I remember hearing or seeing an article that looked at the history of flint knapping. There are possibly more people today that can knap a flint than at any time in history, because there are a huge number that do it as a hobby. And almost every one of those has learnt by demonstration from somebody else who can do it.
And if you trace back who taught whom, sometime last century, one of the last Amerindian flint knappers taught a small bunch of hobbyists, who have been teaching others since. And that Amerindian had learnt from his master, and so on, in a master/student chain that stretched back hundreds of thousands of years.