Final answer:
Present-day Australian Aborigines and Africans share a common ancient lineage from Africa but have distinct genetic identities and cultural customs due to their separate historical developments.
Step-by-step explanation:
The correct answer is a. They are both descended from an ancient proto-African society. This is based on the widely accepted theory that modern humans originated in Africa and later migrated across the globe. Genetic studies support this theory, revealing that human genomes tested outside of Africa show close ties to those in Africa with a genetic diversity that's specific to Africa and not found elsewhere. Additionally, while it is true that present-day Australian Aborigines and present-day Africans share the same ancient ancestry, they are not genetically identical, nor do they necessarily have many of the same cultural beliefs and customs, as these can vary widely due to their different historical developments and adaptations to their environments. Aboriginal people have a distinct history especially in their migration to Australia over 40,000 years ago and their unique cultural evolution since then.