What is the basis of the LDS teaching that the angel Michael became Adam? The answer to another question referenced a website that discusses the LDS endowment ceremony.  I was looking through the part about creation and was a bit surprised to see that the angel Michael actually takes on flesh and becomes Adam.  I had read that Brigham Young had once taught the so-called "Adam-God" theory, but I had never heard the "Adam-Michael" concept.


  JEHOVAH: Brethren and sisters, this is Michael, who helped form the earth. When he awakens from the sleep which we have caused to come upon him, he will be known as Adam and, having forgotten all, will have become as a little child.


So, my question is, "What specifically is the basis for the LDS teaching that Michael took on flesh and became Adam, the first man?"  Is this in the D &amp; C or anywhere else in particular?

With apologies to anyone who might be offended by this question... I understand that this is from the sacred endowment ceremony.  However, I am asking just about the doctrine itself, which happens to appear in the endowment ceremony.  I am assuming that the basis for the doctrine is not the ceremony itself, but comes from elsewhere.  That is what I am asking about.
Doctrine and Covenants 107:53-56


  53 Three years previous to the death of Adam, he called Seth, Enos,
  Cainan, Mahalaleel, Jared, Enoch, and Methuselah, who were all high
  priests, with the residue of his posterity who were righteous, into
  the valley of Adam-ondi-Ahman, and there bestowed upon them his last
  blessing.
  
  54 And the Lord appeared unto them, and they rose up and blessed
  Adam, and called him Michael, the prince, the archangel.
  
  55 And the Lord administered comfort unto Adam, and said unto him: I have set thee to be at the head; a multitude of nations shall come of thee, and thou art a prince over them forever.
  
  56 And Adam stood up in the midst of the congregation; and, notwithstanding he was bowed down with age, being full of the Holy Ghost, predicted whatsoever should befall his posterity unto the latest generation.