Population Bottlenecks and crisis wars
"Recently, Bret Weinstein, one of the most brilliant thinkers in Evolutionary Theory, introduced me to the fascinating notion of a “population bottleneck.” You see, for the most part, in an ordinary population under ordinary circumstances, you will have an average number of descendents and your descendents will have an average number of descendents and so on. Since this is broadly true of everyone else, the net result is that after ten generations, your genes show up in the population at roughly the same rate as they do right now. Your genes are treading water — but they aren’t really winning.
But sometimes something happens that changes the game. Perhaps some great disaster occurs, resulting in a die-off with few survivors. Or perhaps some new environment (like Australia or Madagascar) is discovered that only a few can manage to explore and exploit. In either case, the result is a population bottleneck. On one side of the bottleneck the ordinary population. On the other side, some new population — all of whom are descended from the precious few who managed to traverse the bottleneck.
These bottlenecks occur throughout evolutionary history. There is good evidence, for example, that two bottlenecks shaped much of modern human genetic diversity in just the past 50,000 years. And here is the point: if your genes happen to be among those that manage to traverse the bottleneck, they “win” at a level that is utterly impossible by nearly any other means.
Traversing a bottleneck is extremely risky. Accordingly, it makes little sense to venture a bottleneck under ordinary circumstances. But it is also extremely high reward and for the entirety of our evolutionary history up until now, population bottlenecks have been the great lottery system deciding the long term winners and losers.
This truth is coded deeply into our genes and its logic is crystal clear: if you think you see a bottleneck coming, and in particular if you think you see one before everyone else sees it, be the first through the bottleneck and then slam the door shut behind you." (https://medium.com/emergent-culture/and-fear-no-darkness-7079dc86d5f4)