Genesis 3: 1: Now the serpent was more subtil than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?
The Serpent was an animal in an image similar to man whose seed could mix with humanity. The Serpent was the King of the beasts and was transformed into a snake after the Fall; Genesis 3: 14: And the LORD God said unto the serpent, Because thou hast done this, thou art cursed above all cattle, and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life:
Genesis 3: 6: And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
The original sin in the Garden of Eden was Eve having a sexual relationship with the Serpent; Proverbs 30: 20: Such is the way of an adulterous woman; she eateth, and wipeth her mouth, and saith, I have done no wickedness.
The Serpent was anointed by Satan; therefore the Serpent became the Tree of Knowledge that Eve “ate of” by her having an affair with the Serpent.
Adam ate of the Tree of Knowledge when he placed his seed inside his perverted bride (she became the Tree of Knowledge because she had eaten of the Tree of Knowledge) to save her from immediate death, for God could not kill Eve if Adam’s seed was inside her; if God killed her after she had received Adam’s seed, then God would be killing part of Himself because Adam was made in the image of God.
Genesis 4: 1 - 2: And Adam knew Eve his wife; and she conceived, and bare Cain, and said, I have gotten a man from the LORD. And she again bare his brother Abel. And Abel was a keeper of sheep, but Cain was a tiller of the ground.
Children were the result of the eating of the Tree of Knowledge; Cain was born by Eve’s union with the Serpent, whilst Abel was born by Eve’s union with Adam.
Cain was the product of Satan’s using the Serpent to seduce Eve, thus Cain was the son of the wicked one (1 John 3: 12: Not as Cain, who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother's righteous.).