Who makes those claims? Ward Churchill? I don't hear anything like that from the indigenous groups I live with or any other I've come across. Funnily enough, it's usually the "educated" ones that largely abandoned their cultures making that claim. I've found that the oral histories are usually much more detailed and that stuff like "growing out of the ground" are used as interpretive symbolism more than anything.

But you did say across the world so it could be a group or individual that takes their oral history more literally than what I've come across.