Posted by:
Lot's Wife
(
)
Date: September 05, 2023 08:00PM
While I suspect that some pockets of Mormons in isolated areas may have suffered from inbreeding, the general numbers you cite are far larger than necessary to avoid such problems.
Throughout the vast majority of human history people routinely mated with their relatives. Recall that most hunter-gatherer clans numbered less than 200 individuals--the most that could be sustained in a manageable territory-and that the reproductive population would have been less than half of that. Moreover, any inter-community exchanges would have occurred with neighboring, and therefore probably related, groups. In such clans there would have been far fewer than "1,000 unrelated lines" and possibly as few as a dozen or less.
We also know that hominin populations have at various points in the geological record barely survived. Nearly a million years ago, for example, the total number of breeding humans fell to less than 1,300 individuals and stayed there for roughly 100,000 years.* The actual breeding groups would have been considerably smaller than 1,300 because, especially in environmentally precarious conditions, the upper limit on clan size must have been significantly below the normal range of close to 200.
So you end up with relatively isolated families/clans/tribes of perhaps 100-150 individuals, less than half of whom are reproductive--and that situation persists for thousands of generations. In most of those groups the number of distinct genetic "lines" would be close to unity within a few centuries. In short, while the notion of sleeping with one's cousin is unsettling, in human history it is probably more "normal" than the way we live today.
Where this gets interesting is the possibility that the near extinction may have driven the separation of the ancestors of homo sapiens sapiens on the one hand and of Denisovans/Neanderthals on the other. Because if you take that hypothetical population of 1,300 and divide it into two or more clusters of groups separated by geography or climate, the founder effect would become salient and the groups would genetically diverge. A bottleneck at 900,000 years ago would fit nicely with the genetic record of a separation between HSS and HD/HN around 750,000 years ago.
* Sources:
ETA: The original publication.
https://www.science.org/action/downloadSupplement?doi=10.1126%2Fscience.abq7487&file=science.abq7487_sm.pdfSecondary sources:
https://www.livescience.com/archaeology/humans-faced-a-close-call-with-extinction-nearly-a-million-years-agohttps://www.msn.com/en-gb/news/world/human-ancestors-were-near-extinction-some-900000-years-ago-says-study/ar-AA1gbbmmhttps://www.nytimes.com/2023/08/31/science/human-survival-bottleneck.htmlEdited 1 time(s). Last edit at 09/06/2023 02:00AM by Lot's Wife.