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.
One question that comes up in verse 1 is about the use of and. Is and used in such a way as to indicate an event that follows the events mentioned before it in time or is it used to insert other, relevant information into the text that we are supposed to regard as giving context that was not important to the narrative that preceded it?
So, the question is, did Adam and Eve have sexual relations and children before they sinned against God? There are some Christian faith traditions that view sex as the thing that brought them down. Typically, these traditions have a very cold, Victorian era view of sex even between a husband and wife, more as a necessary duty than as a joy, a bonding between two people committed for life. It is to be a desire expressed discretely by the husband and a burden to be accepted by the wife. These faith traditions and cultural views would necessarily view the physical union of husband and wife talked about in 2:24 as more of a curse than the blessing which it was intended to be. I believe that clearly Adam and Eve had many children and the curse expressed in 3:16 was not a statement about which Eve would have been ignorant from lack of experience.
In any event, whether you believe there was no sexual union before the Fall or if you believe that and shows an insertion of information that was not relevant previously but revealed events already under way when Adam and Eve fell from grace here is the birth of Cain and Abel. Some commentators have said that as there is no conception mentioned between Cain and Abel, as in the repeating of Adam knew Eve his wife, that they were twins.
Notice, though, the Bible does make careful mention of twins.
Genesis 25:24 And when her days to be delivered were fulfilled, behold, there were twins in her womb.
Genesis 38:27 And it came to pass in the time of her travail, that, behold, twins were in her womb.
Do you not think that if Cain and Abel were twins that the Holy Spirit could have said it was so? Just considering the question the text raises.
Abel was a shepherd but Cain tilled the ground. Neither statement is declaring that one is more righteous an occupation than the other. Farmers are not cursed because Cain was a tiller of the ground. The curse on the ground comes from the curse on Adam. But what comes next will begin to divide humanity into two groups with regard to religious expression and has a profound effect on the history of the world.