Sleeping through Change

I stumbled across something very intriguing a while ago. We all know the story of Rip Van Winkle who went to sleep under a tree and woke up 70 years later as an old man.

What's fascinating/strange is that apparently the same theme of "someone falling asleep for years together and waking up to a changed world" is there in so many cultures. I found 8 references to 8 different cultures with a similar story, in here - see under "Literary Forerunners" - http://en.wikipedia.org/wiki/Rip_Van_Winkle

What is it about this theme that people across so many races/countries/centuries thought about it and created stories based on it?

Would it have just travelled from one country to the other? Or was it just a coincidence?

Or did it originate from some primitive memory of something written into our genes when we made our way out of East Africa?

Or was there some disease which spread across the world where people fell asleep for long periods?!

Or something so obvious I missed it?  Would love to hear your ideas on this.

Literary Forerunners (see link above)

• "...The story is similar to the German folktale "Peter Klaus"[4] by J. C. C. Nachtigal, which is a shorter story set in a German village
• ...The story is also similar to the ancient Jewish story about Honi M'agel.......
• ...The story is also similar to a 3rd century AD Chinese tale of Ranka, as retold by Lionel Giles in A Gallery of Chinese Immortals, and an 8th-century Japanese tale, "Urashima Tarō".
• ...In Orkney there is a similar and ancient folklore tale linked to the Burial mound of Salt Knowe adjacent to the Ring of Brodgar.
• ...And in Ireland there is the story of Niamh and Oisin, which deals with a similar theme.
• ...Another story was by Diogenes Laertius, an Epicurean philosopher circa early half third century, in his book On the Lives, Opinions, and Sayings of Famous Philosophers.
• ...A similar story is told of the Seven Sleepers of Ephesus, Christian saints who fall asleep in a cave while avoiding Roman persecution and awake more than a century later to find that Christianity has become the official religion of the Empire."