Question

Can you think of a biological reason why so many different cultures around the world converged on the idea that mating between close relatives should be discouraged (this started long before anyone knew about genetics)? Explain your answer.

Answer 1

Mating between genetically close relatives is called inbreeding. It greatly reduces the genetic variation and increases the homozygosity. If the inbreeding population has a disease allele which is recessive ( expressed only in homozygous condition) increase in homozygosity increases the occurrence of the disease in the population. So long before people knew genetics they would have observed the heritability of the disease in inbreeding population. and would also have noticed increased the occurrence of the disease in the inbreeding population. Which would have led them to conclude the factors responsible for the disease is carried from one generation to another remained in the family since there was no outside interference, They would have also observed that mating between genetically non related individuals decreased the occurrence of the disease. Which would have led them to finally conclude that that it is better to discourage mating between close relatives in order to reduce the occurrence of familial diseases so that their offsprings will have a better chance to survive and live disease free healthy life.