Some may infer from my prominent brow and grazed knuckles that I am somewhat less evolved than others but I assure you that it’s just that i’m a balding tradesman.
When I first saw this cache page I said "Ooook" and scratched myself somewhere, then after bashing the keyboard for a while I said to my other half “Oooook oook ooooook”. She said: “Yes, alright and we can go on to Dyrham Park afterwards." "Ok" (a short form of "Ook" - which means "Yes, Dear)
We set out and soon were standing (or squatting, in my case) under a tree. I slapped the trunk a few times and then swung myself up into the canopy. I had a quick scratch. I spotted something odd. I used my opposable digits to open it. I looked at it and thought "Ooook" (which is short for "Aaah, I see) and I swung down from the tree more enlightened than before. 
This pattern was repeated until I stood below the final tree. I said "Hmmmm". My arms were shorter than when we set out so my usual method of swinging myself up was not an option, but my prefrontal cortex was definitely bigger and more developed so I grabbed a nearby object to use as a tool and was soon up into the lower reaches of the majestic broadleaf. I clambered up and up and up and soon discovered the final treasure. I signed the log using my recently refined motor skills and alphabet recognition and returned to earth (attempting to do so as nonchalantly as possible so as not to worry my mate, sorry, wife). 
We then returned home (via the actually quite disappointing Dryham Park), sporting a fine sense of achievement. What a fantastic adventure. 
It's at this point in my personal evolution that I feel I can make a smart alec observation about Abanazar's post about a van der Graaf Generator and the fact that van der Graaf Generator are a prog rock band who's founding member lives just up the road from me. Although some may also point out that prog rock is an evolutionary step backwards. 
I must also admit that I had an unfair advantage on this cache as I've spent my sabbatical from Groundspeak caches climbing trees to place caches but you'll have to wait a while to see the fruits of my labours.
Anyway, thanks very much for another excellent cache. That final climb was really epic (although all climbs were managed without kit and without incident).