ESPM 24__________
Discussions on Evolutionary Biology
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Introduction.
The individual articles used in the course present a collage of topics scattered across the spectrum of evolutionary biology. All were written for the general educated public. The majority were published either in The American Scientist, the monthly magazine of the national scientific research society Sigma Xi, or in Natural History Magazine from the American Museum of Natural History in New York City.The readings assigned for the second through fifth weeks of the semester address the topic of evolutionary biology in broad philosophical terms. These readings have direct connections to questions regarding the relationship between science and religion in general as well as to popular debates between evolutionary biology and creationism. These connections are, however, ancillary to the course. Students who desire to pursue further matters concerning science and religion are encouraged to explore the resources available on the web sites for CTNS and NCSE. Two particularly good books are:
The
April 2002 issue of Natural History contained a special report,
available
on-line, consisting of short articles devoted to the Intelligent Design
movement.
Beginning with the sixth assignment, the readings focus on specific topics in the field of evolutionary biology. The choice of readings is topical and not intended to provide a systematical introduction to evolutionary biology. Nevertheless there are several themes in common that provide a mental check list to apply while reading the articles. In particular, ask two questions while reading:
Question 1. What can you learn from the reading about How Science is Done? What questions were the scientists asking? What kinds of data were they obtaining and discussing? How did they get their data? Science depends upon having techniques that enable investigators to obtain data that shed light on the questions they are trying to answer. The development of new techniques is often the breakthrough that makes it possible to ask and get answers to a whole new set of questions. Pay attention to the techniques used. In addition, science, especially an historical science such as evolutionary biology, is in many ways a detective game. Think as if you were reading a murder mystery. What are the clues? If no one else was there when the murder occurred, how did Holmes figure out who the murderer is?
Question 2. What can you learn from the reading about the History of Life on Earth? What were the changes that occurred? What were the circumstances and conditions under which the changes occurred? What were the processes that brought about the changes? What were the consequences of the changes? A leitmotif that runs throughout the course is the concept of a Key Innovation. First introduced by Berkeley zoologist Alden Miller in 1949, the concept refers to situations in which a small, discrete change opens up a new range of possibilities which, in turn, lead to a comparatively rapid diversification of the lineage. For instance, a discrete change in the structure of the jaw bones may lead to rapid diversification of new feeding strategies and a subsequent diversification into related species. Miller developed the concept of key innovations in the context of a morphological change that opened new ecological opportunities, leading in turn to further, varied, morphological changes. However, the concept can be more general. Watch for examples of key innovations.
Finally, when reading the articles try, to the extent it is possible to do so, to consider the context in which the article was written. Why and for whom was the article written? Look beyond the authors' attention gainers and particular details that are limited to the context for which the article was written to find more general issues and principles that transcend the scope of the specific topics addressed by the articles.
Notes on the Articles.
Tidbits to Note:
Throughout the articles there occur numerous brief discussions of people, concepts, or events that have greater significance than the context of the article in which they are mentioned. In the following notes these Tidbits to Note are flagged so that you may make a point of adding them to your intellectual toolbox.
Evolutionary biology and the study of human nature. (Assignment 1.)
This article was written for a consultation of the Presbyterian Church (U.S.A.) on "The Church and Contemporary Cosmology" held in 1988. The author's goals in writing the article were two-fold: The beginning and ending sections offer thoughts on the interface between evolutionary biology and theology. The middle sections, which may be read in PDF format, were written to provide the consultation's participants, most of whom were either cosmologists or theologians, with an historical perspective for understanding the major features of contemporary evolutionary biology. Focus on these two sections. Pay particular attention to the distinctions between the principle of genealogical relatedness versus processes of evolutionary change and reconstruction of historical scenarios. Note, however, that all these components of evolutionary biology are based upon a large body of factual knowledge. Tidbits to Note: "Scientific naturalism." Argument for design. The New Synthesis. "Populational thinking" versus "typological thinking."
Darwinism defined: the difference between fact and theory. (Assignment 2.)
Stephen J. Gould was a Harvard paleontologist and a prolific writer of popular essays on evolutionary biology. In this essay he turned his attention to disentangling a misunderstanding of evolutionary biology that arose from the common error of confusing the fact of common descent with modification, on the one hand, with theories that provide explanations of evolutionary processes, on the other hand. [Sidelight: how many meanings of the word "theory" can you find in a dictionary?] Tidbits to Note: Cladistics. Historical vs. experimental sciences. William Whewell and "consilience".
Science and Myth. (Assignment 3.)
A creative thinker and writer, John Maynard Smith has been a leading theoretical population geneticist for more than half a century. While reading this article, try to answer the question of whether or not science-as-a-way-of-knowing is different from other forms of human inquiry. Do not take the word "myth" in Maynard Smith's title in its vulgar sense. The "Science" and "Myth" in the title refer to Gould's two magisteria (whether nonoverlapping or not). Tidbits to Note: Karl Popper and "falsifiability". Thomas Kuhn and "paradigm shifts". Marxism vs. Darwinism.
Nonoverlapping Magisteria. (Assignment 4.)
This was Gould's column in Natural History in which he introduced his philosophical concept of NOMA. He subsequently expanded his discussion of NOMA in a full length book: Rocks of Ages: Science and Religion in the Fullness of Life. Ballantine. New York (1999). Many scientists, and some theologians, who write favorably upon both science and religion express some form of NOMA. [f.y.i. --- Fuller, more formal, discussions of relationships between the two magisteria can be found in John Haught's article in Evolving Dialogue and in chapter 4 in Ian Barbour's book.] Tidbits to Note: Be sure to read the postscript --- Stephen Jay Gould died on 20 May 2002.
Life's Grand Design. (Assignment 5.)
The latest attempt to present creationism as a "scientific" alternative to contemporary evolutionary biology comes from the "Intelligent Design" movement, which has revived the early 19th century philosophical ideas of the British cleric William Paley. This article directly addresses the concept of intelligent design. The biological examples presented in the article illustrate important, and intriguing, facets of biological evolution. [f.y.i. - To read more on the current ID arguments, see the special report that was published in the April, 2002, issue of Natural History. Also, see the quotes and notes for the articles by Durant, Dembski, and Grizzle in Evolving Diologue.] Tidbits to Note: Wm. Paley. Beta globin genes. Gene duplications. Pseudogenes.
At this point in the course, we put philosophy aside and turn our attention to getting to know a few tidbits of biology in general and evolutionary biology in particular. Before reading the next article, review the two questions that are posed above in the Introduction to these notes.
Early Life on Land. (Assignment 6.)
Shedding light on a major event that occurred deep in the history of life on earth is the subject of this article. It is a detective game. The case is not yet ready for the DA, but there are lots of clues. What are the major clues? Questions to ask yourself while reading: What were some of the problems that had to be solved in order for life to succeed on land? What were some of the key innovations that solved those problems? [For an interesting addition to the story, look at this U.C. press release of 14 Sep 2000.] Tidbits to Note: Sporopollenin. Spore tetrads. Trilete spores. Lignin. Acid bath technique.
Giardia: A Missing Link between Prokaryotes and Eukaryotes. (Assignment 7.)
This article takes us back to an even earlier stage in the history of life. It begins with an overview of some fascinating details of cell biology and the differences between the two major cell types: prokaryotes and eukaryotes. What are major features in common to both types? What are major differences between the two types? What can be said about the events that led to the evolution of the more complex eukaryotes from their simpler relatives? What major changes in the environment occurred in those days? There are good clues, but the picture is still fragmentary. The authors work with a pesky little organism named Giardia which is intermediate between prokaryotes and eukaryotes. Tidbits to Note: Anaerobic vs. aerobic respiration. Mitochondria. Archebacteria vs Eubacteria. Cytoskeletons. Endocytosis and exocytosis. Ribosomal RNA and molecular phylogenies. Haploid-Diploid-Dikaryotic.
The Early Evolution of the Domestic Dog. (Assignment 8.)
Natural selection did not cease when humans began mucking around with nature. Rather, human activities simply added additional factors to the equation. This article ponders the evolutionary consequences that transpired when humans and wolfs formed mutual associations in a process(es) that led to the domestic dogs we know and love today. First there is the question of what characteristics of wolves and humans predisposed them to be able to form a successful association? Next there are some fascinating biological consequences that occurred from the association. Perhaps the most interesting is the phenomenon of paedomorphosis, which occurred in both morphological and behavioral traits during the transformations from wolves to dogs. Keep in mind the fundamental question: Who will be parents of the next generation? (Note: Current molecular and behavioral data indicate that domestication occurred multiple times and involved various subspecies of wolves. Modern wolves and dogs are interfertile, and taxonomists consider them a single species.) Tidbits to Note: Artificial selection vs. natural selection. Imprinting. Paedomophosis. "r" and "K" selection. Allometry.
Spacious Skies and Tilted Axes. (Assignment 9.)
Agriculture is the foundation upon which civilizations are built. What are the biological histories of the foods we eat? In this article Jared Diamond discusses the history of the domestication of crops and live stock, with special focus on the conditions that conferred disproportionate significance upon events that occurred a mere 10,000 years ago in the Fertile Crescent of the Mid-East. [f.y.i. - The geneticist, L. L. Cavalli-Sforza has spent fifty years studying the spread of human populations from the Fertile Crescent across Eurasia using a wide assortment of genetic data and also linguistic data. He presents the story in his easily readable book The Great Human Diasporas: The History of Diversity and Evolution published by Addison-Wesley in 1995.] Tidbits to Note: Single vs. multiple occurrences of domestication. Environmental barriers and corridors to migration.
The Evolutionary Potential of Crop Pests. (Assignment 10.)
Evolution on the farm (and in the hospital) occurs in front of our noses. The "evolutionary arms race" between hosts and pathogens was underway long before humans escalated the conflict by intervening on behalf of host plants. (Why are chili peppers hot and poison oak poisonous?) In this article, examples of evolution in weeds, pathogens, and insects provide marvelous illustrations of natural selection in action. Enjoy them. The latter portions of the article, which become a bit more technical, introduce several current issues and tricks that concern agricultural scientists in their fight against the continual evolution of crop pests. Tidbits to Note: Variation and local adaptation. Mutation versus hybridization. Mimicry. Juvenile hormone. B.t.
Founding Fathers and Mothers. (Assignment 11.)
The "founder effect" is a well known phenomenon of population genetics. In this article Jared Diamond illustrates its significance in small isolated populations. Diamond's examples are of human birth defects; conservation geneticists confront similar problems when dealing with rare and endangered species. At a higher level, the phenomenon underscores the significance of historical contingencies in the course of evolutionary change. In the latter portion of this article, Diamond speculates on the possible role founder effects may have played in the genetic history of the human species as a whole. Tidbits to Note: Recessive genetic birth defects. "Private" genes. Inbreeding. Malarial resistance.
In this milestone essay (it was his 200th column in Natural History) Stephen Gould indulges in a bit of personal history. The reader is treated to an "insider's" account of the origin of the theory of Punctuated Equilibrium, which Gould and Niles Eldredge formulated in 1971. Pay attention to Gould's description of the intellectual environment in which he and Eldredge developed their concept of punctuated equilibrium. (In the 1960's there was still a fair degree of intellectual isolationism among different branches of the biological sciences.) Publication of "Punk eke" created a definite brouhaha, due in no small part to the hype with which Gould himself promoted his ideas. In this article you can read Gould's own take on the affair from the perspective of 20 years hindsight. [See also H. Allen Orr's essay "The Descent of Gould" in the September 30, 2002, issue of The New Yorker Magazine.] Tidbits to Note: Time scales. Micro- versus macro-evolution. Anagenesis and cladogenesis.
© 2002 by Philip T. Spieth
