Looking at other animals, such as wolves, monkeys and wild dogs, we notice that they often form packs that cooperate in obtaining food and they protect the weaker members of the pack. There seems to be a limit to the size of the pack, perhaps because packs that are too large are too difficult to organize into an efficient unit. If that is the case with humans as well, the future looks bleak unless we conquer our hereditary instincts.
Inherited instincts are hard to overcome but most of us have been able to prevail over some of those instincts, which don’t suit our modern way of life, to a great extent, such as rape and killing, by our ability to reason rather than to rely on instincts. We, humans, might be successful eventually by realizing we are one tribe instead of fractionalizing into smaller groups.
It is an interesting topic and the above is a quick reaction to the question and I realize to have to do a lot more research and reading about this subject before a reasonable theory can be drawn. Sometimes I am overwhelmed, not only because of the amount of information, but also for verification of reliable sources of such data. The truth is very hard to find.