Oh darn, and here all along I thought it was Topsy. Topsy will be badly shaken to know this.
Oh, my condolences to Topsy! But ask Topsy which model of the "common ancestor" he prefers: (a) percolating muck that just gets lucky; or (b) the grey-eyed goddess of Reason.
My suspicion is the truth of the matter lies somewhere in between.
But having said that, still we have only a possible description of original events. Nowhere do we see any clue into the action at the "event" of the Beginning.
It's always so good to see you again, dear YHAOS! Thank you so much for writing.