Mandan myth of emergence

From: http://www.geocities.com/RainForest/Canopy/7979/indian/Mandanem.html

NOTE: As in the Navajo myth of the five worlds, emergence from an underground world is a theme in the myths of a number of North American peoples. Here is the myth of the and the Mandan Sioux and the Mojave Apache, who lived in the southwestern deserts not far from the Navajo, which comes to us from the Dakotas, thousands of miles from the home of the Mojave.*

What is the significance of such myths? Are they representative of successive stages of cultural development or consciousness? Are they evolutionary?

The earliest people lived under the ground near a beautiful lake. Once, a great grapevine grew above their home. A root from the grapevine poked down into the village of the underground people. A few of the most courageous then climbed the vine into the world above.

When these explorers returned, they reported that the world above was more beautiful than anything they had imagined, teeming with fish and game, full of light and beautiful flowers. Soon large numbers of people began climbing the vine into the new world above.

One day, however, an obese woman began to climb and the root broke, leaving half of the people underground, where they remain to this day. When we die, we rejoin our cousins under the earth.

*The Mojave Apache myth is virtually identical to the Mandan myth-with only one difference. In the Mojave version, a hummingbird is first sent to the world above as a guide.