Common descent is a conclusion based on the scientific theory of evolution that argues which of the following? a. all living organisms are descended from a single ancestral species are are thus related to each other. selected: b. all living things have descended, with changes from a series of separate ancestors. each of which has its own single point of origin. this answer is incorrect. c. living things have had common decent patters over the course of the last 4.6 billion years. d. humans and primates all share a single common ancestor, other living things hare another common ancestor separate from ours.