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Extinction: Bad Genes or Bad Luck?

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David M. Raup does an extraordinary job in this fine work on the mysteries of extinction. Addressing not only the infamous K-T extinction event that wiped out the dinosaurs, pterosaurs, prehistoric marine reptiles, ammonites, and many less well known organims of the Mesozoic, he addresses other significant extinction events in earth's history, ranging from the Cambrian period all the way up to extinctions in recent centuries, such as the heath hen in the eastern United States. Raup is able to draw many interesting theories and conclusions by analyzing extinction as an event and process seperate from and beyond the details of the individual organisms. Too many works, at least popular works, dwell overmuch on the extinction of the dinosaurs and related archosaur fauna (and to a lesser extent the mammalian and avian megafauna at the end of the Pleistocene)and fail to draw overall conclusions about what extinction is, how it comes about, and what roles it plays in the history of life on earth. Though the details of particular organims that become extinct are important, Raup seeks to draw broader and more widely applicable conclusions, and in this he succeeds brilliantly.

Raup analyzes and addresses a variety of potential causes of extinction from biological (such as predation, epidemic disease, etc.) to physical (sea level rises and falls, volcanism, etc.) to fairly exotic (cosmic radiation, asteroid impact, etc.), as well of course interactions between various causes. He also discusses the importance of small population sizes playing a role in and of themselves in a species extinction, how small populations (using the heath hen as an example) are uniquely vulnerable to such factors as demographic stochasticity, extrinsic forces, social dysfunction, and so forth, all described in informative but very readable format. The debate over the role of small population size is particularly interesting in discussions of potential modern day extinctions, a probelm faced by modern day conservationists and environmentalists.

Weaving in discussions of probability, statistics, geology, astronomy, climate, and the overall history of life on earth, Raup does an excellent job on the subject of extinction. Any amateur paleontologist or indeed biologist, as well as those involved in conservation efforts, would be well served by this book.

Raup does a great job outlining many of the leading ideas regarding extinction theory. Ideas in the book are presented with examples that are easy to follow, and Raup points out possibilities without overburdening the reader with a heavy-handed dose of bias, leaving readers to make up their own minds about things. I particularly appreciated the range of ideas covered by the author regarding current thought about extinction. The book seemed a bit light for a scientific audience, but it is pitched well for the lay naturalist reader. I'm glad I read it.

This is a delightfully well written book on the phenomenon of extinction, from the background rates of species death to the massive die-offs of the KT and other major extinction events. The author approaches the subject from a statistical/probabilities standpoint, looking at extinction as a continuum which is characterised, as he notes, by "long periods of boredom interrupted occasionally by panic." He introduces the concept of Gambler's Ruin, which makes his thesis understandable even to the statistically challenged like myself. The sense of humor with which he injects his work makes a complex subject entirely enjoyable.

This book by David M. Raup, a biologist at the University of Chicago, of the Stephen Jay Gould genre, identifies everything about extinction that we thought was true but is not. The author's main thesis is that extinction is a mostly random event; due to catastrophes and bad luck, and not related to the process of evolution that is part and parcel of the Darwinian idea. The author believes that the most likely explanation for the major extinctions that we have had is not competition, nature, or physical causes, but meteorites of colossal energy that fell on the earth regularly some 18 million years ago and still threaten us today.

In the process of debunking everything that we have been taught about extinction the author comes to six conclusions that are of great explanatory value for all species, all companies, and all investment styles:

Species are temporary. Almost all species die out, and almost all lifetimes are very small relative to the age of the earth.
Species with small populations are easy to kill. This is a consequence of gambler's ruin, that if you let random events run for a long enough time you are bound to hit the zero point, unless the probability of success is inordinately high. This is something that all traders with fixed systems, and all companies with specialized technological innovations and unique niches should contemplate.
Widely spread species are harder to kill. Geographic diversity, and niche diversity are very important in precluding narrow events from causing a species' extinction.
It is much easier to kill a species if you get a substantial number with the first strike. The importance of not losing too much in one fell swoop is paramount in any field.
Extinction is most often caused by new stresses that the organism is not accustomed to. Long-lived species have usually developed mechanisms to cope with everything that has occurred to them in the past, so the thing they must fear the most is the meteor ... or the spacemen!
Mass extinctions require stresses that cut across all biological boundaries. In the market this would be such a thing as a big war or a global rise in interest rates.
There have been five major extinctions in the history of the earth. They are usually classified as Ordovician-Silurian, 440 million years before present, Late Devonian, 365 b.p., Permian-Triassic 250 b.p., End Triassic 200 b.p., and Cretaceous-Tertiary, 65 b.p., and a high percentage of species and genera were killed off in the years surrounding each of these markers. The author has developed some nice graphs to show what the likely number of species that died are, given the number of genera that were killed in each cataclysm.


There is an interesting but naive chapter in the book on the relation of extinction to industries. Raup argues that most of the companies around today were not in existence 50 years ago, and the cause of their disappearance, merger or bankruptcy corresponds to the causes of species disappearance or phyletic transformation. The author draws parallels between such things as that the total number of companies names was lower 50 years ago, just as biodiversity was less, and that certain industries wax and wane just as species do:

Above all, stock prices as well as the composition of the entire market, are virtually unpredictable from ... decade to decade. And so it it was with biological evolution in ... the most recent 500 million years.
There is an excellent chapter in this book on the history of life, some nice methods of graphing durations and the branching of species, and some good anecdotes about all the famous species like the trilobites and the dinosaurs that did disappear with a debunking of the common explanations.

The book focuses on an extremely important part of the process of life, and shows some interesting methods for sorting fact from fiction.

This thought provoking book covers details not discussed in many books about past life and past extinctions. Looking at the big picture of extinction, he provides insight to the nature of evolution, our past and possible futures. Using a skillful combination of specific data on individual mass die-offs and statistical examination of the entire history of life on this planet, he brings many difficult (or unpleasant) theories of extinction into focus. He analyzes many theories, from older standard views to the downright wacky, but eventually makes a strong case for celestial impacts as cause of many mass extinctions.

Raup's thesis (that die-offs occur because of large meteor strikes) is interesting because there is some support for it in the paleontological record, such as the infamous K-T extinction of the dinosaurs. His application of statistics to catastrophic die-offs and extinctions is a major facet of the book, but you don't really need to know much math to understand it, so don't let that put you off. He explains everything very well.

The most important concept in the book is the diagram where he shows the frequency of die-offs as a function of the diameter of the meteor. It's been several years since I read the book, but if I recall right, a meteor 100 miles in diameter is considered enough to basically wipe out all life. However, Raup points out that this sort of strike would only be expected to occur every 100 million years, or more. For smaller meteor strikes the damage goes down proportionally but the frequency of the strikes, of course, goes up. These smaller meteors account for smaller, but more frequent, die-offs that have occurred over geological time.

The greater number of smaller strikes and die-offs is the most interesting thing in the whole book, if Raup's interpretation of the evidence is correct. But another thing Raup points out is that we have become better at identifying meteor strikes that occurred millions of years ago. This has increased the total of strikes known and provided a larger sample for Raup to work from in deriving his interesting graph. Such a smaller strike wouldn't wipe out all life, but it could be enough to cause complete destruction to an area tens or hundreds of thousands of square miles in area. (For example, the state of Colorado is just under 270,000 square miles, which is also almost exactly the size of the country of New Zealand).

Also on this note, I recall back in the early 60's, the asteroid Eros, which is fairly thin but about 20 miles in diameter (essentially it's about the size and shape of Manhatten Island) passed within a million miles of earth. That's just a hair by astronomical standards, and that was within recent memory.

So maybe Raup is just possibly onto something?

In addition to Raup's idea that meteors account for periodic die-offs, his idea is interesting for another reason.

Back in the early 19th century, when geology and paleontology were becoming sciences, it used to be thought that sudden, catastrophic changes in the earth's geology were the main mechanisms by which the earth's surface was changed over time and transformed.

For example, there were the Vulcanists (no, they are not from Star Trek) who believed that diastrophic processes (i.e., vulcanism and other heat-generated processes) were responsible for transforming the earth's surface and atmosphere in geologic times.

Then there were the Neptunists, who held that great floods had transformed the earth's surface (such as in the case of the Noachian Deluge, in the Bible).

Then in the mid-1800's came Charles Lyell (who was also Darwin's geology professor), who documented gradual changes, such as those occurring as a result of erosion. Lyell's ideas become known as Uniformitarianism, which contrasted with the earlier theories of Catastrophism, of which Vulcanism and Neptunism are examples.

So Raup's idea is essentially a return to an earlier form of geological explanation, in that it lands him back in the Catastrophism camp.

Overall, a good book on the catastrophic theory of extinctions due to meteor strikes.

Non-fiction titles generally lend themselves to summaries a little bit more easily than non-fiction and I'd be hard pressed to beat the information the publishers have provided on the back cover. In "Extinction: Bad Luck or Bad Genes", David M Raup has provided a layman's overview and discussion of the theories, assumptions and difficulties associated with the new, emerging science of the study of species extinction. A relatively lightweight, easy-going read (as science titles go), Raup has ended with the easily anticipated bet-hedging conclusion that extinction is generally a combination of bad luck and bad genes. But he did go so far as to lean strongly in the direction of bad luck, suggesting that most species "die because they are subjected to biological or physical stress not anticipated in their prior evolution and because time is not available for Darwinian natural selection to help them adapt." He summarized his thoughts by providing six generalities that, while sounding simple on their face, are still founded in considerable research and careful thought:

1. Species are temporary
2. Species with very small populations are easy to kill
3. Widespread species are hard to kill
4. The extinction of widespread species is favored by a first strike
5. The extinction of widespread species is favored by stresses not normally experienced by the species
6. The simultaneous extinction of many species requires stresses that cut across ecological lines

He also concluded that "wanton extinction" - selective extinction where some kinds of organisms survive preferentially but NOT because they are better adapted to their normal environment - was the primary ingredient in producing the kinds of results we see in the fossil record. For my money, this was the most interesting statement in the entire book because it seemed so fundamentally counter-intuitive!

All very interesting stuff indeed for those of us that enjoy paleontology and the topic of dinosaurs, in particular. But sadly, Raup's popular science writing suffers by comparison to the likes of Simon Winchester, Jay Ingram or Simon Singh who seem blessed with the ability to write about esoteric scientific topics positively lifting them off the page and compelling the reader to turn pages ever more quickly. That said, I'm happy to recommend it as a good read for those that enjoy their science-based non-fiction.

Paul Weiss

Raup's book is fascinating. It's a scientific explanation of how mass extinction affects speciation, etc. Very interesting for those interested in evolutionary biology and the selection process. Extinction provides another twist that must be considered. Raup is not only a paleontologist, but a statistician. He does a wonderful job of explaining analysis techniques that are in fact quite complex.

Raup, very clearly delivers a powerful glimpse at extinction. He manages to put matters of beginnings and ends into perspective. The work is an intelligent and gripping one. I found it difficult to put down and find myself occasionally re-reading sections of it. It is one of those that if you are initiated you are glad someone is sharing... and if you are not, you're your concept of nature, and the immeasurable honor it is to exist at all, is expanded.

Raup, very clearly puts matters of extinction into perspective. His work is an intelligent and gripping one. I found it difficult to put down and find myself occasionally re-reading sections of it. It is one of those that if you are initiated you are glad someone is sharing... and if you are not, you're your concept of nature, and the immeasurable honor it is to exist at all, is expanded.