James Henry Bowker was the youngest of the eleven children of the 1820 settlers Miles Bowker and his wife Anna Maria Mitford. He grew up on the eastern frontier of the Cape Colony and became a soldier, administrator and farmer. His participation in the frontier wars of 1846-7 and 1850-3 made him an experienced campaigner with an ability to lead in the field. In 1855 he was appointed as an inspector of the Frontier Armed and Mounted Police (later the Cape Mounted Rifles) and promoted to Commandant in 1858. He took part in a scheme to settle the Mfengu in the Transkei and was appointed with the rank of Colonel in charge of the force which was left in occupation of the territory. Around 1860 he built Fort Bowker there, near Idutywa, but the scheme was abandoned in 1865. In 1868 he took part in expeditions to Basutoland (now Lesotho) and after its annexation commanded a small police force in the territory. He was appointed commander of the Frontier Armed and Mounted Police in 1870 and the next year commanded the expedition which led to the annexation of the diamond fields of Griqualand West by the Cape Colony. A convinced supporter of British expansionism in southern Africa, he retired to Durban in 1878. In 1889 he was appointed justice of the peace at Malvern, Durban.
Bowker had a strong interest in natural history, probably instilled by his older brother Thomas H. Bowker* and his sister Mary E. Barber* (born Bowker), and made significant contributions to entomology, archaeology and botany over a period of almost 40 years. His main scientific interest was in butterflies, on which he became an authority and the leading local collector of his time, discovering some 40 new species and the new genus Deloneura, named by Roland Trimen* in 1868. In 1860 he presented his first collection of insects to the South African Museum and in November the next year met Trimen, the museum's entomologist. His first donation was followed by an extensive series of South African lepidoptera in 1863 and by additional collections from King Williams Town (1866), Kaffraria (1876), Lesotho, Griqualand West, Natal and Zululand over the next 30 years. After his retirement, between 1878 and 1893, he donated many more zoological specimens from Natal to the museum, especially insects. In recognition of his contributions he was named as one of only nine correspondents of the museum in 1899. His specimens and notes on the habits, distribution and life histories of butterflies were so important that he is named on the title page of Trimen's South African butterflies... (1887-1889) as having assisted with its compilation.
In 1880 his sister Mary presented a collection by him of 800 Lepidoptera (butterflies and moths), representing 68 species, to the Albany Museum. It was regarded as the museum's most important acquisition that year. He followed it up with some 400 butterflies from Natal in 1884.
Bowker was active in archaeological investigations from about 1867, when he sent a collection of stone artifacts from East London to Sir Joseph Hooker* in England. According to his sister Mary he was the first to discover stone implements in the diamond diggings at Pniel on the Vaal River. He also collected artifacts near Maputo and Inhambane in Mozambique, in Zululand, and elsewhere. According to W.D. Gooch* in 1881, the only known excavation of a cave deposit in South Africa at that time had been carried out by Bowker in Lesotho just before 1870. (Bowker, with Dr Bleek and Dr John Beddoe, published an account of this venture in "The cave cannibals of South Africa", Anthropological Review, 1869, pp. 121-128). The artifacts found were again sent to Sir Joseph Hooker, at that time president of the Royal Society of London. At least some of his finds ended up in the British Museum. However, he also presented many stone artefacts from south-east Africa and the Free State to the South African Museum in 1877, with more artefacts and pottery following in 1882.
Bowker was also interested in contemporary equivalents of prehistoric implements. For example, he found that the Bushmen in Lesotho had used discarded glass bottles as source material to make arrowheads. In two local publications he referred to archaeological matters. In 1872 he wrote an addendum to a paper by P.D. Martin*, published in the Cape Monthly Magazine, in which he briefly described middens and stone artifacts (and arrowheads made from modern glass) that he found in various places throughout the country. And in a paper "Other days in South Africa" in the Transactions of the South African Philosophical Society (1884, Vol. 3, pp. 68-73) he mentions his cave excavation in Lesotho.
Bowker's interest in botany was already evident in 1853, during a visit to London, when he sold 350 plant specimens to Sir William Hooker, then director of Kew Gardens. He collected many plants during his lifetime, particularly during his stay in the Transkei and later in Natal and Zululand, and was also closely involved in his sister Mary's botanical work. Their contributions were acknowledged by Harvey* and Sonder* in the preface to Volumes 1 and 3 of the Flora Capensis(1859-1865). During the eighteen-eighties Bowker became greatly interested in mushrooms and sent specimens to Kew Gardens. His botanical specimens are housed in several local and overseas herbaria. He was commemorated in the genus Bowkeria (named for him and Mary) and in the species names Bauhinia bowkeri and Ceropegia bowkeri.
Bowker was a Fellow of the Linnaean Society, the Zoological Society of London, the Statistical Society, and the Royal Geographical Society. He assisted in setting up the Durban Natural History Museum in November 1885 and served on its committee of management until just before his death. He also assisted the Port Elizabeth Museum in natural history and with donations in 1888 and 1889. In 1887 he became a patron of the Eastern Province Naturalist's Society and a few years later presented it with a collection of shells. He was a corresponding member of the South African Philosophical Society shortly after its foundation in 1877 and also served on the committee of the Durban Botanic Society. He never married and died intestate in Durban, his estate being divided among his nephews and nieces.