Robert Todd Carroll also states that a more likely source of the knowledge of the Sirius star system is from contemporary, terrestrial sources who provided information to interested members of the tribes. James Oberg, however, citing these suspicions notes their completely speculative nature, writing that, "The obviously advanced astronomical knowledge must have come from somewhere, but is it an ancient bequest or a modern graft? Although Temple fails to prove its antiquity, the evidence for the recent acquisition of the information is still entirely circumstantial." Additionally, James Clifford notes that Griaule sought informants best qualified to speak of traditional lore, and deeply mistrusted converts to Christianity, Islam, or people with too much contact with whites.