Portal:History of science/Article/2006 archive
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This is an archive of article summaries that have appeared in the Selected article section of Portal:History of science in 2006. For past archives, see the Portal:History of science/Article.
[edit] February 8 - February 17, 2006
The Voyage of the Beagle is a title commonly given to the book written by Charles Darwin published in 1839 as his Journal and Remarks, which brought him considerable fame and respect. The title refers to the second survey expedition of the ship HMS Beagle which set out on 27 December 1831 under the command of captain Robert FitzRoy. While the expedition was originally planned to last two years, it lasted almost five—the Beagle did not return until 2 October 1836. Darwin spent most of this time exploring on land (three years and three months on land; 18 months at sea).
Darwin's account of the voyage is a vivid and exciting travel memoir as well as a detailed scientific field journal covering biology, geology and anthropology that demonstrates Darwin's keen powers of observation, written at a time when the West were still discovering and exploring much of the rest of the world. With hindsight, one can find hints of the ideas Darwin would later develop into the theory of evolution.
[edit] February 17 - March 3, 2006
The Great Chain of Being is a classical and western medieval conception of the order of the universe, whose chief characteristic is a strict hierarchal system.
It is a conception of the world's structure that was accepted, and unquestioned, by most educated men from the time of Lucretius until the Copernican revolution and the ultimate flowering of the Renaissance. The Chain of Being is composed of a great number of hierarchal links, from the most base and foundational elements up to the very highest perfection - in other words, God, or the Prime Mover.
Moving on up the chain, each succeeding link contains the positive attributes of the previous link, and adds (at least) one other. Rocks possess only existence; the next link up, plants, possess life and existence. Beasts add not only motion, but appetite as well. Man is a special instance in this conception. He is both mortal flesh, as those below him, and also spirit, like the angels and God above.
The Great Chain of Being was central to work in natural history before the time of Linnaeus and Buffon.
In the late 19th century luminiferous aether ("light-bearing aether") was the term used to describe a medium for the propagation of light. Later theories including special relativity were formulated without the ether concept, and today the aether is considered to be an obsolete scientific theory.
Isaac Newton had assumed that light was made up of numerous small particles, in order to explain features such as its ability to travel in straight lines and reflect off surfaces. This theory was known to have its problems; although it explained reflection well, its explanation of refraction and diffraction was less pleasing. In order to explain refraction, in fact, Newton's Opticks (1704) postulated an "Aethereal Medium" transmitting vibrations faster than light, by which light (when overtaken) is put into "Fits of easy Reflexion and easy Transmission" (causing refraction and diffraction).
As optical theories changed, new, increasingly technical ether theories were proposed to explain the known properties of light; by the late 19th century, ether theories were important across the sciences, from physical chemistry to electron theory to optics and astronomy. In the early 20th century, after the acceptance of special relativity, many of the aether's hypothetical functions quickly became unnecessary.
The French Academy of Sciences (Académie des sciences) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at the forefront of scientific developments in Europe in the 17th and 18th centuries.
The Academy of Sciences owes its origin to Colbert's plan to create a general academy. He chose a small group of scholars who met on December 22, 1666 in the King's library, and thereafter held twice-weekly working meetings there. The first 30 years of the Academy's existence were relatively informal, since no statutes had as yet been laid down for the institution.
On January 20, 1699, Louis XIV gave the Company its first rules. The Academy received the title of Royal Academy of Sciences and was installed in the Louvre in Paris. On August 8, 1793, the National Convention abolished all the academies. On August 22, 1795, a National Institute of Sciences and Arts was put in place, bringing together the old academies of the sciences, literature and arts. In 1816, the Academy of Sciences became autonomous, while forming part of the Institute of France; the head of State remained its patron. The Academy proceedings were published under the name Comptes Rendues de l'Académie des Sciences.
The Einstein-Szilárd letter was a letter sent to President Franklin Delano Roosevelt in August 1939 signed by Albert Einstein but largely written by Leó Szilárd in consultation with fellow Hungarian physicists Edward Teller and Eugene Wigner. The letter advised Roosevelt that Nazi Germany might be conducting research into the possibility of using nuclear fission to create atomic bombs, and suggested that the United States should begin researching the possibility itself.
The letter has often been seen as the origins of the Manhattan Project, the successful wartime nuclear weapons project which produced the bombs which were dropped on Hiroshima and Nagasaki in 1945, though the path from the letter to the bombings though is considerably longer than just this.
Inherit the Wind is a play by Jerome Lawrence and Robert Edwin Lee. It is frequently cited as being a fictionalized account of the Scopes Trial. The play first appeared on Broadway in January 1955.
The real-life opposing attorneys William Jennings Bryan and Clarence Darrow are roughly portrayed as Matthew Harrison Brady and Henry Drummond respectively, while John Scopes is remade in the character Bertram Cates and journalist H.L. Mencken becomes E.K. Hornbeck. But despite the similarities, the play is not intended to be a historical documentary-drama, but a fictional social commentary on McCarthyism based loosely on an historical event. Although the play reflects on what has been claimed as one of the darkest events in American history, it has been hailed one of the great American plays of the 20th Century, with themes about religious tolerance, belief and freedom of thought that have considerable resonance to this day.
Deutsche Physik (literally: "German Physics") or Aryan Physics was the name given to a reactionary movement in the German physics community in the early 1930s against the work of Albert Einstein, labeled Jewish Physics. The term was taken from the title of a 4-volume physics textbook by Philipp Lenard in the 1930s.
The movement itself began as an extension of a German nationalist movement in the physics community which went back as far as World War I. A number of German physicists, including Wilhelm Wien and the especially passionate Philipp Lenard had then signed a number of "declarations" that there was a need to remove a perceived unfair amount of British influence from physics (such as the renaming of German-discovered phenomena with perceived English-derived names, such as "X-ray" instead of "Röntgen ray"), and a declaration of the national character of science as a method of emphasising local differences in theory and practice.
When the Nazis entered the political scene, Lenard quickly attempted to ally himself with them, joining the party long before it was fashionable to do so. With another Nobel Prize in Physics laureate, Johannes Stark, Lenard began a core campaign to label Einstein's Relativity as Jewish Physics, decrying it as overly abstract, out of touch with reality, closely linked to moral relativism, and practiced exclusively by Jews and Jewish sympathisers.
The Tychonic system (or Tychonian system) was an effort by Tycho Brahe to create a model of the solar system which would combine what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. It is essentially a geocentric model (with the Earth at the center of the universe), around which revolves the Sun, and around the Sun revolve the other planets. It can be shown through a geometric argument that the motions of the planets and the Sun relative to the Earth in the Tychonic system are equivalent to the motions in the Copernican system, and the Tychonic system has the advantage of not predicting stellar parallax, which was not observable until the 19th century.
Paradigm shift is the term first used by Thomas Kuhn in his 1962 book The Structure of Scientific Revolutions to describe the process and result of a change in basic assumptions within the ruling theory of science. A scientific revolution occurs, according to Kuhn, when scientists encounter anomalies which cannot be explained by the universally accepted paradigm within which scientific progress has thereto been made. The paradigm, in Kuhn's view, is not simply the current theory, but the entire worldview in which it exists, and all of the implications which come with it. There are anomalies for all paradigms, Kuhn maintained, that are brushed away as acceptable levels of error, or simply ignored and not dealt with (a principal argument Kuhn uses to reject Karl Popper's model of falsifiability as the key force involved in scientific change). Rather, according to Kuhn, anomalies have various levels of significance to the practitioners of science at the time. To put it in the context of early 20th century physics, some scientists found the problems with calculating Mercury's perihelion more troubling than the Michelson-Morley experiment results, and some the other way around. Kuhn's model of scientific change differs here, and in many places, from that of the logical positivists in that it puts an enhanced emphasis on the individual humans involved as scientists, rather than abstracting science into a purely logical or philosophical venture.
The conflict thesis, also known as the warfare thesis, the warfare model or the Draper-White thesis, is an interpretive model of the relationship between religion and science. According to the conflict thesis, any interaction between religion and science almost inevitably leads to open hostility, with religion usually taking the part of the aggressor against new scientific ideas. The conflict thesis was a popular historiographical approach in the history of science during the late 19th and early 20th centuries, but many historians of science and related academics no longer accept it. It remains popular with a general audience, and is often invoked both by advocates of science and religion alike with stakes in making science and religion seem irreconcilable.
The most influential exponents of the conflict thesis were John William Draper and Andrew Dickson White. In the early 1870s, Draper was invited to write a book on History of the Conflict between Religion and Science (1874). He directed his criticism primarily against Roman Catholicism, while assessing Islam and Protestantism as having a friendly relationship toward science. In 1896, White published the History of the Warfare of Science with Theology in Christendom, the culmination of thirty years of research and publication on the subject. His target was any form of restrictive, dogmatic Christianity. Most advocates of the conflict thesis, like Draper and White, have focused on the alleged hostility of Christianity toward science, though Islam has received some criticism of its own.
Archaeoastronomy (also spelled archeoastronomy) is the study of ancient or traditional astronomies in their cultural context, utilising archaeological and anthropological evidence. It is closely associated with sister disciplines ethnoastronomy, the study of astronomical practice in contemporary societies and historical astronomy, the use of historical records of heavenly events to answer astronomical problems. Another similar discipline is history of astronomy, which uses written records to evaluate prior astronomical traditions.
Archaeoastronomy is almost as old as archaeology itself. Norman Lockyer was arguably the first archaeoastronomer working at the end of the nineteenth century and the start of the twentieth. His studies included an examinations of Egyptian temples in The Dawn of Astronomy in 1894 and of Stonehenge published as Stonehenge and Other British Stone Monuments Astronomically Considered in 1906. Some archaeologists followed. Francis Penrose published extensively in the Philosophical Transactions of the Royal Society on the astronomical alignment of Greek temples in the Mediterranean in the same period. Archaeoastronomy was, for a while, a respectable subject. The first issue of the archaeological journal Antiquity includes an article on archaeoastronomical research.
Tests of Einstein's general theory of relativity did not provide an experimental foundation for the theory until well after it was introduced in 1915. Physicists accepted the theory because it correctly accounted for the precession of the perihelion of Mercury, a phenomenon which had long baffled physicists, and because it unified Newton's law of universal gravitation with special relativity in a conceptually simple way. (Einstein has been famously quoted as saying that if his theory was falsified, then he would have felt "sorry for the dear Lord.") Despite Einstein's proposal of three classical tests, the theory was without strong experimental support until a program of precision tests was started in 1959. This program has systematically tested general relativity in weak gravitational fields and severely limited possible deviations from the theory. Since 1974, Hulse and Taylor have studied stronger gravitational fields in binary pulsars. In these regimes, on typical solar system scales, general relativity has been extremely well tested.
On the largest scales, such as galactic and cosmological scales, general relativity has not yet been subject to precision tests. Some have interpreted dark matter and dark energy as a failure of Einstein's theory at large distances, small accelerations, or small curvatures. Likewise, the very strong fields around black holes, especially supermassive black holes, which are thought to power quasars and less dramatic active galactic nuclei, are still an object of intense study. Observations of these objects are difficult, and the interpretation of these observations is heavily dependent upon astrophysics other than general relativity or competing fundamental theories of gravitation, but they are qualitatively consistent with the black hole concept as modeled in general relativity.
Lysenkoism was a campaign against genetics and geneticists which happened in the Soviet Union from the middle of the 1930s to the middle of the 1960s, centered around the figure of Trofim Denisovich Lysenko. In a broader context, Lysenkoism is often invoked to imply the overt subversion of science by political forces.
When Lysenko began his fieldwork in the Soviet Union of the 1930s, the agriculture of the Soviet Union was in a massive crisis due to the forced collectivization movement. There were few agricultural specialists who were willing to work committedly towards the success of the new and troubled collective farms. Among biologists of the day, the most popular topic was not agriculture at all but the new genetics that was emerging out of studies of Drosophila melanogaster, fruit flies with very simplistic genetic structures which allowed for easy studying of Mendelian ratios and heritability. Only much later would this research have obvious application to the problem of agriculture, and during the 1920s and 1930s it was easy for a radical like Lysenko to castigate these theoretical biologists for spending their time bent over trays of fruit flies while famine raged on around them.
In 1928, a previously unknown agronomist, Trofim Lysenko "invented" a new agricultural technique, vernalization (using humidity and low temperatures to make wheat grow in spring). Soviet mass media presented him as a genius who had developed a new, revolutionary technique. He was supported by the Soviet propaganda machine, which overstated his successes and omitted mention of his failures. Instead of making controlled experiments, Lysenko relied upon questionnaires from farmers, using them to "prove" that vernalization increases wheat yields by 15%. Lysenko's influence continued to grow, and in 1948, genetics was officially declared "a bourgeois pseudoscience"; all geneticists were fired from work (some were also arrested), and all genetic research was discontinued.
The Space Race was an informal competition between the United States and the Soviet Union that lasted roughly from 1957 to 1975. It involved the parallel efforts by each of those countries to explore outer space with artificial satellites, to send humans into space, and to land people on the Moon.
Though its roots lie in early rocket technology and in the international tensions following World War II, the Space Race effectively began after the Soviet launch of Sputnik 1 on 4 October 1957. The term originated as an analogy to the arms race. The Space Race became an important part of the cultural and technological rivalry between the USSR and the United States during the Cold War. Space technology became a particularly important arena in this conflict, both because of its potential military applications and due to the morale-boosting psychological benefits.
- Weeks 34 & 35
- August 20-September 2
The German nuclear energy project was an endeavor by scientists during World War II in Nazi Germany to develop nuclear energy and an atomic bomb for practical use. Unlike the competing Allied effort to develop a nuclear weapon the German effort resulted in two rival teams, one working for the military, the second, a civilian effort co-ordinated by the German Post Office.
The nuclear research effort most widely discussed was that of the Kaiser Wilhelm Institute team led by the physicist Werner Heisenberg. The second was a military team under the scientific leadership of Prof. Kurt Diebner. This military team was also associated with Dr. Paul Harteck, who helped to develop the gaseous uranium centrifuge invented by Dr. Erich Bagge in 1942. Their team was part of the German Army (Heereswaffenamt Forschungsstelle E), the Kriegsmarine (navy) had a subsidiary team looking at nuclear propulsion for U-boats under Dr. Otto Haxel. Konteradmiral Karl Witzell and Konteradmiral Wilhelm Rein were military leaders of the naval nuclear project.
The intentions of Heisenberg's team are a matter of historical controversy, centering on whether or not the scientists involved were genuinely attempting to build an atomic bomb for Nazi dictator Adolf Hitler. The project was not a military success by any measure.
- Weeks 36 & 37
- September 3-September 16
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The history of biology traces man's understanding of the living world from the earliest recorded history to modern times. Though the concept of biology as a single coherent field of knowledge only arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to the ancient Greeks (particularly Galen and Aristotle, respectively).
During the Renaissance and Age of Discovery, renewed interest in empiricism as well as the rapidly increasing number of known organisms led to significant developments in biological thought; Vesalius inaugurated the rise of experimentation and careful observation in physiology, and a series of naturalists culminating with Linnaeus and Buffon began to create a conceptual framework for analyzing the diversity of life and the fossil record, as well as the development and behavior of plants and animals. The growing importance of natural theology—partly a response to the rise of mechanical philosophy—was also an important impetus for the growth of natural history (though it also further entrenched the argument from design).
In the 18th century many fields of science—including botany, zoology, and geology—began to professionalize, forming the precursors of scientific disciplines in the modern sense (though the process would not be complete until the late 1800s). Lavoisier and other physical scientists began to connect the animate and inanimate worlds through the techniques and theory of physics and chemistry. Into the 19th century, explorer-naturalists such as Alexander von Humboldt tried to elucidate the interactions between organisms and their environment, and the ways these relationships depend on geography—creating the foundations for biogeography, ecology and ethology. Many naturalists began to reject essentialism and seriously consider the possibilities of extinction and the mutability of species. These developments, as well as the results of new fields such as embryology and paleontology, were synthesized in Darwin's theory of evolution by natural selection. The end of the 19th century saw debates over spontaneous generation and the rise of the germ theory of disease and the fields of cytology, bacteriology and physiological chemistry, though the problem of inheritance was still a mystery.
- Weeks 38 & 39
- September 17-September 30
The military funding of science has had a powerful transformative effect on the practice and products of scientific research since the early 20th century. Particularly since World War I, advanced science-based technologies have been viewed as essential elements of a successful military. World War I is often called "the chemists’ war", both for the extensive use of poison gas and the importance of nitrates and advanced high explosives. Poison gas, beginning in 1915 with chlorine from the powerful German dye industry, was used extensively by the Germans and the British ; over the course of the war, scientists on both sides raced to develop more and more potent chemicals and devise countermeasures against the newest enemy gases. Physicists also contributed to the war effort, developing wireless communication technologies and sound-based methods of detecting U-boats, resulting in the first tenuous long-term connections between academic science and the military.
World War II marked a massive increase in the military funding of science, particularly physics. In addition to the Manhattan Project and the resulting atomic bomb, British and American work on radar was widespread and ultimately highly influential in the course of the war; radar detection of enemy ships and aircraft, as well as the radar-based proximity fuze. Mathematical cryptography, meteorology, and rocket science were also central to the war effort, with military-funded wartime advances having a significant long-term effect on each discipline. The technologies employed at the end—jet aircraft, radar and proximity fuzes, and the atomic bomb—were radically different from pre-war technology; military leaders came to view continued advances in technology as the critical element for success in future wars. The advent of the Cold War solidified the links between military institutions and academic science, particularly in the United States. and the Soviet Union, so that even during a period of nominal peace military funding continued to expand. Funding spread to the social sciences as well as the natural sciences, and whole new fields, such as digital computing, were born of military patronage. Following the end of the Cold War and the collapse of the Soviet Union, military funding of science has decreased substantially, but much of the American military-scientific complex remains in place.
- Weeks 40 & 41
- October 1-October 14
Women in science, technology, and medicine have made diverse contributions, from antiquity to the present day. However, the exclusion of women from most formal education, particularly from around 1600 until the latter part of the nineteenth century, has severely restricted women's ability to contribute in these areas. Women's participation has often involved one or more of aristocratic position, family connections and communities isolated from society. The application of practical "housewifely" crafts or traditionally "feminine" pursuits, such as art, translation and writing, has provided a means of entrance into scientific research. The exigencies of war have also led to opportunities for women.
Entry into higher education without formal restriction during much of the twentieth century, at least in the US and Europe, has resulted in more frequent contributions from women across all areas of scientific study. However, women remain greatly underrepresented in some areas, such as physical sciences, computing and engineering.
- Weeks 42 & 43
- October 15-October 28
Cabinets of curiosities (also known as Wunderkammer or wonder-rooms) were collections of natural history artifacts kept by many early practitioners of science in Europe, and were precursors to natural history museums.
Two of the most famously described cabinets were those of Ole Worm (also known as Olaus Wormius) and Athanasius Kircher. These 17th-century cabinets, actually room-sized collections, were filled with preserved animals, horns, tusks, skeletons, minerals, and so on. Often they would contain a mix of fact and fiction, including apparently mythical creatures. Worm's collection contained, for example, what he thought was a Scythian Lamb, a wooly fern thought to be a plant/sheep fabulous creature. The specimens displayed were often collected during exploring expeditions and trading voyages.
Cabinets of curiosities would often serve scientific advancement when images of their contents were published. The catalog of Worm's collection, published as the Museum Wormianum (1655), used the collection artifacts as a starting point for Worm's speculations on philosophy, science, natural history, and more.
Obviously cabinets of curiosities were limited to those who could afford to create and maintain them. Many monarchs, in particular, developed large collections. Frederick III of Denmark, who added Worm's collection to his own after Worm's death, was one such monarch. Another example is the Kunstkamera founded by Peter the Great in Saint Petersburg in 1727.
- Weeks 44 & 45
- October 29-November 11
Electrochemistry a branch of chemistry suffered several changes on its evolution from early principles related to magnets in the early 16th and 17th centuries to complex theories involving conductivity, electrical charge and mathematical methods to describe electrical phenomena in the late 19th century and 20th century. Nowadays this branch of chemistry is a valuable source of investigation, many scientists are developing further methods related to batteries and fuel cells, avoiding corrosion or improving refining techniques by electrolysis.
The 16th century marked the beginning of the electrical understanding that culminated with the industrial production of electrical power in the late 19th century.
On 1550s English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity. For his work on magnets, Gilbert became known as the "Father of Magnetism." He discovered various methods for producing and strengthening magnets. Gilbert's De Magnete quickly became the standard work throughout Europe on electrical and magnetic phenomena. Gilbert made the first clear distinction between magnetic and the amber effect (static electricity, as is known today). On his book "De Magnete" William stated a comprehensive review of what was known about the nature of magnetism. But it wasn't until the advent of the following century when the electrical concept gained scientific importance.
- Weeks 46 & 47
- November 12-November 25
The history of physics involves not only fundamental changes in ideas about the material world, mathematics and philosophy, but also, through technology, a transformation of society. Physics is considered both a body of knowledge and the practice that makes and transmits it. The scientific revolution, beginning about year 1600, is a convenient boundary between ancient thought and classical physics. The year 1900 marks the beginnings of a more modern physics; today, the science shows no sign of completion, as more issues are raised, with questions rising from the age of the universe, to the nature of the vacuum, to the ultimate nature of the properties of subatomic particles. Partial theories are currently the best that physics has to offer, at the present time. The list of unsolved problems in physics is large.
Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. Also a mystery was the character of the universe, such as the form of the Earth and the behavior of celestial objects such as the Sun and the Moon. Typically the behavior and nature of the world was explained by invoking the actions of gods. Eventually speculative natural explanations were proposed based on considering such questions; most of them were wrong, but this is part of the nature of the enterprise of systematic explanation, and even modern theories of quantum mechanics and relativity are merely considered "theories that haven't been broken yet". Physical theories in antiquity were largely couched in philosophical terms, and rarely verified by systematic experimental testing.
- Weeks 48 & 49
- November 26-December 9
The creation-evolution controversy (also termed the creation vs. evolution debate or the origins debate) is a recurring dispute in the popular arena about the origins of the Earth, humanity, life, and the universe. The debate is most prevalent and visible in certain regions of the United States, where it is often portrayed in the mass media in the broader context of the culture wars or a supposed dispute between religion and science. The main opposing positions are held by those who espouse the validity and superiority of a particular creation myth and those who support naturalistic or scientific accounts provided by astrophysics, geology and biology. It should be noted, however, that, despite the controversy, many people believe that scientific ideas, including biological evolution, need not contradict their personal religious beliefs.
The conflict centers primarily on the defensibility of creationism (especially the forms of creationism derived from fundamentalist or religiously conservative Abrahamic accounts of origins), a view that regards scientific explanations of origins as antithetical to divine creation, and often, more specifically, Creation according to Genesis. The key contention of such creationists is that only a supernatural miracle and not "unguided evolution" can account for origins. This view is overwhelmingly rejected by the scientific community and academia, who point to the strong correspondence of reality with the theory, and how, as in the title of a famous essay by Theodosius Dobzhansky, Nothing in Biology Makes Sense Except in the Light of Evolution.
Evolution is often expanded by creationists to include such things as the Big Bang Theory, abiogenesis, and the formation of stars, however, although the word evolution is used as part of several astronomical terms such as stellar evolution, none of these are implied by the term evolution alone. Which specific scientific ideas conflict with their concept of creationism, and would therefore comprise "evolution", can vary from creationist to creationist.
- Weeks 50 & 51
- December 10-December 23
The history of paleontology has been an ongoing effort to understand the history of life on Earth by understanding the fossil record left behind by living organisms. Inevitably it has been closely tied to geology and the effort to understand the history of the Earth itself. In the 17th and 18th centuries there was progress made in understanding the nature of fossils and the at the end of the 18th century the work of Georges Cuvier lead to the emergence of paleontology, in association with comparative anatomy, as a scientific discipline. The expanding knowledge of the fossil record also played an increasing role in the development of geology, particularly stratigraphy. The first half of the 19th century saw a rapid increase in knowledge about the past history of life on Earth and the progress towards definition of the geologic time scale. After Charles Darwin published the Origin of Species in 1859, much of the focus of paleontology shifted to understanding evolutionary paths, including human evolution, and evolutionary theory. The last half of the 20th century saw a renewal of interest in mass extinctions and their role in history of life on Earth.
As early as the 6th century BC Xenophanes of Colophon recognized that some fossil shells were remains of shellfish and indicated that what was now dry land was once under the sea. It is also well known that in one of his unpublished notebooks Leonardo da Vinci (1452-1519) concluded that some fossil sea shells were the remains of shellfish. However in both cases it is clear that the fossils were relatively complete remains of mollusk species that very closely resembled living species and thus were relatively easy to classify.
- Weeks 52 & 53
- December 24-January 6, 2007
The history of evolutionary thought has endured from antiquity, since the idea of biological evolution has derived as a philosophical idea since the Ancient Greek and Roman eras. Scientific formulations of the idea did not arise until the 18th and 19th centuries, when scientists such as Lord Monboddo and Erasmus Darwin, Charles Darwin's grandfather, proposed that living organisms were derived from a common ancestor. A hypothesized mechanism for biological descent with modification was proposed by Jean-Baptiste Lamarck, who suggested that organisms inherit the characteristics acquired by their parents during the course of life. This since-discredited hypothesis is referred to as inheritance of acquired characteristics. The modern theory referred to as Darwinism was first publicly put forth by Charles Darwin and Alfred Russel Wallace and discussed in great detail in Darwin's later publications, including his most famous exposition of the theory, On the Origin of Species. Darwin emphasized the difference between two main points: establishing the fact of biological evolution, and proposing the theory of natural selection to explain its mechanism
Although Darwin's theory offered a substantive explanation of a wealth of biological observations, the mechanism of biological inheritance was not yet known at the time of his work; although the person commonly considered the originator of modern genetic theory, Gregor Mendel, was a contemporary of Darwin, Mendel's work was largely neglected until the early 20th century. The combination of the Darwinian proposal of natural selection with classical genetics is known as the modern evolutionary synthesis. Later work identified the gene, or the basic unit of inheritance in organisms, as encoded in DNA molecules carried by all living cells; subsequent work in molecular genetics has led to additional work in evolutionary theory such as the neutral theory of molecular evolution, which presents a role in biological evolution for genetic drift as well as natural selection.
