This theory can serve as one model for the rise and fall of civilizations, and in this context leftism can be seen as just another “fall,” but it is not a recurrent pattern throughout history: our particular leftism is very specifically a reaction against Christianity. The most heinously consequential (from a material standpoint) philosophical effect off fighting against Christianity has been the perversion of the legal notion of personhood (a Christian concept), and therefore the erosion all of the social and legal constructs that have been built around that notion.
With regards to K-selection, though, I’m not sure I agree that civilization removes Darwinian selection entirely from a populace. Perhaps if you consider “leftist human rights” synonymous with “civilized,” but consider this: Britain’s crime rate in the early industrial period was alarmingly high but it fell dramatically by the first half of the twentieth century. Why? Because they had hanged most of the criminal elements and effectively removed that tendency from the British gene pool. (Mind you, since 1960 they’ve been doing a very fine job reintroducing it through Third World immigration, and in both Britain and Ireland social revolutions have exposed tendencies that in a more civilized context would never get as out of control as they are today. We have the same problem in France, as well: crime is spiking all over Western Europe and not just among immigrant-derived populations.)
My view (and it could be wrong, as it is just an impression) is that civilization begins as K-selected competitors organizing thing to work well together, and avoid unnecessary suffering. This somewhat eliminates the state of nature, which would generally result in guys like Rahm Emmanuel and Saul Alinsky getting their heads bashed in by K-selected Competitors, who are programmed to view them as the enemy.
Since that early civilization offers them protection, it eliminates the selective effect, to a small degree, and these r-selected individuals persist and reproduce. Since r-selected individuals are programmed to reproduce in quantity over quality, they reproduce faster than K-selected individuals. As time goes on, the frequency of their trait increases. As it does, the r-selected individuals affect the nature of their civilization, reducing the selective effect ever further, by making the society more Liberal/Anticompetitive. Welfare increases, cultural discriminations between right and wrong are attacked, and all manner of deviancy are either tolerated, or rewarded with government protection from assail. The successful K-selected individuals are portrayed as the enemies, due to their success, even though they are all that keeps the society running. Eventually, you have a society predominated by r-selected individuals on their front stoops, getting checks for nothing from the government, and still reproducing.
At that point, the incentive to produce diminishes, production diminishes, resources diminish, and a much more competitive environment ensues, which culls the dead wood by necessity.
I knew a woman who lived in the Depression as a child. She said it was crazy, with rail thin people coming to her family’s back door begging desperately for food – yet there was nothing anyone could do. And now, here we go again. I hate to sound cold, but you see that kind of thing in nature all the time. I think its silly to think we are different, or that our population can multiply absent the cold hard effects of Darwin forever.
That said, I should add that the problem with Christianity (from an r-selected individual’s perspective)is that it publicly supports K-selected drives, towards individual subservience to group for group competitions, responibility, careful childrearing, monogamy, loyalty, fairness, freedom, and decency.
These drives are the r-selected individual’s enemy. Christianity is just the means by which these urges are most obvioulsy pursued today, so Christianity is the target today.
I’m sure Roman Legionaries exhibited many of these drives, and they were reviled by the Anticompetitive Liberals of that day - Anticompetitors who increased taxes exorbinantly, expanded government beyond all bounds, offered generous welfare to every person who didn’t want to work, and who invited foreign barbarians into the government, to help lead their empire.
This theory obviously will not apply in every single case, but it will be a common theme to many.