  In a population practicing consanguineous marriage, rare recessive lethal
alleles (RRLA) have higher chances of affecting phenotypes. As inbreeding
causes more homozygosity and subsequently more deaths, the loss of individuals
with RRLA decreases the frequency of these alleles. Although this phenomenon is
well studied in general, here some hitherto unstudied cases are presented. An
analytical formula for the RRLA frequency is presented for infinite monoecious
population practicing several different types of inbreeding. In finite diecious
populations, it is found that more severe inbreeding leads to quicker RRLA
losses, making the upcoming generations healthier. A population of size 10,000
practicing 30% half-sib marriages loses more than 95% of its RRLA in 100
generations; a population practicing 30% cousin marriages loses about 75% of
its RRLA. Our findings also suggest that given enough resources to grow, a
small inbred population will be able to rebound while losing the RRLA.
