E. O. Guerrant claims that Latter-day Saints believe that "Adam is the Mormon God" and that Gods, angels, and men "are all of one species."
E. O. Guerrant, The Mormons (Richmond, VA: Presbyterian Committee of Publication, 1899), 6
DOCTRINE.
For doctrine, the Mormon Church rests on two pillars—Polytheism and Polygamy—twin relics of heathenism, many gods and many wives. Take these away, and it falls like the temple of Dagon.
Adam is the Mormon God, and all the rest of their gods were men, and became gods by practicing polygamy. They teach that "God, angels, and men are all of one species."