>We believe this movement of the stars can help to explain two puzzles: the similarity of Greek and Aboriginal stories about these stars, and the fact so many cultures call the cluster “seven sisters” even though we only see six stars today.
They only use that as an explanation for one of those two puzzles, and then by taking that explanation as a given, they formulate a second hypothesis for the other puzzle. That is, they posit the change in appearance of the star cluster as an explanation for why they story/myth has a hidden/lost seventh sister, and then use the timeline of that explanation to posit that, if this first explanation is true, then the commonality of the myth might be due to it dating from a common origin from when the star cluster looked like it had seven stars. But the first hypothesis being true doesn't imply the second hypothesis is true, because there are alternative explanations; e.g. that similar myths about the same changing star cluster were developed independently by different cultures, perhaps due to some common trends in human thinking and cultural conventions(which may themselves inherit from some prehistoric time, even if the myth doesn't).
Its an important distinction because claiming their observation about the stars explains two mysteries without recognizing this weak chaining of those explanations over-estimates the explanatory power of the hypothesis.
They only use that as an explanation for one of those two puzzles, and then by taking that explanation as a given, they formulate a second hypothesis for the other puzzle. That is, they posit the change in appearance of the star cluster as an explanation for why they story/myth has a hidden/lost seventh sister, and then use the timeline of that explanation to posit that, if this first explanation is true, then the commonality of the myth might be due to it dating from a common origin from when the star cluster looked like it had seven stars. But the first hypothesis being true doesn't imply the second hypothesis is true, because there are alternative explanations; e.g. that similar myths about the same changing star cluster were developed independently by different cultures, perhaps due to some common trends in human thinking and cultural conventions(which may themselves inherit from some prehistoric time, even if the myth doesn't).
Its an important distinction because claiming their observation about the stars explains two mysteries without recognizing this weak chaining of those explanations over-estimates the explanatory power of the hypothesis.