We do not know when the first alphabet was created. We have evidence of things written in alphabets at such and such a time, and for the time before that, we speculate, until we find still older artifacts of alphabetic writing. Same with writing itself, which is a couple of thousand years older than alphabetic writing -- we think, because we're guessing about the ages of both.
Writing is extremely helpful in knowing about historical subjects; in fact, the border between phehistorical and historical, for most practical purposes, is the time when writing begins. And so for example, what we know about what happened to Scythians and Germanic peoples over long periods of time mostly has to do with when they interacted with Greeks or Persians or Romans, because the Greeks and Persians and Roman wrote during those long periods of time and the Scythians and Germanic peoples didn't. Go to the first pages of a general volume of German history, and you'll have some mention of what Tacitus and some other Romans had to say about Germanic people, and not much more, until the Germanic people themselves began to write Latin in the 4th century. And so for another example, a great deal of what we might have known about Mayan history was destroyed by idiotic Christian priests in the 16th century, who systematically destroyed as much Mayan writing as they could, before less idiotic Christian priests stopped them.
Belief in Hell, in an unpleasant afterlife, seems to have been around among the people who produced the earliest writing we know, people living in Mesopotamia before 3000 BC. And that belief doesn't seem to have been new at that time. We haven't found any indication that some individual Mesopotamian of the time announced that there was a Hell to people who had never heard of such a thing. It may well be that the Egyptians and the Israelites and the Greeks and Romans all got their ideas of Hell directly or indirectly from these Mesopotamians. But where the Mesopotamians got the idea, and how long they or other people had the idea before the earliest writing we know of, nobody knows. We can guess if we like, but nobody knows.
So whenever someone talks to you about when and why Hell was invented, they're making stuff up. Nobody knows who invented Hell, or when, or where or why. I'm talking about New Atheists now, who often will say that Hell was invented in order to frighten people and control them, or that religion was invented in order to frighten people and control them.
We don't know that these things were consciously invented at all. That is, for all we know, the first religions could have been created by people who believed in them quite sincerely, as opposed to people who were consciously manipulating others. In fact, to people who study such things full time, for a living -- and that certainly isn't the same people telling you that religion and/or Hell was invented for such and such a reason -- the widespread impression is that people tended to believe in religions for a long long time before anyone -- anyone started to wonder whether or not actually were things such as gods, and whether or not the old legends made any sense.
Now of course, in very many times and places, religion has proven to be very useful to ruling classes in holding on to their power. But just because a piece of nonsense helps a powerful person keep his position of power, that doesn't necessarily mean that the powerful person will see through the nonsense. The exact opposite has been asserted, for example by Robert Musil in his novel Der Mann ohne Eigenschaften, set in the Austro-Hungarian Empire before World War I. This was a very, very Catholic Empire, and Musil compared Catholic faith to a ski-lift, and the position of the ski-lift to a person's position in the Empire's society: a person at the bottom of the society, a poor person with no special privileges, was like a person in a ski-lift at the bottom of the ski run, on the ground. If he abandoned his Catholic faith, he lost nothing, just as a person stepping out of a ski lift on the ground risked no injury. But the higher a person's position in that society was, the more special privileges and opportunities he had which were directly connected to the Catholic Church. Renouncing his faith could be like jumping out of a ski lift which was very, very high up: quite scary. (I can't find the passage at the moment and I don't remember whether Musil compared pre-World-War-I Austrians who remained Catholic to people who never got out of a ski lift, but rode it back down to the bottom of the slope instead of skiing down.)
But that's still more conjecture, guessing that the privileged classes may in some cases be more sincerely religious than others, not less. The wise ones, here in the study of the history and prehistory of religion as in every other area of life, are very careful to separate their knowledge from their conjectures, and very very careful indeed never to give the impression that they know something when they don't.
Basically the exact opposite of a New Atheist talking about the origins of religion or Hell.