You may choose speech, genocide, or of course the old favorite, the opposable thumb, but today I believe that the thing that distinguishes humanity from the rest of the animal kingdom is our ability to recognize different kinds of exhaustion. Beasts and babies don’t do this, because they don’t have to engage in fatigue management. They’re up until they’re down; when they get tired, they just go to sleep. But not long after we learn to walk, humans are expected to conform to schedules, and schedules lead to weariness diversification.
Why does this happen? Schedules mean expectations, which mean the loss of spontaneity. Six thousand years ago, Mem-oog of the Fertile Crescent couldn’t just curl up in a ball if he felt drowsy after lunch, because agriculture had just been invented and “after lunch” meant “time to spread manure.” Today, if I’m fuzz-brained after four consecutive student conferences, I can’t just nap on my desk, because I’ve got three more student conferences right afterwards. Plus I have to prepare the soil for future harvests: plan my lecture for next week, make sure my student database is up to date, confer with colleagues on ongoing projects, and work on the syllabus for the summer program. Someone else might have less gainful duties – enduring a departmental meeting, say, or drafting an indecipherable memo – but in the end, we all have to spread manure when we might rather be snoozing.
Humans with schedules quickly learn to accept that they must bear varying levels of weariness much of the time. Of course, having a schedule also means being able to assign specific times for rest. The invention of a calendar coincides with the invention of a Sabbath. But until we get to our break times, we carry our enervation with us. And when you spend that much time with fatigue, you learn to recognize its subtle varieties.
There’s the mental exasperation that comes from the repetition of dealing with the same task, complaint, or error over and over again. Then there’s the deeper fatigue that feels like brain cells shorting out when we’re required to really concentrate on novel or difficult problems over a long period of time. Communicating face-to-face with people can be particularly prostrating for introverts, but even extroverts who thrive on such interaction can find themselves overwhelmed and tongue-tied after a full day of confabulation. There are spiritual depletions: you can feel the triumphant tiredness that washes over you when you finally complete a grueling but worthwhile endeavor and you finally allow yourself to feel the burnout; but then there’s also the soul-drained debilitation that comes from having to fend off repeated crises, the cumulative backlash of adrenalin spike after adrenalin spike. Even pure physical exhaustion can be parsed into different sorts; sometimes it is due to muscular overexertion, other times to illness or, probably most commonly, to simple lack of sleep.
Being able to recognize these various states of fatigue can be part of what helps us bear them. I know that the kind of weariness that I feel after four student appointments in a row is different from what I can expect from commenting on papers for a couple of hours, so I can welcome the transition from the former to the latter. The conversational part of me gets to take a break while my critical eye puts its nose to the grindstone. A little thought and perceptiveness about what is making us tired in the moment — and what we can expect to make us tired in the future — can help us to plan our schedules to maximize efficiency and minimize discomfort. But in the long run, it only works if you also make room for time for recuperation. Work is what makes leisure valuable, but leisure is what makes work sustainable.