extinction: past as key to the present

Update TRENDS in Ecology and Evolution Vol.20 No.7 July 2005 365

Book Reviews

Extinction: past as key to the presentExtinctions in the History of Life edited by Paul D. Taylor. Cambridge University Press, 2005. US$70/£38.00 hbk (191 pages)

ISBN 0521842247

Nan Crystal Arens

Department of Geoscience, Hobart & William Smith Colleges, Geneva, NY 14456, USA

Extinctions in the History of Life is asvelte, unpretentious little volumethat might easily be overlooked onthe bookseller’s table. Its goal (tosynthesize the major findings ofextinction research for an under-graduate audience) is as modest asthe fading ammonite on the cover.However, editor Paul D. Taylor andan all-star cast of contributors have

transcended synthesis to weave a cautionary tale aboutthe modern biodiversity crisis.

Since the codification of the Big Five mass extinctionsby David Raup and the late Jack Sepkoski in 1982 [1],extinction has been the focus of some of the most intensestudy and bitter debate in the geological sciences. The twoor three meters of sediment surrounding the Cretaceous–Tertiary boundary (extinction no. 5, famed for snuffing outthe dinosaurs) has been more carefully scrutinized thanhas the rest of the Phanerozoic rock pile put together.Careers have been made and friendships broken over thepattern and process of dying. And it made wonderfultelevision. Scientists, windblown and dusty, traipsed thebadlands of the American west in search of clues. Cut to ananimation of frightened Triceratops, as an ominousmushroom cloud rose from the crater of doom. Or did thevolcanoes do it in India with the noxious gas? Lost amongthe partisan rancor is the reality that extinction researchhas produced innovative science, forcing its practitionersto pioneer novel techniques (e.g. stable isotopes in naturalabundance and numerical analysis of fossil assemblages),to look at data in new ways (e.g. rethinking the strati-graphic distribution of fossils), and to ask hard questionsabout traditionally held assumptions (e.g. catastrophesmight be important after all!). Enter Taylor andcolleagues.

Extinctions in the History of Life purposefully ignoresthe polarizations of the past two decades. Instead,contributors focus on what we have learned and how wehave learned it. In the opening chapter, Taylor elegantlydescribes the subtleties of the stratigraphic record, andhow it can mislead the unwary. David J. Bottjer uses thereefs of the Triassic as a case study of the destructivepower of long-term environmental degradation. TheTriassic extinction, being the least charismatic of the BigFive, has largely escaped popular notice and scientificpreconception, which enables Bottjer to make the

Corresponding author: Arens, N.C. (arens@hws.edu).Available online 28 March 2005

www.sciencedirect.com

point that, in spite of the attention of many great minds,there remains no unifying theory of mass extinction.Paul B. Wignall picks up the torch with a thorough andthoughtful review of the wide range of extinction mechan-isms. From asteroid impact to flood basalts, climaticwarming to climatic cooling, he outlines the evidenceand overstatement of each proposed extinction cause withenergy, objectivity and candor. David Jablonski closes thevolume by summarizing the biological consequences ofmass extinction. He notes that the rewriting of life’s rulesduring extinction events and the elimination of previouslydominant clades catalyzed evolutionary innovation amongsome, but not all, surviving lineages. The volume alsocontains original insight. Scott L. Wing asks whetherplants experience mass extinction, and notes the plantparadox: when looking at single localities or even regions,many plant species disappear at mass extinction horizons.However, global compilations of higher taxa, such as thatused by Sepkoski to recognize mass extinction in marineinvertebrates, show no intervals of elevated extinction inplants. Wing deduces that the environmental pertur-bations causing extinction in animals also eliminatedplant species en masse. However, whole plant clades wererarely extinguished during such events because thediversity of life forms among member species virtuallyensures that some will survive to radiate again.

Woven through the discussion of past extinctions is amessage for today. In the long term, mass extinctions arecreative events that can fundamentally transform andrenew ecosystems. Our own mammal lineage owes itsvariety not to inherent superiority, but to the dumb luckthat dominant dinosaurs perished in the terminalCretaceous extinction. Yet, although extinction happensin a geological instant, evolutionary recovery requirestens of millions of years. Thus, the havoc that we wreak oncontemporary ecosystems cannot be repaired during thelifetimes of our great-great grandchildren, or, perhaps,even our species. Thus, the silent compendium of extinctlife reminds us that we will never again know the sheerdiversity of life that our ancestors revered.

References

1 Raup, D.M. and Sepkoski, J.J. (1982) Mass extinctions in the marinefossil record. Science 215, 1501–1503

0169-5347/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.tree.2005.03.010