Is it true that Eve committed adultery with the serpent? Where was Adam when this sin was committed? If the serpent was a beast why was Cain a proper human being?
What is the biblical position on this issue?
Questions like these wouldn't even come up if people read their Old Testaments. The circumstances of Eve's sin is recorded in Genesis 3.
"Now the serpent was more cunning than any beast of the field which the LORD God had made. And he said to the woman, "Has God indeed said, 'You shall not eat of every tree of the garden'?"
And the woman said to the serpent, "We may eat the fruit of the trees of the garden; but of the fruit of the tree which is in the midst of the garden, God has said, 'You shall not eat it, nor shall you touch it, lest you die.'"
Then the serpent said to the woman, "You will not surely die. For God knows that in the day you eat of it your eyes will be opened, and you will be like God, knowing good and evil."
So when the woman saw that the tree was good for food, that it was pleasant to the eyes, and a tree desirable to make one wise, she took of its fruit and ate. She also gave to her husband with her, and he ate. Then the eyes of both of them were opened, and they knew that they were naked; and they sewed fig leaves together and made themselves coverings" (Genesis 3:1-7).
Eve's sin and Adam's sin was violating a simple command of God not to eat of the fruit of one tree in the garden (Genesis 2:16-17). I suppose people can't believe that violating such a simple command could have impacted the world to such an extent. Thus, they make up other events which they believe to be more horrific. However, disobedience is sin and what is disobeyed doesn't make that much difference. Sin brought death into the world (Romans 6:23).
You don't have to dress up the truth. The sadness in this story is that neither Adam or Eve had to sin. There was an abundant number of fruit trees in the garden that had to be ignored just to get to this one tree (Genesis 2:9). That Satan talked Eve into breaking this simple command shows how weak we are in resisting temptation and how responsible we are for giving into sin. The truth is much more powerful than the made-up story.
And besides, Cain was Adam's son, not the serpent's. "Now Adam knew Eve his wife, and she conceived and bore Cain, and said, 'I have acquired a man from the LORD'" (Genesis 4:1).
This nonsensical teaching has been around for a long while. It is found in the Gnostic writing: The Gospel of Philip, written about 350 A. D. Gnosticism was a system of false doctrine that revolved around the idea that there was hidden knowledge needed to be saved that only a few were privileged to know. This particular false teaching was picked up by the Christian Identity Movement to justify their hatred of non-Caucasian people. They want to claim that non-white skinned people descended from an illicit union of Eve and the serpent. The whole concept is lies being perpetuated from a foundation of lies.