Philologos wrote:
Insufficient data as currently worded.
Do we take a particular document - for argument, the Torah - to be authoritative revelation and locate the first listed monotheist? [and if so would the first created human count?]
Do we take the available record of human history and select the earliest documented monotheist?
Do we include the possibility of theist aliens predating umans somewhere in the Kosmos?
Do we let belief in angels, dryads, ancestor spirits and the like undermine a person'de status as monotheist?
How do we handle trinities and other X-in-ones and avatars?
Would a serial polytheism [not quite like the Mormons, think Tammuz maybe] count as monotheism?
I think this answer is much better. I hope someone would like to give it a limit.
I do not think the question has an answer.