The UPenn IE Tree (the stem)

[Max Dashu]

>The only node on that tree that represents a non-innovating language is
>marked PIE.  And this tree also posits a group of speakers who are always
>non-innovators, node after node.  And because they are not the innovators,
>they remain PIE.  Right down to the last node.  Unless of course they are the
>last node.

I doubt that any human language ever existed that has not innovated over time.