The paleocontact hypothesis is the notion originally proposed by Matest M. Agrest and others on a serious academic level, and frequently put forward in pseudo-scientific and pseudo-historic literature since the 1960s, that advanced extraterrestrials have played an influential role in past human affairs. Its most outspoken and commercially successful advocate has been the writer Erich von Däniken. Although not an unreasonable idea in principle (see sentinel hypothesis and alien artifacts), there is a lack of convincing, substantive evidence to support it. Moreover, when specific claims are examined in detail, other, less exotic explanations can usually be found. A case in point concerns the Dogon tribe and their remarkable knowledge of the star Sirius (see Sirius, mystery of red color).