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29 of 30 people found the following review helpful:
5.0 out of 5 stars
Gaining Ground: The Origin & Evolution of Tetrapods, February 10, 2003
This review is from: Gaining Ground: The Origin and Early Evolution of Tetrapods (Hardcover)
Gaining Ground: The Origin and Evolution of Tetrapods written by Jennifer A. Clark is a book on comparative anatomy of tetrapods on Earth. The origin and evolution of tetrapods started about 370 million years ago, something strange and significant happened on Earth. That time, part of an interval of Earth's history called the Devonian Period by scientists such as geologists and paleontologists, is known popularly as the Age of Fishes. After about 200 million years of earlier evolution, the vertebrates... animals with backbones... had produced an explosion of fishlike animals that lived in the lakes, rivers, lagoons, and estuaries of the time. The strange thing that happened during the later parts of the Devonian period is that some of these fishlike animals evolved limbs with digits, fingers and toes. Over the ensuing 350 million years or so, these so-caled tetrapods gradually evolved from their aquatic ancestry into walking terrestrial vertebrates, and these have dominated the land since their own explosive radiation allowed them to colonize and exploit the land and its opportunities. The tetrapods, with limbs, fingers, and toes, include humans, so this distant Devonian event is profoundly significant for humans as well as for the planet. This book tells the story of the evolution of tetrapods from their fish ancestry and puts the sequence of events into its ecological context. The story if founded on an understanding of the evolutionary relationships between tetrapods and their fishy relatives... their phylogeny... and traces the family tree of tetrapods from its roots to the point at which the major groups of modern tetrapods branch off from its original trunk. The tetrapod family tree is in fact more like a bush, with several main branches, some of which have died out during the course of evolution and some of which have become large and important from small beginnings. This book looks at the changes that occured in the transition from creatures with fins and scales to those with limbs and digits in an attempt to understand how, as well as when, these changes occurred, and to do this, it is necessary to understand something of the anatomy of the animals involved. Chapters 2 & 3 are devoted to these parts of the story. Chapters 4,5,& 6 set out what is currently known of the earliest tetrapods and their lifestyles. By careful analysis of what is known of them from fossils, and by comparison with modern animals that live at the transition between water and land, it may be possible to understand a little of how the early tetrapods worked as animals. After the tetrapods had become established, they radiated into a ranges of forms requiring modification of the original tetrapod pattern. Chapters 7,8,& 9 carry the story forward from the origin of tetrapods to their ultimate conquest of terrestrial living. The final chapter drws together some of the threads that have been taken up in the preceding chapters and shows how they impact the study and understanding of tetrapods today. All in all, this is a well- written, illustrated, and organized book, making for a fairly fast read even though there is a lot of material covered. Devonian environment and the timing of anatomical changes was fascinating.
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16 of 16 people found the following review helpful:
5.0 out of 5 stars
One Layman's Experience of, November 23, 2005
This review is from: Gaining Ground: The Origin and Early Evolution of Tetrapods (Hardcover)
Other reviews on this page describe the contents well, so I'll focus on my own experience in the hope that it will be helpful to others with similar backgrounds. I have no formal education in science past the high-school level. I learn about science by reading and Scientific American is my favorite source, although I sometimes read more technical material. Gaining Ground falls into the "more technical" category.
One thing I found is that I can't keep track of all the terminology. For example, Clack describes changes in the structures of skulls and that involves a lot of bones I had never heard of before. But by concentrating on the things that I could keep track of, I could follow her basic points. For example, as our ancestors moved to land, where the buoyancy of water no longer kept their heads from sagging, the many skull bones were consolidated into a smaller number for strength. I'll never remember the names of all the bones, but I'll always remember why they changed. The same is true of the separation of the skull from the shoulder girdle and the formation of the neck, and of various other changes. I was content with the fact that there was much I couldn't follow because there was much that I could follow and learn from. And I enjoyed reading it.
Since I read the book, an article by Clack appeared in Scientific American (Dec. 2005) giving an overview of the origin of tetrapods, without most of the technical detail. It is excellent and I will tuck a copy into the book before I read it the next time. If you're unsure about buying the book, read the article. Then tuck a copy into the book as soon as you get it.
[...].
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12 of 12 people found the following review helpful:
5.0 out of 5 stars
A humerus tale . . ., May 23, 2005
This review is from: Gaining Ground: The Origin and Early Evolution of Tetrapods (Hardcover)
. . . along with some ribs, vertebrae and shoulder bones. But it's the skull that captures the most attention. The multitude of variations that occurred as animals moved in delicate steps from water onto land that make the story most interesting. And Jenny Clack's story of our four-legged forebears is a wondrous tale. Ever since Charles Darwin explained the nature of life's evolution, the question of how sea creatures moved to the land has been an enigma. Consider the many issues involved: walking, breathing air instead of filtering water, hearing in air instead of water, how to feed - and where, and protecting eggs. Clack shows how these topics were addressed by slow, incremental changes in body plan, with changes in one area integrated with those in another.
Walking on land meant not only building bones strong enough to support the body, but muscles to drive them. The humerus, the single bone in your upper arm, not only had to be stronger, it had to have joints for a new form of movement. A stride is far different from the flapping of a fin, so the paddling fin had to change. Clack discounts the older, simpler views that the "lobe-finned" fish just developed better "legs". Moving from the sea requires more than just crawling up the beach. There had to be an intermediate step. Clack finds that step in brackish lagoons and shallow, meandering rivers. There, the new four-legged creatures learned to walk on silty soils and learn to mix air and water breathing methods.
It was a reinforcing cycle as the change in surroundings developed new capacities. Diet went from fish to insects. No longer able to simply swallow prey as fish do, tetrapods began feeding on insects and their own smaller cousins. That meant biting and chewing, requiring stronger jaws and specialised teeth. Skulls once short and narrow became wide and flat. This reorganising of the entire skull required new musclature for support. The more time on land, Clack shows, meant not only stronger legs, but a sturdier backbone. Ribs developed that held muscles for breathing. Although the earliest tetrapods likely gulped air as a fish gulps water, before long they were using their nostrils to fill lungs.
As should be obvious, this isn't a simple narrative. The fossil bones are meticulously detailed - when they are available. Clack's task is rendered more difficult by the paucity of fossils. She has been lucky in her own finds in Greenland and Scotland. Others have encountered Carboniferous fossils in the Ohio Valley, Nova Scotia and Australia. The real treasures should be in coal seams where plant remains have become burnable stone. However, mining operations leave little opportunity for discovery. What has been found has often been misinterpreted. In order to depict what happened to tetrapod bodies over time, she is meticulous in describing individual bone types and how they changed. She helps the description with photographs and a wealth of line drawings. Still, this isn't a book for the uninitiated. It requires careful reading and no little back-flipping of the pages. The endeavour is well worth the effort, however. Clack has established an new foundation for understanding where and how creatures like ourselves originated. [stephen a. haines - Ottawa, Canada]
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