Hard inheritance

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Hard inheritance was a model of heredity that explicitly excludes any acquired characteristics, such as of Lamarckism. It is the exact opposite of soft inheritance, coined by Ernst Mayr to contrast ideas about inheritance.

Heredity passing of traits to offspring from its parents or ancestor

Heredity is the passing on of traits from parents to their offspring, either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection. The study of heredity in biology is genetics.

Lamarckism is the hypothesis that an organism can pass on characteristics that it has acquired through use or disuse during its lifetime to its offspring. It is also known as the inheritance of acquired characteristics or soft inheritance. It is inaccurately named after the French biologist Jean-Baptiste Lamarck (1744–1829), who incorporated the action of soft inheritance into his evolutionary theories as a supplement to his concept of orthogenesis, a drive towards complexity. The theory is cited in textbooks to contrast with Darwinism. This paints a false picture of the history of biology, as Lamarck did not originate the idea of soft inheritance, which was known from the classical era onwards, and it was not the primary focus of Lamarck's theory of evolution. Further, in On the Origin of Species (1859), Charles Darwin supported the idea of "use and disuse inheritance", though rejecting other aspects of Lamarck's theory; and his pangenesis theory implied soft inheritance.

Ernst Mayr German-American evolutionary biologist

Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, philosopher of biology, and historian of science. His work contributed to the conceptual revolution that led to the modern evolutionary synthesis of Mendelian genetics, systematics, and Darwinian evolution, and to the development of the biological species concept.

Hard inheritance states that characteristics of an organism's offspring (passed on through DNA) will not be affected by the actions that the parental organism performs during its lifetime. For example: a medieval blacksmith who uses only his right arm to forge steel will not sire a son with a stronger right arm than left because the blacksmith's actions do not alter his genetic code. Inheritance due to usage and non-usage is excluded. Inheritance works as described in the modern synthesis of evolutionary biology. [1]

DNA Molecule that encodes the genetic instructions used in the development and functioning of all known organisms and many viruses

Deoxyribonucleic acid is a molecule composed of two chains that coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning, and reproduction of all known organisms and many viruses. DNA and ribonucleic acid (RNA) are nucleic acids; alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life.

Organism Any individual living physical entity

In biology, an organism is any individual entity that exhibits the properties of life. It is a synonym for "life form".

Blacksmith person who creates wrought iron or steel products by forging, hammering, bending, and cutting

A blacksmith is a metalsmith who creates objects from wrought iron or steel by forging the metal, using tools to hammer, bend, and cut. Blacksmiths produce objects such as gates, grilles, railings, light fixtures, furniture, sculpture, tools, agricultural implements, decorative and religious items, cooking utensils and weapons.

The existence of inherited epigenetic variants has led to renewed interest in soft inheritance. [2]

Epigenetics study of changes in gene expression or cellular phenotype

Epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence. The Greek prefix epi- in epigenetics implies features that are "on top of" or "in addition to" the traditional genetic basis for inheritance. Epigenetics most often denotes changes that affect gene activity and expression, but can also be used to describe any heritable phenotypic change. Such effects on cellular and physiological phenotypic traits may result from external or environmental factors, or be part of normal development. The standard definition of epigenetics requires these alterations to be heritable, either in the progeny of cells or of organisms.

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Neo-Darwinism

Neo-Darwinism is the interpretation of Darwinian evolution through natural selection as it has variously been modified since it was first proposed. It was early on used to name Charles Darwin's ideas of natural selection separated from his hypothesis of pangenesis as a Lamarckian source of variation involving blending inheritance.

August Weismann German evolutionary biologist

August Friedrich Leopold Weismann was a German evolutionary biologist. Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg.

Modern synthesis (20th century) Combination of Darwins theory of evolution with natural selection and Mendels findings on heredity

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, Evolution: The Modern Synthesis.

Jean-Baptiste Lamarck French naturalist

Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck, often known simply as Lamarck, was a French naturalist. He was a soldier, biologist, academic, and an early proponent of the idea that biological evolution occurred and proceeded in accordance with natural laws.

Structural inheritance

Structural inheritance or cortical inheritance is the transmission of an epigenetic trait in a living organism by a self-perpetuating spatial structures. This is in contrast to the transmission of digital information such as is found in DNA sequences, which accounts for the vast majority of known genetic variation.

Adaptation Trait with a current functional role in the life history of an organism maintained and evolved by natural selection

In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection.

C. H. Waddington British biologist

Conrad Hal Waddington CBE FRS FRSE was a British developmental biologist, paleontologist, geneticist, embryologist and philosopher who laid the foundations for systems biology, epigenetics, and evolutionary developmental biology.

<i>Genetics and the Origin of Species</i> book by Theodosius Dobzhansky

Genetics and the Origin of Species is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky. It is regarded as one of the most important works of the modern synthesis, and was one of the earliest. The book popularized the work of population genetics to other biologists, and influenced their appreciation for the genetic basis of evolution. In his book, Dobzhansky applied the theoretical work of Sewall Wright (1889-1988) to the study of natural populations, allowing him to address evolutionary problems in a novel way during his time. Dobzhansky implements theories of mutation, natural selection, and speciation throughout his book to explain habits of populations and the resulting effects on their genetic behavior. The book explains evolution in depth as a process over time that accounts for the diversity of all life on Earth. The study of evolution was present, but greatly neglected at the time. Dobzhansky illustrates that evolution regarding the origin and nature of species during this time in history was deemed mysterious, but had expanding potential for progress to be made in its field.

Teleonomy is the quality of apparent purposefulness and goal-directedness of structures and functions in living organisms brought about by the exercise, augmentation, and, improvement of reasoning. The term derives from two Greek words, τέλος telos and νόμος nomos ("law"), and means "end-directed". Teleonomy is sometimes contrasted with teleology, where the latter is understood as a purposeful goal-directedness brought about through human or divine intention. Teleonomy is thought to derive from evolutionary history, adaptation for reproductive success, and/or the operation of a program. Teleonomy is related to programmatic or computational aspects of purpose.

Eva Jablonka is an Israeli theorist and geneticist, known especially for her interest in epigenetic inheritance. Born in 1952 in Poland, she emigrated to Israel in 1957. She is a professor at the Cohn Institute for the History of Philosophy of Science and Ideas at Tel Aviv University. In 1981 she was awarded the Landau prize of Israel for outstanding Master of Science (M.Sc) work and in 1988, the Marcus prize for outstanding Ph.D work. She is a proponent of academic freedom, recognising that on such matters, "academic and political issues cannot really be kept apart", although she is not a proponent of simplistic solutions, and shows a preference to describe her own position.

Genetic assimilation is a process by which a phenotype originally produced in response to an environmental condition, such as exposure to a teratogen, later becomes genetically encoded via artificial selection or natural selection. Despite superficial appearances, this does not require the (Lamarckian) inheritance of acquired characters, although epigenetic inheritance could potentially influence the result. Genetic assimilation overcomes the barrier to selection imposed by genetic canalization of developmental pathways.

Marion J. Lamb was Senior Lecturer at Birkbeck, University of London, before her retirement. She studied the effect of environmental conditions such as heat, radiation and pollution on metabolic activity and genetic mutability in the fruit fly Drosophila. From the late 1980s, Lamb collaborated with Eva Jablonka, researching and writing on the inheritance of epigenetic variations, and in 2005 they co-authored the book Evolution in Four Dimensions, considered by some to be in the vanguard of an ongoing revolution within evolutionary biology.

The eclipse of Darwinism The period when evolution was widely accepted, but natural selection was not

Julian Huxley used the phrase “the eclipse of Darwinism” to describe the state of affairs prior to what he called the modern synthesis, when evolution was widely accepted in scientific circles but relatively few biologists believed that natural selection was its primary mechanism. Historians of science such as Peter J. Bowler have used the same phrase as a label for the period within the history of evolutionary thought from the 1880s to around 1920, when alternatives to natural selection were developed and explored—as many biologists considered natural selection to have been a wrong guess on Charles Darwin's part, or at least as of relatively minor importance. An alternative term, the interphase of Darwinism, has been proposed to avoid the largely incorrect implication that the putative eclipse was preceded by a period of vigorous Darwinian research.

Transgenerational epigenetic inheritance

Transgenerational epigenetic inheritance is the transmission of information from one generation of an organism to the next that affects the traits of offspring without alteration of the primary structure of DNA —in other words, epigenetically. The less precise term "epigenetic inheritance" may be used to describe both cell–cell and organism–organism information transfer. Although these two levels of epigenetic inheritance are equivalent in unicellular organisms, they may have distinct mechanisms and evolutionary distinctions in multicellular organisms.

Extended evolutionary synthesis

The extended evolutionary synthesis consists of a set of theoretical concepts argued to be more comprehensive than the earlier modern synthesis of evolutionary biology that took place between 1918 and 1942. The extended evolutionary synthesis was called for in the 1950s by C. H. Waddington, argued for on the basis of punctuated equilibrium by Stephen Jay Gould and Niles Eldredge in the 1980s, and was reconceptualized in 2007 by Massimo Pigliucci and Gerd B. Müller.

In biology, reciprocal causation arises when developing organisms are both products of evolution as well as causes of evolution. Formally, reciprocal causation exists when process A is a cause of process B and, subsequently, process B is a cause of process A, with this feedback potentially repeated. Some researchers, particularly advocates of the extended evolutionary synthesis, promote the view that causation in biological systems is inherently reciprocal.

In biology, constructive development refers to the hypothesis that organisms shape their own developmental trajectory by constantly responding to, and causing, changes in both their internal state and their external environment. Constructive development can be contrasted with programmed development, the hypothesis that organisms develop according to a genetic program or blueprint. The constructivist perspective is found in philosophy, most notably developmental systems theory, and in the biological and social sciences, including developmental psychobiology and key themes of the extended evolutionary synthesis. Constructive development may be important to evolution because it enables organisms to produce functional phenotypes in response to genetic or environmental perturbation, and thereby contributes to adaptation and diversification.

References

  1. Mayr, Ernst (1980). Provine, William B.; Mayr, Ernst. ed. The Evolutionary synthesis: perspectives on the unification of biology. Cambridge: Harvard University Press. pp. 1–48. ISBN   0-674-27225-0
  2. Richards, E. J. (May 2006). "Inherited epigenetic variation—revisiting soft inheritance". Nature Reviews Genetics 7 (5): 395–401. doi : 10.1038/nrg1834. PMID   16534512