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Exploring Earth and Life Through Time
In Steven Stanley's introductory text "Exploring Earth and Life Through Time", he reviews the history of physical environments on Earth and the evolution and extinction of life from early on in the planet's history to the present day. Accessible to reader with no previous exposure to the field, the text first provides the foundation for understanding the history of Earth and its biota, and then integrates biological and physical history within the unifying context of plate tectonics. The book shows students how Earth's ecosystem has changed through time and how events in the past provide a perspective for dealing with present and future changes.
538 pages, Paperback
First published March 1, 1992
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March 8, 2025
A TEXTBOOK INTENDED TO BE ‘ACCESSIBLE’ TO STUDENTS
Paleobiologist Steven Stanley wrote in the Preface of this 1993 book, “My aim in writing this concise version of ‘Earth and Life Through Time’ has been to make the history of our planet and its inhabitants accessible to a wider range of students.”
He states in the first chapter, “An understanding of Earth history helps us to address problems caused by changes that are now taking place in the world, or that will be occurring soon. The rock record also sheds light on ways in which a broad array of factors cause environmental change and on the rates at which various kinds of change occur…The geologic record of the history of life also provides a unique perspective on the numerous extinctions of animals and plants that are now resulting from human activities. Humans are causing extinction by destroying forests and other habitats, but our collective behavior also affects life profoundly in less direct ways. Very soon human activities will cause average temperatures at Earth’s surface to rise in many areas of the world. The geologic record of ancient life reveals how climatic change has affected life in the past… As we come to understand the speed and profundity of natural environmental change and the transience of assemblages of species, we begin to appreciate the fragility of the world we live in… having studied the past, we can make more intelligent choices as we contemplate the future of our changing planet.” (Pg. 2)
He cautions, “Although fossils occur with great frequency in many sedimentary rocks, it is important to recognize that most species of animals and plants have never been discovered in the fossil record. Rare species and those that lack skeletons are especially unlikely to be found in fossilized form. Even most species with skeletons have left no permanent fossil record. A variety of processes destroy skeletons… Even after burial, many fossils fail to survive diagenesis, metamorphism, and erosion of the sedimentary rocks in which they are embedded. Finally, many fossil species remain entombed in rocks that have never been exposed at Earth’s surface or sampled by drilling operations.” (Pg. 12)
He explains that ‘index fossils’ “are easily distinguished from other taxa… They are geographically widespread and thus can be used to correlate rocks over a large area... [They] can be found in many places… They are restricted to narrow stratigraphic intervals, and thus allow for precise correlation. Unfortunately, few index fossils exhibit all of these traits as strongly as we could wish…” (Pg. 81-82)
He acknowledges, “fundamental uncertainties are inherent in radiometric dating. Most published radiometric dates… [indicate] uncertainty that is attributable to possible errors in the measurement of the quantities of parent and daughter elements… In accepting a date… we are assuming that a dated rock has remained a closed system… Unfortunately, this is not always the case… These types of errors sometimes add up to sizable total errors, especially when very old rocks are being dated.” (Pg. 88)
He reports, “When Darwin… weighed… evidence indicating that one type or organism evolved from another, he found that certain anatomical relationships seemed to build an especially compelling case… Darwin was intrigued by the admission of Louis Agassiz… that he could not distinguish an early embryo of a mammal from that of a bird or a reptile… Equally convincing to Darwin was the evidence of HOMOLOGY---the presence, in two different groups of animals or plants, or organs that have the same ancestral origin but serve different functions… The vestigial organs---organs that serve no apparent purpose but resemble organs that do perform functions in other creatures… Whales, for example, have apparently useless bones that resemble the pelvic bones of other mammals.” (Pg. 108)
He notes, “According to the traditional GRADUALISTIC model of evolution, most evolutionary change takes place in small steps within well-established species. the very slow rate of evolution that characterizes many well-established species has led some paleontologists to … conclude that most evolution must be associated with speciation… the rapid evolution of new species from others. This is the PUNCTUATIONAL model of evolution. Another line of evidence … is the evolutionary history that typifies long, narrow segments of phylogeny---segments that undergo little branching but span long intervals of geologic time… such segments of phylogeny would be expected to exhibit little evolution for the reason that they have experienced very little speciation.” (Pg. 123)
He points out, “Collision with a very large extraterrestrial object … should have serious consequences for environments on Earth… The energy of the explosion would convert atmospheric nitrogen to acidic nitrous oxides. As a result, atmospheric moisture would fall to Earth as acid rain. Acid rain could damage many forms of life… What forms of life would survive such changes? We have no certain answers; we can only wonder whether the arrival of an extraterrestrial object 10… or 20 kilometers in diameter may someday bring an end to our species’ reign on Earth.” (Pg. 197)
He suggests, “Although the fossil record will never tell us a great deal about the earliest stages of organic evolution, such information has been derived from other sources. In the early 1950s, for example, researchers [he cites Stanley Miller’s experiment] found that they could readily produce amino acids in the laboratory by sending electrical sparks through sealed vessels containing ammonia, methane, hydrogen, and steam.” (Pg. 205)
He contends, “An engineer with the power to design and build a shark would produce a better jaw than the primitive one that evolved from the gill bar. The skeleton of the early jaw consisted of soft cartilage rather than bone, and it floated loosely in soft tissue, without connection to the braincase. The primitive teeth also remained too much like denticles to function as effectively as those that an engineer might design or those that evolution eventually produced… It is easy to see why evolution has produced many organisms that seem highly imperfect and why it has failed to produce all kinds of organisms that our imaginations can conjure up.” (Pg. 281)
He argues, “The lung, which was occasionally used by early fishes to breathe air, was available for exploitation long before amphibians evolved. In the way the lung became a full-time supplier of oxygen we can see yet another example of the ‘opportunism’ of evolution. Unlike the gill supports, which evolved into jaws earlier in invertebrate evolution, the lungs developed from a preexisting structure that required very little evolutionary modification to open up an entirely new mode of life.” (Pg. 285)
He states, “The greatest controversy about dinosaurs … has related to their metabolism… it has been assumed that they were ectothermic (or cold-blooded). It has recently been argued, however, that dinosaurs were actually endothermic, or warm-blooded. The newer idea stems in part from evidence that dinosaurs were very active animals and in part from indication that they were more successful during the Mesozoic Era than were warm-blooded early mammals… Finally, the rapid growth of juvenile dinosaurs points to a high metabolism. Modern reptiles grow more slowly than dinosaurs did.” (Pg. 355)
He recounts, “In 1981 a team … led by the physicist Luis Alvarez and his son, Watler, a geologist, discovered an abnormally high concentration of the element iridium precisely at the level of the Cretaceous-Paleogene boundary… at Gubbio, Italy. Soon a comparable ‘iridium anomaly’ was found at the same stratigraphic level in many other regions of the world. Since iridium is very rare on Earth but fairly abundant in meteorites, the Alvarez team advanced the hypothesis that a large meteorite struck the Earth at the end of the Cretaceous… Other geologists suggested… a massive episode of volcanic activity… Nonetheless, two additional kinds of evidence favor the … idea that the course for the widespread iridium anomaly was extraterrestrial. Each is a type of grain that can form only under very intense pressure, such as the pressure that results when a large extraterrestrial body collides with Earth.” (Pg. 389)
“The evidence that heavy extinction was going on in the marine realm before the very end of the Cretaceous… and that the dinosaur community was also stressed raises an interesting possibility. Perhaps a bolide impact under these conditions was much more devastating to life than it would have been when ecosystems were healthy.” (Pg. 392)
This book will be very helpful for students (and others!) wanting an introductory text.
Paleobiologist Steven Stanley wrote in the Preface of this 1993 book, “My aim in writing this concise version of ‘Earth and Life Through Time’ has been to make the history of our planet and its inhabitants accessible to a wider range of students.”
He states in the first chapter, “An understanding of Earth history helps us to address problems caused by changes that are now taking place in the world, or that will be occurring soon. The rock record also sheds light on ways in which a broad array of factors cause environmental change and on the rates at which various kinds of change occur…The geologic record of the history of life also provides a unique perspective on the numerous extinctions of animals and plants that are now resulting from human activities. Humans are causing extinction by destroying forests and other habitats, but our collective behavior also affects life profoundly in less direct ways. Very soon human activities will cause average temperatures at Earth’s surface to rise in many areas of the world. The geologic record of ancient life reveals how climatic change has affected life in the past… As we come to understand the speed and profundity of natural environmental change and the transience of assemblages of species, we begin to appreciate the fragility of the world we live in… having studied the past, we can make more intelligent choices as we contemplate the future of our changing planet.” (Pg. 2)
He cautions, “Although fossils occur with great frequency in many sedimentary rocks, it is important to recognize that most species of animals and plants have never been discovered in the fossil record. Rare species and those that lack skeletons are especially unlikely to be found in fossilized form. Even most species with skeletons have left no permanent fossil record. A variety of processes destroy skeletons… Even after burial, many fossils fail to survive diagenesis, metamorphism, and erosion of the sedimentary rocks in which they are embedded. Finally, many fossil species remain entombed in rocks that have never been exposed at Earth’s surface or sampled by drilling operations.” (Pg. 12)
He explains that ‘index fossils’ “are easily distinguished from other taxa… They are geographically widespread and thus can be used to correlate rocks over a large area... [They] can be found in many places… They are restricted to narrow stratigraphic intervals, and thus allow for precise correlation. Unfortunately, few index fossils exhibit all of these traits as strongly as we could wish…” (Pg. 81-82)
He acknowledges, “fundamental uncertainties are inherent in radiometric dating. Most published radiometric dates… [indicate] uncertainty that is attributable to possible errors in the measurement of the quantities of parent and daughter elements… In accepting a date… we are assuming that a dated rock has remained a closed system… Unfortunately, this is not always the case… These types of errors sometimes add up to sizable total errors, especially when very old rocks are being dated.” (Pg. 88)
He reports, “When Darwin… weighed… evidence indicating that one type or organism evolved from another, he found that certain anatomical relationships seemed to build an especially compelling case… Darwin was intrigued by the admission of Louis Agassiz… that he could not distinguish an early embryo of a mammal from that of a bird or a reptile… Equally convincing to Darwin was the evidence of HOMOLOGY---the presence, in two different groups of animals or plants, or organs that have the same ancestral origin but serve different functions… The vestigial organs---organs that serve no apparent purpose but resemble organs that do perform functions in other creatures… Whales, for example, have apparently useless bones that resemble the pelvic bones of other mammals.” (Pg. 108)
He notes, “According to the traditional GRADUALISTIC model of evolution, most evolutionary change takes place in small steps within well-established species. the very slow rate of evolution that characterizes many well-established species has led some paleontologists to … conclude that most evolution must be associated with speciation… the rapid evolution of new species from others. This is the PUNCTUATIONAL model of evolution. Another line of evidence … is the evolutionary history that typifies long, narrow segments of phylogeny---segments that undergo little branching but span long intervals of geologic time… such segments of phylogeny would be expected to exhibit little evolution for the reason that they have experienced very little speciation.” (Pg. 123)
He points out, “Collision with a very large extraterrestrial object … should have serious consequences for environments on Earth… The energy of the explosion would convert atmospheric nitrogen to acidic nitrous oxides. As a result, atmospheric moisture would fall to Earth as acid rain. Acid rain could damage many forms of life… What forms of life would survive such changes? We have no certain answers; we can only wonder whether the arrival of an extraterrestrial object 10… or 20 kilometers in diameter may someday bring an end to our species’ reign on Earth.” (Pg. 197)
He suggests, “Although the fossil record will never tell us a great deal about the earliest stages of organic evolution, such information has been derived from other sources. In the early 1950s, for example, researchers [he cites Stanley Miller’s experiment] found that they could readily produce amino acids in the laboratory by sending electrical sparks through sealed vessels containing ammonia, methane, hydrogen, and steam.” (Pg. 205)
He contends, “An engineer with the power to design and build a shark would produce a better jaw than the primitive one that evolved from the gill bar. The skeleton of the early jaw consisted of soft cartilage rather than bone, and it floated loosely in soft tissue, without connection to the braincase. The primitive teeth also remained too much like denticles to function as effectively as those that an engineer might design or those that evolution eventually produced… It is easy to see why evolution has produced many organisms that seem highly imperfect and why it has failed to produce all kinds of organisms that our imaginations can conjure up.” (Pg. 281)
He argues, “The lung, which was occasionally used by early fishes to breathe air, was available for exploitation long before amphibians evolved. In the way the lung became a full-time supplier of oxygen we can see yet another example of the ‘opportunism’ of evolution. Unlike the gill supports, which evolved into jaws earlier in invertebrate evolution, the lungs developed from a preexisting structure that required very little evolutionary modification to open up an entirely new mode of life.” (Pg. 285)
He states, “The greatest controversy about dinosaurs … has related to their metabolism… it has been assumed that they were ectothermic (or cold-blooded). It has recently been argued, however, that dinosaurs were actually endothermic, or warm-blooded. The newer idea stems in part from evidence that dinosaurs were very active animals and in part from indication that they were more successful during the Mesozoic Era than were warm-blooded early mammals… Finally, the rapid growth of juvenile dinosaurs points to a high metabolism. Modern reptiles grow more slowly than dinosaurs did.” (Pg. 355)
He recounts, “In 1981 a team … led by the physicist Luis Alvarez and his son, Watler, a geologist, discovered an abnormally high concentration of the element iridium precisely at the level of the Cretaceous-Paleogene boundary… at Gubbio, Italy. Soon a comparable ‘iridium anomaly’ was found at the same stratigraphic level in many other regions of the world. Since iridium is very rare on Earth but fairly abundant in meteorites, the Alvarez team advanced the hypothesis that a large meteorite struck the Earth at the end of the Cretaceous… Other geologists suggested… a massive episode of volcanic activity… Nonetheless, two additional kinds of evidence favor the … idea that the course for the widespread iridium anomaly was extraterrestrial. Each is a type of grain that can form only under very intense pressure, such as the pressure that results when a large extraterrestrial body collides with Earth.” (Pg. 389)
“The evidence that heavy extinction was going on in the marine realm before the very end of the Cretaceous… and that the dinosaur community was also stressed raises an interesting possibility. Perhaps a bolide impact under these conditions was much more devastating to life than it would have been when ecosystems were healthy.” (Pg. 392)
This book will be very helpful for students (and others!) wanting an introductory text.
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