Towards Civilization; One Step

Take an educated person, and put him in a featureless, soundless room
with uniform lighting( either it is lighted 24x7x365, or it is not ).
Sooner or later, the person will try to devise a way to keep track of
the passage of time. The easiest way to do so would be by tracking the
sleep-cycle.

Now we change the scenario a little; instead of a featureless room we
put him in a room with uniform features. The outcome will be similar,
if not identical.

Change the scenario a little more; make the features non-uniform and
endlessly varying. Allow sound to impinge on the senses at random.
Allow the light to vary at random. The outcome will still be similar.

Now assume the person to be you. You are placed on Earth at a random
location in a distant time when the concept of a static human
population did not exist even in thought. The endlessly varying
features are those of Nature. The endless variation in light is that
from the Sun, the Moon, and the Stars. The random noises are the
sounds of Nature, and her other creations. You realize, dimly, that
you are a little different from the rest around you; not provided with
boundless strength, or venom, or claws. That great meat-eating beast
does not always hunt you. Sometimes it hunts you stealthily, and
sometimes it merely growls at you without making a charge. The nest
from which the snake devoured eggs, sometimes has no eggs in it... and
sometimes there are eggs in the nest the very next day.

It's all very puzzling, except that you don't know the word yet.

Suddenly one day, you realize the answer. The behaviour of the beast
is similar to your own. When you hunt, you're stealthy too. When
you've eaten to your fill, you don't chase your prey; why spend energy
on another chase when, now that the cramps from hunger are finally
gone, you may finally sleep. This leads to another discovery – the
huge beast must stay full longer too, even though it's stomach,
appetite, and size are so much larger. Through a sequence of such
small discoveries communicated wordlessly across generations the
balance shifts.

The greatest such discovery is that there is a cycle to all events.
Looking around there is nothing to relate the cycles too. Everything
around you is bound to it's own cycle of transience. The light dawns
upon you; up there, high above you is a marker, the Moon. Each time
you sleep, the Moon shows a particular face.

In a major move towards order, and civilization; you have discovered a calendar,

and a means to mark time.