Ever read about the Tasmanian Aborigines? They walked to Tasmania when the island was still a part of Australia. When the waters rose 10,000 years ago, they were cut off from the rest of humanity.....
Yes, was just trying to place a lower limit on the number of people that could make a word-of-mouth chain all the way back. If over the years life expectancy were something lower, say, 25, the number of people in the chain would have to be a larger number. With more retellings, the chance of getting more than one garbled version today of something that happened 30,000 years ago seems virtually certain.
Just like if 1200 people attended a memorable high school basketball game, each would notice different features of the game and 10 years later some story versions might not be recognizable even to others who were physically present in the bleachers at the time.
This is all pretty well obvious, but the small necessary size of the minimum human chain to prehistoric times was kind of interesting. I was actually thinking of eyewitnesses to the Crucifixion when I first started thinking this way. It's only 20 people. 20 could fit in an elevator, or be waiting for burgers at the local instameal.
Looked at this way, something that happened in Serbia 700 years ago, or in Arabia 1300 years ago, or that happened in America in 1776 could reasonably be viewed as nearly current events.