In the 1920s and 1930s the so-called modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that applied generally to any branch of biology. The modern synthesis explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology. The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance. Molecular biology improved understanding of the relationship between genotype and phenotype. Advancements were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees.
The 'modern synthesis'
Evolution
Evolution | The 'modern synthesis'
It explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology. It explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology. The modern synthesis explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology. In the 1920s and 1930s the so-called modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that applied generally to any branch of biology.
which of the following is the ultimate result of evolution
user
Sorry. I cannot find the answer based on the context.
assistant
what is evolution?
user
It is change in the heritable characteristics of biological populations over successive generations.
assistant
who was the first to study this?
user
Charles Darwin and Alfred Russel Wallace
assistant
when was the first one born?
user
Shrewsbury, Shropshire
assistant
did he suffer from any illness?
user
He had "an uncomfortable palpitation of the heart".
assistant
did he publish anything?
user
Yes, his theory of evolution with compelling evidence in his 1859 book "On the Origin of Species".
assistant
what does modern synthesis state about evolution?
user
In 1973, evolutionary biologist Theodosius Dobzhansky penned that "nothing in biology makes sense except in the light of evolution," because it has brought to light the relations of what first seemed disjointed facts in natural history into a coherent explanatory body of knowledge that describes and predicts many observable facts about life on this planet.
Evolution | The 'modern synthesis'
In the 1944 book "Tempo and Mode in Evolution", George Gaylord Simpson showed that the fossil record was consistent with the irregular non-directional pattern predicted by the developing evolutionary synthesis, and that the linear trends that earlier paleontologists had claimed supported orthogenesis and neo-Lamarckism did not hold up to closer examination. In 1950, G. Ledyard Stebbins published "Variation and Evolution in Plants", which helped to integrate botany into the synthesis. The emerging cross-disciplinary consensus on the workings of evolution would be known as the modern synthesis. It received its name from the 1942 book "" by Julian Huxley.
History of evolutionary thought | The modern synthesis
The result was "bitter controversy".
Modern synthesis (20th century) | The Society for the Study of Evolution, 1946
Allen & Unwin, London. (1942, reprinted 1943, 1944, 1945, 1948, 1955; 2nd ed, with new introduction and bibliography by the author, 1963; 3rd ed, with new introduction and bibliography by nine contributors, 1974). U.S. first edition by Harper, 1943.
Evolution: The Modern Synthesis | Publication history
In 2009, Darwin's 200th anniversary, the "Origin of Species" 150th, and the 200th of Lamarck's "early evolutionary synthesis", "Philosophie Zoologique", the evolutionary biologist Eugene Koonin stated that while "the edifice of the [early 20th century] Modern Synthesis has crumbled, apparently, beyond repair", a new 21st century synthesis could be glimpsed. Three interlocking revolutions had, he argued, taken place in evolutionary biology: molecular, microbiological, and genomic. The molecular revolution included the neutral theory, that most mutations are neutral and that negative selection happens more often than the positive form, and that all current life evolved from a single common ancestor. In microbiology, the synthesis has expanded to cover the prokaryotes, using ribosomal RNA to form a tree of life.
Modern synthesis (20th century) | Koonin's 'post-modern' evolutionary synthesis, 2009
The modern synthesis was the widely accepted early-20th-century synthesis reconciling Charles Darwin's theory of evolution by natural selection and Gregor Mendel's theory of genetics in a joint mathematical framework. It established evolution as biology's central paradigm. The 19th-century ideas of natural selection by Darwin and Mendelian genetics were united by researchers who included Ronald Fisher, one of the three founders of population genetics, and J. B. S. Haldane and Sewall Wright, between 1918 and 1932. Julian Huxley introduced the phrase "modern synthesis" in his 1942 book, "".
Extended evolutionary synthesis | The preceding "modern synthesis"
Evolution: The Modern Synthesis, a popularising 1942 book by Julian Huxley (grandson of T.H. Huxley), set out his vision of the modern synthesis of evolutionary biology of the mid-20th century. It was enthusiastically reviewed in academic biology journals.
Evolution: The Modern Synthesis | Introduction
In 1982, a historical note on a series of evolutionary biology books could state without qualification that evolution is the central organizing principle of biology. Smocovitis commented on this that "What the architects of the synthesis had worked to construct had by 1982 become a matter of fact", adding in a footnote that "the centrality of evolution had thus been rendered tacit knowledge, part of the received wisdom of the profession". By the late 20th century, however, the modern synthesis was showing its age, and fresh syntheses to remedy its defects and fill in its gaps were proposed from different directions.
Modern synthesis (20th century) | Later syntheses
By 1911 Castle noted that the results could be explained by Darwinian selection on heritable variation of a sufficient number of Mendelian genes.
Modern synthesis (20th century) | Castle's hooded rats, 1911
Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely:
Modern synthesis | Introduction
In the view of the evolutionary biologist Eugene Koonin in 2009, the modern synthesis will be replaced by a 'post-modern' synthesis that will include revolutionary changes in molecular biology, the study of prokaryotes and the resulting tree of life, and genomics.
Modern synthesis (20th century) | Introduction
Huxley's belief in progress within evolution and evolutionary humanism was shared in various forms by Dobzhansky, Mayr, Simpson and Stebbins, all of them writing about "the future of Mankind". Both Huxley and Dobzhansky admired the palaeontologist priest Pierre Teilhard de Chardin, Huxley writing the introduction to Teilhard's 1955 book on orthogenesis, "The Phenomenon of Man". This vision required evolution to be seen as the central and guiding principle of biology.
Modern synthesis (20th century) | Huxley's popularising synthesis, 1942
In the 1920s and 1930s the so-called modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that applied generally to any branch of biology. The modern synthesis explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology. The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance. Molecular biology improved understanding of the relationship between genotype and phenotype. Advancements were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees.
Evolution | The 'modern synthesis'
Lamm notes, too, that Huxley anticipated evolutionary developmental biology's attention to embryonic development for understanding evolution. Finally, the review observes that "It has long been debated whether the so-called Modern Synthesis was overall a positive force in biology, or whether its lacunae [gaps] undermine its contributions" and notes that people (such as Massimo Pigliucci) have called for a renewed synthesis, though biologists differ about its direction.
Evolution: The Modern Synthesis | Modern
Mayr, on the basis of an understanding of genes and direct observations of evolutionary processes from field research, introduced the biological species concept, which defined a species as a group of interbreeding or potentially interbreeding populations that are reproductively isolated from all other populations. Both Dobzhansky and Mayr emphasised the importance of subspecies reproductively isolated by geographical barriers in the emergence of new species. The palaeontologist George Gaylord Simpson helped to incorporate palaeontology with a statistical analysis of the fossil record that showed a pattern consistent with the branching and non-directional pathway of evolution of organisms predicted by the modern synthesis.
Introduction to evolution | Modern synthesis
The modern synthesis was the early 20th-century synthesis reconciling Charles Darwin's theory of evolution and Gregor Mendel's ideas on heredity in a joint mathematical framework. Julian Huxley coined the term in his 1942 book, "". The 19th century ideas of natural selection and Mendelian genetics were put together with population genetics, early in the twentieth century. The modern synthesis also addressed the relationship between the broad-scale changes of macroevolution seen by palaeontologists and the small-scale microevolution of local populations of living organisms. The synthesis was defined differently by its founders, with Ernst Mayr in 1959, G. Ledyard Stebbins in 1966 and Theodosius Dobzhansky in 1974 offering differing numbers of basic postulates, though they all included natural selection, working on heritable variation supplied by mutation.
Modern synthesis (20th century) | Introduction
Natural selection was in his view a "fact of nature capable of verification by observation and experiment", while the "period of synthesis" of the 1920s and 1930s had formed a "more unified science", rivalling physics and enabling the "rebirth of Darwinism". However, the book was not the research text that it appeared to be. In the view of the philosopher of science Michael Ruse, and in Huxley's own opinion, Huxley was "a generalist, a synthesizer of ideas, rather than a specialist". Ruse observes that Huxley wrote as if he were adding empirical evidence to the mathematical framework established by Fisher and the population geneticists, but that this was not so.
Modern synthesis (20th century) | Huxley's popularising synthesis, 1942
During the war, Mayr edited a series of bulletins of the Committee on Common Problems of Genetics, Paleontology, and Systematics, formed in 1943, reporting on discussions of a "synthetic attack" on the interdisciplinary problems of evolution. In 1946, the committee became the Society for the Study of Evolution, with Mayr, Dobzhansky and Sewall Wright the first of the signatories. Mayr became the editor of its journal, "Evolution". From Mayr and Dobzhansky's point of view, suggests the historian of science Betty Smocovitis, Darwinism was reborn, evolutionary biology was legitimised, and genetics and evolution were synthesised into a newly unified science. Everything fitted in to the new framework, except "heretics" like Richard Goldschmidt who annoyed Mayr and Dobzhansky by insisting on the possibility of speciation by macromutation, creating "hopeful monsters".
Modern synthesis (20th century) | The Society for the Study of Evolution, 1946
Charles Darwin's 1859 book "On the Origin of Species" was successful in convincing most biologists that evolution had occurred, but was less successful in convincing them that natural selection was its primary mechanism. In the 19th and early 20th centuries, variations of Lamarckism (inheritance of acquired characteristics), orthogenesis (progressive evolution), saltationism (evolution by jumps) and mutationism (evolution driven by mutations) were discussed as alternatives. Alfred Russel Wallace advocated a selectionist version of evolution, and unlike Darwin completely rejected Lamarckism. In 1880, Wallace's view was labelled neo-Darwinism by Samuel Butler.
Modern synthesis (20th century) | Darwin's evolution by natural selection, 1859
The biologist Eugene Koonin wrote in 2009 that "the new developments in evolutionary biology by no account should be viewed as refutation of Darwin. On the contrary, they are widening the trails that Darwin blazed 150 years ago and reveal the extraordinary fertility of his thinking."
Extended evolutionary synthesis | Recent history
In 1942, Julian Huxley's serious but popularising "" introduced a name for the synthesis and intentionally set out to promote a "synthetic point of view" on the evolutionary process. He imagined a wide synthesis of many sciences: genetics, developmental physiology, ecology, systematics, palaeontology, cytology, and mathematical analysis of biology, and assumed that evolution would proceed differently in different groups of organisms according to how their genetic material was organised and their strategies for reproduction, leading to progressive but varying evolutionary trends. His vision was of an "evolutionary humanism", with a system of ethics and a meaningful place for "Man" in the world grounded in a unified theory of evolution which would demonstrate progress leading to man at its summit.
Modern synthesis (20th century) | Huxley's popularising synthesis, 1942
The modern evolutionary synthesis is based on the concept that populations of organisms have significant genetic variation caused by mutation and by the recombination of genes during sexual reproduction. It defines evolution as the change in allelic frequencies within a population caused by genetic drift, gene flow between sub populations, and natural selection. Natural selection is emphasised as the most important mechanism of evolution; large changes are the result of the gradual accumulation of small changes over long periods of time. The modern evolutionary synthesis is the outcome of a merger of several different scientific fields to produce a more cohesive understanding of evolutionary theory.
Introduction to evolution | Modern synthesis
Other major figures in the synthesis included E. B. Ford, Bernhard Rensch, Ivan Schmalhausen, and George Gaylord Simpson. An early event in the modern synthesis was R. A. Fisher's 1918 paper on mathematical population genetics, but William Bateson, and separately Udny Yule, were already starting to show how Mendelian genetics could work in evolution in 1902. Different syntheses followed, accompanying the gradual breakup of the early 20th century synthesis, including with social behaviour in E. O. Wilson's sociobiology in 1975, evolutionary developmental biology's integration of embryology with genetics and evolution, starting in 1977, and Massimo Pigliucci's proposed extended evolutionary synthesis of 2007.
Modern synthesis (20th century) | Introduction
His 1937 work "Genetics and the Origin of Species" was a key step in bridging the gap between population geneticists and field naturalists. It presented the conclusions reached by Fisher, Haldane, and especially Wright in their highly mathematical papers in a form that was easily accessible to others. Further, Dobzhansky asserted that evolution was based on material genes, arranged in a string on physical hereditary structures, the chromosomes, and linked more or less strongly to each other according to their physical distances from each other on the chromosomes. As with Haldane and Fisher, Dobzhansky's "evolutionary genetics" was a genuine science, now unifying cell biology, genetics, and both micro- and macroevolution.
Modern synthesis (20th century) | Dobzhansky's evolutionary genetics, 1937
After the synthesis, evolutionary biology continued to develop with major contributions from workers including W. D. Hamilton, George C. Williams, E. O. Wilson, Edward B. Lewis and others.
Modern synthesis (20th century) | After the synthesis
Sewall Wright elucidated the nature of selection and adaptation. In his book "Genetics and the Origin of Species" (1937), Theodosius Dobzhansky established the idea that mutation, once seen as a rival to selection, actually supplied the raw material for natural selection by creating genetic diversity.
Natural selection | The modern synthesis
These have included such diverse fields as the study of society, developmental biology, epigenetics, molecular biology, microbiology, genomics, symbiogenesis, and horizontal gene transfer. The physiologist Denis Noble argues that these additions render neo-Darwinism in the sense of the early 20th century's modern synthesis "at the least, incomplete as a theory of evolution", and one that has been falsified by later biological research. Michael Rose and Todd Oakley note that evolutionary biology, formerly divided and "Balkanized", has been brought together by genomics. It has in their view discarded at least five common assumptions from the modern synthesis, namely that the genome is always a well-organised set of genes; that each gene has a single function; that species are well adapted biochemically to their ecological niches; that species are the durable units of evolution, and all levels from organism to organ, cell and molecule within the species are characteristic of it; and that the design of every organism and cell is efficient.
Modern synthesis (20th century) | Later syntheses
From the 1880s onwards, there was a widespread belief among biologists that Darwinian evolution was in deep trouble. This eclipse of Darwinism (in Julian Huxley's phrase) grew out of the weaknesses in Darwin's account, written with an incorrect view of inheritance. Darwin himself believed in blending inheritance, which implied that any new variation, even if beneficial, would be weakened by 50% at each generation, as the engineer Fleeming Jenkin correctly noted in 1868. This in turn meant that small variations would not survive long enough to be selected. Blending would therefore directly oppose natural selection. In addition, Darwin and others considered Lamarckian inheritance of acquired characteristics entirely possible, and Darwin's 1868 theory of pangenesis, with contributions to the next generation (gemmules) flowing from all parts of the body, actually implied Lamarckism as well as blending.
Modern synthesis (20th century) | The eclipse of Darwinism, 1880s onwards
George Gaylord Simpson was responsible for showing that the modern synthesis was compatible with palaeontology in his 1944 book "Tempo and Mode in Evolution". Simpson's work was crucial because so many palaeontologists had disagreed, in some cases vigorously, with the idea that natural selection was the main mechanism of evolution. It showed that the trends of linear progression (in for example the evolution of the horse) that earlier palaeontologists had used as support for neo-Lamarckism and orthogenesis did not hold up under careful examination. Instead the fossil record was consistent with the irregular, branching, and non-directional pattern predicted by the modern synthesis.
Modern synthesis (20th century) | Simpson's palaeontology, 1944
The historian and philosopher of science Ehud Lamm, on the book's reissue in 2010 for Darwin's bicentenary, writes that at almost 800 pages it was longer than the other "milestone" 1942 book on the modern synthesis, Ernst Mayr's "Systematics and the Origin of Species". Lamm calls it remarkable that both books were described as popular accounts at the time, and notes that Huxley states in his introduction that he was setting out to promote a "synthetic point of view" on Darwinian evolution. Huxley was not just trying to synthesise natural selection with Mendelian genetics "as the Modern Synthesis is often presented", writes Lamm, but to include also "genetics, developmental physiology, ecology, systematics, paleontology, cytology [cell biology], and mathematical analysis." Lamm notes that the book was successful, with revised editions in 1963 and 1974, both of which added lengthy introductions that attempted to bring the book "at least partly up to date", given what Lamm and Huxley agreed were very large changes in the field.
Evolution: The Modern Synthesis | Modern
He argued strongly and dogmatically for Darwinism and against Lamarckism, polarising opinions among other scientists. This increased anti-Darwinian feeling, contributing to its eclipse.
Modern synthesis (20th century) | Weismann's germ plasm, 1892
Dobzhansky called the work "an important missing link in the modern view of evolution".
Modern synthesis (20th century) | Schmalhausen's stabilizing selection, 1941
In 2007, more than half a century after the modern synthesis, Massimo Pigliucci called for an extended evolutionary synthesis to incorporate aspects of biology that had not been included or had not existed in the mid-20th century. It revisits the relative importance of different factors, challenges assumptions made in the modern synthesis, and adds new factors such as multilevel selection, transgenerational epigenetic inheritance, niche construction, and evolvability.
Modern synthesis (20th century) | Pigliucci's extended evolutionary synthesis, 2007
They argue that the "new biology" integrates genomics, bioinformatics, and evolutionary genetics into a general-purpose toolkit for a "Postmodern Synthesis".
Modern synthesis (20th century) | Later syntheses
Additionally, the modern evolutionary synthesis draws no distinction in the processes described by the theory of evolution when considering macroevolution and microevolution as the former is simply at the species level or above and the latter is below the species level. An example of this is ring species.
Objections to evolution | Lack of observation
have an existence that is independent of the human observer. In the 1920s and 1930s, Mendel's theory of inheritance and Darwin's theory of evolution by natural selection were joined in what was called the modern synthesis. This conjunction of theories also had a large impact on how biologists think about species. Edward Poulton anticipated many ideas on species that today are well accepted, and that were later more fully developed by Theodosius Dobzhansky and Ernst Mayr, two of the architects of the modern synthesis. Dobzhansky's 1937 book articulated the genetic processes that occur when incipient species are beginning to diverge.
Species concept | From Darwin to Mayr
It was not until the modern evolutionary synthesis in the 1930s and 1940s that a model of heredity became completely integrated with a model of variation. This modern evolutionary synthesis had been dubbed Neo Darwinian Evolution because it encompasses Charles Darwin's theories of evolution with Gregor Mendel's theories of genetic inheritance.
On the Origin of Species | Variation and heredity
Looking back at the conflicting accounts of the modern synthesis, the historian Betty Smocovitis notes in her 1996 book "Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology" that both historians and philosophers of biology have attempted to grasp its scientific meaning, but have found it "a moving target"; the only thing they agreed on was that it was a historical event. In her words"by the late 1980s the notoriety of the evolutionary synthesis was recognized ... So notorious did 'the synthesis' become, that few serious historically minded analysts would touch the subject, let alone know where to begin to sort through the interpretive mess left behind by the numerous critics and commentators".
Modern synthesis (20th century) | Historiography
The 1942 text however was "a more tolerant, pluralistic, view of evolution than we have come to expect in the wake of the "hardening of the synthesis" (as Stephen Gould so aptly put it)," with plenty of coverage of two "rebels", the discoverer of chromosomal crossover, Cyril Darlington, and the "avowedly anti-neoDarwinian" mutationist Richard Goldschmidt. Lamm notes that Goldschmidt's ideas on "genome-wide upheavals" may after all not be far wrong, given the epigenetic changes that can be caused by environmental stress. Huxley agreed with Darlington that hybridization and the polyploidy it could cause could result in increased variation and speciation.
Evolution: The Modern Synthesis | Modern
In the book, Huxley tackles the subject of evolution at full length, in what became the defining work of his life. His role was that of a synthesiser rather than a researcher, and it helped that he had met many of the other participants. His book was written whilst he was Secretary to the Zoological Society of London, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942.
Evolution: The Modern Synthesis | Significance
Biologists disagree on the need for an extended synthesis. Opponents contend that the modern synthesis is able to fully account for the newer observations, whereas others criticize the extended synthesis for not being radical enough. Proponents think that the conceptions of evolution at the core of the modern synthesis are too narrow and that even when the modern synthesis allows for the ideas in the extended synthesis, using the modern synthesis affects the way that biologists think about evolution. For example, Denis Noble says that using terms and categories of the modern synthesis distort the picture of biology that modern experimentation has discovered.
Extended evolutionary synthesis | Status
Many of the scientists in question did some early work on the mechanisms of evolution, e.g., the modern evolutionary synthesis combines Darwin's theory of evolution with Mendel's theories of inheritance and genetics. Though biological evolution of some sort had become the primary mode of discussing speciation within science by the late-19th century, it was not until the mid-20th century that evolutionary theories stabilized into the modern synthesis. Geneticist and evolutionary biologist Theodosius Dobzhansky, called the Father of the Modern Synthesis, argued that "Nothing in biology makes sense except in the light of evolution," and saw no conflict between evolutionary and his religious beliefs.
Rejection of evolution by religious groups | Religion and historical scientists
Before he left Germany for the United States in 1930, Mayr had been influenced by the work of the German biologist Bernhard Rensch, who in the 1920s had analyzed the geographic distribution of polytypic species, paying particular attention to how variations between populations correlated with factors such as differences in climate.
Modern synthesis (20th century) | Mayr's allopatric speciation, 1942
This, de Beer argued, could cause apparently sudden changes in the fossil record, since embryos fossilise poorly. As the gaps in the fossil record had been used as an argument against Darwin's gradualist evolution, de Beer's explanation supported the Darwinian position. However, despite de Beer, the modern synthesis largely ignored embryonic development to explain the form of organisms, since population genetics appeared to be an adequate explanation of how forms evolved.
Evolutionary developmental biology | The modern synthesis of the early 20th century
Huxley avoided mathematics, for instance not even mentioning Fisher's fundamental theorem of natural selection. Instead, Huxley used a mass of examples to demonstrate that natural selection is powerful, and that it works on Mendelian genes. The book was successful in its goal of persuading readers of the reality of evolution, effectively illustrating topics such as island biogeography, speciation, and competition. Huxley further showed that the appearance of long-term orthogenetic trends – predictable directions for evolution – in the fossil record were readily explained as allometric growth (since parts are interconnected). All the same, Huxley did not reject orthogenesis out of hand, but maintained a belief in progress all his life, with "Homo sapiens" as the end point, and he had since 1912 been influenced by the vitalist philosopher Henri Bergson, though in public he maintained an atheistic position on evolution.
Modern synthesis (20th century) | Huxley's popularising synthesis, 1942
With the development of the modern evolutionary synthesis in the 1930s and 1940s, Darwin's concept of evolutionary adaptation through natural selection became central to modern evolutionary theory, and it has now become the unifying concept of the life sciences.
On the Origin of Species | Introduction
The botanist G. Ledyard Stebbins extended the synthesis to encompass botany. He described the important effects on speciation of hybridization and polyploidy in plants in his 1950 book "Variation and Evolution in Plants". These permitted evolution to proceed rapidly at times, polyploidy in particular evidently being able to create new species effectively instantaneously.
Modern synthesis (20th century) | Stebbins's botany, 1950
The modern synthesis refers to the merger of genetics with natural selection which occurred in the 1930s and 1940s and offers a reasonably complete framework for understanding the emergence of biological complexity. Although there remain significant gaps in biological knowledge surrounding questions such as the origin of life and the emergence of sexual reproduction, the modern synthesis represents the most complete and well-substantiated joint point.
Tree of knowledge system | The modern synthesis
By the late 1930s, Mayr and Theodosius Dobzhansky had synthesized the ideas of population genetics with the knowledge of field naturalists about the amount of genetic diversity in wild populations, and the importance of genetically distinct subpopulations (especially when isolated from one another by geographical barriers) to create the early 20th century modern synthesis. In 1944 George Gaylord Simpson integrated paleontology into the synthesis by statistically analyzing the fossil record to show that it was consistent with the branching non-directional form of evolution predicted by the modern synthesis, and in particular that the linear trends cited by earlier paleontologists in support of Lamarckism and orthogenesis did not stand up to careful analysis.
The eclipse of Darwinism | End of the eclipse
Reviewing the book for "American Scientist" in 1943, the geologist Kirtley Mather wrote that the book provided "an admirable digest" of decades of work by many scientists. Mather commented "Of general interest is Huxley’s defense of the Darwinian concept of evolution, under attack by Hogben, Bateson and other biologists, amusingly reminiscent of bygone days when another Huxley championed the cause of evolution in a wholly different battle." Mather noted, too, that Huxley emphasises evolutionary progress, not by assuming that it means specialisation or "improvement" over earlier forms, but that attaining greater control over the environment and independence from it show man's progress at a new direction or rather at a higher level with "increases of aesthetic, intellectual, and spiritual experience and satisfaction."
Evolution: The Modern Synthesis | Contemporary
The traditional view is that developmental biology played little part in the modern synthesis, but in his 1930 book "Embryos and Ancestors", the evolutionary embryologist Gavin de Beer anticipated evolutionary developmental biology by showing that evolution could occur by heterochrony, such as in the retention of juvenile features in the adult. This, de Beer argued, could cause apparently sudden changes in the fossil record, since embryos fossilise poorly. As the gaps in the fossil record had been used as an argument against Darwin's gradualist evolution, de Beer's explanation supported the Darwinian position. However, despite de Beer, the modern synthesis largely ignored embryonic development to explain the form of organisms, since population genetics appeared to be an adequate explanation of how forms evolved.
Modern synthesis (20th century) | De Beer's embryology, 1930
Biologists, alongside scholars of the history and philosophy of biology, have continued to debate the need for, and possible nature of, a replacement synthesis. For example, in 2017 Philippe Huneman and Denis M. Walsh stated in their book "Challenging the Modern Synthesis" that numerous theorists had pointed out that the disciplines of embryological developmental theory, morphology, and ecology had been omitted. They noted that all such arguments amounted to a continuing desire to replace the modern synthesis with one that united "all biological fields of research related to evolution, adaptation, and diversity in a single theoretical frame." They observed further that there are two groups of challenges to the way the modern synthesis viewed inheritance.
Modern synthesis (20th century) | Towards a replacement synthesis
In the first few decades of the 20th century, most field naturalists continued to believe that alternative mechanisms of evolution such as Lamarckism and orthogenesis provided the best explanation for the complexity they observed in the living world. But as the field of genetics continued to develop, those views became less tenable. Theodosius Dobzhansky, a postdoctoral worker in Thomas Hunt Morgan's lab, had been influenced by the work on genetic diversity by Russian geneticists such as Sergei Chetverikov. He helped to bridge the divide between the foundations of microevolution developed by the population geneticists and the patterns of macroevolution observed by field biologists, with his 1937 book "Genetics and the Origin of Species".
History of evolutionary thought | The modern synthesis
Ledyard Stebbins. The emerging synthesis was called the evolutionary synthesis by Julian Huxley in his book, "". In 1947, a diverse collection of biologists met at a symposium in Princeton and declared their acceptance of this synthesis. However, it was not yet complete. Developmental biologists did not accept that the theory explained their observations, and it was not until the 1970s and 1980s that molecular biology bridged the gap. Also, for decades there was disagreement over whether the unit of selection was the gene or the individual as a whole. In 1974 all the living founders of the modern synthesis (with the exception of Simpson and Bernhard Rensch) met with historians of biology in a conference to evaluate their work.
Genetics and the Origin of Species | Historical impact
During the 1950s, the English biologist C. H. Waddington called for an extended synthesis based on his research on epigenetics and genetic assimilation. An extended synthesis was also proposed by the Austrian zoologist Rupert Riedl, with the study of evolvability. In 1978, Michael J. D. White wrote about an extension of the modern synthesis based on new research from speciation.
Extended evolutionary synthesis | Early history
Next, genetic drift (he used the term in 1941), selection, migration, and geographical isolation could change gene frequencies. Thirdly, mechanisms like ecological or sexual isolation and hybrid sterility could fix the results of the earlier processes.
Modern synthesis (20th century) | Dobzhansky's evolutionary genetics, 1937
The traditional claim that Mendelians rejected the idea of continuous variation is false; as early as 1902, Bateson and Saunders wrote that "If there were even so few as, say, four or five pairs of possible allelomorphs, the various homo- and hetero-zygous combinations might, on seriation, give so near an approach to a continuous curve, that the purity of the elements would be unsuspected". Also in 1902, the statistician Udny Yule showed mathematically that given multiple factors, Mendel's theory enabled continuous variation. Yule criticised Bateson's approach as confrontational, but failed to prevent the Mendelians and the biometricians from falling out.
Modern synthesis (20th century) | Genetics, mutationism and biometrics, 1900–1918
The mathematics of population genetics were originally developed as the beginning of the modern synthesis. Authors such as Beatty have asserted that population genetics defines the core of the modern synthesis. For the first few decades of the 20th century, most field naturalists continued to believe that Lamarckism and orthogenesis provided the best explanation for the complexity they observed in the living world. During the modern synthesis, these ideas were purged, and only evolutionary causes that could be expressed in the mathematical framework of population genetics were retained. Consensus was reached as to which evolutionary factors might influence evolution, but not as to the relative importance of the various factors.
Population genetics | Modern synthesis
Riedl held the opinion that the modern synthesis of the mid-20th century had ignored the role of development and morphology in evolution. He argued that the modern synthesis had failed to explain the origin of body plans and patterns at the macroevolutionary level. He presented his evolutionary theory in "Order in Living Organisms: A Systems Analysis of Evolution" (translated, 1978). He called for an extended evolutionary synthesis to integrate processes from developmental biology and macroevolutionary perspectives. Riedl and Michael Conrad in the 1970s were the first two scientists to propose explicit mechanisms for the evolution of evolvability.
Rupert Riedl | Evolutionary views
The modern synthesis was defined differently by its various founders, with differing numbers of basic postulates, as shown in the table.
Modern synthesis (20th century) | Definitions by the founders
Both workers, and others such as Dobzhansky and Wright, explicitly intended to bring biology up to the philosophical standard of the physical sciences, making it firmly based in mathematical modelling, its predictions confirmed by experiment. Natural selection, once considered hopelessly unverifiable speculation about history, was becoming predictable, measurable, and testable.
Modern synthesis (20th century) | Fisher and Haldane's mathematical population genetics, 1918–1930
The evolutionary biologist Ernst Mayr was influenced by the work of the German biologist Bernhard Rensch showing the influence of local environmental factors on the geographic distribution of sub-species and closely related species. Mayr followed up on Dobzhansky's work with the 1942 book "Systematics and the Origin of Species", which emphasized the importance of allopatric speciation in the formation of new species. This form of speciation occurs when the geographical isolation of a sub-population is followed by the development of mechanisms for reproductive isolation. Mayr also formulated the biological species concept that defined a species as a group of interbreeding or potentially interbreeding populations that were reproductively isolated from all other populations.
History of evolutionary thought | The modern synthesis
All I can presently say is that my chemical tools do not permit my assessment of intelligent design." He explained that he felt the explanations offered by evolution are incomplete, and he found it hard to believe that nature can produce the machinery of cells through random processes. On his website, he writes that "In biology, the mechanisms for such transformations are complete mysteries. I posit that the gross chemical changes needed for macroevolution (defined here as origin of the major organism groups, i.e. of body plans) are not understood and presently we cannot even suggest the mechanisms, let alone observe them…One day the requisite chemical basis might become apparent so that the questions can be answered.
James Tour | A Scientific Dissent From Darwinism
A traditional view is that the biometricians and the Mendelians rejected natural selection and argued for their separate theories for 20 years, the debate only resolved by the development of population genetics. A more recent view is that Bateson, de Vries, Thomas Hunt Morgan and Reginald Punnett had by 1918 formed a synthesis of Mendelism and mutationism. The understanding achieved by these geneticists spanned the action of natural selection on alleles (alternative forms of a gene), the Hardy–Weinberg equilibrium, the evolution of continuously-varying traits (like height), and the probability that a new mutation will become fixed. In this view, the early geneticists accepted natural selection but rejected Darwin's non-Mendelian ideas about variation and heredity, and the synthesis began soon after 1900.
Modern synthesis (20th century) | Genetics, mutationism and biometrics, 1900–1918
In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern evolutionary synthesis. The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that: The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view is that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by Stephen Jay Gould suggests he may be an exception.
Heredity | Modern development of genetics and heredity
Only with the modern synthesis, was it established that variation needed to be heritable to act as the raw material for selection.
Wilhelm Johannsen | Biography
Support for orthogenesis began to decline during the modern synthesis in the 1940s, when it became apparent that orthogenesis could not explain the complex branching patterns of evolution revealed by statistical analysis of the fossil record by paleontologists. A few biologists however hung on to the idea of orthogenesis as late as the 1950s, claiming that the processes of macroevolution, the long term trends in evolution, were distinct from the processes of microevolution.
The eclipse of Darwinism | Orthogenesis
Emergent evolution was revived by Robert G. B. Reid (March 20, 1939 - May 28, 2016), a biology professor at the University of Victoria (in British Columbia, Canada). In his book "Evolutionary Theory: The Unfinished Synthesis" (1985), he stated that the modern evolutionary synthesis with its emphasis on natural selection is an incomplete picture of evolution, and emergent evolution can explain the origin of genetic variation. Biologist Ernst Mayr heavily criticized the book claiming it was a misinformed attack on natural selection. Mayr commented that Reid was working from an "obsolete conceptual framework", provided no solid evidence and that he was arguing for a teleological process of evolution.
Emergent evolution | Robert G. B. Reid
Furthermore, this extended to plants as well as animals with G. Ledyard Stebbins’s book, "Variation and Evolution in Plants" and the much later, 1981 book, "Plant Speciation" by Verne Grant. In 1947, "a consensus had been achieved among geneticists, paleontologists and systematists and that evolutionary biology as an independent biological discipline had been established" during a Princeton University conference. This 20th century synthesis incorporated speciation. Since then, the ideas have been consistently and repeatedly confirmed.
History of speciation | Modern evolutionary synthesis
Dobzhansky examined the genetic diversity of wild populations and showed that, contrary to the assumptions of the population geneticists, these populations had large amounts of genetic diversity, with marked differences between sub-populations. The book also took the highly mathematical work of the population geneticists and put it into a more accessible form. In Britain, E. B. Ford, the pioneer of ecological genetics, continued throughout the 1930s and 1940s to demonstrate the power of selection due to ecological factors including the ability to maintain genetic diversity through genetic polymorphisms such as human blood types. Ford's work would contribute to a shift in emphasis during the course of the modern synthesis towards natural selection over genetic drift.
History of evolutionary thought | The modern synthesis
In the 19th century, particularly after the publication of "On the Origin of Species" in 1859, the idea that life had evolved was an active source of academic debate centred on the philosophical, social and religious implications of evolution. Today, the modern evolutionary synthesis is accepted by a vast majority of scientists. However, evolution remains a contentious concept for some theists. While various religions and denominations have reconciled their beliefs with evolution through concepts such as theistic evolution, there are creationists who believe that evolution is contradicted by the creation myths found in their religions and who raise various objections to evolution.
Evolution | Social and cultural responses
For one contemporary reviewer, his claim that "Species is the product of external circumstances, acting through millions of years" was "bold, disgusting, and gratuitous atheism." In modern terms, he proposed a theory of saltatory evolution, in which "deformations" in embryonic development produced "hopeful monsters" that, if fortuitously suited to the prevailing environmental conditions, gave rise to new species in a single, macroevolutionary leap. In 1857 he wrote: "The conversion of one of these species into another cannot be so difficult a matter with Nature, especially when all or most of the specific characters are already present in the young. Thus a given species may perish, but another of the same consanguinité takes its place in space: it is a question of time...
Robert Knox | Evolution
The theories developed in the early 20th century to integrate Mendelian genetics with Darwinian evolution are called the modern synthesis, a term introduced by Julian Huxley. Evolutionary biologists have subsequently modified this concept, such as George C. Williams' gene-centric view of evolution. He proposed an evolutionary concept of the gene as a unit of natural selection with the definition: "that which segregates and recombines with appreciable frequency." In this view, the molecular gene "transcribes" as a unit, and the evolutionary gene "inherits" as a unit. Related ideas emphasizing the centrality of genes in evolution were popularized by Richard Dawkins.
Gene | Modern synthesis and its successors
But present-day biology is far from providing even a chemical proposal for body plan changes, let alone a data-substantiated chemical mechanism." In his lectures, Tour has referred to modern biology’s explanations for evolution of complex systems as little more than story-telling.
James Tour | A Scientific Dissent From Darwinism
Noble has called for an extended evolutionary synthesis, and more controversially a replacement for the modern synthesis. He has argued that from research in epigenetics, acquired characteristics can be inherited and in contrast to the modern synthesis, genetic change is "far from random" and not always gradual. He has also claimed that the central dogma of molecular biology has been broken as an "embodiment of the Weismann Barrier", and a new synthesis will integrate research from physiology with evolutionary biology.
Denis Noble | Evolution
Just as there is no such thing as a "living fossil", and all modern species are cousins, so too, the amino acid sequences for all living species have been evolving since the time of their divergence from a common ancestor. A modern carp is not an ancestor to a frog; frogs are not ancestors to turtles; turtles are not ancestors to rabbits. Similarly, the variations in eukaryotic cytochrome c structure with respect to bacteria are all due to mutations taking place since divergence from the common ancestor of these different organisms. It thus is not surprising that they show a similar level of divergence and equidistance of this type was even predicted and confirmed by researchers as early as 1963.
Evolution: A Theory in Crisis | Molecular equidistance
Ernst Mayr's key contribution to the synthesis was "Systematics and the Origin of Species", published in 1942. It asserted the importance of and set out to explain population variation in evolutionary processes including speciation. He analysed in particular the effects of polytypic species, geographic variation, and isolation by geographic and other means. Mayr emphasized the importance of allopatric speciation, where geographically isolated sub-populations diverge so far that reproductive isolation occurs. He was skeptical of the reality of sympatric speciation believing that geographical isolation was a prerequisite for building up intrinsic (reproductive) isolating mechanisms. Mayr also introduced the biological species concept that defined a species as a group of interbreeding or potentially interbreeding populations that were reproductively isolated from all other populations.
Modern synthesis (20th century) | Mayr's allopatric speciation, 1942
With the emergence of the modern synthesis, in which genetics was integrated with evolution, orthogenesis and other alternatives to Darwinism were largely abandoned by biologists, but the notion that evolution represents progress is still widely shared. The evolutionary biologist Ernst Mayr made the term effectively taboo in the journal "Nature" in 1948, by stating that it implied "some supernatural force". The American paleontologist George Gaylord Simpson (1953) attacked orthogenesis, linking it with vitalism by describing it as "the mysterious inner force". Modern supporters include E. O. Wilson and Simon Conway Morris, while museum displays and textbook illustrations continue to give the impression of progress in evolution.
Orthogenesis | Introduction
Embryos do undergo a period or phylotypic stage where their morphology is strongly shaped by their phylogenetic position, rather than selective pressures, but that means only that they resemble other embryos at that stage, not ancestral adults as Haeckel had claimed. The modern view is summarised by the University of California Museum of Paleontology:
Recapitulation theory | Modern status
In 1966, George C. Williams published "Adaptation and Natural Selection", outlined a gene-centred view of evolution following Hamilton's concepts, disputing the idea of evolutionary progress, and attacking the then widespread theory of group selection. Williams argued that natural selection worked by changing the frequency of alleles, and could not work at the level of groups. Gene-centred evolution was popularised by Richard Dawkins in his 1976 book "The Selfish Gene" and developed in his more technical writings.
Modern synthesis (20th century) | Williams's gene-centred evolution, 1966
The study of reticulate evolution is said to have been largely excluded from the modern synthesis. The urgent need for new models which take reticulate evolution into account has been stressed by many evolutionary biologists, such as Nathalie Gontier who has stated ""reticulate evolution today is a vernacular concept for evolutionary change induced by mechanisms and processes of symbiosis, symbiogenesis, lateral gene transfer, hybridization, or divergence with gene flow, and infectious heredity"". She calls for an extended evolutionary synthesis that integrates these mechanisms and processes of evolution.
Reticulate evolution | Models
The 643-page book cites more than 1,250 references and was the longest of the four books associated with the modern evolutionary synthesis. The other key works of the modern synthesis, whose publication also followed their authors' Jesup lectures, are Theodosius Dobzhansky's "Genetics and the Origin of Species", Ernst Mayr's "Systematics and the Origin of Species" and George Gaylord Simpson's "Tempo and Mode in Evolution". The great significance of "Variation and Evolution in Plants" is that it effectively killed any serious belief in alternative mechanisms of evolution for plants, such as Lamarckian evolution or soft inheritance, which were still upheld by some botanists.
Variation and Evolution in Plants | Significance
His efforts stimulated the biologist J. B. S. Haldane to push for the axiomatisation of biology, and by influencing thinkers such as Huxley, helped to bring about the modern synthesis. The positivist climate made natural history unfashionable, and in America, research and university-level teaching on evolution declined almost to nothing by the late 1930s. The Harvard physiologist William John Crozier told his students that evolution was not even a science: "You can't experiment with two million years!" The tide of opinion turned with the adoption of mathematical modelling and controlled experimentation in population genetics, combining genetics, ecology and evolution in a framework acceptable to positivism.
Modern synthesis (20th century) | An obstruction: Woodger's positivism, 1929
August Weismann's idea, set out in his 1892 book "Das Keimplasma: eine Theorie der Vererbung" (The Germ Plasm: a Theory of Inheritance), was that the hereditary material, which he called the germ plasm, and the rest of the body (the soma) had a one-way relationship: the germ-plasm formed the body, but the body did not influence the germ-plasm, except indirectly in its participation in a population subject to natural selection. If correct, this made Darwin's pangenesis wrong, and Lamarckian inheritance impossible. His experiment on mice, cutting off their tails and showing that their offspring had normal tails, demonstrated that inheritance was 'hard'.
Modern synthesis (20th century) | Weismann's germ plasm, 1892
There is a discontinuity between the appearance of the offspring; de Vries coined the term allele for a variant form of an inherited characteristic. This reinforced a major division of thought, already present in the 1890s, between gradualists who followed Darwin, and saltationists such as Bateson. The two schools were the Mendelians, such as Bateson and de Vries, who favoured mutationism, evolution driven by mutation, based on genes whose alleles segregated discretely like Mendel's peas; and the biometric school, led by Karl Pearson and Walter Weldon. The biometricians argued vigorously against mutationism, saying that empirical evidence indicated that variation was continuous in most organisms, not discrete as Mendelism seemed to predict; they wrongly believed that Mendelism inevitably implied evolution in discontinuous jumps.
Modern synthesis (20th century) | Genetics, mutationism and biometrics, 1900–1918
The first is that other modes such as epigenetic inheritance, phenotypic plasticity, the Baldwin effect, and the maternal effect allow new characteristics to arise and be passed on, and for the genes to catch up with the new adaptations later. The second is that all such mechanisms are part, not of an inheritance system, but a developmental system: the fundamental unit is not a discrete selfishly competing gene, but a collaborating system that works at all levels from genes and cells to organisms and cultures to guide evolution.
Modern synthesis (20th century) | Towards a replacement synthesis
Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology. It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-World War II era.
Heredity | Modern development of genetics and heredity
His writings on evolution and heredity are of interest as examples of thinking in this field at a time when the new science of genetics was in turmoil, following the rediscovery of the work of Gregor Mendel which appeared to conflict with Darwin's theory of evolution by natural selection. This was the start of a period in which the Modern evolutionary synthesis came into being.
G. Archdall Reid | Writings on evolution and heredity
Hugo de Vries tried to link the new genetics with evolution; building on his work with heredity and hybridization, he proposed a theory of mutationism, which was widely accepted in the early 20th century. Lamarckism also had many adherents. Darwinism was seen as incompatible with the continuously variable traits studied by biometricians, which seemed only partially heritable. In the 1920s and 1930s—following the acceptance of the Mendelian-chromosome theory— the emergence of the discipline of population genetics, with the work of R.A. Fisher, J.B.S. Haldane and Sewall Wright, unified the idea of evolution by natural selection with Mendelian genetics, producing the modern synthesis.
History of zoology since 1859 | Classical genetics, the modern synthesis, and evolutionary theory
The work of Fisher, Haldane and Wright helped to found the discipline of theoretical population genetics.
Modern synthesis (20th century) | Wright's adaptive landscape, 1932
In 1975, E. O. Wilson published his controversial book "", the subtitle alluding to the modern synthesis as he attempted to bring the study of animal society into the evolutionary fold. This appeared radically new, although Wilson was following Darwin, Fisher, Dawkins and others. Critics such as Gerhard Lenski noted that he was following Huxley, Simpson and Dobzhansky's approach, which Lenski considered needlessly reductive as far as human society was concerned. By 2000, the proposed discipline of sociobiology had morphed into the relatively well-accepted discipline of evolutionary psychology.
Modern synthesis (20th century) | Wilson's sociobiology, 1975
In the so-called modern synthesis of the early 20th century, Ronald Fisher brought together Darwin's theory of evolution, with its insistence on natural selection, heredity, and variation, and Gregor Mendel's laws of genetics into a coherent structure for evolutionary biology. Biologists assumed that an organism was a straightforward reflection of its component genes: the genes coded for proteins, which built the organism's body. Biochemical pathways (and, they supposed, new species) evolved through mutations in these genes. It was a simple, clear and nearly comprehensive picture: but it did not explain embryology. The evolutionary embryologist Gavin de Beer anticipated evolutionary developmental biology in his 1930 book "Embryos and Ancestors", by showing that evolution could occur by heterochrony, such as in the retention of juvenile features in the adult.
Evolutionary developmental biology | The modern synthesis of the early 20th century
Biologists, however, have not limited their application of the term "neo-Darwinism" to the historical synthesis. For example, Ernst Mayr wrote in 1984 that: Publications such as "Encyclopædia Britannica" use "neo-Darwinism" to refer to current-consensus evolutionary theory, not the version prevalent during the early 20th century. Similarly, Richard Dawkins and Stephen Jay Gould have used "neo-Darwinism" in their writings and lectures to denote the forms of evolutionary biology that were contemporary when they were writing.
Neo-Darwinism | Current meaning
Dobzhansky, a geneticist, published "Genetics and the Origin of Species" in 1937, in which he formulated the genetic framework for how speciation could occur. He recognized that speciation was an unsolved problem in biology at the time, rejecting Darwin's position that new species arose by occupation of new niches — contending that reproductive isolation was instead based on barriers to gene flow. Subsequently, Mayr conducted extensive work on the geography of species, emphasizing the importance of geographic separation and isolation, in which he filled Dobzhansky's gaps concerning the origin of biodiversity (in his 1942 book). Both of their works gave rise, not without controversy, to the modern understanding of speciation; stimulating a wealth of research on the topic.
History of speciation | Modern evolutionary synthesis
Thomas Hunt Morgan began his career in genetics as a saltationist, and started out trying to demonstrate that mutations could produce new species in fruit flies. However, the experimental work at his lab with the fruit fly, "Drosophila melanogaster" demonstrated that rather than creating new species in a single step, mutations increased the supply of genetic variation in the population. By 1912, after years of work on the genetics of fruit flies, Morgan showed that these insects had many small Mendelian factors (discovered as mutant flies) on which Darwinian evolution could work as if variation was fully continuous. The way was open for geneticists to conclude that Mendelism supported Darwinism.
Modern synthesis (20th century) | Morgan's fruit flies, 1912
Geological estimates disputed Kelvin's age of the earth, and the geological approach gained strength in 1907 when radioactive dating of rocks revealed the Earth as billions of years old. The specific hereditary mechanism which Darwin hypothesized, pangenesis, which supported gradualism, also lacked any supporting evidence and was disputed by the empirical tests (1869 onwards) of Francis Galton. Although evolution itself was scientifically unchallenged, uncertainties about the mechanism in the era of "the eclipse of Darwinism" persisted from the 1880s until the 1930s' inclusion of Mendelian inheritance and the rise of the modern evolutionary synthesis. The modern synthesis rose to universal acceptance among biologists with the help of new evidence, such as that from genetics, which confirmed Darwin's predictions and refuted the competing theories.
Objections to evolution | History
Various alternative evolutionary mechanisms favoured during "the eclipse of Darwinism" became untenable as more was learned about inheritance and mutation. The full significance of natural selection was at last accepted in the 1930s and 1940s as part of the modern evolutionary synthesis. During that synthesis biologists and statisticians, including R. A. Fisher, Sewall Wright and J. B. S. Haldane, merged Darwinian selection with a statistical understanding of Mendelian genetics. Modern evolutionary theory continues to develop. Darwin's theory of evolution by natural selection, with its tree-like model of branching common descent, has become the unifying theory of the life sciences. The theory explains the diversity of living organisms and their adaptation to the environment.
On the Origin of Species | Modern influence
Finally, genomics brought together the molecular and microbiological syntheses - in particular, horizontal gene transfer between bacteria shows that prokaryotes can freely share genes. Many of these points had already been made by other researchers such as Ulrich Kutschera and Karl J. Niklas.
Modern synthesis (20th century) | Koonin's 'post-modern' evolutionary synthesis, 2009
The book's title quotes from the last sentence of Charles Darwin's 1859 "The Origin of Species", in which he described the evolution of all living organisms from a common ancestor: "endless forms most beautiful and most wonderful have been, and are being, evolved." Darwin, however, was unable to explain how those body forms actually came into being. The early 20th century modern synthesis of evolution and genetics, too, largely ignored embryonic development to explain the form of organisms, since population genetics appeared to be an adequate explanation of how forms evolved. That task was finally undertaken at the end of the 20th century with the arrival of recombinant DNA technology, when biologists were able to start to explore how development was actually controlled.
Endless Forms Most Beautiful (book) | Context
The conventional view had been that developmental biology had little influence on the modern synthesis, but the following assessment suggests otherwise, at least as far as de Beer is concerned: In his 1971 work "Homology: An Unsolved Problem", de Beer summarized that: "It is now clear that the pride with which it was assumed that the inheritance of homologous structures from a common ancestor explained homology was misplaced; for such inheritance cannot be ascribed to identity of genes. The attempt to find 'homologous' genes, except in closely related species, has been given up as hopeless."
Gavin de Beer | De Beer and the modern synthesis