Or maybe normal people today simply have expectations in keeping with modern technology? I'm sure modern Excel jockeys are fully capable of slogging through one of those assembly language manuals for dozens of hours. I think they could also calculate radicals to five significant figures using pen-and-paper algorithms, 19th-century style. Or till their own fields using oxen, 18th-century style. That these are all "unthinkable" today doesn't mean humans have suddenly become stupider and weaker (the opposite is true); it means they're immensely labor-consuming tasks which no longer serve a purpose, and to perform them would be an astonishing waste of effort.