Part 2/9:
The biological consequences of incestuous relationships are evident in species, including humans. Inbreeding increases the likelihood of harmful recessive genes being expressed. This leads to reduced biological fitness known as inbreeding depression which manifests in lower fertility rates, higher juvenile mortality, and greater susceptibility to diseases.
Notably, examples of inbreeding can be observed in isolated animal populations, like the infamous case of the "blue people" of Kentucky, a family with a genetic disorder caused by inter-family marriages. The implications of inbreeding stretch beyond mere genetics; they can threaten the survival of entire populations due to a lack of genetic diversity, as seen in the dwindling cheetah populations.