Would you choose to have a part of your body live on after you died? How might your choice affect your relatives or even your entire community?
The first is a question people face when they donate organs. The second comes up when they participate in genetic research. This is because DNA from even a single individual can reveal a web of relationships, even helping law enforcement to solve crimes committed by distant relatives they have never met. And as you continue to go back in time, the web becomes ever more tangled.