I’m wondering if this disease or some others showed up back when J.Smith gave the go ahead for polygamy?
Was there inbreeding back then and if so how closely were they related?
questions questions questions!
Maybe yes, and maybe no.
The LDS Church at that time was much more diverse than this FLDS cult is. Latter-day Saints were coming from Canada, Britain, Wales and other parts of the U.S., gathering together and moving to Utah. So, the gene pool would have been much wider than the FLDS, which basically started with two families.
On the other hand, the percentage of LDS that practiced polygamy during the Brigham Young days was quite small. Perhaps only 10% of LDS men ever entered into polygamous marriages. That may have kept the polygamous gene pool a bit smaller—with only certain families engaging in plural marriages.
[And in the interest of full disclosure, yes, I am LDS. And yes, I am very glad we stopped doing the polygamy thing 120 years ago. One wife is more than enough for me.]