Final answer:
Endogamous societies like the Australian Aborigines experience decreased genetic diversity due to limited gene flow and admixture, leading to an increased frequency of rare alleles and potentially maladaptive genes.
Step-by-step explanation:
Australian aborigines being an endogamous society means that they marry and reproduce within their group. This often leads to decreased genetic diversity due to a lack of admixture or gene flow with other populations. In such societies, the effects of genetic drift can lead to an increase in the frequency of rare alleles, which may include maladaptive gene variants. Contrary to increasing diversity, it decreases over time compared to what would be observed in an exogamous society where there is interbreeding between different populations.
For example, disorders like Tay-Sachs disease have become more common in certain endogamous populations, like Ashkenazi Jews or French Canadians, due to this isolation. Therefore, the answer to the student's question is D: decreased genetic diversity due to a lack of admixture or gene flow with other populations.