Eqyptian
        sib-sib mating
Sib - Sib Marriages in the Egyptian Dynasties

    Full sibs have a relatedness r = 1/2, and their offspring have an inbreeding coefficient F = 1/4. This means they are identical by descent at one-quarter of their loci. If any of these loci involve recessive homozygotes that affect pre- or perinatal health
(especially, novel mutations to deleterious or lethal alleles), delays to time of offspring and mortality rates of such children will be higher then those from marriages between unrelated persons. The expectation of reduced health of inbred offspring of such marriages is called inbreeding depression.

    In most societies, the consequences of inbreeding depression are recognized and discouraged or prohibited by taboos against close marriages, sometimes including First Cousins. In others, including Egyptian dynasties [above] and Native Hawai'ian royal families, marriages between close relatives were encouraged as a means of preserving power.

    Homework: Identify the number and type of consanguineous marriages in the above pedigree. Recall the convention that consanguineous marriages are indicated by double lines.


Text material © 2024 by Steven M. Carr