Gary Fisher has let it be known that he considers himself the "father of mountain biking", because he was the first of the Marin County crew to put derailleurs and multiple gears on his clunker bike. The ability to gear down did make a huge difference, but he wasn't the first to do so.
In 1973,for instance, I was riding the trails on a geared bike, in Savannah, Tennessee. The bike in question was my sister's Sears Free Spirit 10-speed, with 27x1-1/8" tires, rather than a 1930s Schwinn with Stronglight touring components. But, I was "mountain biking" at least a couple of years before GF.
Of course, I totally destroyed the bike, riding off-road. But, that's beside the point.
Still, "Jon Grinder, the Father of Mountain Biking", has a certain ring to it.
Fisher's first company, with his partner Charlie Kelley, was called "MountainBikes". The term was co-opted by the industry, and became a generic word for the type of bike. So, if I had followed the same path as Gary, we might all be riding "hill grinder" bikes, instead of mountain bikes.
Just something to think about. If the physicists are right, with the whole "String Theory" thing, then there might well be a universe where that is the way it turned out.