When Is Extinction Really Extinction?
We hear in the media almost daily about the loss of species and habitats around the world. Debates rage over the question of just how many species are disappearing annually or even daily. Whatever the number, virtually everyone agrees that extinctions are happening at a rate higher than in the recent and probably more distant past.
As with most people aware of this situation, I worry about what kind of world (if any) we will leave to future generations. As a paleontologist I have a further interest, as well. I study one of the allegedly greatest episodes of extinction from the dim, distant past of Earth's history--the demise of the dinosaurs. I say allegedly, because as will become apparent in this book there are many misperceptions of dinosaur extinction.
A very real problem in analyzing the fossil record is determining whether the disappearance of a fossil species from any given area is really an extinction or some other phenomenon requiring explanation. This might at first glance seem a nonproblem. Shouldn't any disappearance in the fossil record be taken as an extinction? In this chapter I will argue that a disappearance from the fossil record should not automatically be assumed an extinction. Such an assumption, moreover, can lead to severe misunderstandings of the fossil record.
A starting point for this examination is a definition of extinction. This might seem an odd and unnecessary endeavor, but as will become clear, extinction covers various concepts, depending upon