Here's a question by a reader named Seldon:

"Do you have any references to support the idea that God the Father was once a man? Also how can you reconcile this idea with the Old Testament scriptures that only one God exists (as found in the book Of Isaiah) Finally do you think the Church teaches the existence of an infinite series of gods. thanks"

I'll break your query up into two parts:

Question 1: Can there be other Gods?

Answer 1: In answer to this question, Mormons usually refer to 1 Cor. 8:5-6, where Paul says there are "gods many, and lords many," but "to us" there is only "one God, the Father" and "one Lord, Jesus Christ." Mainstream Christians usually say this refers to false gods, but Paul clearly referred to those that are "called gods", as well as beings who "are" gods. Origen (ca. 250 A.D.) said that indeed, Christians regarded this passage as referring to real gods, specifically men who had been deified:

"Now it is possible that some may dislike what we have said representing the Father as the one true God, but admitting other beings besides the true God, who have become gods by having a share of God. They may fear that the glory of Him who surpasses all creation may be lowered to the level of those other beings called gods. We drew this distinction between Him and them that we showed God the Word to be to all the other gods the minister of their divinity.... As, then, there are many gods, but to us there is but one God the Father, and many Lords, but to us there is one Lord, Jesus Christ...." [Origen, Commentary on John 2:3, in ANF 10:323.]

Mormons expand this principle to include Gods who may have gone before the being who is the "one God" to us. In any case, it is clear that this does not negate the OT (and NT) teaching that there is "one God," because "to us" this is true.

Question 2: Did any early Christians teach that God was once a man, or that there could be a god above our God?

Answer 2: I've never found any statements to this effect in any early Christian literature. This can be explained in two ways:

1) This principle may not have been revealed to the early Church. It must be remembered that Joseph Smith preached that "things that have not been before revealed" would be known in this dispensation. [Smith, ed., Teachings of the Prophet Joseph Smith, p. 345.] In any case, we can find every other element of Joseph Smith's doctrine of God which leads up to this. I showed in the article you read that the earliest Christians believed in an anthropomorphic God who is "one" with the other members of the Godhead in the context of will and love, creation out of chaotic matter, pre-existent souls, and deification. It's just one more step to the conclusion that God was once a man, and may have a god above Him.

2) This principle was revealed to the apostles, but was lost shortly after they left the scene. I find this one most likely because during the second century the God of the Greek philosophers was rapidly replacing the anthropomorphic God of the earliest Christians. Consider the reaction Paul got when he preached the resurrection of Christ to the Greek intellectuals at Mars Hill in Athens - they laughed their heads off because the idea of a God who would have anything to do with the material world was absolutely crass to them. Accordingly, as Christians adopted a more Greek conception of God, the idea of God having once been a man would have been dropped quite quickly. I've found one piece of evidence from the writings of the early Fathers to indicate that this might have been the case. Irenaeus of Lyons (ca. 180 A.D.) said that Christians shouldn't argue about whether there is a God above God, because it would be speculation:

"The Father, therefore, has been declared by our Lord to excel with respect to knowledge; for this reason, that we, too, as long as we are connected with the scheme of things in this world, should leave perfect knowledge, and such questions [as have been mentioned], to God, and should not by any chance, while we seek to investigate the sublime nature of the Father, fall into the danger of starting the question whether there is another God above God." [Irenaeus, Against Heresies 2:27:8, in ANF 1:402.]

From this statement of Irenaeus, we may conclude that 1) there were some Christians who DID believe there was a God above God, and 2) the idea of it wasn't totally antithetical to Irenaeus' conception of God - he just didn't think it was proper to speculate about such things. This last point is important because it illustrates the fact that the concept of God radically changed over the first few Christian centuries. If you asked either the later fathers or modern mainstream Christians whether there could be a God above God, they would say, "NO!!!!" They would never EVER, say, "We shouldn't speculate about such things."

Hope this helps!

Barry

P.S. You asked whether the Church teaches that there is "an infinite series of Gods." I think you could definitely interpret it that way, but I believe the teachings in this area are a little vague, since they are on the "frontier" of our revealed knowledge.