116-458: In biological phylogenetics , a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi )
232-591: A Lamarckian heredity, made unscientific pronouncements on agriculture, used his influence to destroy classical genetics in Russia and to move genuine scientists from their posts. In 1940, the leading botanical geneticist Nikolai Vavilov was arrested, and Lysenko replaced him as director of the Institute of Genetics. In 1941, Vavilov was tried, found guilty of 'sabotage' and sentenced to death. Reprieved, he died in jail of malnutrition in 1943. Lysenko's machinations were
348-476: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
464-601: A Soviet mental hospital, and Vavilov's reputation was posthumously restored in 1955. In the 1950s Huxley played a role in bringing to the English-speaking public the work of the French Jesuit - palaeontologist Pierre Teilhard de Chardin , who he believed had been unfairly treated by the Catholic and Jesuit hierarchy. Both men believed in evolution, but differed in its interpretation as Teilhard de Chardin
580-728: A bacterial genome over three types of outbreak contact networks—homogeneous, super-spreading, and chain-like. They summarized the resulting phylogenies with five metrics describing tree shape. Figures 2 and 3 illustrate the distributions of these metrics across the three types of outbreaks, revealing clear differences in tree topology depending on the underlying host contact network. Super-spreader networks give rise to phylogenies with higher Colless imbalance, longer ladder patterns, lower Δw, and deeper trees than those from homogeneous contact networks. Trees from chain-like networks are less variable, deeper, more imbalanced, and narrower than those from other networks. Scatter plots can be used to visualize
696-620: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
812-763: A close association with the British rationalist and secular humanist movements. He was an Honorary Associate of the Rationalist Press Association from 1927 until his death, and on the formation of the British Humanist Association in 1963 became its first President, to be succeeded by A. J. Ayer in 1965. He was also closely involved with the International Humanist and Ethical Union . Many of Huxley's books address humanist themes. In 1962 Huxley accepted
928-499: A disproof of a previously widely accepted theory. During the late 19th century, Ernst Haeckel 's recapitulation theory , or "biogenetic fundamental law", was widely popular. It was often expressed as " ontogeny recapitulates phylogeny", i.e. the development of a single organism during its lifetime, from germ to adult, successively mirrors the adult stages of successive ancestors of the species to which it belongs. But this theory has long been rejected. Instead, ontogeny evolves –
1044-636: A fortnight he dashed off a 60-page booklet on the purpose and philosophy of UNESCO, eventually printed and issued as an official document. There were, however, many conservative opponents of his scientific humanism. His idea of restraining population growth with birth control was anathema to both the Catholic Church and the Comintern / Cominform . In its first few years UNESCO was dynamic and broke new ground; since Huxley it has become larger, more bureaucratic and stable. The personal and social side of
1160-695: A half-salary cut at the start of the war, and no salary at all whilst he was in America, the council's action was widely read as a personal attack on Huxley. A public controversy ensued, but eventually the Council got its way. In 1943 he was asked by the British government to join the Colonial Commission on Higher Education. The commission's remit was to survey the West African Commonwealth countries for suitable locations for
1276-536: A language as an evolutionary system. The evolution of human language closely corresponds with human's biological evolution which allows phylogenetic methods to be applied. The concept of a "tree" serves as an efficient way to represent relationships between languages and language splits. It also serves as a way of testing hypotheses about the connections and ages of language families. For example, relationships among languages can be shown by using cognates as characters. The phylogenetic tree of Indo-European languages shows
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#17327876183021392-640: A lifelong internationalist with a concern for education, got involved in the creation of the United Nations Educational, Scientific and Cultural Organization ( UNESCO ), and became the organization's first director-general in 1946. His term of office, six years in the Charter, was cut down to two years at the behest of the American delegation. The reasons are not known for sure, but his left-wing tendencies and humanism were likely factors. In
1508-420: A new method of evolution: the transmission of organized experience by way of tradition, which… largely overrides the automatic process of natural selection as the agent of change." Both Huxley and his grandfather gave Romanes Lectures on the possible connection between evolution and ethics (see evolutionary ethics ). Huxley's views on God could be described as being that of an agnostic atheist . Huxley had
1624-420: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
1740-670: A scholarship in Zoology to Balliol College, Oxford and took up the place in 1906 after spending the summer in Germany. He developed a particular interest in embryology and protozoa and developed a friendship with the ornithologist William Warde Fowler . In the autumn term of his final year, 1908, his mother died from cancer at the age of 46. In his final year he won the Newdigate Prize for his poem "Holyrood". In 1909 he graduated with first class honours, and spent that July at
1856-676: A series of sub-species with continuous change in characters over a geographical area. The classic example of a cline is the circle of subspecies of the gull Larus round the Arctic zone. This cline is an example of a ring species . Some of Huxley's last contributions to the evolutionary synthesis were on the subject of ecological genetics . He noted how widespread polymorphism is in nature, with visible morphism much more prevalent in some groups than others. The immense diversity of colour and pattern in small bivalve molluscs, brittlestars, sea-anemones, tubicular polychaetes and various grasshoppers
1972-700: A shared evolutionary history. There are debates if increasing the number of taxa sampled improves phylogenetic accuracy more than increasing the number of genes sampled per taxon. Differences in each method's sampling impact the number of nucleotide sites utilized in a sequence alignment, which may contribute to disagreements. For example, phylogenetic trees constructed utilizing a more significant number of total nucleotides are generally more accurate, as supported by phylogenetic trees' bootstrapping replicability from random sampling. The graphic presented in Taxon Sampling, Bioinformatics, and Phylogenomics , compares
2088-462: A significant source of error within phylogenetic analysis occurs due to inadequate taxon samples. Accuracy may be improved by increasing the number of genetic samples within its monophyletic group. Conversely, increasing sampling from outgroups extraneous to the target stratified population may decrease accuracy. Long branch attraction is an attributed theory for this occurrence, where nonrelated branches are incorrectly classified together, insinuating
2204-631: A single tree with true claim. The same process can be applied to texts and manuscripts. In Paleography , the study of historical writings and manuscripts, texts were replicated by scribes who copied from their source and alterations - i.e., 'mutations' - occurred when the scribe did not precisely copy the source. Phylogenetics has been applied to archaeological artefacts such as the early hominin hand-axes, late Palaeolithic figurines, Neolithic stone arrowheads, Bronze Age ceramics, and historical-period houses. Bayesian methods have also been employed by archaeologists in an attempt to quantify uncertainty in
2320-594: A small group of taxa to represent the evolutionary history of its broader population. This process is also known as stratified sampling or clade-based sampling. The practice occurs given limited resources to compare and analyze every species within a target population. Based on the representative group selected, the construction and accuracy of phylogenetic trees vary, which impacts derived phylogenetic inferences. Unavailable datasets, such as an organism's incomplete DNA and protein amino acid sequences in genomic databases, directly restrict taxonomic sampling. Consequently,
2436-592: A species to uncover either a higher abundance of important bioactive compounds (e.g., species of Taxus for taxol) or natural variants of known pharmaceuticals (e.g., species of Catharanthus for different forms of vincristine or vinblastine). Phylogenetic analysis has also been applied to biodiversity studies within the fungi family. Phylogenetic analysis helps understand the evolutionary history of various groups of organisms, identify relationships between different species, and predict future evolutionary changes. Emerging imagery systems and new analysis techniques allow for
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#17327876183022552-426: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
2668-508: A word he coined. Thomas was also a friend and supporter of Charles Darwin and proponent of evolution. Huxley's father was writer and editor Leonard Huxley and his mother was Julia Arnold , a graduate of Somerville College, Oxford, who had gained a First in English Literature there in 1882. Julia and Leonard married in 1885 and they had four children: Margaret (1899–1981), the novelist Aldous , Trevenen and Julian. Huxley
2784-550: Is "tree shape." These approaches, while computationally intensive, have the potential to provide valuable insights into pathogen transmission dynamics. The structure of the host contact network significantly impacts the dynamics of outbreaks, and management strategies rely on understanding these transmission patterns. Pathogen genomes spreading through different contact network structures, such as chains, homogeneous networks, or networks with super-spreaders, accumulate mutations in distinct patterns, resulting in noticeable differences in
2900-413: Is a component of systematics that uses similarities and differences of the characteristics of species to interpret their evolutionary relationships and origins. Phylogenetics focuses on whether the characteristics of a species reinforce a phylogenetic inference that it diverged from the most recent common ancestor of a taxonomic group. In the field of cancer research, phylogenetics can be used to study
3016-497: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,
3132-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
3248-442: Is known as phylogenetic inference . It establishes the relationship between organisms with the empirical data and observed heritable traits of DNA sequences, protein amino acid sequences, and morphology . The results are a phylogenetic tree —a diagram setting the hypothetical relationships between organisms and their evolutionary history. The tips of a phylogenetic tree can be living taxa or fossils , which represent
3364-426: Is no basic cleavage between science and religion;… I believe that [a] drastic reorganization of our pattern of religious thought is now becoming necessary, from a god-centered to an evolutionary-centred pattern." Some believe the appropriate label for these views is religious naturalism . Many people assert that this abandonment of the god hypothesis means the abandonment of all religion and all moral sanctions. This
3480-422: Is perhaps maintained by making recognition by predators more difficult. Although Huxley believed that on a broad view evolution led to advances in organisation, he rejected classical Aristotelian teleology : "The ordinary man, or at least the ordinary poet, philosopher and theologian, always was anxious to find purpose in the evolutionary process. I believe this reasoning to be totally false.". Huxley coined
3596-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
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3712-488: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
3828-469: Is unquestionable. Their lesser weight in Huxley's citations was caused by the early publication date of his book. Huxley's book is not strong in palaeontology, which illustrates perfectly why Simpson's later works were such an important contribution. Huxley coined the terms the new synthesis and evolutionary synthesis ; he also invented the term cline in 1938 to refer to species whose members fall into
3944-555: Is used rather than the English form. Clades are the fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over
4060-651: The American Humanist Association 's annual "Humanist of the Year" award. Huxley also presided over the founding Congress of the International Humanist and Ethical Union and served with John Dewey , Albert Einstein and Thomas Mann on the founding advisory board of the First Humanist Society of New York. Huxley wrote that "There is no separate supernatural realm: all phenomena are part of one natural process of evolution. There
4176-591: The Lasker Foundation in the category Planned Parenthood – World Population . Huxley came from the Huxley family on his father's side and the Arnold family on his mother's. His great-grandfather was Thomas Arnold of Rugby School , his great-uncle Matthew Arnold , and his aunt, Mrs Humphry Ward . His grandfather Thomas Henry Huxley was raised Anglican but eventually became an advocate of Agnosticism ,
4292-494: The University of Oxford , and started on the systematic observation of the courtship habits of water birds, such as the common redshank (a wader) and grebes (which are divers). Bird watching in childhood had given Huxley his interest in ornithology , and he helped devise systems for the surveying and conservation of birds. His particular interest was bird behaviour, especially the courtship of water birds. His 1914 paper on
4408-696: The battle of the Somme on the Western Front . The ecological geneticist E. B. Ford always remembered his openness and encouragement at the start of his career. In 1925 Huxley moved to King's College London as Professor of Zoology , but in 1927, to the amazement of his colleagues and on the prodding of H. G. Wells whom he had promised 1,000 words a day, he resigned his chair to work full-time with Wells and his son G. P. Wells on The Science of Life ( see below ). For some time Huxley retained his room at King's College, continuing as Honorary Lecturer in
4524-570: The great crested grebe , later published as a book, was a landmark in avian ethology ; his invention of vivid labels for the rituals (such as 'penguin dance', 'plesiosaurus race' etc.) made the ideas memorable and interesting to the general reader. In 1912 Huxley was asked by Edgar Odell Lovett to set up the Department of Biology at the newly created Rice Institute (now Rice University ) in Houston , Texas, which he accepted, planning to start
4640-566: The 1930s Huxley visited Kenya and other East African countries to see the conservation work, including the creation of national parks . In 1933, he was one of eleven people involved in the appeal that led to the foundation of the British Trust for Ornithology (BTO), an organisation for the study of birds in the British Isles. From 1933 to 1938 he was a member of the committee for Lord Hailey's African Survey. In 1935 Huxley
4756-558: The German Phylogenie , introduced by Haeckel in 1866, and the Darwinian approach to classification became known as the "phyletic" approach. It can be traced back to Aristotle , who wrote in his Posterior Analytics , "We may assume the superiority ceteris paribus [other things being equal] of the demonstration which derives from fewer postulates or hypotheses." The modern concept of phylogenetics evolved primarily as
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4872-589: The Huxley family grave in Watts Cemetery, Compton. Huxley grew up at the family home in Shackleford , Surrey , England, where he showed an early interest in nature, as he was given lessons by his grandfather, Thomas Henry Huxley . When he heard his grandfather talking at dinner about the lack of parental care in fish, Julian piped up with "What about the stickleback , Gran'pater?". His grandfather also took him to visit Joseph Dalton Hooker at Kew. At
4988-605: The US, without success. As the 1930s started, Huxley travelled widely and took part in a variety of activities which were partly scientific and partly political. In 1931 Huxley visited the USSR at the invitation of Intourist , where initially he admired the results of social and economic planning on a large scale. Later, back in the United Kingdom, he became a founding member of the think tank Political and Economic Planning . In
5104-725: The United States should join World War II : a few weeks later came the attack on Pearl Harbor . When the US joined the war, he found it difficult to get a passage back to the UK, and his lecture tour was extended. The Council of the Zoological Society—"a curious assemblage… of wealthy amateurs, self-perpetuating and autocratic" —uneasy with their secretary, used this as an opportunity to remove him. This they did by abolishing his post "to save expenses". Since Huxley had taken
5220-512: The United States. He was therefore able to learn from and influence other scientists, naturalists and administrators. In the US he was able to meet other evolutionists at a critical time in the reassessment of natural selection . In Africa he was able to influence colonial administrators about education and wildlife conservation . In Europe, through UNESCO , he was at the centre of the post- World War II revival of education. In Russia, however, his experiences were mixed. His initially favourable view
5336-560: The Zoo Magazine. Fellows and their guests had the privilege of free entry on Sundays, a closed day to the general public. Today, that would be unthinkable, and Sundays are now open to the public. Huxley's mild suggestion (that the guests should pay) encroached on territory the Fellows thought was theirs by right. In 1941 Huxley was invited to the United States on a lecturing tour, and generated some controversy by saying that he thought
5452-724: The Zoology Department, and from 1927 to 1931 he was also Fullerian Professor of Physiology at the Royal Institution , where he gave an annual lectures series, but this marked the end of his life as a university academic. In 1929, after finishing work on The Science of Life , Huxley visited East Africa to advise the Colonial Office on education in British East Africa (for the most part Kenya , Uganda and Tanganyika ). He discovered that
5568-399: The age of thirteen Huxley attended Eton College as a King's Scholar , and continued to develop scientific interests; his grandfather had influenced the school to build science laboratories much earlier. At Eton he developed an interest in ornithology, guided by science master W. D. "Piggy" Hill. "Piggy was a genius as a teacher ... I have always been grateful to him." In 1905 Huxley won
5684-414: The basis of a computational classifier used to analyze real-world outbreaks. Computational predictions of transmission dynamics for each outbreak often align with known epidemiological data. Different transmission networks result in quantitatively different tree shapes. To determine whether tree shapes captured information about underlying disease transmission patterns, researchers simulated the evolution of
5800-408: The biologists and Nobel laureates Konrad Lorenz and Niko Tinbergen , and taught and encouraged many others. In general, he was more of an all-round naturalist than his famous grandfather, and contributed much to the acceptance of natural selection. His outlook was international, and somewhat idealistic: his interest in progress and evolutionary humanism runs through much of his published work. He
5916-436: The branching pattern and "degree of difference" to find a compromise between them. Usual methods of phylogenetic inference involve computational approaches implementing the optimality criteria and methods of parsimony , maximum likelihood (ML), and MCMC -based Bayesian inference . All these depend upon an implicit or explicit mathematical model describing the evolution of characters observed. Phenetics , popular in
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#17327876183026032-586: The cause of his arrest. Worse still, Lysenkoism not only denied proven genetic facts, it stopped the artificial selection of crops on Darwinian principles. This may have contributed to the regular shortage of food from the Soviet agricultural system ( Soviet famines ). Huxley, who had twice visited the Soviet Union, was originally not anti-communist, but the ruthless adoption of Lysenkoism by Joseph Stalin ended his tolerant attitude. Lysenko ended his days in
6148-408: The clonal evolution of tumors and molecular chronology , predicting and showing how cell populations vary throughout the progression of the disease and during treatment, using whole genome sequencing techniques. The evolutionary processes behind cancer progression are quite different from those in most species and are important to phylogenetic inference; these differences manifest in several areas:
6264-400: The correctness of phylogenetic trees generated using fewer taxa and more sites per taxon on the x-axis to more taxa and fewer sites per taxon on the y-axis. With fewer taxa, more genes are sampled amongst the taxonomic group; in comparison, with more taxa added to the taxonomic sampling group, fewer genes are sampled. Each method has the same total number of nucleotide sites sampled. Furthermore,
6380-496: The courtship takes place mostly after mate selection, not before. Huxley tackled the subject of evolution at full length, in what became the defining work of his life. His role was that of a synthesiser, and it helped that he had met many of the other participants. His book Evolution: The Modern Synthesis was written while he was secretary to the Zoological Society, and made use of his collection of reprints covering
6496-412: The creation of universities. There he acquired a disease, went down with hepatitis , and had a serious mental breakdown. He was completely disabled, treated with ECT , and took a full year to recover. He was 55. In 1945, Huxley proposed to melt the polar ice caps by igniting atomic bombs to moderate the world climate in the northern hemisphere, and permit shipping across the top of the world. Huxley,
6612-413: The data distribution. They may be used to quickly identify differences or similarities in the transmission data. Phylogenetic tools and representations (trees and networks) can also be applied to philology , the study of the evolution of oral languages and written text and manuscripts, such as in the field of quantitative comparative linguistics . Computational phylogenetics can be used to investigate
6728-448: The differences in HIV genes and determine the relatedness of two samples. Phylogenetic analysis has been used in criminal trials to exonerate or hold individuals. HIV forensics does have its limitations, i.e., it cannot be the sole proof of transmission between individuals and phylogenetic analysis which shows transmission relatedness does not indicate direction of transmission. Taxonomy is
6844-597: The discovery of more genetic relationships in biodiverse fields, which can aid in conservation efforts by identifying rare species that could benefit ecosystems globally. Whole-genome sequence data from outbreaks or epidemics of infectious diseases can provide important insights into transmission dynamics and inform public health strategies. Traditionally, studies have combined genomic and epidemiological data to reconstruct transmission events. However, recent research has explored deducing transmission patterns solely from genomic data using phylodynamics , which involves analyzing
6960-488: The dotted line represents a 1:1 accuracy between the two sampling methods. As seen in the graphic, most of the plotted points are located below the dotted line, which indicates gravitation toward increased accuracy when sampling fewer taxa with more sites per taxon. The research performed utilizes four different phylogenetic tree construction models to verify the theory; neighbor-joining (NJ), minimum evolution (ME), unweighted maximum parsimony (MP), and maximum likelihood (ML). In
7076-408: The early days… [and in] the far-reaching influence he exerted [on] the international community." In addition to his international and humanist concerns, his research interests covered evolution in all its aspects, ethology , embryology , genetics , anthropology and to some extent the infant field of cell biology . Julian's eminence as an advocate for evolution, and especially his contribution to
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#17327876183027192-668: The emergence of biochemistry , organism classifications are now usually based on phylogenetic data, and many systematists contend that only monophyletic taxa should be recognized as named groups. The degree to which classification depends on inferred evolutionary history differs depending on the school of taxonomy: phenetics ignores phylogenetic speculation altogether, trying to represent the similarity between organisms instead; cladistics (phylogenetic systematics) tries to reflect phylogeny in its classifications by only recognizing groups based on shared, derived characters ( synapomorphies ); evolutionary taxonomy tries to take into account both
7308-591: The first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing". Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr , Theodosius Dobzhansky , George Gaylord Simpson , Bernhard Rensch , Ledyard Stebbins and
7424-607: The following year. Huxley made an exploratory trip to the United States in September 1912, visiting a number of leading universities as well as the Rice Institute. At T. H. Morgan 's fly lab ( Columbia University ) he invited H. J. Muller to join him at Rice. Muller agreed to be his deputy, hurried to complete his PhD and moved to Houston for the beginning of the 1915–1916 academic year. At Rice, Muller taught biology and continued Drosophila lab work. Before taking up
7540-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
7656-447: The human body. For example, in drug discovery, venom -producing animals are particularly useful. Venoms from these animals produce several important drugs, e.g., ACE inhibitors and Prialt ( Ziconotide ). To find new venoms, scientists turn to phylogenetics to screen for closely related species that may have the same useful traits. The phylogenetic tree shows which species of fish have an origin of venom, and related fish they may contain
7772-434: The identification, naming, and classification of organisms. Compared to systemization, classification emphasizes whether a species has characteristics of a taxonomic group. The Linnaean classification system developed in the 1700s by Carolus Linnaeus is the foundation for modern classification methods. Linnaean classification relies on an organism's phenotype or physical characteristics to group and organize species. With
7888-487: The international gathering for the centenary of Darwin's birth, held at the University of Cambridge . Huxley was awarded a scholarship to spend a year at the Naples Marine Biological Station, where he developed his interest in developmental biology by investigating sea squirts and sea urchins . In 1910 he was appointed as Demonstrator in the Department of Zoology and Comparative Anatomy at
8004-588: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"
8120-468: The latter part of the twentieth century with objections from Cladists , among others, to any suggestion that one group could be scientifically described as "advanced" and another as 'primitive'. Modern assessments of these views have been surveyed in Nitecki and Dawkins. Huxley's humanism came from his appreciation that mankind was in charge of its own destiny (at least in principle), and this raised
8236-517: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
8352-475: The majority of models, sampling fewer taxon with more sites per taxon demonstrated higher accuracy. Generally, with the alignment of a relatively equal number of total nucleotide sites, sampling more genes per taxon has higher bootstrapping replicability than sampling more taxa. However, unbalanced datasets within genomic databases make increasing the gene comparison per taxon in uncommonly sampled organisms increasingly difficult. The term "phylogeny" derives from
8468-525: The mere microscopic eye-spots of early forms of life. [Over] the whole range of evolutionary time we see general advance—improvement in all the main properties of life, including its general organization. 'Advance' is thus a useful term for long-term improvement in some general property of life. [But] improvement is not universal. Lower forms manage to survive alongside higher". Huxley's views on progressive evolution were similar to those of G. Ledyard Stebbins and Bernhard Rensch , and were challenged in
8584-621: The mid-20th century but now largely obsolete, used distance matrix -based methods to construct trees based on overall similarity in morphology or similar observable traits (i.e. in the phenotype or the overall similarity of DNA , not the DNA sequence ), which was often assumed to approximate phylogenetic relationships. Prior to 1950, phylogenetic inferences were generally presented as narrative scenarios. Such methods are often ambiguous and lack explicit criteria for evaluating alternative hypotheses. In phylogenetic analysis, taxon sampling selects
8700-617: The minority of biologists who believed that natural selection was the main driving force of evolution, and that evolution occurred by small steps and not by saltation (jumps). These opinions are now standard. Though his time as an academic was quite brief, he taught and encouraged evolutionary biologists at the University of Oxford in the 1920s. Charles Elton (ecology), Alister Hardy ( marine biology ) and John Baker ( cytology ) all became highly successful, and Baker eventually wrote Huxley's Royal Society obituary memoir. Perhaps
8816-429: The modern evolutionary synthesis which took place around the time of World War II . The synthesis of genetic and population ideas produced a consensus which reigned in biology from about 1940, and which is still broadly tenable. "The most informative episode in the history of evolutionary biology was the establishment of the 'neo-Darwinian synthesis'." The synthesis was brought about "not by one side being proved right and
8932-667: The modern evolutionary synthesis, led to his awards of the Darwin Medal of the Royal Society in 1956, and the Darwin–Wallace Medal of the Linnaean Society in 1958. 1958 was the centenary anniversary of the joint presentation On the tendency of species to form varieties; and the perpetuation of varieties and species by natural means of selection by Darwin and Wallace. Huxley was a friend and mentor of
9048-459: The modern synthesis shows indirectly those whom Huxley regarded as the most important contributors to the synthesis up to 1941 (the book was published in 1942, and references go up to 1941). The authorities cited 20 or more times are: Darlington , Darwin , Dobzhansky , Fisher , Ford , Goldschmidt , Haldane , J. S. Huxley, Muller , Rensch , Turrill , Wright . Goldschmidt was an influential geneticist who advocated evolution by saltation, and
9164-747: The most significant was Edmund Brisco Ford , who founded a field of research called ecological genetics , which played a role in the evolutionary synthesis. Another important disciple was Gavin de Beer , who wrote on evolution and development , and became director of the Natural History Museum . Both these scholars had attended Huxley's lectures on genetics , experimental zoology (including embryology ) and ethology . Later, they became his collaborators, and then leaders in their own right. In an era when scientists did not travel so frequently as today, Huxley travelled widely in Europe, Africa and
9280-418: The need for a sense of direction and a system of ethics. His grandfather T. H. Huxley , when faced with similar problems, had promoted agnosticism, but Julian chose humanism as being more directed to supplying a basis for ethics. Julian's thinking went along these lines: "The critical point in the evolution of man… was when he acquired the use of [language]… Man's development is potentially open… He has developed
9396-538: The others wrong, but by the exchange of the most viable components of the previously competing research strategies". Ernst Mayr, 1980. Huxley's first "trial run" was the treatment of evolution in the Science of Life (1929–30), and in 1936 he published a long and significant paper for the British Association . In 1938 came three lengthy reviews on major evolutionary topics. Two of these papers were on
9512-739: The pairs displaying to each other, and with secondary sexual characteristics equally developed in both sexes. In September 1916 Huxley returned to England from Texas to assist in the war effort. He was commissioned a temporary second lieutenant in the Royal Army Service Corps on 25 May 1917, and was transferred to the General List, working in the British Army Intelligence Corps from 26 January 1918, first in Sussex , and then in northern Italy. He
9628-551: The phrase Progress without a goal to summarise his case in Evolution the modern synthesis that evolutionary progress was "a raising of the upper level of biological efficiency, this being defined as increased control over and independence of the environment." In Evolution in action he wrote that Natural selection plus time produces biological improvement… 'Improvement' is not yet a recognised technical term in biology … however, living things are improved during evolution… Darwin
9744-528: The phylogenetic history of a species cannot be read directly from its ontogeny, as Haeckel thought would be possible, but characters from ontogeny can be (and have been) used as data for phylogenetic analyses; the more closely related two species are, the more apomorphies their embryos share. One use of phylogenetic analysis involves the pharmacological examination of closely related groups of organisms. Advances in cladistics analysis through faster computer programs and improved molecular techniques have increased
9860-440: The population geneticists J. B. S. Haldane , Ronald Fisher and Sewall Wright . However, at the time of Huxley's book several of these had yet to make their distinctive contribution. Certainly, for Huxley, E. B. Ford and his co-workers in ecological genetics were at least as important; and Cyril Darlington , the chromosome expert, was a notable source of facts and ideas.An analysis of the "authorities cited" index of Evolution
9976-670: The post of assistant professor at the Rice Institute , Huxley spent a year in Germany preparing for his demanding new job. Working in a laboratory just months before the outbreak of World War I , Huxley overheard fellow academics comment on a passing aircraft, "It will not be long before those planes are flying over England." One pleasure of Huxley's life in Texas was the sight of his first hummingbird , though his visit to Edward Avery McIlhenny 's estate on Avery Island in Louisiana
10092-516: The precision of phylogenetic determination, allowing for the identification of species with pharmacological potential. Historically, phylogenetic screens for pharmacological purposes were used in a basic manner, such as studying the Apocynaceae family of plants, which includes alkaloid-producing species like Catharanthus , known for producing vincristine , an antileukemia drug. Modern techniques now enable researchers to study close relatives of
10208-699: The present time or "end" of an evolutionary lineage, respectively. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the tree. An unrooted tree diagram (a network) makes no assumption about the ancestral line, and does not show the origin or "root" of the taxa in question or the direction of inferred evolutionary transformations. In addition to their use for inferring phylogenetic patterns among taxa, phylogenetic analyses are often employed to represent relationships among genes or individual organisms. Such uses have become central to understanding biodiversity , evolution, ecology , and genomes . Phylogenetics
10324-418: The properties of pathogen phylogenies. Phylodynamics uses theoretical models to compare predicted branch lengths with actual branch lengths in phylogenies to infer transmission patterns. Additionally, coalescent theory , which describes probability distributions on trees based on population size, has been adapted for epidemiological purposes. Another source of information within phylogenies that has been explored
10440-543: The relationship between two variables in pathogen transmission analysis, such as the number of infected individuals and the time since infection. These plots can help identify trends and patterns, such as whether the spread of the pathogen is increasing or decreasing over time, and can highlight potential transmission routes or super-spreader events. Box plots displaying the range, median, quartiles, and potential outliers datasets can also be valuable for analyzing pathogen transmission data, helping to identify important features in
10556-410: The relationships between several of the languages in a timeline, as well as the similarity between words and word order. There are three types of criticisms about using phylogenetics in philology, the first arguing that languages and species are different entities, therefore you can not use the same methods to study both. The second being how phylogenetic methods are being applied to linguistic data. And
10672-484: The shape of phylogenetic trees, as illustrated in Fig. 1. Researchers have analyzed the structural characteristics of phylogenetic trees generated from simulated bacterial genome evolution across multiple types of contact networks. By examining simple topological properties of these trees, researchers can classify them into chain-like, homogeneous, or super-spreading dynamics, revealing transmission patterns. These properties form
10788-508: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Phylogenetics In biology , phylogenetics ( / ˌ f aɪ l oʊ dʒ ə ˈ n ɛ t ɪ k s , - l ə -/ ) is the study of the evolutionary history of life using genetics, which
10904-443: The subject of sexual selection , an idea of Darwin's whose standing has been revived in recent times. Huxley thought that sexual selection was "…merely an aspect of natural selection which… is concerned with characters which subserve mating, and are usually sex-limited ". This rather grudging acceptance of sexual selection was influenced by his studies on the courtship of the great crested grebe (and other birds that pair for life):
11020-421: The third, discusses the types of data that is being used to construct the trees. Bayesian phylogenetic methods, which are sensitive to how treelike the data is, allow for the reconstruction of relationships among languages, locally and globally. The main two reasons for the use of Bayesian phylogenetics are that (1) diverse scenarios can be included in calculations and (2) the output is a sample of trees and not
11136-484: The trait. Using this approach in studying venomous fish, biologists are able to identify the fish species that may be venomous. Biologist have used this approach in many species such as snakes and lizards. In forensic science , phylogenetic tools are useful to assess DNA evidence for court cases. The simple phylogenetic tree of viruses A-E shows the relationships between viruses e.g., all viruses are descendants of Virus A. HIV forensics uses phylogenetic analysis to track
11252-504: The tree topology and divergence times of stone projectile point shapes in the European Final Palaeolithic and earliest Mesolithic. Julian Huxley Sir Julian Sorell Huxley FRS (22 June 1887 – 14 February 1975) was an English evolutionary biologist , eugenicist , and internationalist . He was a proponent of natural selection , and a leading figure in the mid-twentieth century modern synthesis . He
11368-460: The types of aberrations that occur, the rates of mutation , the high heterogeneity (variability) of tumor cell subclones, and the absence of genetic recombination . Phylogenetics can also aid in drug design and discovery. Phylogenetics allows scientists to organize species and can show which species are likely to have inherited particular traits that are medically useful, such as producing biologically active compounds - those that have effects on
11484-601: The wildlife on the Serengeti plain was almost undisturbed because the tsetse fly (the vector for the trypanosome parasite which causes sleeping sickness in humans) prevented human settlement there. He tells about these experiences in Africa view (1931), and so does his wife. She reveals that he fell in love with an 18-year-old American girl on board ship (when Juliette was not present), and then presented Juliette with his ideas for an open marriage: "What Julian really wanted
11600-586: The years in Paris are well described by his wife. Huxley's internationalist and conservation interests also led him, with Victor Stolan , Sir Peter Scott , Max Nicholson and Guy Mountfort , to set up the WWF ( World Wide Fund for Nature under its former name of the World Wildlife Fund ). Another post-war activity was Huxley's attack on the Soviet politico-scientist Trofim Lysenko , who had espoused
11716-407: Was a Christian, whilst Huxley was an atheist. Huxley wrote the foreword to The Phenomenon of Man (1959) and was bitterly attacked by his rationalist friends for doing so. On Huxley's death at 87 on 14 February 1975, John Owen (Director of National Parks for Tanganyika ) wrote, "Julian Huxley was one of the world's great men … he played a seminal role in wild life conservation in [East] Africa in
11832-400: Was a pupil at Prior's Field, Compton, the school his mother had founded and run. During 1913 the relationship broke down and Huxley had a nervous breakdown which a biographer described as caused by 'conflict between desire and guilt'. In the first months of 1914 Huxley had severe depression and lived for some weeks at The Hermitage, a small private nursing home. In August 1914 while Huxley
11948-551: Was advanced in grade within the Intelligence Corps on 3 May 1918, relinquished his intelligence appointment on 10 January 1919 and was demobilised five days later, retaining his rank. After the war he became a Fellow at New College, Oxford , and was made Senior Demonstrator in the University Department of Zoology. In fact, Huxley took the place of his old tutor Geoffrey Smith, who had been killed in
12064-556: Was appointed secretary to the Zoological Society of London , and spent much of the next seven years running the society and its zoological gardens, the London Zoo and Whipsnade Park , alongside his writing and research. The previous Director, Peter Chalmers Mitchell , had been in post for many years, and had skillfully avoided conflict with the Fellows and Council. Things were rather different when Huxley arrived. Huxley
12180-478: Was awarded UNESCO's Kalinga Prize for the popularisation of science in 1953, the Darwin Medal of the Royal Society in 1956, and the Darwin–Wallace Medal of the Linnaean Society in 1958. He was also knighted in the 1958 New Year Honours , a hundred years after Charles Darwin and Alfred Russel Wallace announced the theory of evolution by natural selection. In 1956 he received a Special Award from
12296-513: Was born on 22 June 1887, at the London house of his aunt. His mother opened a school in Compton, Guildford in 1902 and died in 1908, when he was 21. In 1912, his father married Rosalind Bruce, who was the same age as Julian, and he later acquired half-brothers Andrew Huxley and David Huxley. In 1911, Huxley became informally engaged to Kathleen Fordham, whom he had met some years earlier when she
12412-517: Was changed by his growing awareness of Stalin's murderous repression, and the Lysenko affair. There seems little evidence that he had any effect on the Soviet Union , and the same could be said for some other Western scientists. "Marxist-Leninism had become a dogmatic religion… and like all dogmatic religions, it had turned from reform to persecution." Huxley was one of the main architects of
12528-475: Was in Scotland, his brother Trevenen also had a nervous breakdown and stayed in the same nursing home. Trevenen was worried about how he had treated one of his women friends and committed suicide whilst there. In 1919, Huxley married Juliette Baillot (1896–1994) a French Swiss woman whom he had met while she was employed as a governess at Garsington Manor , the country house of Lady Ottoline Morrell . Huxley
12644-677: Was later unfaithful to Baillot and told her that he wanted an open marriage. One of his affairs was with the poet May Sarton who in turn fell in love with Baillot and had a brief affair with her as well. Huxley described himself in print as suffering from manic depression, and his wife's autobiography suggests that Julian Huxley suffered from a bipolar disorder . He relied on his wife to provide moral and practical support throughout his life. Sir Julian and Lady Juliette Huxley had two sons: Anthony Huxley (1920–1992) and Francis Huxley (1923–2016), who both became scientists. His ashes are buried with his wife, son Anthony, parents and brother at
12760-469: Was more significant. The McIlhennys and their Avery cousins owned the entire island, and the McIlhenny branch used it to produce their famous Tabasco sauce . Birds were one of McIlhenny's passions, however, and around 1895 he had set up a private sanctuary on the island, called Bird City. There Huxley found egrets , herons and bitterns . These water birds, like the grebes, exhibit mutual courtship, with
12876-529: Was not a skilled administrator; his wife said "He was impatient… and lacked tact". He instituted a number of changes and innovations, more than some approved of. For example, Huxley introduced a whole range of ideas designed to make the Zoo child-friendly. Today, this would pass without comment; but then it was more controversial. He fenced off the Fellows' Lawn to establish Pets Corner; he appointed new assistant curators, encouraging them to talk to children; he initiated
12992-407: Was not afraid to use the word for the results of natural selection in general… I believe that improvement can become one of the key concepts in evolutionary biology. Can it be scientifically defined? Improvements in biological machinery… the limbs and teeth of grazing horses… the increase in brain-power… The eyes of a dragon-fly, which can see all round [it] in every direction, are an improvement over
13108-475: Was one of the signers of the Humanist Manifesto . Huxley and biologist August Weismann insisted on natural selection as the primary agent in evolution . Huxley was a major player in the mid-twentieth century modern evolutionary synthesis. He was a prominent populariser of biological science to the public , with a focus on three aspects in particular. In the early 20th century he was one of
13224-499: Was secretary of the Zoological Society of London (1935–1942), the first director of UNESCO , a founding member of the World Wildlife Fund , the president of the British Eugenics Society (1959–1962), and the first president of the British Humanist Association . Huxley was well known for his presentation of science in books and articles, and on radio and television. He directed an Oscar-winning wildlife film. He
13340-399: Was sometimes mentioned in disagreement. Turrill provided Huxley with botanical information. The list omits three key members of the synthesis who are listed above: Mayr , Stebbins the botanist and Simpson the palaeontologist. Mayr gets 16 citations and more in the two later editions; all three published outstanding and relevant books some years later, and their contribution to the synthesis
13456-414: Was … a definite freedom from the conventional bonds of marriage." The couple separated for a while; Julian travelled to the US, hoping to land a suitable appointment and, in due course, to marry Miss Weldmeier. He left no account of what transpired, but he was evidently not successful, and returned to England to resume his marriage in 1931. For the next couple of years Huxley still angled for an appointment in
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