lpetrich

In 1902, British author Rudyard Kipling wrote a whimsical children's book about how camels got their humps and so forth -- "Just So Stories".

And it seems like the early parts of the Bible have several such stories.

The second creation story of Genesis seems like a "Just So Story" that explains:

Why snakes crawl on our bellies
Why we do not like to expose our sex organs

And although snakes may seem well-positioned to eat the "dust of the Earth", the authors of G2 do not seem to have observed snakes carefully enough to notice that they eat only small animals about the size of their mouths. At least the authors of the Exodus sticks-to-snakes story got it right -- Moses's and Aaron's stick-snakes ate those of the Egyptian magicians.

In the Noah's Flood story, God makes a rainbow as an assurance that he will never create another big flood.

The Tower of Babel story may explain some partially-built or eroded ziggurat in Babylon or nearby.
And also why people speak many different languages.

The story of Sodom and Gomorrah may have been inspired by various ruins of cities and salt deposits; those cities' names can be loosely interpreted as "Burntville" and "Rubbleheap", and Lot's wife got turned into a pillar of salt. Over the millennia, many Middle Eastern cities would be destroyed and rebuilt, and some would be abandoned and never rebuilt. So I'm sure that the writers of the Bible had seen some abandoned cities here and there.

There are lots of bones of extinct beasts in the eastern Mediterranean area, and these were sometimes interpreted as the remains of various heroes and monsters (Adrienne Mayor, The First Fossil Hunters). So could some fossil rhinos have inspired those stories of "giants"/"Nephilim" on the loose? (Genesis 6)

Moving to various customs, there is the interesting question of what pagan practices had been co-opted rather than abolished by giving them various "virtuous" associations. Thus, Passover may originally have been an agricultural festival that was co-opted by being associated with the Exodus events. And the Nehushtan, a snake-shaped brass rod in the Temple, may have been justified by that sticks-to-snakes trick mentioned earlier. But that did not stop it from ultimately being removed, presumably because it was too idolatrous.

There are also some put-downs, like the Exodus story of the golden calf being a put-down of the northern kingdom's taste for statues of bulls as religious symbols. If Moses's staff was bad, then those bulls were even worse, I suppose. Also, the Book of Leviticus tells us that Nadab and Abihu got zapped for burning some incorrect incense, and in 2 Samuel 6, Uzzah got zapped for unauthorized touching of the Ark of the Covenant as he tried to keep it from touching the ground.

Even the creation of the Universe is involved; in the G1 creation story, God observes the first seventh-day Sabbath in the history of the Universe.

And the stories of legendary ancestors in Genesis may have been justifications of the status of various peoples. God decided that Abraham was a very worthy follower, and the ancestors of the Twelve Tribes each get some land for their descendants. But various other peoples get put down by stories of unsavory origins.

The descendants of Ham, especially Canaan, get put down by the story of Ham having been a Peeping Tom when his father Noah got drunk and accidentally exposed himself. I've seen speculation that Ham had gone farther than ogle his father's sex organs, but I won't pursure the matter any further.

And the Ammonites and the Moabites got put down by the story that their ancestral mothers, Lot's daughters, had made their ancestral father, Lot, drunk so he could have sex with them and make them have children.

Robert M. Price mentions several other origin-myth examples in his Of Myth and Men; he even finds hints of backbiting among different factions of the ancient-Israelite priesthood.

(Edit: added "speaking many different languages" to Tower of Babel, and turned "making" into "burning" for Nadab and Abihu)