Back in the day — yes, that day — when I thought I knew everything, or at least everything I needed to know at that moment, evolution and erosion seemed like fairly simple concepts. People evolved; the planet eroded; life proceeded apace. Simple. What don't you understand about that?
But someone, maybe Albert Einstein — though given the quaint, archaic, journalistic hangup about getting quotes right I'm not about to put my neck on the line and say it was him — said something like, "All major breakthroughs occur at the borders of known science when some smart cookie bridges the gap between what's known in two different disciplines." Of course, if, and I'm not stating it as a fact, but if it was Einstein who said something like that, he said it with something like an Austrian accent which is devilishly hard to get across in print. So use your imagination.
I wasn't thinking particularly about either earth science or human evolution the day I finally grasped both the profundity of that idea and the oversimplification of my understanding of the difference between erosion and evolution. I was eating lunch... hanging from a rope... dangling more feet above the ground than I ever want to fall... on a mountain. Eating lunch under those circumstances is more likely to lead to indigestion and numb legs than it is to deep thought but then, it was an extraordinary day.
A loud "crack," reminiscent of thunder and lightning occurring so close to where you are standing — or hanging, as the case may be — that there is no discernible gap between your perception of the two, broke my monotonous, cowlike grazing and I spun around in my sling to witness, for the first and only time in my life, massive erosion taking place in real time. A flake of granite the size of a small subdivision, having not moved for maybe a couple of million years, secure in its relationship with the other granite around it since before tectonic forces thrust it up off prehistoric seabed, chose that precise moment to give itself over to gravity.
It slid down the face of a well-climbed route on a snaggletooth spire of rock called, unimaginatively, The Spire, broke into innumerable smaller pieces when it met the rocky approach slope below, dislodged several times its bulk and weight in other rocks, trees and earth, and tumbled ass over teakettle down the draw for a couple of hundred yards. It all took 15 seconds, maybe 20 — time having, metaphorically, stood still — and with the billowing cloud of dust it threw up still swirling in the air, silence returned to the mountain. Silence punctuated only by an insignificant cry of, "Hey Zeus Christo!"