Cain and Abel

Cain and Abel were sons of Adam and Eve. Traditionally, and by implication in the book of Genesis, they were the first two men to be born (rather than created by God directly). Their story is that of the first murder in the Bible.

The first murder
Cain, the firstborn, grew crops, while Abel raised animals. One day they both decided to offer some of what they had to God, so Cain brought some of his crops and Abel brought the fat of some of the firstborn of his animals. God liked Abel's sacrifice but does not like Cain's (and admonishes Cain for being disappointed at this).

Cain, being jealous of Abel, then takes him out into the field and kills him. Later God stops by and asks where Abel is, to which Cain famously replies "Am I my brother's keeper?" God then recognizes that Abel is dead and says that Cain is cursed, so that crops will no longer grow for him and he will be driven to wander across the Earth. But Cain is very upset about this and says that anyone that finds him will kill him. So God puts a mark on him that shows that anyone who kills Cain will have vengeance taken upon him sevenfold.

Cain then goes off to found the city of Enoch with his wife, and has children and many other descendants, including Lamech.

Oddities and confusions
This story raises several confusing questions, including the following:


 * Why does God always seem to prefer animal sacrifices?
 * God apparently likes to just stop by and visit with Adam's family, and he is immediately involved in Cain's motivation for this murder. Why does God not step in and drive Cain away before he kills Abel (see the problem of evil)?
 * Who is Cain worried will kill him? Unless his immediate family wants vengeance, there doesn't seem to be anyone else to kill him.
 * God doesn't shy away from eye-for-an-eye justice, capital punishment, and even genocide in most of the Old Testament. Why does he not only allow Cain to live as a fugitive, but protects him from any form of vengeance using a special mark (especially since his very next acts in Genesis are to shorten the human lifespan and kill nearly every air-breathing creature in the world in a flood)?
 * Is Cain really a wandering fugitive if he gets to settle down, raise kids, and build a city? Does this make God's curse false?
 * Is Cain's wife a close relative or did she come from some other creation event so that Adam's descendants are not forced to engage in incest?

One of the many faults of Genesis is that it provides hundreds of questions like these, about which anyone can speculate endlessly. However, there is fundamentally no way whatsoever to answer these questions because the answers are simply not given in the Bible. And since there is no independent source or physical evidence to consult about these events (because they seem not to have really happened), the book must remain a source of confusing absurdities and wild speculation.