I've just tweeted a link on the evolution of folk tales on which I want to say a little more.
Once when watching Xena Warrior Princess (yes, I know) I was suddenly struck by the fact that the centaurs were also smiths. Now Xena had plotlines that were clearly plundered from Roman and Greek myth and history - I always suspected a rogue classicist in the script writing department - so I checked it out. Yes the Centaurs knew how to work iron, and then I suddenly realised that the centaur tale was about the invasion of a people who made iron tools and rode horses - and probably had its origins in the greek dark ages.
Such a story shouldn't surprise us. The Incas, we know, were initially confused by the Conquistadores.
So folk tales usually encompas something that someone thought important enough - either as history to be remembered - such as the earleir sections of the Anglo saxon chronicle - or as a way of imparting a warning or a truth in a way it would be remembered.
What the Telegraph article doesn't reveal is how the worked it out - certainly it would be interesting to do some cluster analysis to see how the variations were distributed through space (and time).