Moritz Wagner
Encyclopedia
Moritz Wagner was a German explorer, collector, geographer and natural historian. Wagner devoted three years (1836–1839) to the exploration of Algiers
: it was here that he made important observations in natural history, which he later supplemented and developed: that geographical isolation could play a key role in speciation
.
From 1852–1855, together with Carl Scherzer
, Wagner travelled through North and Central America and the Caribbean. In May 1843, Wagner toured the Lake Sevan
region of Armenia with Armenian writer Khachatur Abovian
. He committed suicide in Munich, aged 73. His brother Rudolf
was a physiologist and anatomist.
, the evolutionist and historian of biology, has given an account of Wagner's significance.p562–565. However, others disagree with this account . During his three years in Algeria
, he (amongst other activities) studied the flightless beetles Pimelia
and Melasoma. In these genera, a number of species are each confined to a stretch of the north coast between rivers which descend from the Atlas mountains
to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.
Wagner made similar observations in the Caucasus
and in the Andean valleys, leading him to conclude, after the Origin of Species had been published:
This was an early description of the process of geographic speciation
by means of the founder effect
. Another formulation of this idea came later: "Organisms which never leave their ancient area of distribution will never change".
Wagner's idea met with a mixed reception. "Unfortunately, Wagner combined [his idea] with some peculiar ideas on variation and selection" (Mayr). The leading evolutionists (Darwin
, Wallace
, Weismann
) attacked Wagner's idea of geographic speciation, and it suffered a long decline until in 1942 it was reintroduced by Mayr. The importance of geographic speciation became one of the core ideas of the evolutionary synthesis.
, Jerry Coyne
and H. Allen Orr
, argue that Wagner pioneered the idea geographical speciation, and that Darwin had not appreciated it. However, Wagner's "migration theory" was based on a rather simple, Lamarckian idea of evolution. Wagner argued in letters to Darwin that the latter had missed a vital geographic component in understanding the evolution of new species. Darwin at first responded in a friendly way to these letters, and agreed that geographic isolation was important (although not the only cause of speciation), and pointed out that he had in fact dealt with geographic speciation in The Origin of Species
. Wagner in his later articles totally rejected the importance of natural selection. He again pointed out the importance of intercrossing in preventing divergence, and thus for geographic separation in allowing divergence. Wagner argued that Darwin had not understood this, although these ideas are present in The Origin of Species
. Darwin found Wagner's increasingly hysterical tone and one-sided argument upsetting, and wrote across his copy of Wagner's 1875 paper "most wretched rubbish."
As well as Darwin, the Reverend J.T. Gulick
also found Wagner's theories overstated. Gulick was apparently responding to David Starr Jordan
, who approved of Wagner's geographic speciation ideas in a paper which is often cited as providing early support of geographical speciation. Jordan later wrote a brief note of correction agreeing with some of Gulick's criticisms:
In a later paper Gulick says that "Moritz Wagner, in his 'Law of the Migration of Organisms,' was the first to insist on the importance of geographical isolation as a factor in evolution, but when he asserted that without geographical isolation natural selection could have no effect in producing new species he went beyond what could be sustained by facts".
Mayr's formulation has been argued to have cleared up issues which Wagner had left unresolved: "A new species develops if a population which has become isolated from its parental species acquires during this period of isolation characters which promote or guarantee isolation when the external barriers break down".p155 The zoological taxonomist Bernhard Rensch
was also significant in keeping geographical speciation on the evolutionary menu. He identified geographical separation as the most frequent initial step towards cladogenesis (phylogenetic branching). However, a variety of species concepts compete with Mayr's isolation concept of species today, and so Mayr's account can no longer be accepted to be the gold standard.
The importance of Wagner's insight is highly debatable today, as it is clear that geographical isolation is not the only mechanism which causes species-splitting. Furthermore, it is generally accepted that natural selection is the most important cause of speciation, even when the geographical milieu is in isolation. There is room for debate as to whether Charles Darwin had reached a similar conclusion at the same time. The Origin of Species was published nearly twenty years after Wagner's first account, but more relevant is the evidence of his notebooks. The evidence of Darwin's notebooks (which were not published until the mid-20th century) shows a "clear description of reproductive isolation, maintained by ethological
[behavioural] isolating mechanisms"p266; the same ideas are also present in The Origin of Species
, but are often not recognized as such by modern biologists. On the other hand, there is no single example in the notebooks quite so clear as Wagner's flightless beetles. Much of the good in Wagner's ideas is masked by his other, mistaken, beliefs, but his inferences about geographical speciation were important insights gained by observation of insects in their natural habitats.
But again, see Sulloway's article.
Algiers
' is the capital and largest city of Algeria. According to the 1998 census, the population of the city proper was 1,519,570 and that of the urban agglomeration was 2,135,630. In 2009, the population was about 3,500,000...
: it was here that he made important observations in natural history, which he later supplemented and developed: that geographical isolation could play a key role in speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
.
From 1852–1855, together with Carl Scherzer
Karl von Scherzer
Karl Ritter von Scherzer was an Austrian explorer, diplomat and natural scientist.-Biography:...
, Wagner travelled through North and Central America and the Caribbean. In May 1843, Wagner toured the Lake Sevan
Lake Sevan
Lake Sevan is the largest lake in Armenia and the Caucasus region. It is one of the largest high-altitude lakes in the world.Lake Sevan is situated in the central part of the Republic of Armenia, inside the Gegharkunik Province, at the altitude of 1,900m above sea level...
region of Armenia with Armenian writer Khachatur Abovian
Khachatur Abovian
Khachatur Abovian ; ) was an Armenian writer and national public figure of the early 19th century who mysteriously vanished in 1848 and was presumed dead. He was an educator, poet and an advocate of modernization...
. He committed suicide in Munich, aged 73. His brother Rudolf
Rudolf Wagner
Rudolf Wagner was a German anatomist and physiologist and the co-discoverer of the germinal vesicle. He made important investigations on ganglia, nerve-endings, and the sympathetic nerves.-Life:...
was a physiologist and anatomist.
Wagner's significance in evolutionary biology
Wagner's early career was as a geographer, and he published a number of geographical books about North Africa, the Middle East, and Tropical America. He was also a keen naturalist and collector, and it is for this work he is best known among biologists. Ernst MayrErnst Mayr
Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...
, the evolutionist and historian of biology, has given an account of Wagner's significance.p562–565. However, others disagree with this account . During his three years in Algeria
Algeria
Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...
, he (amongst other activities) studied the flightless beetles Pimelia
Pimelia
Not to be confused with the plant genus Pimelea, which often is incorrectly spelt "Pimelia".Pimelia is a genus of darkling beetle in the subfamily Pimeliinae.There are many species, some of them listed at Wikispecies...
and Melasoma. In these genera, a number of species are each confined to a stretch of the north coast between rivers which descend from the Atlas mountains
Atlas Mountains
The Atlas Mountains is a mountain range across a northern stretch of Africa extending about through Morocco, Algeria, and Tunisia. The highest peak is Toubkal, with an elevation of in southwestern Morocco. The Atlas ranges separate the Mediterranean and Atlantic coastlines from the Sahara Desert...
to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.
Wagner made similar observations in the Caucasus
Caucasus
The Caucasus, also Caucas or Caucasia , is a geopolitical region at the border of Europe and Asia, and situated between the Black and the Caspian sea...
and in the Andean valleys, leading him to conclude, after the Origin of Species had been published:
- "... an incipient species will only [arise] when a few individuals transgress the limiting borders of their range... the formation of a new race will never succeed... without a long continued separation of the colonists from the other members of their species."
This was an early description of the process of geographic speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
by means of the founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
. Another formulation of this idea came later: "Organisms which never leave their ancient area of distribution will never change".
Wagner's idea met with a mixed reception. "Unfortunately, Wagner combined [his idea] with some peculiar ideas on variation and selection" (Mayr). The leading evolutionists (Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
, Wallace
Alfred Russel Wallace
Alfred Russel Wallace, OM, FRS was a British naturalist, explorer, geographer, anthropologist and biologist...
, Weismann
August Weismann
Friedrich Leopold August Weismann was a German evolutionary biologist. Ernst Mayr ranked him the second most notable evolutionary theorist of the 19th century, after Charles Darwin...
) attacked Wagner's idea of geographic speciation, and it suffered a long decline until in 1942 it was reintroduced by Mayr. The importance of geographic speciation became one of the core ideas of the evolutionary synthesis.
Criticism
Some modern experts such as Ernst MayrErnst Mayr
Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...
, Jerry Coyne
Jerry Coyne
-Online articles:* , The New Republic* , The New Republic* , The New Republic* ", The New Republic * -Online articles:* , The New Republic* , The New Republic* , The New Republic* ", The New Republic (Review of Michael Behe's The Edge of Evolution)* -Online articles:* , The New Republic* , The...
and H. Allen Orr
H. Allen Orr
H. Allen Orr is University Professor and Shirley Cox Kearns Professor of Biology at the University of Rochester.- Education and career :He earned his Bachelor’s degree in Biology and Philosophy from the College of William and Mary and his Ph.D. in Biology from the University of Chicago. At...
, argue that Wagner pioneered the idea geographical speciation, and that Darwin had not appreciated it. However, Wagner's "migration theory" was based on a rather simple, Lamarckian idea of evolution. Wagner argued in letters to Darwin that the latter had missed a vital geographic component in understanding the evolution of new species. Darwin at first responded in a friendly way to these letters, and agreed that geographic isolation was important (although not the only cause of speciation), and pointed out that he had in fact dealt with geographic speciation in The Origin of Species
The Origin of Species
Charles Darwin's On the Origin of Species, published on 24 November 1859, is a work of scientific literature which is considered to be the foundation of evolutionary biology. Its full title was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the...
. Wagner in his later articles totally rejected the importance of natural selection. He again pointed out the importance of intercrossing in preventing divergence, and thus for geographic separation in allowing divergence. Wagner argued that Darwin had not understood this, although these ideas are present in The Origin of Species
The Origin of Species
Charles Darwin's On the Origin of Species, published on 24 November 1859, is a work of scientific literature which is considered to be the foundation of evolutionary biology. Its full title was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the...
. Darwin found Wagner's increasingly hysterical tone and one-sided argument upsetting, and wrote across his copy of Wagner's 1875 paper "most wretched rubbish."
As well as Darwin, the Reverend J.T. Gulick
J.T. Gulick
John Thomas Gulick was an American missionary and naturalist. He is credited with some of the first modern evolutionary study, starting with a collection of Hawaiian land snails.-Life:...
also found Wagner's theories overstated. Gulick was apparently responding to David Starr Jordan
David Starr Jordan
David Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
, who approved of Wagner's geographic speciation ideas in a paper which is often cited as providing early support of geographical speciation. Jordan later wrote a brief note of correction agreeing with some of Gulick's criticisms:
- "Mr. Gulick corrects certain erroneous assumptions on the part of Dr. Moritz Wagner. Mr. Gulick says:
- Separate generation is a necessary condition for divergent evolution but not for the transformation of all the survivors of a species in one way.
- Separation does not necessarily imply any external barriers or even the occupation of separate districts.
- Diversity of natural selection is not necessary to diversity of evolution.
- Difference of external conditions is not necessary to diversity of evolution. Separation and variation—that is, variation not overwhelmed by crossing—is all that is necessary to secure divergence of type in the descendants of one stock, though external conditions remain the same and though the separation is other than geological. ...
- All of this is in general accord with my own experience."
In a later paper Gulick says that "Moritz Wagner, in his 'Law of the Migration of Organisms,' was the first to insist on the importance of geographical isolation as a factor in evolution, but when he asserted that without geographical isolation natural selection could have no effect in producing new species he went beyond what could be sustained by facts".
Mayr's formulation has been argued to have cleared up issues which Wagner had left unresolved: "A new species develops if a population which has become isolated from its parental species acquires during this period of isolation characters which promote or guarantee isolation when the external barriers break down".p155 The zoological taxonomist Bernhard Rensch
Bernhard Rensch
Bernhard Rensch was a German evolutionary biologist, and ornithologist who did field work in Indonesia and India. He is probably best known as one of the architects of the modern evolutionary synthesis, which he popularised in Germany...
was also significant in keeping geographical speciation on the evolutionary menu. He identified geographical separation as the most frequent initial step towards cladogenesis (phylogenetic branching). However, a variety of species concepts compete with Mayr's isolation concept of species today, and so Mayr's account can no longer be accepted to be the gold standard.
The importance of Wagner's insight is highly debatable today, as it is clear that geographical isolation is not the only mechanism which causes species-splitting. Furthermore, it is generally accepted that natural selection is the most important cause of speciation, even when the geographical milieu is in isolation. There is room for debate as to whether Charles Darwin had reached a similar conclusion at the same time. The Origin of Species was published nearly twenty years after Wagner's first account, but more relevant is the evidence of his notebooks. The evidence of Darwin's notebooks (which were not published until the mid-20th century) shows a "clear description of reproductive isolation, maintained by ethological
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....
[behavioural] isolating mechanisms"p266; the same ideas are also present in The Origin of Species
The Origin of Species
Charles Darwin's On the Origin of Species, published on 24 November 1859, is a work of scientific literature which is considered to be the foundation of evolutionary biology. Its full title was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the...
, but are often not recognized as such by modern biologists. On the other hand, there is no single example in the notebooks quite so clear as Wagner's flightless beetles. Much of the good in Wagner's ideas is masked by his other, mistaken, beliefs, but his inferences about geographical speciation were important insights gained by observation of insects in their natural habitats.
- "It took more than 60 years after 1859 until the leading specialists... [agreed] that this geographical approach was the way to solve the problem of speciation... a new species may evolve when a population acquires isolating mechanisms while isolated from its parent population." .
But again, see Sulloway's article.
Publications
- Reisen in der Regentschaft Algier in den Jahren 1836, 1837 und 1838. 3 Bde. LeipzigLeipzigLeipzig Leipzig has always been a trade city, situated during the time of the Holy Roman Empire at the intersection of the Via Regia and Via Imperii, two important trade routes. At one time, Leipzig was one of the major European centres of learning and culture in fields such as music and publishing...
1841. - Der kaukasus und das Land der Kosaken. 2 Bde. Leipzig 1847.
- Reise nach Kolchis. Leipzig 1850.
- Reise nach dem Ararat und dem Hochlande Armeniens. StuttgartStuttgartStuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....
1848. - Reise nach Persien und dem Lande der Kurden. 2 Bde. Leipzig 1851.
- Die Republik Costa-RicaCosta RicaCosta Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
. Leipzig 1856. - Über die hydrogaphischen Verhältnisse und das Vorkommen der Süßwasserfische in den Staaten PanamaPanamaPanama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
und EcuadorEcuadorEcuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
. Abhandlungen der königlich bayerischen Akademie der Wissenschaften, II Classe 11 (I Abt.) - Reisen in Nordamerika in den Jahren 1852 und 1853. (with Carl Scherzer) 3 vols, Gotha 1861.
- Die Darwinsche Theorie und das Migrationsgesetz der Organismen. Leipzig 1868. English edition: Wagner M. 1873. The Darwinian theory and the law of the migration of organisms. Translated by J.L. Laird, London. Google Books: http://books.google.com/books?id=o9faAAAAMAAJ&printsec=frontcover&source=gbs_v2_summary_r&cad=0#v=onepage&q&f=false
- Naturwissenschaftliche Reisen im tropischen Amerika. Stuttgart 1870.
- Über den Einfluß der geographischen Isolierung und Kolonienbildung auf die morphologischen Veränderungen der Organismen. München 1871.
- Die Entstehung der Arten durch räumliche Sonderung. [The origin of species by spacial separation] Gesammelte Aufsätze. Benno Schwalbe, Basel 1889.