Gerhardus Petrus Frederik (often Frederick) van Dam was the son of Johannes Leonardus van Dam and his wife Maria Elizabeth, born Steenkamp. He entered the civil service of the Transvaal Colony on 1 May 1908 as a clerk or messenger at the Transvaal Museum (now the Ditsong National Museum of Natural History), Pretoria, and on 1 June 1911 was appointed as assistant for lower vertebrates. He went on various field excursions for the museum during which he collected a variety of specimens. Some of the lizards he collected were described by him in two papers, 'Descriptions of new species of Zonurus, and notes on the species of Zonurus occurring in the Transvaal' and 'Description of a new variety of a South African lizard of the family Geckonidae' (Annals of the Transvaal Museum, 1921, Vol. 7(4), pp. 239-244 and p. 244). Van Dam's Girdled Lizard, Cordylus (Warreni) vandami, and Van Dam's Round-headed Worm Lizard, Zygaspis vandami, were named after him by V.F.M. FitzSimons in 1930.
With Austin Roberts he collected trapdoor spiders around Pretoria and, with Roberts as co-author, published 'Notes on nests of some trapdoor spiders and the nest of Calommata transvaalicus Hwtt' (Annals of the Transvaal Museum, 1917, Vol. 5(4), pp. 218-223). He also collected plants in South Africa and Mozambique, often jointly with more senior staff members such as V.F.M. FitzSimons, and 645 of the specimens he collected later went to the National Herbarium in Pretoria. The Lepidoptera (butterflies and moths) he collected are in still in the Ditsong Museum.
Van Dam died in a motor accident in Pretoria in 1927. He was married to Johanna Catharina Rossouw, with whom he had a son and three daughters.