It's a manipulation of another myth. In Hesiod's "Theogony" and "Works and days" are also listed the myths of the five ages and of Pandora. A very common interpretation is that the first decline of the humankind (age of gold to silver) has been manipulated by christianity as the flight from Eden (and thus Pandora opening the box as Eve committing the original sin).
This is badly resumed, but it's been years since I had to translate those kind of works. I suggest taking a quick read to some steps, some are really fascinating.
I like that book, by Hesiod, though I tend to think its message has been hijacked by the wrong people, the meaning I take form it is pretty different to a lot of the work ethicist conservatives.