Furthest Right

How (some) inbreeding prevents destructive genetic diversity

Too much diversity = chaos, just like too much similarity = collapse.

One side of the political spectrum warns of one, the other of the other, and they don’t agree on what’s in the middle: the target of healthy breeding.

Inbreeding experiments involving sib mating in mice and Drosophila subobscura10, and successive bottlenecks in house flies11 have yielded some evidence consistent with the purging hypothesis. Here, we report results of an experiment demonstrating a prolonged time-course of recovery of mean fitness under self-fertilization of a naturally outcrossing plant, and also compare our results with expectations derived by computer calculations. Our results show that the genetic load present in an outcrossing population can be explained only with a high mutation rate to partially recessive deleterious alleles, and that inbreeding purges the population of mutant alleles.


And if we need to determine how much inbreeding is bad/good for humans:

In 2002, the anthropologist John H. Moore estimated that a population of 150–180 would allow normal reproduction for 60 to 80 generations — equivalent to 2000 years.

A much smaller initial population of as little as two female humans should be viable as long as human embryos are available from Earth. Use of a sperm bank from Earth also allows a smaller starting base with negligible inbreeding.

Researchers in conservation biology have tended to adopt the “50/500” rule of thumb initially advanced by Franklin and Soule. This rule says a short-term effective population size (Ne) of 50 is needed to prevent an unacceptable rate of inbreeding, while a long‐term Ne of 500 is required to maintain overall genetic variability. The Ne = 50 prescription corresponds to an inbreeding rate of 1% per generation, approximately half the maximum rate tolerated by domestic animal breeders. The Ne = 500 value attempts to balance the rate of gain in genetic variation due to mutation with the rate of loss due to genetic drift.


So 200 individuals breeding together produces no risk of inbreeding in the negative sense.

I guess “fear of inbreeding” can be checked off the list of objections to monoculturalism.

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