History of the theory of evolution
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The history of the theory of evolution begins in antiquity and extends through Charles Darwin (1809–1882) to the present, where it flows into the synthetic theory of evolution .
Ancient to Middle Ages
The creation myths of different cultures represent an archaic answer to the question of the origin of living beings , especially humans .
Original ideas have come down to us from several Greek natural philosophers . in the 6th century BC Thales of Miletus believed that water is the origin of all things; in doing so he tried to give a non-mythological explanation. His student Anaximander developed this idea further and spoke of a spontaneous generation: The first animals and humans emerged in the damp and later went to the dry land. They developed ( ontogenetically ) through a metamorphosis from fish-like shapes.
In the 5th century BC Empedocles worked in Sicily. He said that the plants emerged first, then the animals. However, they did not come into being completely; instead, parts emerged first that accidentally grew together. Only what fit together remained alive, the other perished.
Aristotle (384–322 BC), on the other hand, believed, derived from observations on insect brood, that all living things develop from dirt and mud ( spontaneous generation ).
Ancient Christianity , as well as Judaism and Islam , included the doctrine of the constancy of species, but also established the dogma that species did not arise naturally, but in an act of creation by God . In the Middle Ages there were other approaches to classifying, grouping and assigning plants and animals to lower or higher levels of life, for example by Islamic scholars such as Ibn Chaldūn or Nasir ad-Din at-Tusi . A scientific systematics or even the idea of a continuous further development of the species was missing in this still theologically founded natural philosophy, and it was assumed that creation was complete.
Modern times
With the astronomical and geographical discoveries in the 14th and 15th centuries, the question of a natural explanation of the origin of living things came back to the fore. The discovery of numerous new animal and plant species raised the question of whether all of these animals could have found a place in Noah's ark of the Bible . The discovery of numerous extinct fossil species that lived exclusively in water could not be explained by the Flood .
Petrifications, which for a long time were considered to be games of nature, first had to be interpreted as the remains of organisms, in today's parlance as fossils. There was also evidence of extinct species. This advance in scientific knowledge was undone by the explanation of species extinction in the Flood. It was only the development of stratigraphy that brought about major innovations.
The importance of species concepts for the theory of evolution
Carl von Linné (1707–1778) was the first to propose a simple and uniform system for naming plant and animal species, which is the basis of the current designation of animal and plant species: binary nomenclature with generic and species names . In addition to naming, he introduced a hierarchical system that divides animal and plant species into groups of decreasing similarity.
This system was important for the development of the idea of evolution for three reasons:
- On the one hand, it made it possible to record the enormous biological diversity of species, which became known through the discoveries, especially from the 19th century.
- Secondly, systematic questions about the correct grouping and animal geography were possible for the first time.
- The third reason is Linnaeus' assumption of the 'constancy of species', which subsequently stimulated scientific contradiction and accelerated the search for a theory of evolution.
Disaster theory
Georges Cuvier (1769–1832) is the founder of zoological palaeontology . He developed the reconstruction technique . Due to the comparison of the anatomy, that is to say especially the bones of fossil and recent animals (animals of the present), he discovered the orderly connection between different bones of different body regions. This can be jokingly illustrated by his saying: The devil is a herbivore, he has hooves and horns . Cuvier can thus reconstruct fossil finds or assign them to groups, even if only parts of the fossil were preserved.
Cuvier laid the foundations for zoological systematics and established a system of animals with the four main groups molluscs , articulated animals , radiata and vertebrates through comparative anatomy . Each group has its typical blueprint. From today's perspective, the analogies pose a problem in his system .
Observations:
- Cats , monkeys and birds of prey found in ancient Egyptian tombs are no different from recent animals. (From today's perspective, the time span of a few thousand years is too short for significant morphological changes.)
- Older fossils are more simply built than younger fossils.
- The finds are incomplete. Due to the gaps in the find, no transitions between the individual species of successive layers can be proven.
- Furthermore, the fossil finds document numerous new, partly extinct species that do not appear in the biblical account of creation.
Theory:
- Species are immutable. They are created once, but can become extinct.
- The species in an area are suddenly wiped out by natural disasters ( cataclysm theory ).
- This area is then populated in an act of creation by further developed or new species.
see also history of geology # actualism and catastrophism
Evolution theories
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The theory of evolution contains a number of statements. The focus is on the statement that life on earth has developed. There are also theses such as the descent of all living beings from a common ancestor, the origin of life itself, the mechanism of evolution and other details.
Jean-Baptiste de Lamarck (1744-1829)
Jean-Baptiste de Lamarck applied Lyell's geological continuity principle (see below) to biology: Species are changeable and change in small steps (“Nature doesn't make jumps!”), But cannot become extinct. (Today we know that the majority of animals were extinct in prehistoric times.) Lamarck is thus a representative of gradualism .
In accordance with the notion of the scale of nature, Lamarck established a relationship between the degree of perfection and the age of the species: the more perfect a species, the longer its evolution must have taken and the older it is. (This would mean that bacteria should be considered a very young species, while humans are the oldest. Modern methods of determining the age of fossil finds, however, give a different picture.) New species must therefore always arise through spontaneous generation . In the course of its evolution, a species goes through, according to Lamarck, a specific sequence of stages in the direction of its perfection. Such ideas of a teleological direction of evolution are no longer contained in today's evolution theory.
As a mechanism of species change, he set up the theory of the inheritance of acquired properties in 1809 : an “instinct for perfection” resides in organisms. Through use or non-use, the shape and function of the organs of a living being are modified in adaptation to the requirements of the environment. According to Lamarck's theory, these individually acquired changes can be passed on to the offspring.
With his theory, Lamarck put the systematics on a scientific basis, while Linnaeus was still trying to research the divine order. In his time Lamarck's theory represented a viable model for explaining numerous phenomena in biology. The idea of the variability of species in small steps also played a decisive role for Darwin and Haeckel. The phenomena of biogeography and speciation through isolation and competition, which are important pillars of Darwin's theory, were not yet addressed by Lamarck.
Research into inheritance processes only began around 1900 with August Weismann . Until then, their mode of action was completely unknown. That is why Darwin and Haeckel have similar ideas about the inheritance of acquired traits, which are no longer tenable today.
Up to the present day attempts have been made again and again to scientifically prove Lamarck's thesis of the inheritance of individual adaptations and acquired properties, but this did not succeed (see Lamarckism ).
Étienne Geoffroy de Saint-Hilaire (1772–1844)
Étienne Geoffroy de Saint-Hilaire , a French zoologist, is considered to be the founder of homology research. Together with Jean-Baptiste Lamarck and Georges Cuvier, he was appointed professor of vertebrate zoology at the Musée National d'Histoire Naturelle , founded in 1793 .
Geoffroy Saint-Hilaire postulated a common basic plan for all animals known at the time . This was in contrast to Cuvier's four basic plans. On the basis of the continuity principle, he hypothesized that the birds must have descended from primeval reptiles .
Geoffroy Saint-Hilaire was also one of the first to deal experimentally with the mechanisms of evolution by triggering changes in the germinal development of vertebrates through changes in environmental influences and thus introducing teratology as a research method.
Geoffroy Saint-Hilaire also had a great influence on Johann Wolfgang Goethe's theory of evolution ; he was very interested in the Paris academy dispute (1830) between Geoffroy Saint-Hilaires and Cuvier, while apparently he had taken no notice of Lamarck.
Charles Lyell (1797-1875)
Charles Lyell is considered to be the co-founder of modern geology . In contrast to the catastrophe theory and creation theory, he assumed that all geological phenomena can be explained by slow and constant changes ( continuity principle ). The forces of these changes are still effective today and influence living beings (principle of actuality ). Lamarck and Darwin then also applied this principle to the evolution of living things.
On the importance of Lyell for the implementation of Darwin's theory of evolution, see Alfred Russel Wallace .
As an indication that there are also global catastrophes that affect living beings, the extinction of the dinosaurs applies today.
The notion that all phylogenetic developments take place only in small steps and gradually is called gradualism . In contrast to this, the concept of punctualism has recently been developed, but the two concepts only represent different possibilities of evolution. (See evolution theory # Further historical development )
Charles Darwin (1809-1882)
Among other things, inspired by the theoretical considerations on population growth contained in the book “An Essay on the Principle of Population” by the British economist Thomas Robert Malthus , published in 1798, Darwin's 1859 book On the Origin of Species by means of Natural Selection, or the Preservation of appeared Favored Races in the Struggle for Life (literally: on the origin of species through the means of natural selection, or the preservation of preferred races in the struggle for life). This can be seen as the first work that summarizes the theories and hypotheses already existing at its time on the evolution of living beings and substantiates it with a wealth of observations:
- Evolution theory: Organisms are subject to constant change over many generations. This means a departure from the doctrine of creation . Darwin did not use the term "evolution" in his works.
- This change happens gradually, in small steps. This view is called gradualism and is in contradiction to the transmutationism or saltationism of Thomas Huxley .
- Theory of descent (descent theory): The origin of all species can be traced back to an ancestral species.
- Speciation : Over time, a species gives rise to new species. With descent and speciation, Darwin stands in opposition to Lamarck's transformationism , which recognizes the change in species, but this change does not lead to a multiplication of species, but only to their perfection.
Darwin caused a lot of confusion and turmoil in Victorian England: On the one hand, his theory was in conflict with the uniqueness of man, on the other hand, when it appeared, it also expanded the understanding of time and history into barely imaginable temporal dimensions. Because he feared this reaction, Darwin had refrained from publishing his manuscripts, which were largely written as early as 1839, for about two decades.
The special achievement of Darwin and Alfred Russel Wallace lies in the explanation of the evolutionary mechanism through the principle of the mutual relationship between variation and selection, which is still valid today :
- Overproduction: Although the animal and plant species produce far more offspring than can ultimately survive or reproduce, their population size hardly changes.
- Variation: The individuals of animal and plant species are not the same, but rather show small differences in construction and performance characteristics that are passed on to the next generation.
- Selection: Since the resources are only sufficient for a limited number of individuals, there is competition for them. Those individuals who prevail over others in this competition have a greater reproductive success, which Darwin called the Survival of the fittest (survival of the fittest ).
Based on geological and geographical knowledge as well as his own research in South America, Charles Darwin knew that the South American continent had existed for a long time and was populated with plants and animals before the Galápagos Islands emerged from undersea lava eruptions in a relatively recent geological period. On the islands he discovered animals and plants that were similar to the species of South America, but represented species of their own.
Thus the teachings that were widespread at that time that living beings came into being in a unique act of creation and did not change (constancy of species) could not be correct. Obviously, after the formation of the Galápagos Islands, organisms from South America had come here, reproduced there and developed further from individual parent species.
Darwin concluded from the observations of his long-term breeding attempts with domestic pigeons that the variety of forms in nature also came about through a selection process that he called "natural selection". Darwin's theory of evolution is - like the theories that arose from it - a theory of descent .
Alfred Russel Wallace (1823-1913)
From his view as an animal collector, Alfred Russel Wallace developed a similar explanation of the origin of species about twenty years after Darwin, which he sent to Darwin before publication. Without knowing it, Wallace forced Darwin in turn to publish his major work, whereby Wallace's draft, also known as the Ternate manuscript , was published at the same time as Darwin's text in 1858.
Ernst Haeckel (1834-1919)
Besides the popularization of Darwinism, Ernst Haeckel's main contribution to the theory of evolution consists of four parts:
- Using the basic biogenetic law (ontogenesis is the brief, extracts recapitulation of phylogenesis ), parts of the tribal history can be reconstructed by comparing the embryos and their precursors of different animal species, of which fossils are inadequate then and in some cases still today. This theory is considered obsolete in this form.
- Ernst Haeckel designed the first detailed family trees of the animal and plant world.
- He postulated the common origin of all organisms. An idea that is still valid.
- The General Morphology (1866) was the world's first textbook of biology on the basis of Darwin's theory of evolution.
- In Anthropogenie (1874), Haeckel demonstrated the position of humans within primates and vertebrates on the basis of comparative anatomy and embryology using the organ systems. He reconstructed the human family tree from the vertebrates and postulated fossil finds that prove this tribal history. Even if many of these ideas are empirically outdated or have been refined in detail, the basic idea has retained its validity to this day.
In addition, Haeckel was of considerable importance for the dissemination of the theory of evolution through many public lectures as well as some very popular books: The "world bestseller" "Die Weltraethsel" ( Jena 1903) and the art book "Kunstformen der Natur" (Jena 1899). Haeckel also designed a monistic natural philosophy on a scientific basis, which is strongly influenced by the theory of evolution . Violent arguments broke out between Haeckel and the Catholic Church. According to Haeckel, there were mainly three groups who were opposed to development theory: the church, dualistic metaphysics and the empiricists. At the International Freethinker Congress in Rome in 1904, Haeckel was officially proclaimed an " antipope " for this reason .
Richard von Hertwig (1850–1937)
Under the influence of Ernst Haeckel, Richard von Hertwig shifted his interests from the field of medicine to zoology and botany . Together with his brother Oskar Hertwig, he developed the Coelom theory in 1881 : At the beginning of its ontogenetic development, the germ in all multicellular animals differentiates into different cell layers ( germ layers ), which further develop into certain organ systems . In the phylogeny of the multicellular cell, two cotyledons ( ectoderm and endoderm ) emerged. This organization can be found, for example, in hollow animals . A third cotyledon ( mesoderm ) was added later. A coelom is now a fluid-filled cavity in the mesoderm. All animals that have this Coelom are grouped under the name Coelomata and can therefore be traced back to a common ancestor. They include the annelids (Annelidae) and the back-stringed animals ( Chordata ) with all vertebrates.
Richard von Hertwig was also the first to discover through studies on the sea urchin egg that the egg and sperm core fuse during fertilization .
With his nephew Günther Hertwig and his niece Paula Hertwig he investigated the effects of radium rays on the development of germs.
Evolutionarily important fossils
Archeopteryx (from 1860)
In 1860 the paleontologist Hermann von Meyer published a short note about a feather found in Solnhofen limestone , which he calls Archeopteryx . A fossil now known as the London specimen is later sold to the British Museum under Richard Owen . The creationist interpretations of Meyer and Owen are refuted by Thomas Henry Huxley . In 1871, Huxley introduced the family of primeval birds (Archeopterygidae). The proven mistakes that Owen had made in his description cost him a good part of his scientific reputation and thus permanently weakened creationism in the UK. At first glance, Archeopteryx represented a missing link for the theory of evolution , since this fossil contains features of both birds and reptiles and thus stands between two groups of vertebrates , which otherwise cannot be easily deduced from one another.
Planorbis multiformis
Based on the fossil snail species Planorbis multiformis , which occurred in the Steinheim basin , Franz Hilgendorf (1839–1904) was the first to prove the theory of evolution using fossils. The Steinheimer Schneckensand thus takes on a special role in the history of science.
Pedigree of horses (from 1870)
In 1870, Othniel Charles Marsh (1831–1899) created a morphological series of horse fossils that document the evolution from the unspecialized multi-rayed extremity to the single-toed horse leg. This series was considered excellent evidence of evolution in its time.
The integration of heredity (genetics) and population genetics
Heredity, or genetics, was a largely untreated field in Darwin's day . It was only after his death that ideas could prevail that are still valid today - much more refined. In Darwin's time, there were two assumptions about inheritance that can be described using the keywords blending inheritance (German, for example, mixing inheritance, as in color mixing) and "particular inheritance".
An inheritance hypothesis put forward by Darwin on inheritance was based on the assumption that every cell of an organism secrete small particles so-called gemmulae and these accumulate in the sex products; Changes in the body cells would also mean a change in the information passed on during inheritance. Such theories of pangenisis (generation from the whole) have a problem: they can only explain with the help of a latency hypothesis with an unexplained mechanism why some features appear in grandparents and grandchildren but not in the parents - which in Mendel's attempt at explanation does not cause any problems. After all, inheritance has a solid basis in the form of inheritance particles - albeit of an unknown form.
One form of the inheritance of properties acquired through the use and non-use of an organ , shared by many contemporary biologists, can be found in the example of the giraffes attributed to Lamarck : giraffes originally had normal necks and obtained their long necks only by stretching them for food in tree tops. A giraffe with a long neck has now sired descendants and therefore also inherited the long necks. Darwin advocated this explanation, for example, in the case of captive waterfowl, whose wings often wither and tend to have stronger feet.
Gregor Mendel (1822-1884)
Before 1865, Gregor Mendel carried out well thought-out experiments with peas, the consequences of which went unnoticed for a long time. They were only rediscovered at the beginning of the 20th century by Hugo de Vries , Carl Correns and Erich Tschermak and then went into genetics and evolutionary biology. Mendel's results resulted from the first experiment, which showed that there are two places - one maternal and one paternal - for each trait in the genetic material, which was still unknown at the time, and that traits therefore do not mix, but are passed on in a dominant-recessive inheritance. This is an initial finding which, based on experimental results, contradicted the hypotheses about heredity that Darwin or Haeckel had advocated.
August Weismann (1834–1914)
In school books and popular accounts of the history of evolutionary theory, there is usually only one keyword on August Weismann . Today he is usually only viewed in a very narrow sense as a radical representative of the selection principle and the founder of the germplasm theory. In germplasm theory, the cells of an organism are divided into sex cells and somatic cells . Changes in the body cells, including the use and disuse of the organs made up of body cells, can then have no influence on the evolution of the organisms. Only changes (today: mutations ) in the genome of the sex cells have an impact . Although his idea of separating germ cells and somatic cells was correct, Weismann suspected the genetic material in the wrong cell component: in the plasma . According to current knowledge - which only arose decades later - the DNA in the cell nucleus is the carrier of the genetic information.
Weismann's insight, which emerged from his own observations and theoretical work on the theory of evolution, was the first to define the framework for the incorporation of a later genetic interpretation of the theory of evolution.
Thomas Hunt Morgan (1866-1945)
In 1910, Thomas Hunt Morgan showed that the chromosomes are the carriers of genetic information.
Godfrey Harold Hardy (1877–1947) and Wilhelm Weinberg (1862–1937)
The mathematician Godfrey Harold Hardy and the physician Wilhelm Weinberg set a milestone in population genetics with the Hardy-Weinberg equilibrium in 1908 . According to this, the frequency of the alleles does not change in an ideal population - it is in equilibrium. This means that no evolution takes place in an ideal population. However, since there are no ideal populations, there is such a mathematical proof of evolution: Small population sizes and the restriction of panmixia accelerate evolutionary processes.
Ronald Fisher (1890–1962)
The population geneticist Ronald Fisher defined evolution in 1930 in 'The genetic theory of natural selection' as the change over time in the number of certain genes within a gene pool .
Selected modern theorists
Ernst Mayr (1904-2005)
Ernst Mayr , together with Theodosius Dobzhansky, is considered to be the founder and, to this day, the leading exponent of the modern synthetic theory of evolution , which brought Darwin's concept of selection into harmony with the findings of modern genetics .
He is considered to be the founder of the modern biological species concept. If one takes a closer look at Darwin's idea of the continuous change of one species into another species, the problem arises that the biological concept of species is thereby abolished, since in the uninterrupted series there are no gaps that separate species from species. This long neglected circumstance also had profound consequences for the practice of all biologists.
In biology and paleontology, several species terms exist in parallel. The most important two groups are the morphological and the population genetic species concept. Both terms are related but not identical:
- In the morphological concept of species, differences in characteristics are used to distinguish species from one another. In paleontology it is the only practicable species term.
- The population genetic concept of species, on the other hand, understands species as a reproductive community.
In his fundamental work, Species Concept and Evolution (1967), Ernst Mayr examined what a new interpretation of the biological concept of species could look like in the light of evolutionary theory. The central paradigm is the search for mechanisms that prevent or impede reproduction between individual populations (i.e. hybrids have a lower fitness value or are sterile). Here geographical separation , temporal separation (e.g. non-simultaneous reproduction times) and separation through behavior (different courtship behavior or singing) should be mentioned.
This opens up numerous questions about the microprocess of evolution. The discovery of morphological sibling species, species that have the same characteristics, live in the same area at the same time and still do not reproduce with one another, was important for the reinterpretation. Ernst Mayr defines a species as a "group of mutually reproducing organisms that are reproductively isolated from other such groups". This isolation is therefore the criterion for Ernst Mayr to distinguish between two types.
Stephen Jay Gould (1941-2002)
Stephen Jay Gould was critical of the relationship between evolution and progress.
In his epistemological writings he opposes social Darwinist , pseudoscientific and racist overinterpretations of the theory of evolution, such as those found in intelligence research , for example .
Gould had a long-running argument with Richard Dawkins and other evolutionary biologists about the admissibility of many sociobiological interpretations. This dispute also concerns the interpretation of the evolutionary mechanism.
Richard Dawkins (since 1941)
Richard Dawkins is considered one of the leading proponents of the theory of evolution and at the same time one of its most emphatic proponents.
Dawkins sees the gene as the fundamental unit of selection that the body only uses as a "multiplication machine". Within evolutionary biology, he advocates the thesis that competitive situations or fitness differences on a genetic or at best individual level play a role in evolutionary processes, but group selection plays no role or only a marginal role.
In his TV documentary The Root of All Evil? Dawkins replied to the statement that the theory of evolution is still not called the law of evolution (Orig: "[...] still not called the law of evolution. "), that he calls it the fact of evolution (Orig: "Well, I will call it the fact of evolution! ").
Der Spiegel described Dawkins as the most influential biologist of his time .
Timeline of evolutionary research
The following presentation is intended to give an overview of the history of evolutionary research:
| 1838 | Charles Darwin developed the theory of natural selection of randomly generated variations. |
| 1853 | Gregor Mendel carried out studies on pea breeds and developed the basic rules of inheritance . |
| 1859 | Darwin published his most famous work: "The Origin of Species" . |
| 1880-1882 | Eduard Strasburger and Theodor Boveri described the constancy of the number of chromosomes in different species (this is typical for the respective species) and the individuality of the chromosomes. |
| 1885 | August Weismann published his germplasm theory . |
| 1902-1904 | Walter Sutton and Theodor Boveri showed that chromosomes behave like the genetic factors postulated by Mendel. |
| 1907 | Thomas Hunt Morgan carried out genetic experiments on the fruit fly Drosophila melanogaster . |
| 1908 | GH Hardy (1877–1947) and Wilhelm Weinberg (1862–1937) showed that genetic variability is retained in populations with random matings (Hardy-Weinberg equilibrium). |
| 1928-1930 | Ernst Mayr toured New Guinea and the Solomon Islands and investigated the importance of adaptive geographic variation. |
| 1930 | In The genetical theory of natural selection, population geneticist Ronald Fisher defined evolution as the change over time in the number of certain genes within a gene pool. |
| 1937 | With Genetics and the Origin of Species, Theodosius Dobzhansky presented evolutionary genetics to a wider public. |
| 1942 | The "modern synthesis" was presented: Ernst Mayr's Systematics and the origin of species and Julian Huxley's Evolution: The Modern Synthesis |
| 1970 | George R. Price published the Price equation named after him . |
| 1972 | Stephen Jay Gould and Niles Eldredge proposed punctuated equilibrium punctuated equilibrium . |
literature
- Eve-Marie Engels (Ed.): The reception of evolution theories in the 19th century. Suhrkamp (stw 1229), Frankfurt am Main 1995, ISBN 3-518-28829-6 .
- Thomas Junker , Uwe Hoßfeld : The discovery of evolution. A revolutionary theory and its history. Scientific Book Society, 2nd edition 2009, ISBN 978-3-53422394-7 .
- Wolfgang Wieser (Hrsg.): The evolution of the evolution theory. From Darwin to DNA. Spectrum, Heidelberg 1994, ISBN 978-3-86025241-3 .
- Walter Zimmermann : Evolution. The history of their problems and insights. Verlag Karl Alber, Freiburg / Munich 1953, ISBN 3-495-44108-5 .
Web links
- Data on the history of the thought of evolution ( Memento of December 10, 2012 in the Internet Archive ) (in English)
Individual evidence
- ^ Wilhelm Capelle (ed.): The pre-Socratics. The fragments and source reports . Alfred Kröner, Stuttgart 1968, pp. 214-220: Zoogony .
- ^ Wilhelm Capelle: The problem of spontaneous generation with Aristotle and Theophrast and in the following time.
- ^ So Ernst Haeckel : Natural history of creation . Berlin 1868, 4th and 5th lecture.
- ↑ Autobiography, p. 120 . Darwin Online. Retrieved on July 23, 2009. “[…] it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work; [...] "
- ↑ Seeber, Englische Literaturgeschichte, p. 221.
- ↑ http://www.zum.de/stueber/haeckel/weltraethsel/weltraethsel.html
- ↑ Ernst Haeckel: The struggle for the development idea . Berlin 1905, p. 27 f.
- ↑ Archive link ( Memento from January 9, 2007 in the Internet Archive )
- ↑ J. Baier, A. Scherzinger: The new geological educational trail in the Steinheim impact crater - Jber. Mitt. Oberrhein. geol. Ver, NF 92, 9-24, 2010.
- ↑ Johannes Baier: The Steinheimer Schneckensand - a Miocene fossil deposit of world format. In: fossils. Volume 29, No. 6, 2012, pp. 368-371
- ↑ Jörg Blech: Happier Without God . In: Der Spiegel . No. 43 , 2006, p. 188-190 ( online ).