The first cleaning

Someone, at some point in human history, was the first person to clean.  Someone was the first person to discover that water washes dirt off (probably when a dirty person went for a swim or fell into some water, or got water on themselves in the process of drinking water), and then someone was the first person to do that intentionally.

Which means someone was also the first person to come up with the idea that having no dirt on something was superior to having dirt on it.  (It's also possible that someone came up with this idea before they figured out that water washed dirt off, so they were just thinking "Man, this situation would be way better if there was no dirt on this thing!" but couldn't do anything about it)  Possibly the situation that led to this thought was something drastic, like their food fell into a pile of woolly mammoth poo, but it's also possible that, in a world where it had never before occurred to anyone that food would be better with no poo on it, no one would perceive that as a drastic situation.

Before it occurred to anyone to bathe, everyone must have smelled. Which means that they were probably immune to the fact that everyone smelled.  So imagine the first person to bathe thoroughly enough to wash off their smell. Could they then smell everyone else?  Did they think "OMG, everyone smells!" or did they think "Man, I'm never using water to get the dirt of me again, because doing that makes everyone smell"?  Or did the dirty people think the clean person smelled?

And let's talk about soap!  Soap is made of fat and lye. Lye is made by leaching ashes. Who on earth figured that out??  And imagine trying to explain to other people that really, this will eventually make stuff cleaner!  Did they have other soap-like things before that are now lost to history because they were less effective?

When people lived outdoors or in caves, their floor was, obviously, dirt (or whatever the surrounding environment was made of - the floors of igloos might have been made of snow, for example). And then in the first human-constructed shelters, the floor would have been made of dirt as well. So someone was the first person to think of building a floor out of wood or whatever, and then someone else was probably the first person to think of cleaning the dirt off that floor!

Also, someone was the first person to think of dusting. Once indoors had been invented and material possessions that are kept indoors over long periods of time had been invented (which is a whole other thing, isn't it? The first clutter!), stuff started getting dusty. (Why doesn't stuff that's outdoors get dusty?)  Someone was the first person to realize this was a problem, and to think of wiping stuff down to remove the dust.