I'm having trouble understanding this line of reasoning: > purely due to the founder effect, not an effect of inbreeding per se Genetic bottlenecks greatly am

I'm having trouble understanding this line of reasoning: > purely due to the founder effect, not an effect of inbreeding per se Genetic bottlenecks greatly amplify the effects of any genetic abnormalities for obvious reasons. It sounds like you assume inbreeding and genetic scarcity are two different things when they're not. Yes, the founders brought these genes into the population. That is the whole point when we're making observations based on the inbreeding which caused a higher incidence of symptoms as compared to the mainland human population - exactly because there is a high chance for recessive traits to be expressed. If you mean inbreeding does not necessarily lead to a higher mutation rate, you are correct. But that was not implied by the comment you're quoting.