The genus name "Pan" was first introduced by Lorenz Oken in 1816. An alternative "Theranthropus" was suggested by Brookes 1828 and "Chimpansee" by Voigt 1831. "Troglodytes" was not available, as it had been given as the name of a genus of wren in 1809, for "cave-dweller", reflecting the tendency of some wrens to forage in dark crevices. The International Commission on Zoological Nomenclature adopted "Pan" as the only official name of the genus in 1895, though the "cave-dweller" connection was able to be included, albeit at the species level ("Pan troglodytes" – the common chimpanzee) for one of the two species of "Pan". The genus name is a reference to Pan, the Greek god of nature and wilderness. In his book "The Third Chimpanzee" (1991), Jared Diamond proposes that "P. troglodytes" and "P. paniscus" belong with "H. sapiens" in the genus "Homo", rather than in "Pan". He argues that other species have been reclassified by genus for less genetic similarity than that between humans and chimpanzees.