Tricky pronouns

The paragraph below, from a book, “Dark ages: the case for a science of human behavior by Lee C. McIntyre. is about the dilemma in the social sciences.

In this text can you try to figure out what the underlined pronouns represent?

Often in social scientific practice, even where evidence is used, it is not used in the correct way for adequate scientific testing. In much of social science, evidence is used only to affirm a particular theory ? to search for the positive instances that uphold it. But these are easy to find and lead to the familiar dilemma in the social sciences where we have two conflicting theories, each of which can claim positive empirical evidence in its support but which come to opposite conclusions. How should we decide between them?

these = the positive instances
which = two conflicting theories
it = each (of two conflicting theories)
which = "two conflicting theories"
them = ? (I cannot figure what it stands for)