German geographer and natural historian who travelled extensively in the Americas, North Africa and western Asia. Wagner developed an evolutionary theory that argued geographic separation was the key to speciation, earning him the disapproval of Darwinian thinkers of his era. He was professor of geography and ethnography at Munich from 1862.

Moritz Wagner was born in Bayreuth and spent most of his youth in Augsburg, where his father was a schoolteacher. Having always shown an interest in animals and plants, he studied natural sciences in Paris, Erlangen and Munich before taking off on travels in 1836, intent on making natural history collections. He spent two years in Algeria, appointed on a scientific commission to travelling alongside the French army. He was able to enter the interior of Mascara during this time thanks to the short-lived peace granted by the treaty of Tafna in 1837, and built himself a reputation in the German press with his insightful correspondence published in several newspapers.

On his return to Germany he spent a brief time as editor of the Augsburger Allgemeine Zeitung. Although already armed with a doctorate, he rued his lack of botanical and geological knowledge during his Algerian trip and thus decided to return to university, studying geology at G⟶ttingen from 1840-1842 under J.F.L. Hausmann (1782-1859). The year 1842 saw him begin a four-year odyssey across Armenia and the Caucasus, collecting plants, animals and minerals on behalf of the Berlin Royal Academy of Sciences, followed by a sojourn of three years in Italy, where he met fellow German explorer Karl von Scherzer. Wagner then spent a year in Asia Minor and Central Asia (1850-51) before crossing the Atlantic to explore the Americas, starting with the United States.

After a year in North America he met up with his friend, Scherzer, in 1853 and together they set off from New Orleans to Central America, where they would spend two years on foot and muleback exploring its countries, Wagner paying particular attention to volcanoes and the distribution of species. The pair also made a tour of the West Indian islands before returning to Europe and publishing a number of works on their travels. They travelled together once more in 1857, landing in Panama, from whence Wagner set off inland and then south to Ecuador and the Andes.

After this final voyage of exploration, Wagner set his mind to producing more serious scientific work than he had so far attempted. Despite his wide scientific education he had written accounts of the lands he had visited mainly for a popular audience and supported himself with journalistic articles. He would now use observations he had made over the years to formulate his most remembered work, on the process of geographic speciation. In Algeria he had studied flightless beetles confined to the north coast of the country between rivers flowing into the Mediterranean. He noticed that species did not cross the rivers; closely related but different species were always found on the other side of each river. From observations such as this he formulated his own evolutionary theory, concluding that human, animal and plant populations, dispersed in colonies, had adapted to local conditions in situ. His first essay on the subject, ✢The Darwinian theory and the law of migration of organisms✢, was published in 1868 and translated into English in 1873. The migration theory, based on a simplistic, Lamarckian idea of evolution, irritated Charles Darwin. Growing increasingly frustrated with his German correspondent, he scrawled 'most wretched rubbish' across an 1875 paper by Wagner, who had completely dismissed natural selection by this time. Despite its unpopularity with Darwin and his followers, later theorists such as Ernst Mayr incorporated Wagner's idea as a core aspect of modern evolutionary synthesis. Also notably, the geographer and ethnographer Friedrich Ratzel (1804-1904), who coined the term 'Lebensraum', was heavily influenced by Wagner in his social Darwinist theory.

Notwithstanding divided opinions in learned circles (some dismissed his scientific writings as journalistic), Wagner had established himself in the world of science with a professorship at the University of Munich (1862) and membership of the German Academy of Natural Scientists Leopoldina (1865). In the last years of his life his health began to fail; he had limped since breaking his leg in 1870 and also suffered lung and throat trouble. It has been suggested that these pains caused him to take his own life with a revolver, but otherwise his suicide at the age of 73 appears largely without reason. His Die Entstehung der Arten durch R⟤umliche Sonderung (The origin of species by spatial separation) was posthumously published in 1889.

Sources:
E. Mayr, 1982, The growth of biological thought: diversity, evolution and inheritance: 562-565
C.S. Minot, 1890, Science, 15(380): 305-306
C. Ossenbach, 2005, ✢Fritz Hamer and the German Tradition of Botany in Mesoamerica✢, Selbyana, 25(2): 245
W.B. Provine, 1989, Sewell Wright and Evolutionary Biology: 214-215
F. Ratzel, 1896, in Allgemeine Deutsche Biographie, 40: 532-543
H.P. Riley, 1952, ✢Ecological Barriers✢, The American Naturalist, 86(826): 23-24
K. von Scherzer, 1889, ✢Biographische Skizze✢ in M. Wagner, Die Entstehung der Arten durch r⟤umliche Sonderung: 9-32
F.J. Sulloway, 1979, ✢Geographic isolation in Darwin's thinking: the vicissitudes of a crucial idea✢, Studies in the History of Biology, 3: 23-65.