this correlates pretty well with an earlier post that puts all genentics on the y chromosome as coming from from about 60,000 years ago.
http://www.freerepublic.com/focus/f-news/1285491/posts
This also correlates with female mitochondria dna studies from a decade ago which date from about the same time.
the suggestion has been that there was a major collapse in the number of humans sometime in the 60,000-80,000 year range which would coincide with the shift in cave occupancy.
The Toba Super Volcano is credited with that population reduction 75,000 years ago.
"Their is substantial evidence to show that within the time of the super volcano Toba's eruption in the Indonesian Pacific, the world's population of homo sapiens decreased from over one hundred thousand to less than two thousand, basically because global temperatures dropped five degrees for many years. This was within the current interglacial and at its start."