Etiologies

Critics of Scripture think Genesis contains etiological fables about the origin of the world, origin of life, origin of evil, and origin of death. 

One problem with that analysis is that it's an explanation which demands an explanation. Why would primitive people assume these things even had a point of origin? 

Put yourself in the moccasins of pre-Columbian Plains Indian before white missionaries made contact. All you have to go by is your experience or oral history. As far as you can tell, things have always been this way. The hawks, wolves, bears, bison, and rattlesnakes were always there. The prairies and sandstone buttes were always there. Indians existed for as long as anyone could remember. There was never a time when it wasn't just like this.

Why would they assume humans lost the chance at immortality? Why think human death is any different than animal death? Why think human suffering is not how things were supposed to be? 

The paradise lost motif isn't something you can derive from nature or human experience alone. 

Atheists keep assuring us that an infinite regress is perfectly coherent. So, from that viewpoint, why would primitive people imagine the need for origin myths in the first place? 

That's not to deny that some of them do in fact have such legends. Of course, if humans share a common history in Adam, then ancestral memories may account for that.