When in history have completely random samples of complete strangers been thrown together in life-or-death situations with no ability to communicate with each other and discuss their options?

Artificial studies like this have practically no bearing on actual behavior of real populations in real situations. Try the same study with a family, or a football team or the employees of a company or a military unit and then see what result you get. That's what reality is like. Real people don't live in randomly selected study groups, they live in communities.