I don't know what evidence you'd want. The claim seems self-evidently true to me. You were able to find one wiki article on a curious case of a family who, unl

I don't know what evidence you'd want. The claim seems self-evidently true to me. You were able to find one wiki article on a curious case of a family who, unlike billions of other people, survived as individuals for less than 50 years in partial isolation. That's impressive, but it doesn't change the basic facts of human survival. Case in point, in the first paragraph of the link you provided about the Lykovs, the article says only one daughter yet survives (as of 1988, so they are probably all gone now). Minimum viable populations are partially about day to day survival and team work, but in the long term it's about genetic diversity which is critical for long-term population survival. Evidence: all of biology?