Genesis 4:
""1. And Adam knew Eve his wife; and she conceived, and bare Cain, and said, I have gotten a man from the LORD. 2. And she again bare his brother Abel. And Abel was a keeper of sheep, but Cain was a tiller of the ground.""
From this I count 4 humans alive: Adam, Eve, Cain, and Abel.
""8. And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.""
Now there are 3 humans alive: Adam, Eve, and Cain.
""16. And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden. 17.
And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch.""
Where did Cain find a wife? Who was this unnamed woman? From whence (or who) did she come?
""And Adam knew his wife again; and she bare a son, and called his name Seth: For God, said she, hath appointed me another seed instead of Abel, whom Cain slew.""
Why isn't there a record of Cain's wife's birth? The Bible has a lot of begats and births in chapter 4 ... but nothing about Cain's wife.