Those were the days of the Mousterians who dined off woolly rhinoceros in Jersey.

Their stone implements, worked only on one face, are poor things by comparison with those of late St.Acheul days, though for a time degenerated forms of the latter seem to have remained in use.

What had happened?
We can only guess.

Probably something to do with the climate was at the bottom of this change for the worse.

Thus M.Rutot believes that during the ice-age each big freeze was followed by an equally big flood, preceding each fresh return of milder weather.