Archaeologists excavating a Neanderthal campsite found discarded gazelle teeth there whose coloration indicated that gazelles had been hunted throughout the year. The archaeologists concluded that the Neanderthals had inhabited the campsite year-round and thus were not nomadic. In contrast, the archaeologists cite a neighboring campsite of nomadic Cro-Magnons that contained teeth from gazelles all killed during the same season. Which one of the following, if true, most seriously weakens the archaeologists' reasoning? ['Cro-Magnons usually followed the migrations of the animals they hunted.', 'Cro-Magnons and Neanderthals sometimes exchanged tools.', 'Neanderthals saved gazelle teeth for use in religious rituals and later discarded them.', 'Gazelles inhabited the area around the campsites year-round.']