Jacob and Esau, the twin sons of Isaac (himself the son of Abraham), never got along. Even while they were in the womb Genesis informs us they quarreled (Gen. 25:22). But the most important thing, the Bible makes clear, is that they were twins: alike but very different, and that they, respectively, founded two nations: Jacob the Israelites, and Esau the Edomites. It’s clear that Jacob was, according to the text, a good dude. Esau not so much. He’s mean, warlike, and doesn’t get along with Jacob.
If this sounds familiar, it should be. Much of what we have examined thus far in Genesis has concerned lineages and the first people to found nations (Remember Lot?). The purpose of much this in the text, of course, is not spiritual (after all, what does Esau’s descendants have to do with anything?) and more etiological/historical.
That begs the question: who were the Edomites?
According to historical research, they weren’t too different from the Israelites. Their language/dialect was similar, in fact (according to extant samples found by archeologists), and had otherwise significant connections to the Israelites. And here’s where the twin things are common: this is basically just an etiological way (i.e., the reason for the story) of describing the differences between the Israelites and their fellows. The story is, in other words, “a projection of a later reality” (James Kugel, “How to Read the Bible,” p 143). The Edomites, at the time the Bible was being composed and edited, were mean, warlike, and didn’t get along with Israel.
Does this sound like somebody we know? This, and probably not some fragmentary historical record showing exactly what Esau, if he even existed, was like, is the reasons for Jacob and Esau being twins.