When the Invasion of Land Failed: The Legacy of the Devonian Extinctions

Critical Moments and Perspectives in Earth History and Paleobiology

by George R. McGhee

The invasion of land by ocean-dwelling plants and animals was one of the most revolutionary events in the evolution of life on Earth, yet the animal invasion almost failed—twice—because of the twin mass extinctions of the Late Devonian Epoch. Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a blow that almost drove them back into the sea. If those extinctions had been just a bit more severe, spiders and insects—instead of vertebrates—might have become the ecologically dominant forms of animal life on land.

This book examines the profound evolutionary consequences of the Late Devonian extinctions and the various theories proposed to explain their occurrence. Only one group of four-limbed vertebrates exists on Earth, while other tetrapod-like fishes are extinct. This gap is why the idea of "fish with feet" seems so peculiar to us, yet such animals were once a vital part of our world, and if the Devonian extinctions had not happened, members of these species, like the famous Acanthostega and Ichthyostega, might have continued to live in our rivers and lakes. Synthesizing decades of research and including a wealth of new discoveries, this accessible, comprehensive text explores the causes of the Devonian extinctions, the reasons vertebrates were so severely affected, and the potential evolution of the modern world if the extinctions had never taken place.

Genres: Science, Biology, Evolution, Palaeontology, Nonfiction

447 pages, Kindle Edition

First published January 1, 2013

About the author

George McGhee is Distinguished Professor of Paleobiology in the Department of Earth and Planetary Sciences at Rutgers University and a Member of the Konrad Lorenz Institute for Evolution and Cognition Research in Klosterneuburg, Austria. He is the author of Convergent Evolution: Limited Forms Most Beautiful (MIT Press)

Also published as George R. McGhee Jr.

Reviews

[Donato Colangelo · Rating 5 out of 5]

Excellent summary of the state of the art regarding the search for tetrapod evolution. The author gives interesting information through intriguing narrative while at the same time explaining the many threads that might have brought us here, reading, commenting, living our life. The story of life colonizing the lands is complex because the dynamics of Earth environments are complex, as they are today. Understanding what happened during the Frasnian and during the Fammenian helps us understand why and how only specific boughs of the tetrapod tree eventually made it on dry land and, finally, why we are here. It’s a story of contingency and we need to understand which factors played a role in defining it.
This is a book about evolution and extinction. Many people wonder why do we spend money to study such things. The answer is easy: we face a potential catastrophic extinction on a global level, and only by studying the previous mass extinctions we could hope to contain the damages that might await us and our fellow species.
Last but not least, a thought that came to my mind while reading the last chapter of the book. Was it not for the great “trimming” of all the intermediate forms that were hit during the two evolutionary “bottlenecks” of the Devonian, today the living world might have a face very different from the one we observe with our eyes. Perhaps, if those intermediate forms were about today, Darwin might have lived his life among people who accepted evolution and who thought that perhaps man is not a divine creation.

[Trent Marv · Rating 4 out of 5]

Here is an account of the history of land's attempts at invading land presented the best in book form of any I have read recently. It starts first with context of how plants and insects got on the land and set up the baseline amphibians would have to get going. It then goes over how the first tetrapods in the form of the fishapods like Tiktaalik were successful but wiped out by the first of two Late Devonian Extinctions. Then there was a rebound in the form of such animals as the famous Icthyostega which did well but again the second Devonian extinction, the End Devonian extinction led to them getting pushed down yet again only to finally make it in the Carboniferous.
This book goes into extreme detail on not just our ancestors but also terrestrial invertebrates, plants, climate, geography, and even oxygen levels. It also has a set of pictures and graphs helpful for visualizing the time. Overall good if you want to know about this time but my only criticism is that it can at points veer into being too technical for some to get into it plus it may imply too much determinism in certain things. Lik I have to say even with invertebrates present I think vertebrates of some kind would develop fully terrestrial forms, if only to take advantage of this free food source that can't get as big as they can. Worth a buy indeed!

[H V · Rating 5 out of 5]

This is an excellent book. It mostly covers the Devonian period, starting with the spread of land plants and the subsequent invasion of arthropods in the Silurian, and concludes the narrative in the Carboniferous during the aftermath of late Devonian extinctions. Jennifer Clack's work on tetrapod fossils is often cited. As for the author himself, George McGhee Jr's writing is full of detail and nomenclature (scientific names of animals), but his sentences are clean and straight-to-the-point. He will often rephrase and emphasize concepts to the benefit of the reader. The book goes into climate and geochemistry along with evolution, and lays out the evidence as to why two major Devonian extinctions happened. Spoiler alert: many questions remain!

[Bill · Rating 4 out of 5]

This book will explain in fairly technical language why the Devoian extinction happened and why land animals ultimately won their place on the planet. It is a book to be read with a clear head and some concentration. Not a good bedtime read. If you have any interest in this subject it is a must read.

[David McArthur · Rating 4 out of 5]

I wanted to give this book five stars as it is the only one on this fascinating subject I have ever seen. I learned a huge amount of information but I have to ding it a tiny bit for being so technical. This was not a book for someone who doesn’t have a lot of background in paleontology. Otherwise, very cool book!

[Shrike58 · Rating 3 out of 5]

For me, the question with this type of book is whether it's going to be advanced enough that I feel as though I'm learning something but not so technical that it's simply impenetrable. On the whole McGhee maintains a nice balance in what feels a bit like a textbook for a junior grad student, meaning that this is not the first book one should read on the subject. What McGhee does really well is to make clear what the gaps are in our understanding when it comes to fitting existing hard data (in relation to fossils and geological structures) into plausible explanatory systems. The one bottom line is that it took the evolution of amniotic reproductive systems before terrestrial vertebrates really became viable.

Originally written: October 1, 2019.

Actual rating: 3.5.