Orjan Mikael Olsen, Norwegian physician and explorer, obtained the BA degree at the University of Innsbruck, Austria, and in 1922 qualified as Doctor of Philosophy (PhD). By 1912, when he was associated with Christiania University in Norway, he was recognised as a marine biologist, having described the Pycnogonida (now Pantopoda, an order of marine arthropods commonly known as "sea spiders") collected on the Michael Sars North Atlantic Expedition of 1910. During his career he travelled all over the world, in Europe, China, Japan, Siberia, Central Asia, South and West Asia, Palestine, North Africa, Australia, New Zealand, North America, and Polynesia.
In 1912 Olsen came to South Africa to examine the whales landed at Johan Bryde's whaling stations at Durban and Donkergat (Saldanha Bay), being the first scientist to study the specimens that became available when commercial whaling commenced in South Africa in 1908. He described what was thought to be a new species in a paper, "On the external characteristics and biology of Bryde's whale, Balaenoptera brydei, a new rorqual from the coast of South Africa", published in the Proceedings of the Zoological Society of London in 1913. Although the name was later synonymised with Balaenoptera edeni, the popular name "Bryde's whale" is still used for the species. The overall results of his investigation were published in Hvaler og hvalfangst i Sydafrika (Whales and whaling in South Africa, 56 pp) by Bergen Museum, Norway, in 1915. His work was the first significant study of any marine mammal in South African waters, and remained the most informative study of local humpback whales for the next 75 years.
During his stay in South Africa Olsen furthermore compiled a publication (in Norwegian) on the migratory birds from the northern hemisphere in this country (1913). Other publications by him included books (in Norwegian) on the nomads of Mongolia (Christiania, 1915), the Norwegian expedition of 1914 to Siberia (Christiania, 1915), his travels in New Zealand (Oslo, 1931), and a six volume work on major explorations (1929-1930). The latter work was translated into French and published under the title La conquete de la terre (The conquest of the earth) in 1934-1937.