.

Natural selection and evolution

In 1858, Darwin received a manuscript of Alfred Russel Wallace, a young naturalist who was then studying the distribution of plants and animals in the India and the Malay Peninsula. In that text, Wallace made the idea of natural selection, which had arrived without knowing the Darwinian work, but inspired, as well as Darwin, by the Treaty of Thomas R. Malthus on the growth of the population and the necessary fight for existence. By mutual agreement, that same year Darwin and Wallace presented in cooperation a report on his theory to the Linnean Society of London.

First edition of the origin of species (1859)
The explanation proposed by Darwin and Wallace with respect to the way in which evolution occurs can be summarized as follows:
  • The appearance of new traits or variations is characteristic of all species of animals and plants. Darwin and Wallace believed that variation was one of the innate properties of living beings. Today we know distinguish inherited variations of those not inherited. Only the first, produced by mutations, are important in the evolution, because they become individuals of the following generations.
  • Of any kind are born more individuals who can get enough food to survive. However, as the number of individuals of each species remains more or less constant under natural conditions, it should be inferred that a percentage of the seed perisheth in every generation. If the offspring of a species thrive in its entirety, and on to replicate it, soon you avasallaría any other species on Earth.
  • Sitting that more subjects that can survive are born, it must declare a struggle for existence, a competition looking for space and food. This fight is (between people of the same or different species) or indirectly, like animals and plants to survive to adverse conditions (for example, lack of water or low temperatures) or other unfavorable environmental conditions.
  • Those variations or features that better enable an organism to survive in a given environment favor to their owners on other not so well adapted organisms. The ideas of "fight for survival" and "survival of the fittest" are the essence of the theory of natural selection of Darwin and Wallace.
  • The surviving individuals, to reproduce themselves, will originate the next generation, and thus variations or advantageous traits passed on to successive generations.
Such ideas are also the core of the fundamental work of Charles Darwin, the origin of species (1859), whose full title summarizes his thesis by itself: on the origin of species by means of natural selection or the preservation of the breeds favoured in the struggle for life. The individual with a variation that allows a better adaptation is more likely to emerge victorious in the struggle for existence; their survival increases the probability of reproduction and transmission of the trait to their descendants.
Natural selection thus leads to the preservation of favorable variations and to the Elimination of harmful deviations, by death or overcoming of individuals equipped with such features. As the fittest individuals are more likely to survive, mate and reproduce that the specimens that are not so well adapted to the environment, in each generation increases the number of individuals well adapted to their environment, and the General characteristics of the group are changing as a result of this accommodation. Along with the natural selection acts, in higher animals, "sexual choice", that is, the instinctive preference by individuals more strong, beautiful and healthy in the pairing.
It should be emphasized that what held Lamarck, variations in the characteristics of an organism occur randomly; they are not caused by environment or by the effort of the individual. According to Darwinian theory, and following the same example, the long neck of the giraffe originated by chance: an animal that had the longest neck had food benefits and, therefore, had more chances to leave descendants. These characteristics are transmitted from generation to generation until the least adapted giraffes (that is, those of short neck) disappeared.
The problematic point of the theory was that you unknown mechanism by which transmitting the adaptations that were successful. The solution to this problem was in investigations by a monk and Austrian botanist, Gregor Mendel (1822-1884), who discovered that hereditary characteristics are transmitted in simple units that he called "factors" and that we now know as genes. Mendel's laws, concepts of genotype and phenotype of Wilhelm Ludvig Johannsen and the discoveries of Hugo de Vries mutations led to the development of a synthetic theory inspired the general lines of the approaches to Darwin, which would be called Neodarvinismo and is now accepted by most biologists. Changes in the genetic structure of the species are due to mutations in genes that regulate the expression of the body characteristics. Another factor of change are the sobrecruzamientos that occur between the chromosomes in meiosis, combining characters other than homologous chromosomes.
In the light of such contributions, the natural selection of Darwin can be reformulated in the following way: individuals best suited to their environment are more likely to pass their genes to the next generation than the other members of a population. Today the theory of evolution is the only one that responds to all the facts both genetic and ecological and paleontological. The comparative anatomy very well illustrates the relationships between the various species and families, recently tested by methods of biochemical analysis.

The origin of man

Overcoming the long hesitations based, above all, in fear of the controversies to which the work could give rise, Darwin it took eleven years to publish the origin of man, and selection in relation to sex (1871). In such work collected his notes relating to a specific but very important problem of evolution: the origin of man. According to Darwin, the study of homologous structures in man and the lower animals in zoological evolution scale and the analysis of the Embryological Development of the man and the phenomena of atavism lead to the conclusion that the man descends less highly organized somehow, specifically of a simioide, which, like all vertebrates , would turn their remote origin in some water being similar to the Ascidians.
The greater difficulty to support such theory lies in the fact that man is endowed with intellectual faculties and a moral sense of missing animals. In fact, the same Alfred Wallace never believed that human intelligence could be the result of natural selection, but it thought that the intellect only could have been created by a higher power (God). But Darwin rejected this concept and observe that the interval between the mental powers of the higher apes and those of a fish is huge; for this reason also the intelligence of the man, who does not differ, but in degree from the monkey, is a product of evolution.
Also the moral feelings are developed, due to the evolution of instincts that are found in all animals. Aware that the conclusions of this work would be considered as extremely irreligious, Darwin notes that explain the origin of man as a species that descended from some lower species is not more irreligious which explain the origin of the individual being through the laws of reproduction. The laws of development of man are, for Darwin, identical to the one of other animals.
The ideas of the British naturalist diametrically changed notions about the origin and evolution of man. Darwin disproved the deep-rooted belief that man possessed a divine origin and showed that human beings were the result of a process of biological evolution. Scientific theories he opposed explanations of theological, made character that had a considerable impact on the mentality of the time. The evolution of Darwin caused a huge controversy in the nineteenth-century society and resulted in on discussions. Logical consequence of these discussions was the question of vision antropocentrista of nature: If the man was not a divine creation, as they claimed the beliefs current until the 19th century, there was no reason to hold that it occupied a central place in the natural order.
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