Eugene Nielen Marais, writer, poet, journalist, lawyer and naturalist, was the son of Jan Christiaan Nielen Marais and his wife Catherina Helena Cornelia, born van Niekerk. He received his schooling in Boshof, Free State, and in Paarl, Western Cape, and passed the matriculation examination of the University of the Cape of Good Hope in 1887. His first published poems appeared in the Paarl District Advertiser in 1885. After leaving school he worked for some time as a clerk in an attorney's office and then as a journalist for the Transvaal Advertiser. In 1890, at the age of 19, he became editor of the newspaper Land en Volk, in which he severely criticised the government and policies of President J.S.P. Kruger of the South African Republic (Transvaal). In 1894 he married Aletta (Lettie) Beyers, but she died the next year shortly after the birth of their son. Soon thereafter Marais was becoming addicted to opium (later morphine). He left for England in December 1896, studied law at the University of London, and also seems to have acquired some medical knowledge in Germany. He returned to South Africa towards the end of the Anglo-Boer War (1899-1902) and on his way to South Africa contracted malaria in Mozambique.
After his return to Pretoria Marais was again associated with Land en Volk (of which he was an owner) for some time, before selling the newspaper and moving to Johannesburg as an advocate in 1905. This proved unsuccessful and soon thereafter he settled on the farm Doornhoek in the Waterberg, where he held an appointment as mine doctor for some time. Later he moved to the farm Rietfontein, where he openly practiced as a medical doctor and also used hypnosis in his treatments. Here he studied nature in his spare time, being a keen observer with strong conservationist tendencies. Two articles by him appeared in the Agricultural Journal of the Union of South Africa: 'Wild honey; with notes on the Moka bee' (1912) and 'Notes on some effects of extreme drought in Waterberg' (1914). The latter article, in which he described the effects of drought on plants and animals, was reprinted and distributed by the Smithsonian Institution in the USA.
Though he was increasingly dependent on drugs and suffered periods of depression and fever he continued to write poems and to publish various articles and stories in local magazines. Later, in a book on Natuurkundige en wetenskaplike studies (Natural history and scientific studies, 1928) he reported on his experiments and ideas relating to hypnosis. During the early nineteen-twenties he worked as a lawyer at Erasmus (now Bronkhorstspruit), then lived in Heidelberg for about four years and returned to Pretoria in 1927, living with his friend Gustav Preller and the latter's family. His collected poems were published in Gedigte (Poems, 1925) and he also wrote many short stories and popular articles on scientific subjects. He committed suicide with a shotgun in 1936.
Shortly after settling in the Waterberg Marais and A. Austin studied a troop of baboons in their natural state in the Doringhoek Mountains for three years, concentrating on their social behaviour and psychology. An account of this work was eventually published under Marais' name in Burgers van die berge (1938) and translated into English as My friends the baboons (1939). This study of primate behaviour was probably his most important scientific work. Among others he speculated that the behaviour of a troop of baboons was in part regulated by a collective mind.
During the nineteen-twenties Marais conducted a study of termite nests. He wrote a series of articles on his observations for Die Huisgenoot from 1925 onwards and published these in book form as Die siel van die mier (1934, and several later editions). An English translation, The soul of the white ant (1937) was published shortly after his death, followed by French and German editions. In this work he proposed his theory that a termite colony behaves like a single animal.
Marais' contributions to natural history were controversial. Some regarded his work as of the highest value, for example, R. Ardry described him as a genius and the century's greatest naturalist (Mieny, 1984) and Ryke (1972) described his observations of baboons and termites as pioneering work. Others maintain that he was an unorthodox and unpolished generalist who contributed little of value to biology. Weaknesses in his work included neglecting to test his ideas rigorously, a lack of detailed observations, and his pretence to be an empirical specialist. His observations were useful, but his theories poor, while the holistic approach that he used has become common in the biological sciences (Holm, 1988). The Eugene Marais Chair in Nature Conservation was established in his honour at the University of Pretoria in 1971, and the cycad species Encephalartos Eugene Maraisii was named after him.