Comment by RGamma

"His experiments have never been successfully replicated by other researchers, and wild colonies of rats don't seem to display any of the personality types he so vividly described. He rarely published in mainstream scientific journals, saying that his concerns were so pressing that he didn't have time to wait for peer review. It seems plausible that Calhoun was responsible for creating the conditions for population collapse. He only cleaned out Universe 25 every six to eight weeks; disease and parasitism could account for many of the phenomena he thought were due to mere proximity" - https://www.lrb.co.uk/the-paper/v47/n13/jon-day/the-beautifu... (from the Wikipedia page)