Inevitably, there are skeptics. Carl Sagan made an issue of what the Dogon don't know. He asks why extraterrestrials would tell them about only four of Jupiter's moons, and about Saturn's rings, but nothing about any of the planets beyond Saturn? He suggests that the reason is because these things, along with Sirius B, were what a European visitor would have told the Dogon in the years between 1925 to 1935. Therefore, Sagan and others say, the Dogon must have obtained their knowledge of astronomy from missionaries or traders or other visitors to the area in the years before Griaule was told of their cosmology. He says that the Dogon simply incorporated this new knowledge into their already existing beliefs about Sirius A. Reverence for Sirius A, the brightest star in the sky, was not uncommon among ancient peoples, because its appearance in the dawn sky signaled the nearness of summer, with implications for agriculture.
Were there missionaries among the Dogon before 1931? Robert Temple said in 1990 that he had written to the Father Superior of the White Fathers Mission in Mali, asking when the first missionaries had been sent to the Dogon region. He said that the Father Superior replied that the earliest missionaries had arrived there in 1949. Such things should be verifiable. Missionaries record their activities rather thoroughly and make regular reports to their churches. However, the presence of traders or other Europeans among the Dogon between 1925 and 1931 would be very difficult to verify.
Griaule's colleague and co-author, anthropologist Germaine Dieterlen, who had lived among the Dogon for most of her life, was asked by a reporter for BBC-TV's Horizon program whether the Dogon could have learned the Sirius information from other Europeans. She called the idea "absurd" and displayed a 400-year-old Dogon object that clearly indicated Sirius and its companion stars.
Skeptics say that the object, a ceremonial mask, has never been carbon-dated. In an article called The Dogon Revisited, Bernard R. Ortiz de Montellano flatly questions Griaule's work regarding Dogon cosmology: In fact, the entire Dogon question may be futile theorizing, because Griaule's original data, on which this whole edifice is built, is very questionable. His methodology with its declared intent to redeem African thought, its formal interviews with a single informant through an interpreter, and the absence of texts in the Dogon language have been criticized for years.
Other anthropologists who have studied the Dogon in more recent years, have been unable to find evidence of the knowledge of the Sirius system that was related to Griaule. One of these, a Belgian anthropologist named Walter van Beek, is particularly critical of Griaule, according to de Montellano: Van Beek points out that Griaule's data was developed in long intense sessions with one primary informant, Ambara. In this process, Griaule probably reinterpreted statements from his informant in the light of his own knowledge about Sirius and its heavy companion, which had been much in the news at the time he began his field work. In turn, the Dogon, because Griaule was extremely respected and liked and because the Dogon culture places enormous importance on consensus and in avoiding contradictions, would have accepted his analysis as if it were theirs.
Oddly, in Griaule's first paper on the subject, Un Systeme Soudanais de Sirius, he names his "informants", their tribes, and their languages. There are four of them, and none is named "Ambara." In another place Griaule names his Dogon instructor as Ogotemmeli of Lower Ogol, who claimed authority from the Dogon priests of Sanga. In fact, one of Griaule's papers is called Conversations with Ogotemmeli. One wonders whether the problem here is that the Dogon elders simply do not trust Van Beek and the later anthropologists such as Boujou and Lane as much as they trusted Griaule. One also wonders whether de Montellano's criticisms of Griaule aren't unnecessarily harsh.
Temple's The Sirius Mystery has been the object of much criticism as well. Nowhere in his book does he cite an assertion by Griaule that the Nommo were extraterrestrials who visited the Dogon. Rather, the Nommo are a part of the Dogon creation myth. Nor does Griaule directly state that the Dogon obtained their knowledge of the Sirius system from extraterrestrials. Yet Temple somehow manages to conclude these things from Griaule's data. Temple also takes Benest and Duvent's theory of a small red dwarf in the Sirius system (Sirius C), which is given as a possible explanation for a perturbation, and turns it into confirmation. That's a bit premature.
However one chooses to believe, the question of how the Dogon came by their knowledge of Sirius B and possibly of Sirius C is far from settled.