I remember that I once attended a seminar in which the speaker talked about the heart rate of different kinds of butterflies. Normally, the heart rate of the adult butterfly will be more complex than the heart rate when it is in the larvae form. However, there are some species that have complex heart rates even when they are in the larvae form, and there are others that have simple heart rates even when they are in butterfly form.
So if we are talking about the butterflies' heart, we can say that some species' heart are younger than their real age, while others are older than their real age. What is the name of this phenomenon?