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Keith Stewart Thomson

Autor/a de Fossils: A Very Short Introduction

13 obres 551 Membres 7 Ressenyes

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Obres de Keith Stewart Thomson

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20th Century
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Paleontologist Keith S. Thomson’s Living Fossil, although still a “popular” work, is more technical than Samantha Weinburg’s A Fish Caught In Time; Thomson is also handicapped by publishing before (1993) the second coelacanth species was discovered in Indonesia (1997) and before the discovery of another population off Tanzania (2003). The first third of Living Fossil covers the same ground as Wienburg; the initial discovery in 1938, the second specimen in 1953, the various personality quirks of the discoverers, and so on. For the remainder Thompson goes over what’s known of the biology of coelacanths, including his own adventures in acquiring a fresh frozen specimen from the Comoros. (The fish was packed in a crate addressed to “Dr. Thomson, Peabody Museum, USA” and handed off to a passing fruit boat – bound for Marseille. The ship captain approached the US Consul in Marseille asking what he was supposed to do with; he wanted to shut down his freezers for cleaning. After considerable international phone calling, the fish arrived at Yale still frozen. The letter from the Comoros informing Thomson that a coelacanth was on the way arrived much later).


As mentioned, Thomson’s discussion of the geographical range of coelacanths is now obsolete; at the time he was writing the only known population was in the Comoros (other than the initial discovery off South Africa). There have since been catches in Indonesia and various places on the east African coast. He raises the interesting question, though, which still applies – before Latimeria, the last known coelacanth fossils were from Cretaceous shallow fresh water deposits in Europe; the living species is from deep marine water in the Indian Ocean. What were coelacanths doing in the meantime? Thomson’s answer hinges on the fact that deep marine deposits are always rare in the stratigraphic record; there were probably deep marine coelacanths all along but they just never showed up as fossils. Thompson also critiques some of the speculations based on the Comoros specimens – most were caught between January and March at depths from 150 to 250 meters so it was assumed that was coelacanth habitat. As it turns out, this is when Comoro fishermen do their deep water fishing – it’s when the water is calm offshore – and since they fish with handlines, 150-250 meters is about all they can handle. Thus the fishing records really don’t say that much; they’re where people fish for coelacanths, not where coelacanths actually live.


The biology of the animal is fascinating; genetic studies have made the point that a coelacanth is more closely related – in terms of genetic distance – to a cow than it is to a salmon. It’s certainly a fish on the outside, but that’s a function of where it lives, not what it’s like inside. Coelacanths have a rostral organ – nobody is quite sure yet what it does but the best bet is it has to do with positioning. Submersible observations of coelacanths show positioning is a strong point; the animal swims with its lobe fins (including the little lobe in the middle of the tail) and can swim in any direction in any position – upside down and backwards if that’s what it needs to do. It has an intercranial joint – the skull is hinged in the middle – and that facilitates its hunting tactics, which are to approach a target (again, in any direction and orientation) and suck the prey in with a sudden gulp. It has a hollow, oil-filled notochord, which compensates for relatively small and weak vertebrae. And it has blood isotonic with sea water, a characteristic it shares with elasmobranch fish; coelacanths concentrate urea and trimethylamine oxide in their blood to a level that would be lethal to most vertebrates and use these to make their total osmotic blood concentrations the same as sea water. (Marine actinopterygian fish have blood osmotic concentrations less than sea water and dispose of excess salt through specialized glands in their gills; freshwater fish have mechanisms to concentrate salt and produce copious quantities of very dilute urine to get rid of excess water).


A light read despite some fairly technical discussion of fish physiology; Thomson is a good explainer. Badly needs a second edition, though, to account for all the coelacanth discoveries in the last 20 years. Well referenced; no photographs but good line drawings, graphs, and tables.
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setnahkt | Hi ha 2 ressenyes més | Dec 15, 2017 |
On December 22, 1938, Marjorie Courtney-Latimer, curator of the small natural history museum of East London on the southeastern tip of South Africa, was called to the docks by a friendly trawler captain. Courtney-Latimer had a standing arrangement with local fisherman. They would call her if they discovered any unusual specimens so she could add them to the museum. She was stunned by what she saw on the deck. This fish was unlike anything seen before. It was about 5 feet long, a very strange blue color, and was reported to have been still alive when pulled out of the net; extremely unusual for a fish at the bottom of the net which would have normally asphyxiated. The fish's anatomical construction was also peculiar. It had, in addition to a double tail J two strangely paired fins in front which flopped in all directions very much like legs.

This discovery was to become one of the most exciting in recorded zoological history. Keith S. Thomson, a renowned biologist, tells the fascinating story of this discovery and the research on the coelacanth (pronounced seal-uh-canth.) Fortunately, Courtney-Latimer sent the fish to James L. B. Smith, a professor of chemistry, but a lover of fish who after the war became a celebrated ichthyologist. Smith thought he recognized the fish as a coelacanth, known previously only from the fossil record and thought to have been extinct for many millions of years. The coelacanth was most important, as it was a close relative of an ancient ancestor of land-dwelling vertebrates. Thomson defines "living fossil" (an apparent oxymoron) as the living representative of an ancient group of organisms one would expect to be extinct, formerly distributed over a large geographical area, but now restricted and probably rare or uncommon. The Australian lungfish is an example of living fossil, as is the horseshoe crab. Living fossils are usually quite primitive in comparison with other organisms. (Do you suppose the KKK could be considered a living fossil?) One particularly curious feature about coelacanths is they have only been found near the Comores Islands, a very recent geological structure dating back only some 7,000-8000 years. How did the coelacanths survive if they need the kind of environment that only seems to surround relatively recent geological structures?

This book is a mesmerizing account of the discovery and the tawdry battle among scientists to get their hands on specimens for research. It's also a most elucidating revelation of the scientific method: the building of an hypothesis, testing, refutation, and discarding those theories which are erroneous. Ironically, science now finds itself in the awkward position of perhaps causing the extinction of a unique and valuable species precisely because it is so interesting. The fish has no commercial value in the usual sense, and local fisherman only search for it now because of the relatively enormous sums scientists are willing to pay to obtain one. Some scientists, usually the ones who already have a specimen,) worry that this predatory interest will reduce the population to a point where it will no longer be able to reproduce.
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ecw0647 | Hi ha 2 ressenyes més | Sep 30, 2013 |
Jefferson's Shadow was a good book. It presents Jefferson as a "true" intellectual who had a passion for practical science. The book illuminates how his love of science, technology and invention carried over to his everyday life, and the way he used it in making decisions for his agricultural business and and in his elected positions as Secretary of State and President of the U.S.A. Thomson does a superior job in pointing out not only his contributions, but also his faults and foibles. A good example of this, is how he applied the scientific method in researching information on Megalonyx. He applied an a priori method. He had decideded in advance that Megalonyx was a big cat. He had forgotten Francis Bacon's admonition that no conclusion should be thought of, until the facts are analyzed, because if you first make a conclusion, inevitably, you will find only facts that support your hypothesis. Even when he was proven wrong, his hubris would not allow him to comletely leave it go. We all have these all to human faults. Even the great men among us are subject to it. All in all, this book was a great read, but Benjamin Franklin is still my favorite forefather and science geek, but I may be prejudiced in my opinion, because I too am a Philly boy, however Thomas Jefferson is my second choice as greatest and best forefather. I hope you enjoy this book as much as I did.

Bob Rodgers.
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robrod1 | Mar 11, 2013 |
When we think about the modern biological sciences, one name invariably pops into mind: Charles Darwin. Keith Thomson’s book, “Before Darwin: Reconciling God and Nature,” looks at the approximately two centuries of science that predate Darwin, partially in an attempt to see what influenced him, but mostly because it’s a fascinating history in and of itself. Thomson is almost wholly concerned with an age in which all natural science (then still often called “natural philosophy”) was almost always natural theology – that is, an understanding that the study of science and nature would draw one close to understanding the mind of God. William Paley, the eighteenth-century English naturalist whose book “Natural Theology” had a tremendous influence on Darwin’s early career, thought that the ways of God are shown to man through a rigorous and critical study of the natural world.

We get a quick, breathless account of big scientific developments from Copernicus to Newton, and see that the more we learn about God, the less ground natural theologians have to stand on. Thomson rhetorically asks, “Once Pandora’s Box was opened and a new, lesser, role ascribed to God, who could predict where matters would end?” (p. 44).

The rest of the book is taken up with discussing the contributions of several scientists, many of them not nearly as recognized as they should be, including Thomas Burnet, John Ray, Robert Plot, and Martin Lister. Paley and Ray especially built an argument from design, but there was one glaring problem: it’s clear there are many things in nature that are not perfect, and that don’t look like they were designed. The human eye – commonly adduced by modern-day creationists as an example of “irreducible complexity” – has a blind spot that lacks photoreceptors and therefore would make us more susceptible to attacks from predators if we still lived out in the open. The sacroiliac region at the base of the spine is mechanically imperfect to bear our weight, which often results in back pain as we age. Someone convinced that the human body is a perfectly designed machine can’t explain the appendix, a vestigial organ for which there is no observable purpose.

What Thomson seems to be saying is that natural theology had a historical tendency to reverse engineer science to fit its own theological ends. Therefore, what we see here is not so much science as we would understand the term today, but the use of science as a kind of anthropocentric cherry-picking to shore up preformulated beliefs, namely the creation accounts (there are two of them) in Genesis. Ironically, these culminate in a the work of Steno, a Dutch geologist and anatomist who was blithely unconcerned with how much his own work – the work of a Catholic bishop, mind you – confirmed or denied the accounts in Genesis.

There’s tons of other fascinating stuff in here that I won’t get into about interpretations of the fossil record (apparently people used to think that fossils just grew in place in the ground and that their resemblance to animals was purely coincidental), geology, paleontology, and what everyone thought about the Great Flood. It could also serve as a reference work if you’re interested enough in the history of natural science in the seventeenth and eighteenth centuries. It’s pretty much rekindled my long-dormant interest in the history of science.
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kant1066 | Hi ha 1 ressenya més | Feb 10, 2013 |

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