Good luck finding an answer on that one, as the whole God-man thing is just “speculation”.
From what discussions I have had, there are at least two schools of thought:
1.) God, the Father, was the messiah/Christ, for his “world”, and therefore would have been sinless (ostensably) during that sequence. However this is generally refuted, do to the idea that our Christ’s Atonement is the one and only, eternal, sacrifice which would have been for our world, all the worlds before, and all the worlds after. Those that likethis version are the ones that really go for the endless, eternal progression (as, in order for us to alss become our own Heavenly Father of our own world, we would likewise have to become our own christs/messiahs). The big scriptural reason for this view is when Christ claimed that he did nothing that he did not see the Father do (meaning, he atoned for his world as well). In this scenario, then When God’s Grand father was running the show, then he lived a mortal life like ours, ie full of sin, and it was not until the following “generation” that he would have lead his sinless/messianic life.
2.) (the more naive view, IMHO): As Jesus’ atonement was a singularity, and cannot be repeated, then should we attain exaltation at the judgement, then we (with our spouse(s)) would then get to, rather quickly in the eternal sceme of things, get to be our own Heavenly Fathers & Mothers for our own “generation” of worlds. In this scenario, as we were not sinless prior to ascendance, then drawing the scenario back one “generation”, one could easily see how Heavenly Father would in nowise need to have been sinless during his own mortal incarnation.
Now, as a point, both views take seriously the idea that the progression from one state of being to another theoretically takes place over the course of eons, and so is not so closely structured as I presented, thus is either scenario, God (or us for that matter) can have lived millions of mortal lives on millions of worlds. Why? because the Doctrine promises multiple people each world will attain this “glory”. Even if only .001% of mormons on our world alone attained this (as is promised by the Church if they fulfill their temple obligations), then even if the world was over tomorrow, then we would have produced over 1,000 new gods!
Keep in mind that, according to the D&C (actual scripture, not just the “speculative” Journal of Discourses, or King Follet Discourse) each of us is in actually an uncreated “Intelligence” that existed from the beginning, not a being that was either created by god (they preferr the term “organized”), nor can be destroyed, nor a being that is created in the womb.
Ironically, this scriptural doctrine seems to dis-prove the mormon idea that we each will spawn our own worlds, to be populated by our own “spiritchildren”; or indeed that we are the literal born children of God, as is also commonly asserted by missionaries.
In fin; the great difficulty in researching mormon stuff like this is, they use familliar terms, that do not have the familliar meanings (for a concrete example, Heavenly Father to most Christians means our Creator (made-not begotton), but to a mormon it means our literal spiritual father (begotton of some nameless spirit mother, not made); and that if the belief can’t be explained away, then it is simply labled “speculation”. Someone needs to summon up the ghost of (the prophet, who while not “infallible”, cannot lead the church astray as it is not part of the “plan”-see the Official Declarations regarding polygamy and the canonized explanitory notes) BY, and ask him if the Adam=God=Michael “theory” was just “speculation” .
Sorry, I may have answered more than you were wanting.
Oh, and it doesn’t say what world God was a mortal on, but he currently resides on a planet orbiting a star called Kolob, whose daily rotation is equal to 1,000 of our years. See either the Book of Abraham, or Moses, not sure anymore which (having tossed all my copies when I left the church).
