Okay, I said I had my thoughts on it. The world is not as rigid as my set scale, as you help point out. But could it be such a change as to drop my 20 generation ancestors from over a million to mere thousands? Must've been.
yes.
if you are truly interested in the topic, I'm sure you can find a reputable geneologist who can show you how often the crossings occur, and at what point they become essentially inevitable, using documented lineages of families rather than logical speculation.