We might also note that if an addition is based upon a play in Hebrew language rather than Aramaic, it is likely unoriginal to the Targum. This does not necessarily means that it predates the Targum but that is often a reasonable assumption.

Finally, a very imprecise way, but often employed, for determining if an expansion is a later addition to an earlier Targum Urtext is to see if one can easily excerpt the expansion and still have the remaining Targum text make sense.

In the end, the best I think we can hope for are very early aggadic traditions and some sort of terminus ad quem and then use those as our “goal posts.” No date can be set with great certainty, and I have not even touched upon linguistic evidence (mostly because I think it is far too problematic for dating purposes, but these perhaps the simplest and maybe even best methods we can have for providing a “ball park” date of composition.