Population growth has been a concern for environmentalists, and other interest groups, for more than a century. But the anxiety over the loss of space, and resources, as a result of human growth and consumption, is not simple. We talk with Sam Evans-Brown, host of Outside/In , NHPR's podcast about the natural world and how we use it, about his two-part show on the history of the anxiety of overpopulation. Listen to the episodes of Outside/In on overpopulation here .