Oak and other trees, felled several thousand years ago and used as trackway posts, in buildings, etc are the bread and butter of

* https://en.wikipedia.org/wiki/Dendroarchaeology

Art historians often look at the wood panels of paintings that are 400 years or more old.

You might enjoy reading the general overview: https://en.wikipedia.org/wiki/Dendrochronology

and, ahh, drilling deeper into the onion rings.

The real problem with tree rings here in this specific case is ... Ethiopia .. not a lot of big trees now, nor in the recent past when it was grasslands - but not really my field - there's likely to be very slow growing unassuming trees that are surprisingly old there .. and remains of older trees that have overlapping ring sequences.

But yes - geological / geophysical clues are likely more relevant here.