@First-light I like the experiment a lot and for a long time has never heard any good argument why shouldn't we take it seriously but not literally (except obvious intelligence differences).

Till this month this drawn my attention.

In Universe 25 (the most famous mouse experiment, 1968–1973), only the original eight mice (four pairs) were introduced at the start. No new mice were added at any point, even as numbers plummeted after the peak (~2,200) and reproduction failed. Calhoun allowed the decline to proceed fully to extinction to document the pathology.

In short, Calhoun never tested "immigration" as a fix in his documented utopias — the point was to show how internal social/cultural decay could become self-reinforcing and irreversible, even with abundant resources. His more optimistic side focused on proactive behavioral/cognitive engineering rather than adding fresh outsiders. Recent biographies and analyses (e.g., Lee Alan Dugatkin's book on Calhoun) emphasize this nuance: he saw potential human parallels but believed societal redesign (not just influx of new people) was key to avoiding similar fates.

But... Since the communication techenology development we are in one small-big container and there is Little outside of it.

So the biggest difference is, we are not inbreeding.