At the end, he tangentially mentions that we only know about this calendar because it is described in one of the three surviving books of their culture, out of thousands[1]
> "Just imagine our civilization reduced to three books, just the particular ones left by accident, which ones... So eh.. anyway, I get off the subject..."
The genocide of Native Americans is of course horrible by itself, but somehow this remark made me realize what "genocide" means beyond people being killed en masse. So much culture and knowledge was lost.