Another evolutionary bottleneck.
If groups as large as ones like the Amish are having difficulties because of (essentially) inbreeding, then how did all these evolutionary bottlenecks which allegedly reduced the population to a few thousand go on to produce healthy individuals?
Inbreeding is what produces the breeds of dogs that we have.
By breeding within families, canids are artificially selected for a narrow range of traits deemed desireable, such as a superior sense of smell, very short legs, digging ability, speed, water-loving, etc. Genes become concentrated.
Where some traits can't reasonably be selected for, we must have artifices such as ear-trimming and tail-docking.
Interbreeding concentrates genes that produce some populations of desireable traits (hybrid vigor), but also undesireable traits (diseases).
Inbreeding in humans (and canids) eventually polarizes the gene pool, producing both genius and cluelessness. In canids, those "losers" are euthenized: In humans (to put it bluntly), those "losers" are left out of the breeding stock.
Collectivist societies will attempt to select out traits to produce "desireable" populations.
Some canine diseases, like hip dysplasia aren't discovered in a timely manner, and continue in the breeding stock.
Throughout written history of certain ancient civilizations, one can view the effects of inbreeding because history is written by the successful "genius" aspects of a civilization.
While I'm not the one to ask about the Amish, I'd expect a certain number of the brighter progeny to be selected out. (Abandoning that faith to pursue material happiness, whilst the remainder are left to muddle through).
Inbreeding within ethnicities retains both positive attributes (genius) and negative attributes (certain diseases) which don't manifest themselves until after the carrier has already passed on those negative traits.
Another evolutionary bottleneck.
If groups as large as ones like the Amish are having difficulties because of (essentially) inbreeding, then how did all these evolutionary bottlenecks which allegedly reduced the population to a few thousand go on to produce healthy individuals?
Since I’ve been alive, almost half a century now, I’ve read and seen populations in Africa that are anything but healthy, because of some or all of the following:
war, pestilence, disease, poverty, natural disasters, not to mention inbreedindg and God only knows what else; teenage or even pre-teen girls hardly able to walk themselves, yet they manage to carry to term children that somehow live to be a few months old with swollen bellies, literally starving to death...by the sheer hundreds of millions for decade after decade.
As a whole to say there’s anything “healthy”, both individually and as a society, is a very cruel joke and yet it goes on and on since long before my time actually.