Douglas H. Erwin

Erwin provides us with an entertaining, informative and somewhat technical "whodunit" detective story, examining the "culprits" that may be responsible for the end-Permian mass extinction. The author examines the various geological and paleontological evidence for what happened, when and what effects this may have had; and then tries to piece together which of several hypotheses are the more likely culprites of the extinction and which are just effects.

The six major hypotheses that show some supporting data, and which Erwin focuses on, are as follows:

(1) an extraterrestrial impact of the some sort;
(2) extensive volcanism that produced the Siberian flood basalts (possibly triggered by an extraterrestrial impact), that radically changed the global climate and geochemistry;
(3) continental drift (plate tectonics) with the formation of Pangaea that caused an extensive reduction in biome types;
(4) extensive glaciation that caused a combination of global cooling and a drop in sea levels;
(5) a decrease in oxygen in shallow and deep seas due to one of several possible causes; and
(6) the "Murder on the Orient Express" hypothesis suggesting that a combination of several or all of the other already described events occurred nearly simultaneously

Erwin very helpfully comments on the strenght or weaknesses of the various hypotheses, and finally provides his conclusion based on the evidence. Erwin also takes a look at the recovery of organisms AFTER the extinction, which is something few authors do. However, the book was originally published in 2006, so some of this information is outdated or been superseededby additional information. Erwin does discuss the new findings in his 2015 preface, for an up-to-date examination of the end Pemian extinction. Despite new research into this topic, it seems like the author's "Murder on the Orient Express" hypotheses, where a variety of factors are responsible for the mass extinction, still seems to be valid.

Other useful books:

-When Life Nearly Died: The Greatest Mass Extinction of All Time by Michael J. Benton
-The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions by -Paul B. Wignall
-Life on a Young Planet: The First Three Billion Years of Evolution on Earth by Andrew H. Knoll
-The Goldilocks Planet: The Four Billion Year Story of Earth's Climate by Jan Zalasiewicz and Mark Williams
-The Ends of the World: Supervolcanoes, Lethal Oceans, and the Search for Past Apocalypses by Peter Brannen
-The Emerald Planet: How Plants Changed Earth's History by David Beerling
… (lisätietoja)

Douglas Erwin’s The Great Paleozoic Crisis compared to Peter Ward’s Gorgon.

Douglas H. Erwin’s The Great Paleozoic Crisis is a state-of-the-art exposition of knowledge about the Permo-Triassic transition. Unfortunately, it’s state-of-the-art for 1993, when it was published, and the art has progressed considerably since then. In particular, in 1993 it hadn’t been realized that terrestrial life suffered just as much as marine life; therefore most hypotheses about the PTr focused on wholly marine phenomena – regressions, loss of continental shelf area (because the continents were all merged into Pangaea), loss of ecological provinces (same reason), increasing oceanic salinity (as evaporate deposits from earlier in the Paleozoic are eroded away). Nevertheless, the book is still pretty good. Erwin discusses a lot of PTr evidence in great detail – carbon and sulfur isotope changes, global warming, global cooling, the emplacement of the Siberian flood basalts, impact. The details of PTr stratigraphy are also enlightening; although the extinction event was rapid by geological time standards, it clearly was not as instantaneous as the Cretaceous-Tertiary extinction event. While the KT boundary is always obvious when it exists, the PTr transition is not; different stratigraphers place it at different locations in the same formation. This is because stratigraphic units are often assigned based on their paleontology, and different biota disappear and appear at different times – i.e., there are a number of putative Triassic species that actually appear in the uppermost Permian, and a number of Permian species that linger into the lowermost Triassic. Thus if your stratigraphy is based on the disappearance of the last “Permian” species, the PTr boundary will be too high in the section, and if it’s based on the appearance of the first “Permian” species, the boundary will be too low. Pinning the boundary down requires detailed measurement and collection across the boundary, and that isn’t often done. (It doesn’t help that the best exposures of the PTr transition are in Greenland, Italy, Armenia, central Iran, Pakistan, Kashmir, and south China; with the exception of Italy these are all palaces where climate or geopolitics make paleontology difficult).

(This book goes well coupled with Michael Benton’s When Life Nearly Died, which is more up-to-date but less technical. Erwin has a more recent book, Extinction, but I haven’t read it yet.)

Peter Ward’s Gorgon is idiosyncratic; although nominally about the extinction event, it’s actually sort of a paleontological autobiography. We get a lot of detail about Ward’s relationships with colleagues, the hardships of doing paleontology in the middle of nowhere, and South African politics. Ward’s opinions on other paleontologists are enlightening; he does a lot of damning with faint praise, and I wasn’t surprised when he commented sadly that at least one other geologist refuses to do any work with him, to the point that she threatened to back out of an expedition to Antarctica when she heard Ward was also invited. That’s all well and good (and, to be fair, often fascinating), but that’s not what the book is supposed to be about. Information about the PTr appears sporadically amidst all the anecdotes, and it’s in chronological order – the way Ward experienced it – without synthesis. There is some useful geology – Ward explains one of the problems discussed by Erwin, the long-standing misconception that the PTr didn’t affect the terrestrial environmental – quite well. Vertebrate paleontologists are notorious for being biologists first and geologist second. Historically, a lot of vertebrate fossil collecting has been done by field parties that dig up bones and haul them back to the lab for detailed analysis. In many cases, the geological province of the specimens wasn’t described accurately enough – often just as “upper Permian” or “lower Triassic” without a measured section location or geographic coordinates. This lead to a lot of circular reasoning among the lab people identifying and describing the fossils – since “everybody knew” that the PTr didn’t affect the terrestrial environment, nobody ever questioned the assignment of a particular fossil collection site to the lower Triassic, when it was, in fact, upper Permian. This then worked backward; since subsequent collectors “knew” that many vertebrates straddled the Permo-Triassic boundary, nobody worried much about precisely identifying a collection locality. It’s also enlightening to note that since Erwin (above) “knew” that the PTr didn’t affect terrestrial environments, he didn’t even bother to mention the Karoo in South Africa as a PTr transition locality; since it was all terrestrial he apparently didn’t believe any useful stratigraphic information could come from it.

Although interesting enough as a paleontological gossip book, and with some information about actual paleontology, this definitely should not be your only book on the PTr.… (lisätietoja)

Deliberates the evidence for possible causes of the end Permian extinction and compares it to more well known extinction events. This book is actually quite interesting, now that I've had time to process it. While reading I felt bogged down with all the information - it is probably as well organized as it could be, but I struggled to piece everything together and not get too confused with the jumps around the globe and between different hypotheses. I particularly appreciated how after presenting a theory he discussed how accepted/tested the theory was - ie. mantle plumes aren't well understoond/observed (when my geology textbooks in school seemed to present them as documented facts!). Near the end, he briefly discusses whether or not the massive die-off determined which species survived long term and eventually led to the current diversification of life or if the ones hardest hit by the destructive event(s) had already been in decline. I wish this point would have been explored further, for I found it the most intriguing aspect of the topic.… (lisätietoja)

Some books are like a rising and breaking wave, as the author musters his information and comes to a climax. This book is more like a wave that breaks before it reaches shore, as Erwin examines what we know about the end of the Permian Age, and how this explains the rapid depletion of then-existing life forms. The problem for the reader expecting a nice, tidy explanation is that they will come away a bit disappointed, as Erwin remains unconvinced that there is a catastrophic event that explains this die-off, with the possible exception of massive volcanism in what is now Siberia creating a "greenhouse" scenario. The upside is that this is probably a better illustration of how the scientific endeavor plays out in real life.

Erwin also notes that he is actually rather more interested in the process of environmental renewal, but seemingly implies that these processes are much less well understood than the geology of disaster, a result that doesn't quite match the buildup one was given. The conclusion of the book is a jab at our current environmental situation and how there is hopefully still time to do something about the current mass extinction in process, and that will probably carry our own species away with it if we don't show a little more collective wisdom; the sooner one starts the more full the ark will be.… (lisätietoja)