Shouldn't knowing the very first religion be more important?

Edit: I seem to have worded this post poorly, I do not mean that there was no religion before written religion, that's obvious. What I am talking about here is why hasn't more effort gone into the first WRITTEN religions and the history of them. I know there was religion before writing, that's just not what I'm talking about. I'm talking about the very first written religions, as those would be incredibly important to study thoroughly, I would think.

I have read that Hinduism is the very first (known/documented) religion. But I had also heard of Jainism, and I wasn't sure which was older, so I looked it up.

Nobody knows?? How is that even possible. People are very unsure of which came first, and apparently we'll never know?? I read through some very in depth, and interesting information comparing the two religions, still no clear answer. That just seems wild to me.

Wouldn't there be historians, philosophers, religious leaders and scientists who are incredibly interested in this?? Why haven't they found more information?? It just seems insane to me that in our day and age, with the technology and knowledge that we have, that nobody has figured this out yet. It's such an incredibly important part of history to know and study.