The crux with all of those "first calendars" (idk which one is meant here, but there are multiple who claim this) is that we don't even know if it's a calendar at all. I mean, if this professor's approach serves as an eve-opeher for some, we should retell it whenever possible, yet it doesn't reflect any of the questions we should ask ourselves when seeing 28 carvings in a bone. Assuming that htis can only be a calendar is just the hidden assumption that numbers 25 and up could not have played a role anywhere else, because ppl were to primitive for those numbers somehow.

Perhaps they tracked how many calves in herd they had, or how many horses they had or how many bows they needed to make or how many children there were in the village. Perhaps they wanted to go higher and track something completely different and only got to 28 before they abandoned their approach to whatever they were doing.