انقراض های دسته جمعی و عواقب آنها

This book is not for the amateur interested in a general discussion of dinosaur extinctions. It’s a professional text, probably intended for the paleontologist or paleontology student. If you’re one of those whose avocation is along these lines, however, and you’re able to read and understand the professional journals on the subject, it’s full of information that you might find interesting and useful. If you’re someone whose notion of a “journal” is Discover Magazine, you’ll be bored to tears.This said, Wow! The topic of extinction is of course one of emotive interest to the general public, and of course because of this to the makers of TV documentaries and the authors of popular books on the subject. As Hallam and Wignall point out in Mass Extinctions and their Aftermath, popular interest in the extinction of the Cretaceous dinosaurs is way out of proportion to their importance as one of the world’s life forms and certainly to their representation in the faunal fossil record, so the proliferation of documentaries and books specific to the life form misrepresents the significance of their demise. They also make it seem as though the “problem” is all settled–conveniently by the most dramatic event possible. Unfortunately this focus also makes it seem as though nothing else of significance happened in the rest of geologic history, which is patently untrue, as the authors make abundantly clear. They’ve gone a long way toward correcting the deficit in the literature, with the obvious proviso that non-professionals read the book.For the professional paleontologist, much of general geologic information is probably known to you. If you’ve been long in the field, but behind in your reading, the book will give you an excellent coverage of “what’s new,” and what is, is a lot. Certainly anyone looking to write a paper on a specific topic in extinction will find Hallam and Wignall’s bibliography an excellent starting point for a literature search. The entries are comprehensive, global, and cover most theories. Just the thought of the amount of work involved in compiling this bibiliography, let alone sifting it for well executed research results, is exhausting to me. Presumably some of it was done by computer and some by student “slaves,” but it still represents a major effort on the part of the authors, and I think the book shows it.For the paleontology student, the book is a well conceived text. It describes the divisions of the various biologic eras in a finer detail than I’ve seen done in textbooks in the past. Most importantly, it doesn’t just leave a term like “Maastrichtian”–my favorite–hanging out there in limbo. The authors provide it with a proper nitch among its brethren, identifying “upper, lower, and middle” what-have-you as its temporal location. Although it is not discussed in the text, the graphs and charts make it clear that the stages are derived from “type sites,” and many of the zones by specific “type fossils.” The method of choosing these sites is made clear by discussion of individual locations and their data, as is the ability to change the location of THE site as needed. The authors also show clearly in these charts where globally derived and ocean-terrestrial zones are believed to overlap so that causation can be discussed. That’s a lot of information for a student, information not often easily found in other texts but very important in understanding the literature. This is probably one of the few books on paleontology I’ve read where the charts and graphs are truly an integral part of the learning process and definitely NOT to be neglected by the student. Also for the student–and the interested general reader–the extinction literature is very well presented. The authors provide a very comprehensive discussion of events during each episode of proposed or possible extinction, referring to the pertinent literature world wide. This is significant, because to confirm a “massive” extinction requires world wide research. Events in narrow segments of the globe can always have been “local.” The water column is presented from top to bottom, including information about in-fauna, which makes the discussions about causation of extinction very clear for the reader. It offers the student a window on the thought processes of research in extinction, on insights from technology, and on the causes of disagreement. One of the most significant, though passive, instructions the student receives by reading this text is the very objective, balance, and neutral approach to assessing the work of others–with one exception early in the book. The various differing views, even of the authors, are presented in a clear manner with the authors’ “take” on things generally reserved for the end of the section. Their point of view is documented and discussed, and where they have nothing more to add than the rest of their colleagues, they say so plainly. At no time in the book is the student imposed upon with a biased, one-sided view of the knowledge of the field. Can’t ask for more than that. Research methods are also presented. In particular Hallam and Wignall note that the extinction scientists can’t make blind assumptions about data set. In particular they discusse some of the critics of Sepkowski and Raup’s theories and data. Authors appealed to findings of two specific faunal types, namely fish and echinoderms, but failed to notice that the particular choice of these animals distorted their own results by virtue of the resistance to extinction in the former case and poor representation in the geological record in the second case. Issues like the effect of differential preservation are not always obvious unless the reader does research of a similar kind himself and then, quite obviously, not always then. Certainly the student planning a research project for a degree program would be wise to read the first few chapters of the book to see what pitfalls they need to avoid. In general the text covers the “Big Five” extinctions and discusses some of the smaller ones in as thorough a manner as is possible in the limited number of pages. It certainly gives the student a better comprehension of what constitutes a mass extinction, how such an event is represented in the faunal record, how the data available can be statistically manipulated to produce a clearer understanding of what was occurring at the time, and how all of this information can help identify possible causes for the phenomenon of mass extinction itself. In general a superb presentation of the field, but not really for the uninitiated.