Can you have too many books on the same topic? Not four months after the publication of Cosmic Impact in February 2019, which I reviewed earlier this year, Scribner books published Fire in the Sky in June. The former book was written by astrophysicist Andrew May, while Gordon L. Dillow is a newspaper reporter and war correspondent, coming at the subject from a different angle. Despite touching on many of the same events and topics, he provides a wealth of new information in what is a thoroughly researched work of popular science. But first, let’s go to Arizona and turn back our clocks some 50,000 years.
Fire in the Sky: Cosmic Collisions, Killer Asteroids, and the Race to Defend Earth, written by Gordon L. Dillow, published by Scribner Books in June 2019 (hardback, 277 pages)
As an Arizona resident, it is only logical that Dillow takes Meteor Crater as his starting point. At some 170 metres deep and almost 1200 metres in diameter this impressive astrobleme, or star wound (what a beautiful word he introduces here!), is one of the best-preserved impact sites on our planet. It also plays a large role in the history of impact theory and Dillow skillfully uses it as his jumping-off point for a science history lesson that spins itself out over the first half of the book.
Although Native Americans in the area believed Coon Mountain, as it was known back then, to be an impact structure, the Western academic establishment did not. They were still held in thrall by the geological doctrine of uniformitarianism, which held that changes on Earth happened gradually through known processes. When the famous geologist Grove Karl Gilbert mounted an expedition to Coon Mountain in 1891 to address the question of its nature, he considered the possibility of meteoric impact but rejected it in favour of a volcanic steam explosion. Not that strange, with the 1883 volcanic eruption of Krakatau still fresh in people’s minds. With that, the case was closed for geologists. But it was not for Daniel Moreau Barringer. Nor, later, for Gene Shoemaker.
“[Barringer] made his fortune mining but then wasted it over the next few decades […] digging holes in the crater, obsessed with the idea that there had to be an enormous meteor buried there somewhere.”
Where May’s book focuses more on the technical side complete with diagrams – the celestial mechanics of asteroid orbits, the different types of asteroids – Dillow instead largely focuses on the human story of geology’s history. He gives a delightful introduction to early efforts, including the 1800s group calling themselves the Himmelspolizei or Celestial Police. But the focus is on the fascinating story of both Barringer and Shoemaker. The former made his fortune mining but then wasted it over the next few decades, from 1904 to 1929, digging holes in the crater, obsessed with the idea that there had to be an enormous meteor buried there somewhere. He published academic papers on the topic, but his belligerent attitude made him few friends. The latter, upon visiting the crater in the 1950s, thought it looked like those left by nuclear bomb tests, just bigger. He changed his career from geology to astronomy, joined NASA, and set up the first observatory to find and track asteroids that could pose a risk to Earth.
A recurrent theme in this book is the reticence of the geological establishment to accept the impact theory. Despite mounting evidence, volcanism remained the preferred explanation for craters both here and on the moon. Dillow traces the big change in attitude to two things. He gives an excellent brief history of the dust kicked up by the famous 1980 Alvarez et al. Science paper that proposed the Cretaceous ended with a bang. And while scientists were busy arguing, Shoemaker discovered an asteroid on a collision course with Jupiter, which it hit in 1994.
From here on outwards Dillow makes clear how the sniggering around the wacky concept of giant-rocks-from-space died down, with the 2013 Chelyabinsk meteor a disconcerting reminder that the threat is real. He describes the many initiatives to find and track Near-Earth Objects or NEOs, and joins astronomer Richard Kowalski at the Catalina Sky Survey to learn how asteroid sightings are shared and verified by avocational astronomers around the world.
“There are really only two options to deal with an incoming asteroid: nudging it or nuking it.”
Dillow takes the same historical approach when considering what, if anything, we could do. From the 1967 MIT student project, Project Icarus, that asked participants to come up with solutions, to NASA’s 2005 Deep Impact mission that hurled a heavy projectile at a comet, people have been considering all sorts of strategies. NASA now even has a Planetary Defense Coordination Office and Dillow interviews its officer, Lindley Johnson.
There are really only two options to deal with an incoming asteroid: nudging it or nuking it. Dillow briefly considers the slow-push methods that aim to change an asteroid’s course but spends most time on the idea of the kinetic impactor. Basically, the idea of launching a large object or nuclear warhead to blow up the incoming threat. The latter is, unsurprisingly, controversial, and Dillow examines the different opinions on the topic. For now, it might be our only realistic option though. Similarly insightful is his coverage of several “asteroid war games” conducted by NASA and FEMA (the Federal Emergency Management Agency). These are tabletop exercises to train government officials on how to respond when a natural disaster strikes. Obviously, these drills are somewhat different from the regular ones, both in the likely long lead time where we know an impact is imminent years in advance, and the limited capabilities we currently have to actually do something.
Fire in the Sky is an excellent example of an outsider digging into a topic, doing his homework, talking to experts, and becoming fascinated with the story he uncovers. With a reporter’s flair, he transmits his enthusiasm, making this a fun book that treads lightly on the science side of things. His focus on the human history ensures the book does not simply rehash recent publications such as Cosmic Impact. Dillow makes a convincing case that, despite so many other problems here on Earth requiring our attention, we would do well to apportion some of our funds to keeping an eye on the sky.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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“Cosmic Impact: Understanding the Threat to Earth from Asteroids and Comets”, written by Andrew May, published by Icon Books in February 2019 (paperback, 167 pages)
The story of the extinction of the dinosaurs and its link to the Chixculub impactor has featured repeatedly on this blog. Walter Alvarez told the story in his own words in T. rex and the Crater of Doom, and it featured as one of the big five mass extinctions in Brannen’s The Ends of the World: Volcanic Apocalypses, Lethal Oceans and Our Quest to Understand Earth’s Past Mass Extinctions, while any dinosaur book worth its salt features the topic (see e.g. my reviews of The Rise and Fall of the Dinosaurs: The Untold Story of a Lost World and The Dinosaurs Rediscovered: How a Scientific Revolution is Rewriting History). Now, if someone could please show the dinosaurs the door, because there is far more to the topic than them, or the bad science shown in disaster movies such as Deep Impact and Armageddon.
May starts off with a short history of comets and asteroids. It obviously took a while before shooting stars were recognised for what they were: not bad omens, but hunks of space junk. Even so, the possibility of cosmic impacts was long dismissed. Although May doesn’t mention him by name, it was Scottish geologist Charles Lyell’s doctrine of uniformitarianism (May instead calls it gradualism in this book) that long held sway and pretty much ruled out (cosmic) catastrophes. The pseudoscience espoused in the 1950s by psychologist Immanuel Velikovsky (see The Pseudoscience Wars: Immanuel Velikovsky and the Birth of the Modern Fringe) also did not help its credibility. But, as documented at length elsewhere, it eventually became an accepted idea (see my reviews of Four Revolutions in the Earth Sciences: From Heresy to Truth and Cataclysms: A New Geology for the Twenty-First Century).
“Now, if someone could please show the dinosaurs the door, because there is far more to the topic than them […]”
So, we have dealt with the dinosaurs, and we have the idea on the table as something to be taken seriously. But before May can start talking about the threat to human civilization and what, if anything, can be done to avert it, there is a whole lot of astronomy to be dealt with first.
This is where I feel the book does an excellent job introducing the basic science, although he does seem to falter right at the start in explaining the differences between meteors, asteroids, and comets. Clear-cut definitions have been formulated elsewhere, but May instead focuses on the caveats, pointing out that these names were coined before people really understood what they were talking about. Furthermore, the more we study them, the more their properties seem to overlap. That’s all fair enough, but after a few pages I still was not quite clear on the difference between asteroids and comets.
“It obviously took a while before shooting stars were recognised for what they were: not bad omens, but hunks of space junk.”
Luckily, the more complex topics of the all-important orbits (which determine whether they will cross Earth’s path), the underlying celestial mechanics, and its terminology are all lucidly explained, including helpful diagrams. May briefly covers the different sources for all these rocks (the nearby asteroid belt, the more distant Kuiper belt, and the still more distant and hypothetical Oort Cloud) and the likelihood of impact. He is quick to inject a healthy dose of realism and sobering numbers here, because even the asteroid belt is, in reality, not particularly densely packed with debris. No matter how Star Wars depicted it, the Millenium Falcon could easily coast through this with the crew snoozing and no one would be the worse for wear.
But impacts do happen. Just look at the moon, May says. Although Meteor Crater in Arizona was long recognised as the only clear crater on the face of the Earth, many others have now been found. Coverage of this topic would not be complete without mention of the 1908 Tunguska Event in Siberia (see also The Tunguska Mystery, although May thinks there little mystery left here), the 2013 Chelyabinsk meteor, or the 1994 impact of the Shoemaker-Levy 9 comet on Jupiter (see The Great Comet Crash: The Collision of Comet Shoemaker-Levy 9 and Jupiter).
“No matter how Star Wars depicted it, the Millenium Falcon could easily coast through [the asteroid belt] with the crew snoozing and no one would be the worse for wear”
Now that cosmic impact is a topic that can be brought up again in polite company, new wild ideas have been quick to follow. May gives a quick and appropriately sceptical overview of the revival of the idea of panspermia (comets seeding planets with life), epidemics-from-space, the alleged periodicity of mass extinctions and its link to cosmic phenomena (see the latter part of Cataclysms but especially Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe), or the idea of a dark star companion to our sun (see The Nemesis Affair: A Story of the Death of Dinosaurs and the Ways of Science).
But, to repeat, impacts do happen, and May briefs the reader on NASA’s efforts at monitoring so-called near-earth objects, and the fantastic missions that landed on asteroids. Finally, he seriously considers the various options we have to defend ourselves from incoming asteroids and comets (blow them up, deflect them, redirect their course?).
“Especially the topic of planetary defence has tickled the imagination […]”
Especially the topic of planetary defence has tickled the imagination with a host of books on it in recent years, such as Near-Earth Objects: Finding Them Before They Find Us and The Asteroid Threat: Defending Our Planet from Deadly Near-Earth Objects. And Cosmic Impact is not the final word on the topic, see also my review of Fire in the Sky: Cosmic Collisions, Killer Asteroids, and the Race to Defend Earth.
Of all these, May’s book is the least expensive. At 155 pages his coverage of topics is well-balanced, though necessarily cursory in places. Given the brief of the Hot Science series this book is part of, that is only to be expected though. What it does deliver is a fast-paced and very readable book that avoids hype and is cautiously sceptical where it needs to be. A book that is sure to whet the appetite.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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“The Dinosaurs Rediscovered: How a Scientific Revolution is Rewriting History”, written by Michael J. Benton, published by Thames & Hudson in April 2019 (hardback, 320 pages)
If this sounds familiar, indeed, when I reviewed Steve Brusatte’s book The Rise and Fall of the Dinosaurs: The Untold Story of a Lost World, I praised the enviable ease with which he explained modern methodologies. Now, with all due respect to Brusatte (and I really, really enjoyed his book), Benton has almost 30 years on him. Next to having authored standard textbooks such as Vertebrate Palaeontology (currently in its fourth edition) and co-authored Introduction to Paleobiology and the Fossil Record (currently in its second edition), he is also the series editor for Wiley-Blackwell’s textbook series Topics in Paleobiology, and he has previously authored When Life Nearly Died: The Greatest Mass Extinction of All Time with Thames & Hudson, dealing with the end-Permian mass extinction. With a career spanning some four decades, if anyone can comment first-hand on the evolution of the field, it is Benton.
After a brief introduction on how scientific discoveries are made, and a short foray into the philosophy of science, the bulk of the book consists of nine chapters documenting areas where palaeontology has been revolutionised. Partially by new fossil finds, but, much more importantly, by new tools, new technologies, more powerful computers, lateral thinking, and interdisciplinary approaches.
Benton’s opening of the book is perhaps slightly risky, as he has put the most technical chapters first. There is the question of when the dinosaurs first evolved. After the giants of the Paleozoic went extinct (see my last review of Carboniferous Giants and Mass Extinction: The Late Paleozoic Ice Age World), did the dinosaurs opportunistically explode onto the scene, or did other reptile groups slowly fade with dinosaurs taking over the proverbial relay race? New computational tools have pushed the origin story further back in time, but have also shown that both explanations have something going for it.
“Ancient DNA may have revolutionised archaeology […], but Benton explains why we shouldn’t expect Jurassic Park to become reality anytime soon.”
Similarly, the picture of the dinosaur family tree benefited first from the cladistic revolution, which saw a different way of thinking about classifying species, collecting and analysing as many informative characters as possible to determine relationships. Then, with access to supercomputers, Benton and his team have been involved in producing an all-encompassing family tree, a so-called supertree (which you can explore in all its glory here), revealing how the dinosaur lineage diversified rapidly early on, but the rate of speciation slowed down after that. That things never stay still was shown only recently with Baron et al.‘s 2017 Nature paper that proposed some radical changes to the family tree (for an accessible take on it, see Darren Naish’s blog post at Scientific American).
If this is all a bit technical, despair not, the remainder of the book deals with more “mundane” questions your typical six-year-old might ask. Excavation techniques might have changed little since the dawn of the discipline, but imaging tools such as photogrammetry have revolutionised what palaeontologists can document at a dig site, while CT scanning offers a non-destructive technique afterwards to image what you have dug up. And new microscopy techniques, together with some fantastically preserved fossils, have revealed much about the colour of dinosaurs (and hey, feathers!).
“What really helps this book shine are the illustrations. Thames & Hudson […] has redrawn many of them specifically for this book.”
Ancient DNA may have revolutionised archaeology (see my review of Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past), but Benton explains why we shouldn’t expect Jurassic Park to become reality anytime soon. Nevertheless, even without dinosaurs stomping around here and now, we have learned so much about how they lived. Bone histology and X-ray imaging have revealed growth rates, while finite element analysis (a method borrowed from structural engineers who use it to stress-test designs of bridges and buildings on computers) has allowed calculations of bite forces and how dinosaurs ate, while analyses of microwear on tooth surfaces (see my reviews of The Tales Teeth Tell: Development, Evolution, Behavior and Evolution’s Bite: A Story of Teeth, Diet, and Human Origins) has shed light on their diet. Biomechanical computations and careful analyses of trackways tell us more about their posture, how they moved, whether they could run, and what the deal is with them flying, or at least flapping about.
And there is, of course, the always fascinating topic of their extinction. Benton has first-hand seen the rise and rise of the Alvarez asteroid impact hypothesis (see T. rex and the Crater of Doom and my review of The Ends of the World: Volcanic Apocalypses, Lethal Oceans and Our Quest to Understand Earth’s Past Mass Extinctions), despite the initial pushback from the uniformitarian crowd (see my review of Cataclysms: A New Geology for the Twenty-First Century), and he provides a great overview of why this idea has become so widely accepted. Even here, facts move quicker than book publishing can keep up, and the reveal (not two weeks ago!) of a site potentially recording the direct aftermath of the impact has raised eyebrows around the world (see DePalma et al.‘s PNAS paper and the accompanying article in The New Yorker). And it probably has more than one palaeontologist fervently hoping this is not an elaborate hoax. I am cautiously optimistic so far – this could be mindblowing, but let’s see more hard proof first.
“[Benton] convinces that now is a very exciting time, indeed, to be a palaeontologist. I can’t wait to see what surprises lie in store in the near future.”
In addition to Benton’s accessible writing, what helps this book shine are the illustrations. I regularly bemoan how few publishers get this right; complex figures are reproduced directly from their source in greyscale so you can’t tell apart the different lines and symbols in graphs, they are often too small, or the source material is so poor that resolution suffers or compression artefacts are visible. Not this book. Thames & Hudson is obviously known for their illustrated books, and checking the illustration credits suggests that their in-house art studio (?) has redrawn many of them specifically for this book. This in addition to two colour plate sections and some really nice species profiles. A job well done, and I wish more publishers went to this effort.
The Dinosaurs Rediscovered is easy to recommend. Benton’s enthusiasm is infectious, and his skill at packing so many exciting developments in this book speaks of his deep involvement in this field. He provides a fantastic overview of the revolutions in palaeontology over the last few decades and convinces that now is a very exciting time, indeed, to be a palaeontologist. I can’t wait to see what surprises lie in store in the near future.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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“Cataclysms: A New Geology for the Twenty-First Century”, written by Michael R. Rampino, published in by Columbia University Press in September 2017 (hardback, 211 pages)
So, bit of a history lesson first. The British geologist Charles Lyell (1797-1875) published the textbook Principles of Geology that went through 12 editions between 1830 to 1875 and influenced generations of geologists. Three of his ideas became axioms in geology:
1. Geological change is slow and gradual and the result of processes we can see in operation today (to evolutionary biologists like myself this axiom sounds familiar, as Charles Darwin has written the same about evolution. Not strange when you consider Lyell was Darwin’s contemporary and mentor, and heavily influenced his thinking).
2. No need to invoke astronomical influences, geologic forces are intrinsic to the planet.
3. The geologic record does not contain regular patterns influenced by astronomical cycles.
This idea of slow and gradual change is known as uniformitarianism: “the present is the key to the past”. Lyell was firmly opposed to the idea of past catastrophes having influenced the planet, which at the time often took the form of attempts to shoehorn the Biblical flood into the picture (with the exception of Cuvier and some others, who favoured natural explanations). Mind you, Lyell’s ideas are not free from theological underpinnings either. As Rampino shows, close reading of his work clearly shows that a slow unfolding of geological history was God’s plan to shape a world perfectly suited for humans to live in.
Lyell’s views won the day. Discontinuities in the fossil record were explained away with the argument that the geological and fossil record are highly incomplete and fragmentary, like a book from which many pages are missing. So, what seems like species suddenly disappearing is just an illusion, perhaps the result of missing fossils, or of periods of geological strata not being deposited. If the record were complete, it would reveal gradual extinction. There. Done and dusted.
These views continued to dominate geology well into the 20th century, and with that in mind, you can understand how the Alvarez paper, which proposed the dinosaurs were killed by an asteroid impact, caused such a splash. Rampino spends several chapters describing their work, and the subsequent work to gather more supporting evidence. You see, impacts leave tell-tale signs in the geological record due to the extreme forces and temperatures generated upon impact, and Rampino describes these in much more technical detail than The Ends of the World that I read just before this book. Good job that the book is accessibly written, as I was able to follow along just fine during these chapters. Plenty of these signs have been found at the Cretaceous/Paleogene boundary, 65 million years ago, and by now this impact is a widely accepted fact. But was this a one-off? Rampino argues it was not. He describes work by geoscientists who have found signs of impacts at other times in deep history and tries to link these to other (sometimes minor) mass extinctions. For a while I felt a bit sceptical: was he another person who suddenly saw asteroids everywhere? But Rampino is clear-headed enough to admit that not all mass extinctions are impact-related, and highlights the important role of flood basalt eruptions. These episodes of massive catastrophic volcanism were responsible, amongst others, for the end-Permian mass extinction, which wiped out some 95% of species 252 million years ago.
“It’s an interesting idea, and certainly one step up from the Nemesis hypothesis […]”
Even so, it is clear Rampino favours the impact explanation. He points out the incomplete sampling of the geologic record to detect traces of impact, and the difficulties in finding these. Not every asteroid will be a dino-killer. Size, composition, and location of impact will all influence what traces past impacts have left. Add to that that some impact craters, especially older ones, may never be found if they occurred in regions that have since disappeared down the planet’s gullet in subduction zones and have been erased. Clearly, there is a lot more work to be done before we can pin other extinctions on impacts as clearly as has been done for the end-Cretaceous mass extinction. But he thinks that if we look harder, we’ll find more evidence of this.
Rampino goes a step further though – this is where the book gets more controversial – and suggests these impacts occur at roughly 30-million year intervals. These ideas have met with opposition, as many scientists have hypothesised periodic cycles before that have not stood up to scrutiny.
Rampino and co-workers are convinced they are onto something though. They even have a mechanism in mind that, by their own admission, is rather speculative. As our solar system goes around our galaxy (which, as you might know, we have good reason to believe is a disk-shaped spiral galaxy) it oscillates up and down, passing through this disk at intervals of about 30 million years. This would disturb the Oort cloud, a hypothetical band of icy bodies circling the Sun at a great distance, well beyond Pluto Neptune in interstellar space, sending comets our way. It’s an interesting idea, and certainly one step up from the Nemesis hypothesis, which invoked an as-of-yet undiscovered distant planet as the source of these comets (see The Nemesis Affair: A Story of the Death of Dinosaurs and the Ways of Science for the controversies around that idea).
The really speculative part, which was also recently put forward by Lisa Randall in the book Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe, is the role given to dark matter. Supposedly, above-mentioned disk also houses dark matter, which would add further gravitational pull disturbing the Oort cloud. But wait, there’s more. Some astrophysicists think that dark matter particles could be captured by earth and, once sufficient densities have been reached, could undergo a process of mutual annihilation, producing enormous amounts of heat in the planet’s interior, which would trigger rising plumes of hot material that cause flood basalt eruptions.
“[…] we are at the cusp of a revolution in geological thinking, one that gives more credence to catastrophist explanations, from above and below”
Obviously, these ideas have met with plenty of opposition. Rampino argues that many geologists are still stuck with the heritage of Lyell’s ghost, unwilling to accept any astronomical explanation for geological processes. He thinks we are at the cusp of a revolution in geological thinking, one that gives more credence to catastrophist explanations, from above and below.
I am totally on board with Rampino’s call to abandon Lyell’s uniformitarianism, but almost 40 years after Alvarez’s paper, that’s hardly a revolution anymore, is it? I thought the scientific community is already well on its way to accepting catastrophist explanations. Rampino furthermore outlines some interesting ideas in this book, but until we have gathered more data to support or reject them, they are just that. Speculative ideas. If scientific consensus rolled over at every left-field idea that is presented as the next revolution, we’d be nowhere. So I think the criticism and scepticism levelled at these particular ideas is both necessary and deserved. Luckily, Rampino is enough of a scientist to recognize this himself, which certainly helps his credibility. And Cataclysms is sufficiently well written that I’ll say: “Sure, I’ll entertain your ideas. Let’s see what future research brings.”
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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“The Ends of the World: Volcanic Apocalypses, Lethal Oceans and Our Quest to Understand Earth’s Past Mass Extinctions”, written by Peter Brannen, published in Europe by Oneworld Publications in September 2017 (hardback, 330 pages)
Extinction and speciation happen, geologically speaking, continuously. You may have come across the term “background extinction rates”. But the geological record reveals there are episodes when species diversity, again geologically speaking, suddenly plunges, and a significant proportion of life forms disappear around the globe. If the concept of extinction didn’t really exist until Cuvier put it forward in 1796, the idea of sudden mass extinctions didn’t really catch on until Walter Alvarez and his team published their idea of death by comet in 1980 (Elizabeth Kolbert gives an excellent overview of the intellectual history in The Sixth Extinction).
The Ends of the World is science journalist Peter Brannen’s first foray into book writing. He has set himself the ambitious target to give an overview of what we currently know of the Big Five mass extinctions (end-Ordovician, Devonian, Permian, Triassic, and Cretaceous respectively) by interviewing scores of scientists.
In nimble prose that is readable and amusing (I found myself sniggering throughout the book) he walks us through them chronologically, starting off with the oldest. Without repeating the many fascinating details and ideas covered, the consensus is that if there is one thing that all these events have in common, it is that there never is just a single cause. All of these events are characterised by an extraordinary set of circumstances coming together to create some truly challenging conditions for life on earth. And, despite the popular notion of asteroid impacts, most often the threat has come from within. Twice in the form of ice and anoxic (i.e. oxygen-starved) seas at the ends of the understudied Ordovician (445 million years ago, or mya for short) and Devonian (two extinction pulses at 374 and 359 mya), together with a raft of other circumstances. Twice in the form of volcanism-induced global warming with accompanying misery at the end of the Permian (252 mya) and Triassic (201 mya). And then, of course, the asteroid impact at the end of the Cretaceous (65 mya).
Brannen does an excellent job giving airtime to different viewpoints and theories, because the above summary is very brief, and the science isn’t all settled on this. Even the by now widely accepted asteroid impact hypothesis is more complicated than that. When Walter Alvarez and his team put their theory forward in their 1980 Science paper, it was initially met with disbelief and scepticism. And healthy scientific scepticism is good. It has forced the scientific community to gather more data to see if this idea could be supported. By now enough supporting evidence is available and, after being known to the wrong people for over a decade (geophysicists working for an oil company), we have located the site of impact around the Mexican peninsula of Yucatán (this story is also chronicled in Alvarez’s book T. rex and the Crater of Doom). But other, similarly massive impacts have not caused any mass die-offs, giving more credence to the ideas of a few vocal critics who think earthquakes in the impact’s wake ramped up episodes of ongoing volcanism.
“[…] to be a geologist means changing your perception of time.”
If there is anything that ought to be highlighted in Brannen’s writing, it is how he manages to convey the absolute vastness of the time scales we are dealing with. Consider that all of recorded human history, all the thousands of years, have taken place in the most recent interglacial period, which is only one of twenty such balmy 10,000-year intervals in the earth’s most recent 2.6 million year ice age, and you will come to understand that to be a geologist means changing your perception of time.
The other thing Brannen does exceedingly well is to evoke the sheer scale of the destruction that has been wrought in the distant past. If you thought the 2013 Chelyabinsk meteorite was frightening, buckle up for the end-Cretaceous impactor. Similarly, the volcanism that wiped out some 95% of all life-forms at the end-Permian, making it the single most destructive event in the history of life, is hard to fathom. Forget the picturesque volcanoes that you know: continental flood basalts are literally the earth puking out its guts and covering whole continents with lava that gets stacked up miles high. As we have never witnessed these rare events, they defy comprehension.
Having discussed the Big Five, Brannen is not quite done yet. This book would not be complete if he not also touched upon the current ongoing loss of biodiversity. There is an eerie correlation between our ancestors arriving in new regions and megafauna disappearing. The overkill hypothesis, put forward by Paul S. Martin (also see his book Twilight of the Mammoths), has not been well received by politically correct anthropologists and social scientists, but I see no problem with it. Brannen speaks to British geologist Hallam who thinks it’s high time we get rid of this romanticized notion of the wild savage living in harmony with nature. I couldn’t agree more. [Edit: having now reviewed End of the Megafauna: The Fate of the World’s Hugest, Fiercest, and Strangest Animals, I have changed my mind on this somewhat.]
“The tempo with which we are burning fossil fuels like there is no tomorrow […] is comparable to the episodes of large-scale volcanism of the past. Deep history teaches us how the planet’s climate will react.”
Even so, it’s interesting to read that many of the palaeontologists in this book don’t consider this the sixth extinction. Yet. They all agree that we are inflicting tremendous damage to our environment and have caused the extinction of many species. And the fact that we are exerting multiple pressures (climate change AND overhunting/fishing AND habitat fragmentation etc.) means we could pass a tipping point somewhere along the line. But the current losses pale in comparison with the truly staggering losses incurred during previous mass extinctions. Many palaeontologists think it’s way too early, and overly dramatic, to already talk about a sixth mass extinction, as much as it makes for juicy headlines. In the long run, this may make for no more than a blip in the geological record.
Throughout the book, Brannen skilfully highlights the relevance of studying Earth’s deep history to the here and now. The tempo with which we are burning fossil fuels like there is no tomorrow, and releasing greenhouse gases into the atmosphere is comparable to the episodes of large-scale volcanism of the past. Deep history teaches us how the planet’s climate will react. The geochemistry is simple and uncontested, and our planet has been here many times before. Natural geochemical cycles can mop up this excess, but these cycles play out on time scales of hundreds of thousands of years. As some scientists point out here, it is far more likely that our civilization will buckle under the strain of overpopulation, failing agricultural systems and climate refugees well before we can release comparable amounts of greenhouse gases, as even a few degrees of warming will drastically change the world in which we live.
What could have been a book of doom and gloom has become a phenomenally good read in the hands of Brannen. His writing is witty and irreverent in places and had me both amused and intrigued throughout. His balanced coverage of this massive topic is excellent, giving voice to the many opinions and ideas currently circulating. If you want an up-to-date picture of what we know, this is the best place to start in my opinion.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
Other recommended books mentioned in this review:
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