Suppose you applied hamilton's logic to a situation in which one individual is past reproductive age. could there still be selection for an altruistic act?

Yes, there can still be a selection for an altruistic act by means of post-productive individual that benefits a young relative.

The older individual or the older person cannot be beneficiary because he or she cannot have offspring. But, there is still an exception, the older individual may perform the altruistic act that costs lower than expected for that individual has already reproduced.

what is the other part to the question

swahili is an extremely rich and complex civilization, a set of ethnic groups articulated by a language and a series of cultural elements that fuse the african traditions, islam and indian culture. this growth was largely a result of the indian ocean trading network that brought in not just man-made riches, but also religious ideas, specifically islam, which had a significant impact on the local culture. furthermore, the development of the swahili language gave a common cultural unity to the people.