Jeffrey M. Bradshaw discusses ancient traditions of there being a Heavenly Adam who resembles an earthly Adam; theorizes this may explain some of Brigham's "Adam-God" comments.
Jeffrey M. Bradshaw, In God's Image and Likeness, 2 vols. (Salt Lake City: Eborn Books, 2014), 1:603-5
Excursus 30
Adam-God Theory and the Heavenly and Earthly Adam
Joseph Fielding McConkie cites several reasons why Adam can be seen as a type of his Heavenly Father: “All men have both Adam and God as their father. Each had a son renowned for righteousness and obedience (Christ and Abel), and each had a son who became Perdition (Lucifer and Cain). Both righteous sons were martyred by the shedding of blood at the hands of one called Perdition.”
Munoa cites sources giving support to the idea that Adam and God were not only identical in appearance, but “could be thought to share the same name, even Adam… Lacocque, when discussing how Gnostic speculations about ‘Man’ were anchored in the ‘older Israelite mentality,’ quotes Corpus Hermeticum 10:25 to illustrate how God could be understood as a man: ‘Man on earth is a mortal god; God in the heavens is an immortal man’.” Kabbalistic teachings concerning Adam Kadmon, comparable in some ways to the Anthropos of Gnosticism and Manichaeism, and Adam Kasia of Mandaeism are summarized by Cazenave:
Adam Kadmon [is the] “primordial man,” the archetype of the rest of humanity, and the one to whom we must look to rediscover spiritual truths about our own existence. In a temporal union of opposites, this Adam Kadmon is also the anthropos teleios, the final man toward whom we aspire, who will restore us to our glory and true condition.
Kent Brown cites Gnostic texts that describe “the nature or quality of the Father: he is called ‘the Man,’ ‘the Man of the Greatness,’ and ‘the Man of Truth’; also ‘Man,’ ‘First Man,’ and ‘Immortal Man’… Compare the titles ‘Man of Holiness’ and ‘Man of Counsel’ in Moses 6:57 and 7:35, the former name having been revealed to Adam, father of Seth.” Several cryptic statements by Brigham Young included references to what later became known as the “Adam-God” doctrine. As Bailey summarized:
President Brigham Young expressed the idea in 1852 and later years that Adam “is our Father and our God, and the only God with whom we have to do.” This remark has led some to conjecture that Brigham Young meant that Adam, who was on earth as our progenitor, was in reality God the Father. However, this interpretation has been officially rejected as incorrect. Later in the same speech Brigham Young clearly stated “that the earth was organized by three distinct characters, namely Elohim, Jehovah, and Michael.”
Consistent with some of Brigham Young’s teachings about Adam, early leaders of the Church who conjectured that Adam and Eve already had resurrected bodies when they were placed on earth were necessarily also of the opinion that they did not die in the ordinary sense, but rather were taken up directly to heaven. For example, Elder Heber C. Kimball said that: “Adam offered sacrifices and blessed his sons and then left them and went to heaven.”
Bailey continued:
Additional information about Brigham Young’s feelings on Adam can… be found in a conference speech given October 8, 1854, clarifying somewhat his earlier statement. It is there implied that through a process known as divine investiture, God delegates his power to his children. Adam was the first on earth to receive this authority, which includes all essential keys, titles, and dominions possessed by the Father. Thus, he had conferred upon him all things that were necessary for the accomplishment of his manifold responsibilities, and Adam is a name-title signifying that he is the first man and father of all.
Concerning Brigham Young’s use of the name “Adam” for two distinct individuals, we read:
It is argued that Brigham Young often distinguished between “Father Adam,” referring to the God of the Universe, and “Adam” or “our father Adam,” referring to Adam, the first mortal man. In many of Brigham Young’s controversial discourses, including the alleged “Adam-God” discourse, he attempted to make that distinction that there were two Adams. For example, on 28 December 1845 Brigham Young made an explicit reference to a “more ancient” Adam after whom Michael received the name Adam. “Adam’s name was more ancient than he was. It was the name of a man long before him, who enjoyed the Priesthood.” On 25 April 1855 Brigham Young spoke of Adam (Michael) as having lived for a long time with another Being whom Brigham Young explicitly calls “father Adam.” “Well, you see from this that when you and I have been with and lived with the Lord, we shall know his voice. If father Adam were to come into this house and you were to see him go back and forth, would you know him? No, you would [ever] mistrust it was him unless he revealed himself. But by the time that you have lived with him [father Adam] as long as Adam had before he came here, you will know him and recognize his footsteps, but reading the history will not teach you these things.”
Brigham Young did not find it necessary to elaborate beyond his previous statements, saying at one point: “Whether Adam is the personage that we should consider our heavenly Father, or not, is considerable of a mystery to a good many. I do not care of one moment how that is; it is no matter whether we are to consider Him our God, or whether His Father, or His Grandfather, for in either case we are of one species.” Observed Nibley: “Brigham Young recognized that many people were not prepared to understand the mysteries of God and godhood. ‘I could tell you much more about this,’ he said, speaking of the role of Adam, but checked himself, recognizing that the world would probably misinterpret his teaching.” Robinson has called the Adam-God doctrine a “classic example of an anomaly in the LDS tradition” that the Church has now “set aside”:
On occasion my colleagues and I at Brigham Young University have tried to figure out what Brigham Young might have actually said and what it might have meant, but the attempts have always failed. The reported statements simply do not compute—we cannot make sense out of them. This is not a matter of believing it or disbelieving it; we simply don’t know what “it” is. If Brigham Young were here we could ask him what he actually said and what he meant by it, but he is not here, and even expert students of his thought are left to wonder whether he was misquoted, whether he meant to say one thing and actually said another, whether he was somehow joking with or testing the Saints, or whether some vital element that would make sense out of the reports has been omitted.
Matthew B. Brown interprets Brigham Young’s teachings to be a misunderstanding about the nature of ancient Israelite enthronement rites and a misapplication of doctrines connected with exaltation. See Hale for another helpful perspective on Adam-God teachings.