The Ends of the World

The Ends of the World by Peter Brannen is a book about mass extinctions that have occured in our Earth's history. The book was published by One World Publications in 2017. Peter is an award winning journalist who resides in Boston and has published articles in the New York Times, Atlantic, Washington Post and the Guardian to name a few. 

Before I would get into the review of the book, it would be good to distinguish between Mass Extinctions and Evolution. Evolution is what we associate with Darwin & Alfred Wallace and the often quoted expression 'survival of the fittest'. This is a slow, evolutionary process whereby species evolve, change and some go extinct over time. 

That comes to the point of extinction then. A sobering fact, according to the National Geographic more than 99% of all organisms that have ever lived on planet Earth are extinct. Whilst evolution and the changing ecology have slowly contributed towards species going extinct, there have been sporadic events in the history of the Earth where c. 75% to 90% of all species on Earth have gone extinct in a relatively short time span (short from a geological perspective). That is what is referred to as Mass Extinctions which is the subject of Peter Brannen's book. 

The book is not an easy read for those like myself who are not familiar with geological terms and events. So take your time and do some additional reading / research to supplement the book. Why? Because understanding time, periods, eras, rocks and geology is one the best ways to understand the history of the Earth especially as we shall look back into time. If the book drags in a few sections, persist or even re-read a chapter or two. It will be a very enlightening and enriching experience at the end. 

Firstly, time periods. Humans who read and explore history like to talk in terms of years, centuries or millennia. To appreciate these events we need to completely rescale our definition of time. All of human history is around 150,000 - 200,000 years at maximum (kindly discount some nation creating myths...) but that is considered extremely recent from a geological perspective. Scientists estimate the age of the Earth to be 4.5 billions years old, yes it has celebrated many birthdays! And for around 90% of that time, the planet has been desolate wasteland, quiet and devoid of any life. So one does need to recalibrate their definition of time and history when we look at Mass Extinction Events. 

Since the birth of the Earth, we fast forward many billions of years and come to one of the most defining moments for the planet. Around 540 million years ago (yes that far back), we had a mega event called the Cambrian Explosion. An explosion of life form on the planet. An incredible amount of diverse life-forms came into being. The seas and not land is where all this new life form activity was taking place, land continued to remained barren for a while. This was driven by falling CO2 levels in the sea and rising oxygen levels in the sea which promoted diverse life forms. All the landmass was concentrated in the Southern Hemisphere which is different to today and the Northern Hemisphere was largely water. 

Since the Cambrian, the Earth has witnessed five Mass Extinction Events. What is common to these events is the role of CO2 and the climate. When the CO2 balance alters, the climate changes violently, oxygen levels drop in the atmosphere & oceans and life-form takes a massive hit. Most of the events are caused due to earthly events and less due to extra terrestrial factors like radiation, asteroids etc. The Earth ultimately heals and new set of life forms emerge and come to dominate the Earth. Minnows of the previous eras become masters of the new. Its also rare that there is one single event that is the cause of Mass Extinction. It tends to be a chain of events that operate like a negative spiral / loop. In some cases its just a coincidence of bad luck events. The book reminds us of this well, via a coin toss analogy. The Earth is old; millions of years old. If you toss a coin many millions of times, there could be a day when a 100 tosses all come up tails. When that happens we have such events! 

The first was the End Ordovician Event which occured around 445 million years ago and would be the second worst by impact. All life-forms were in the sea so the event was impacted conditions in the seas. And the seas were dominated by invertebrates (multi cellular, some with eyes, segmented body parts) rather than vertebrates (fish) that we currently associate with sea & ocean life. What brought about this event was a change in the carbon - silicate cycle caused by volcanic rocks pushing upwards, weathering of rock, reduction in CO2 levels etc. That reduced temperatures and continental ice sheets began to form. Water that rained over land (helped by a massive single landmass in the Southern Hemisphere) became ice and did not find its way back into the sea and sea levels dropped. As most of life form existed in shallow seas, there was no where to go as sea levels kept falling.

After 5 million years the planet began to recover. Peter then steps up to his next chapter the Late Devonian Mass Extinction that took place around 374-359 million years ago. Unlike the other mass extinctions, this played out over a long duration of 20-30 million years. This was also the period when life form (plants) began to grow on land. And with this, caused a change in the earth's climate (more a change in the composition of oceans) that led to the second mass extinction. Plants and trees also suck a considerable amount of CO2 which again impacts the climate. Those that survived this event had one essential skill, they could make the move from shallow waters to land. This comes through possessing primitive breathing apparatus commonly called 'lungs' and primitive appendages called legs .

That brings us to the end Permian Mass Extinction around 250 million years ago. The Permian is the time when the Earth is more recognisable in form to us. Trees grew abundantly, animals were able to make a move onto land. Continents fused to form a giant continent called Pangea.  

There are two critical events in Earth's history (nothing to do with humans) (a) the great Cambrian Explosion and (b) the End Permian Mass Extinction where more than 85% of life went extinct - so this was the Big One!! The prime cause was too much CO2 & other GHG's pumped into the atmosphere. Likely reason - Siberian Traps, Continental Flood Basalts. The amount of lava rock ejected would have covered the entire USA with half a mile deep of lava. Temperatures shot up. With such intense heat, heat differentials across the Earth dropped and water circulation patterns in the Oceans stopped. With high CO2 levels, acid rain caused intense rock weathering that amplified ocean anoxia losing their store of oxygen. With that came the deaths of many species. 

Around 200 million years ago, it was devastation time once again with end Triassic Mass Extinction. This was a time that was dominated by the ancestors of modern day crocodiles. And they suffered at the end of the Triassic. Again the main cause of this event - high CO2 levels in the atmosphere, volcanic activity, continental plate movements (split of the mega continent Pangea) and ocean anoxification. It seems like a bad story that keeps repeating but spaced by millions of years. 

Then comes the most interesting chapter of the book. The end Cretaceous period that occurred around 66 million years ago. This is the most interesting event to read about. Thanks to Jurassic Park, we have all become familiar and mesmerised with the world of dinosaurs. These magnificent and fascinating reptiles ruled the Earth for millions of years! And the theory holds they vanished very suddenly. This is one extinction event that was triggered externally - an asteroid impact. The impact of this was quick & sudden and devastation immediate. Additional theories link the massive impact of the asteroid to immense earthquakes (11 on the Richter Scale!) which then triggered massive volcanic activity. The Deccan Traps were already spewing volcanic matter and this was the smoking gun. The Deccan Traps went into over drive thereafter upsetting the entire ecology of the world. The book describes all this is great detail. The end Cretaceous is one of the most highly researched geological events and for good reason. 

https://science.sciencemag.org/content/208/4448/1095
This is one of the most celebrated research papers published in Science in geology; that outlined the asteroid theory as the prime cause for the extinction of dinosaurs. Walter Alvarez was the lead geologist and worked with his father Luis Alvarez (Nobel laureate in Physics) on this paper. 

https://www.youtube.com/watch?v=fOFq11f3wAI
National Geographic Documentary on the extinction of dinosaurs, a good one to watch.

As dinosaurs died, the minnows of the Cretaceous period mammals began to dominate life on Earth.   

Since then the Earth has periodically been faced with an adverse climate including ice ages. But the effects have not been as devastating as the five events above. A lot of people have been talking about the sixth extinction as on on going event, the era that we are in. As humans have come to dominate the planet, the industrial revolution in particular has been injecting large amounts of CO2 and other GHG into the atmosphere. From reading the above events, we know by now what happens when the CO2 concentrations rise, the climate becomes hostile! 

This book was not an easy read. It talks about life on planet Earth a long long way back in time. But its an interesting read if you persist and it will definitely enhance your knowledge about the climate, ecology, CO2 cycles and Mass Extinction Events.  

https://www.amazon.com/Ends-World-Apocalypses-Understand-Extinctions/dp/0062364804