It is worth investigating whether or not NDE phenomenon actually confers any survival benefit, and thus could have evolved as a survival mechanism. I had considered this myself before and saw it mentioned here earlier. Small Dog, I think his name was had made the comment that he feels it could have conferred some survival benefit as it would help "convince others to go out and put their life on the line for the betterment of the village." (Not a direct quote) This statement seems a real stretch for a number of reasons. 1) When this mechanism would have evolved, it would have been extraordinarily rare. Its rare now, it was even more rare a long time ago as rescuscitation techniques were completely non-existent along with other medical treatment. When people were deathly ill, they simply died, and they did not come back (sure there were rare exceptions). In a group of cavemen (say 200 of them), its extraordinarily unlikely that even one of them had an NDE at any point. But even if they did, the contention is that it will make the community "more brave" and that this would confer a benefit in spreading the gene pool. I can only assume he means brave in one of two senses 1) Bravery in war or 2) bravery in hunting large dangerous game. I think its unlikely that being more brave in war makes it more likely for you to spread your genes. Quite the contrary, it makes it more likely that you will be killed, and thus unable to reproduce. As far as hunting is concerned, you hunted regardless of your feelings on the matter, if you didnt, you starved. An NDE is not going to make any pre-historic individual any more likely to hunt.
But lets assume that bravery in war is good for spreading your genes, as is bravery in hunting. Ill just assume thats true for a second. Say we have a group of 200 cavemen. And lets say that (against the odds) one of them does have an NDE and tells his friends about it. 1) Nearly all men before the 18th century believed in the afterlife already regardless anyways, and its probably a very reasonable assumption to assume that cavemen did as well. What we are being asked to believe is this. A caveman nearly dies and comes back to life (much more unlikely then than it is now). He tells his tribe of the incident. Now we are supposed to believe that if this tribe of 200 goes up against another tribe of 200 men, that the tribe with the member who had an NDE is more likely to win because they are more brave due to this NDE? That suggestion sounds pretty silly. It is also worth noting that atheistic societies, think Communist Russia and Nazi Germany, had soldiers that were just as brave as any Allied soldier who may or may not have believed in God or the afterlife.
1) The incidence of NDE in an old tribal society wouldve been so low as to be entirely statistically insignificant. Although some NDEs surely happened and may have even shaped some religious views.
2) It is doubtful whether an individual experiencing an NDE would actually cause an appreciable sum increase in "group bravery."
3) Even if were to succeed in this, it doesnt follow that this "increased bravery" would make one any more likely to be successful in spreading his genes, actually the opposite may be true.
"lets not mess with the Eastern Homo-erectus, they have an individual who experienced an NDE."