Having read Marcus Aurelius extensively, he doesn't seem to expect a personal afterlife at all but rather as a dissolution back into one's constituent parts--material and spiritual--from which new life could arise. He writes repeatedly about the futility of worrying about one's place in history, because of the inevitability not only of one's own death but of the deaths of everyone who could have possibly cared about or remembered one's accomplishments anyway. It's definitely worth a read; the Hays translation in particular is extremely approachable.
Judging by it, it looks like Aurelius expects some kind of after-life. And this is exactly what you suggest not to do "people invent religions that posit some sort of afterlife", so I'm not sure how this quotation from this early AD emperor can either confirm or deny your own statement.