As an example of romance, Vero Wynne-Edwards, Warder Allee, and J. L. Brereton, among others, believed that predators would voluntarily restrain their breeding to avoid overpopulating their habitat and exhausting the prey population.
Obviously, selection on the level of the individual won't produce individual restraint in breeding. Individuals who reproduce unrestrainedly will, naturally, produce more offspring than individuals who restrain themselves.
But suppose that the species population was broken up into subpopulations, which were mostly isolated, and only occasionally interbred. Then, surely, subpopulations that restrained their breeding would be less likely to go extinct, and would send out more messengers, and create new colonies to reinhabit the territories of crashed populations.
The problem with this scenario wasn't that it was mathematically impossible. The problem was that it was possible but very difficult.
A decade after the controversy, a biologist had a fascinating idea. The mathematical conditions for group selection overcoming individual selection were too extreme to be found in Nature. Why not create them artificially, in the laboratory? Michael J. Wade proceeded to do just that, repeatedly selecting populations of insects for low numbers of adults per subpopulation. And what was the result? Did the insects restrain their breeding and live in quiet peace with enough food for all?
No; the adults adapted to cannibalize eggs and larvae, especially female larvae.
Of course selecting for small subpopulation sizes would not select for individuals who restrained their own breeding; it would select for individuals who ate other individuals' children. Especially the girls.
Once you have that experimental result in hand - and it's massively obvious in retrospect - then it suddenly becomes clear how the original group selectionists allowed romanticism, a human sense of aesthetics, to cloud their predictions of Nature.
How evolution ignores our fanciful wishes
A fascinating article by Eliezer Yudkowsky. Excerpts: