One exciting way to track the evolution of our understanding of Proto-Indo-European is to look at the different versions of Schleicher's fable from different years. The more time we spend studying the language, the more 'precise' our reconstructions get, even though they might still be quite far off compared to what PIE actually looked like at any given point in its history. The majority of the reconstructions deal with the 'Classical' stage of PIE (many mainstream versions here), with some proposing versions of Scheicher's fable in Late PIE (somewhat questionable variations on the theme here).
Do we have enough information about the (hypothetical) ergative stage of PIE to, in theory, construct a simple, at least remotely plausible sentence in it?
If yes, how old would that be? What would that sentence look like? Is there any even older language that fits the criterion, e.g. maybe Proto-Afro-Asiatic?
If not, what is the oldest stage of PIE that we can feasibly say something in? When would that approximately be?