Egbert Cornelis Nicolaas van Hoepen, palaeontologist and museum director, was the son of Jan van Hoepen, gold prospector, farmer and photographer, and his wife Johanna Margaretha Goudriaan. He came to South Africa with his parents around 1890, received some education in English and Dutch private schools and later attended the Government Gymnasium in Pretoria. When, at the age of fifteen, the Anglo-Boer War (1899-1902) broke out he joined the Boer forces, but was soon captured and sent back to Pretoria to continue his education. However, he again took part in military operations, was captured a second time when the British forces occupied Pretoria in June 1900 and deported to the Netherlands. There he completed his schooling and qualified as a mining engineer at the Technische Hogeschool in Delft. He continued his studies and was awarded the doctoral degree in 1910 with a thesis entitled De bouw van het Siluur van Gotland (The structure of the Silurian of Gotland [a Swedish island in the Baltic Sea]).
Returning to South Africa van Hoepen was appointed as palaeontologist at the Transvaal Museum (now the Ditsong National Museum of Natural History) in October 1910. His first local scientific paper, written in Dutch and published in the Annals of the Transvaal Museum in November 1910, was a preliminary report on the fossil flora of the Ermelo District. During the next few years he gave much attention to the fossil reptiles of the Karoo and formed the nucleus of the museum's Karoo fossil collection. Some of the specimens he studied were supplied by A.W. Putterill* and Dr D.R. Kannemeyer*. He remained at the museum until the end of 1921, when he accepted an appointment as director of the National Museum in Bloemfontein. He was the first scientist to occupy this position, placed the work and collections of the museum on a scientific footing and in 1928 started its series of scientific publications. To him the museum was primarily a research institution and he gave little attention to its displays or educational function. For many years there was conflict between him and the museum council. Nonetheless he remained at the museum until he was forced to retire in 1950 after a commission of inquiry found irregularities relating to cost of living allowances and concluded that the museum did not meet its objectives as an educational institution. His temperamental personality, poor interpersonal relations, and his preference for the Afrikaans language probably also played a role in his dismissal.
Van Hoepen's scientific work was generally regarded as being of a high standard. He was a keen collector of prehistoric stone artefacts and collected thousands of invertebrate fossil specimens (mainly molluscs) from the Cretaceous strata of Zululand, many of which he later described as new species. During his career he produced about 80 scientific publications in the fields of palaeontology, archaeology and ethnology. Included are his descriptions of several new fossil reptiles from the Karoo strata (1913-1920), 'Contributions to the knowledge of the reptiles of the Karoo' (1914, 1915, 1920), 'Stegocephalia of Senekal, OFS' (1915) and 'Cretaceous Cephalopoda from Pondoland' (1921), all in the Annals of the Transvaal Museum; 'On land connections and the former extent of the African continent' (South African Journal of Natural History, 1922); and 'A new family of keeled ammonites from the Albian of Zululand' (South African Journal of Science, 1955). After 1925 most of his work was published in Afrikaans and dealt with topics such as the relative age of South African stone artefacts (1926) and the Cretaceous deposits of Zululand (1926), both in the South African Journal of Science; the Mossel Bay Culture (1932) and descriptions of various cultural artefacts (1935) in Argeologiese Navorsing van die Nasionale Museum, Bloemfontein; Fossil horses (1930) and fossil pigs (1932) from the Free State in Paleontologiese Navorsing van die Nasionale Museum, Bloemfontein; and the Bushman and his culture (Tydskrif vir Wetenskap en Kuns, 1942). His publications made a significant contribution to the development of Afrikaans as a language of science.
Van Hoepen was a member of the Suid-Afrikaanse Akademie vir Wetenskap en Kuns, was the first editor of its Tydskrif vir Wetenskap en Kuns from 1922 to 1927, served on its council on and off between 1932 and 1952, and was a member of its language commission from 1943-1956. The academy awarded him its Havenga Prize for Biology in 1945 for his palaeontological, archaeological and geological research. In 1916 he became a foundation member of the South African Biological Society and actively participated in its meetings until he left Pretoria. He was a member also of the South African Association for the Advancement of Science and served on its council for 1926/7.
In 1909 van Hoepen married Adele Johanna Weiss, with whom he had two sons and a daughter. After her death in 1942 he married Emerentia Liberta Venter in 1944.