YDNA R and the split between R1b and R1a
The R1b and R1a haplogroups are both subclades of the larger R haplogroup, which is part of the Y-DNA lineage. The split between R1a and R1b is estimated to have occurred around 20,000 to 25,000 years ago, during the Upper Paleolithic period.
Y-DNA haplogroup R is believed to have appeared approximately 25,000 to 30,000 years ago.
This number seems to be 25 or 30 years per generation. It seems to indicate 1000 generations ago. But the real number,which matches actual historical data, is 23 years per generation. Therefore this would be c 23kya. This makes the first estimate even more recent - about 800 to 833 generations ago.
23 x 800 = 18.4kya.
Considering the absolute rubbish linked to OOA, take this with extra caution. I do not trust their ''science'' ..it is fiction in most cases.
The ''birth of ADAM'' matches 23 years x 100 generations ago (the so called mtDNA bottlemeck). That was when sub Saharan DNA entered EGYPT (and it indicates its total collapse).
Anno Mundi 1 matches 250x23 = 5750 years ago (very close to the actual number). This is when sub Saharan DNA was detected in Europe and OUT OF Africa happened FOR THE FIRST TIME.