2800 is the best guess. The Bronze Age was terminated with the destruction of 40 cities. Archaeologist says sampled 3 sites for chemical analysis and they tested positive for meteorite residue. On the other side of the Earth the Maori have legends of a time when burning stones fell from the sky and burned everything up. Carbon 14 dating places it concurrently. The meteor period lasted decades. Something about crossing a debris field and how close you are to the thicker portion.
Some splendid archives at
[link to abob.libs.uga.edu]

You want doom? This is it. It is real and it is cyclical.

Science magazine had an article a few years back about mitochondrial DNA mutation rate and the data extrapolates to 20,000 years ago there were less than 1000 child bearing females. I think that coincides with "Ragnarok" by Ignatius Donneley which documents the cometary strike of Noah's flood.