Lamarckism

Lamarckism is the theory that organisms can inherit characteristics to their offspring, which they have acquired during their life. She is Jean -Baptiste de Lamarck (1744-1829) named after the French biologist who developed one of the first theories of evolution in the 19th century. Unlike many shows the inheritance of acquired characteristics is only one aspect of Lamarck's original theory; the term Lamarckism therefore referred to today usually not Lamarck's theory as a whole.

While the concept of inheritance of acquired characteristics was not immediately controversial and in 1859 again found in Darwin's theory of evolution, was kindled until about 1883 with August Weismann's development of Darwin's theory a debate between neo-Darwinists and Neolamarckisten. This dispute was fought not only on scientific but also on socio-political level to the mid-20th century. With the development of the synthetic theory of evolution, in which the principle of natural selection could be reconciled with genetics, the debate in favor of Darwinism was decided.

Lamarck's theory

The Lamarck in his most famous work philosophy zoologique (1809 ) and in the later Histoire naturelle des animaux sans Vertebres ( 1815-1822 ) designed theory of evolution was one of the first attempts at a systematic theory of evolution. Recent representations characterize Lamarck's theory as an interaction of two factors:

• Undirected adaptation to external changes
• Linear progress on a linear ladder of complexity.

Adaptation to external changes

The background to Lamarck's theory, a combination of geological Uniformitätsprinzip and gradualism. Lamarck assumed that all natural forces that act in the present, have worked well in the past. Singular events, such as in Cuvier's theory of catastrophism, play no role. The nature changes gradually and does not undergo abrupt jumps.

These same gradual changes in the environment are in accordance with Lamarck, a drive of evolution: A change of environment leads to change the habits of the organisms living in, which in turn has the consequence that change the organisms themselves. Caused by changed habits somatic modifications are thus inherited by the next generations. This point in Lamarck's theory is now known as " Lamarckism " or "soft inheritance " and is - in contrast to Lamarck other views - not forgotten.

Today, he is usually illustrated by the example of the giraffe had to stretch in a dry, inhospitable environment after high altitude leaves of trees in order to feed themselves. This has evolved over many generations the long neck. Lamarck used this example as just one among many, it was not for him the central position it has today in many accounts of his theory.

Linear progress

Since, a rising with the time complexity of the organisms can not be explained solely on the " Lamarckian " part of Lamarck's theory, in which adapt the organisms to the undirected external changes into a kind of random motion, requires a consistent theory of the evolution of other supplements.

Lamarck's solution to this problem is to adopt a second evolutionary force. He postulated the existence of a linear taxonomic scale of complexity on which all organisms can be classified and headed by the man. All organisms lives a perfection engine stopped, by which they climb up through gradual changes in the ladder of complexity and on. This process can even be done without environmental changes, it is therefore decoupled from the "soft inheritance ". Lamarck leads the mechanisms for this process of not more accurate than explanation he gives only vague " movements of fluids " and "vital forces " to.

The problem of why there are lower forms of life, but if all organisms move upward on the complexity scale, Lamarck explained by a constant occurring spontaneous generation of lower forms of life. Here again he gives no concrete mechanism.

In contrast to Darwin Lamarck postulated therefore no theory of evolution, but every extant species has her own line of evolution. The most highly evolved organisms arose by spontaneous generation first, the lower organisms later. The evolutionary line to humans is therefore according to Lamarck, the longest and oldest.

The factors in the interaction

The observable in nature biodiversity, as Lamarck had to recognize hardly be explained by a linear scale of complexity, which can therefore only be an idealization. In reality, the linear progress of the species is somehow " disturbed " by the adaptive species to adapt to the changing environment. There is a constant interplay between forwards and sideways Gerichter evolution.

An important issue was excited to Lamarck's time, by finds of fossils, the possible extinction of species. Lamarck largely denied that species may become extinct. One held for extinct species could either continue to exist in unknown parts of the world, or it could have changed a lot by adaptation so that it is no longer recognized. Only the possibility that individual species by the people could be eradicated, Lamarck considered in " prophetic " manner.

Reception

During his lifetime, Lamarck received a few responses to his theory of evolution. This was partly because he was more natural philosopher as a scientist in the style of past centuries with its speculative nature little support found in post-revolutionary France, where the science was always empirical.

Hard criticism Lamarck learned by the influential Georges Cuvier, who took apart his theory calculated in an obituary ( eulogy ). Cuvier criticized for a Lamarck's speculative, only weakly based on empirical evidence theory, a point where today's science historians largely agree with him. On the other hand he drew - Lamarck causal triad of altered environment on habits up to the heredity ignoring - an image of a theory, control the evolution in the will or wishes of the organisms, which meant that Lamarck was later often attributed to the vitalism.

Distorting images like the one just mentioned, which are classified today as " caricature" or " Pseudolamarckismus " permanently imprinted the public perception of Lamarck. In this case, this was a radical materialist and was even criticized in his lifetime of creationist representatives such as William Kirby for this. In fact, a creator plays in his theory, which includes about the emergence of life by spontaneous generation, not matter.

Charles Darwin also did not think much of Lamarck. He had studied his books, but this is rarely mentioned in official writings, describing the books privately as a " veritable rubbish". The appreciation of his friend Charles Lyell for Lamarck he could not quite understand. Nevertheless, it is believed, from today's point of view that Darwin - was more influenced by Lamarck, as it is traditionally attributed to him - directly or indirectly. Darwin's theory of pangenesis also contains the idea of ​​" Lamarckian " inheritance of acquired characteristics. The Darwin as the central principle of natural selection, however, Lamarck was completely alien because differences between individuals of a species played no role in his thinking.

From today's perspective, the ahistorical representation of Lamarck is criticized in textbooks by some historians of science. Perhaps influenced by the later debate between Neolamarckisten and neo-Darwinists, Lamarck have been incorrectly presented as the opponent of Darwin and his theory reduces to the example of the giraffe.

Lamarckism

Lamarckism in the modern sense, ie the concept of inheritance of acquired characteristics, was only towards the end of the 19th century, as a serious alternative had been proposed for this purpose. The reason for this was August Weismann, who with his germ plasm theory Darwinism in a sense all Lamarckian elements "adjusted ". The Weismann barrier prevents any influence of somatic changes back to the genome. In Weismann's theory of natural selection is the only force acting, "soft" inheritance mechanisms do not exist in her.

Between the followers of Weismann and the " Neolamarckisten " called " neo-Darwinists " incurred sharp guided debates. One of the problems of the Darwinian side, it was here to explain the degeneration of organs. The Lamarckists had it difficult, however, to cite experimental evidence for their theses and to bring their theory with the rediscovered turn of the century genetics Gregor Mendel in line.

Compared to 1900, Lamarckism was therefore not a marginal phenomenon that it is today, but a widely accepted position .. Among the supporters of the inheritance of acquired characteristics included, among others, Edward Drinker Cope, Herbert Spencer and Ernst Haeckel.

The dispute was finally performed not only on scientific but also at the political level. First, evolutionary points of view could not be clearly assigned ideological positions. However, this changed with the beginning of the 1930s, when claiming to be affected Darwin and Mendel eugenic theories particularly in Nazi Germany became more important. Lamarckism was henceforth associated with " left " socialist positions. From Nazis, he was viewed as a product of " liberal- Jewish- Bolshevik science."

Paul Kammerer, who had exposed himself anti-Semitic attacks by August Weismann, Fritz Lenz and Ludwig Plate, for its part, accused the followers of Weismann to demand in racist fanaticism that only one race is apparent victorious from a selection process. On the other hand his sights as Lamarckist to improve the well-being of all mankind. One of the points that made Lamarckism for many people appear attractive, was the hope that improvements in the present itself can directly affect the genetic makeup of future generations.

Until the 1920s, the Lamarckism was one of the most important theories of Weismann's neo-Darwinism, in addition to the following. However remained from convincing experimental evidence, scandals such as the affair of Paul Kammerer weakened the Lamarckian position and finally succeeded to combine the genetics continues with Darwinism. With the development of the modern evolutionary synthesis of Lamarckism was finally scientifically obsolete.

In the Soviet Union, however, he had for a while inventory. Agronomist Trofim Denisovich Lysenko, Ukrainian championed during the reign of Joseph Stalin in the USSR shows a modified form of Lamarckism, trying to prove the inheritance of acquired characteristics. On his instruction, considerable areas were planted with wheat, which were not suitable for this climate. The thus caused crop failures aggravated the poor nutrition situation of the Russian population in a time of famine. The practiced by him control of the science by the policy is also known as Lysenkoism. It was not until the mid-1950s Lysenko's influence began to wane in 1962, he was released.

Experimental proof attempts

There have been various attempts by experimentalists to demonstrate Lamarckian inheritance mechanisms. An early example of this is Charles -Edouard Brown - Sequard, who tried to show the inheritance of artificially inflicted epilepsy in guinea pigs. August Weismann also carried out experiments to demonstrate the non-existence of Lamarckism. He cut off the tails of mice out, just to be able to observe in all subsequent generations fully developed tails. These experiments were, however, then as now, criticized, and even Weismann was aware of its inadequacy to the falsification of Lamarckism aware. Even Lamarck had the three- step nature of change on changes in habits (eg, use / non-use of organs ) points towards inheritance - Wounds and external forces were not seen by Lamarckists as a factor influencing the inheritance.

More fundamentally, the attempts of Paul Kammerer, prove the inheritance of acquired characteristics. Inter alia, with experiments of salamanders and toads obstetrician he brought it to temporarily famous. However, its results could not be reproduced because only he could bring to the toads to breed in captivity. When finally inked manipulated toads were found, Kammerer's scientific reputation was destroyed, and in 1926 he took his own life. It is still unknown whether Kammerer, who maintained his innocence until his death, was guilty of fraud. Meanwhile, there is the consideration of whether Kammerer's experiments were re-evaluate on the basis of epigenetics.

The experimental evidence in favor of Lamarckism was therefore rather weak since 1900, especially since it was mostly alternative explanations for the few Lamarckism supportive results. Moral- ideological reasons contributed strongly to the fact that the idea of ​​inheritance of acquired characteristics yet so long remained influential.