Evolution by the Numbers. James Wynn
Читать онлайн книгу.
as how closely species are related and how diseases have emerged and developed over time. Molecular geneticists, for example, might test hypotheses about the degree of relatedness between organisms by developing genetic taxonomies or gene trees. These trees require special algorithms designed to calculate the proximity of organisms to one another based on their genetic divergence in some physical trait. For example, a molecular geneticist might compare the order of amino acids in the red blood cells of humans, pigs, mice, and chickens. Using one or more of a handful of standard mathematical methods for calculating relatedness between organisms, he/she would conclude that, evolutionarily speaking, humans are closer to pigs than chickens (Hartl and Jones 612–13).With these methods, molecular geneticists are beginning to provide better insight into relations of descent between organisms, including ones that would have likely eluded qualitative taxonomists, such as the water lily’s (Nuphar polysepalum) position as the genetic progenitor of the oak tree and all other seed-bearing plants (National Science Foundation).
Along with molecular biologists, population geneticists also use established mathematical algorithms to describe changes in organic populations. They rely, for example, on the algebraic Hardy-Weinberg principle as a model for the distribution of genes in a population under random mating conditions. In this endeavor, mathematics plays a central role because it is used to define a hypothetical baseline for change in the rate of alleles (the different possible gene types at a specific location on a chromosome) in a population against which the effects of natural selection, population size, mutation, migration, and random drift can be assessed. Calculations like these are essential to a number of modern applications, such as scientific breeding programs, assessments of the efficacy of screening for genetic disease factors, and the estimation of biodiversity.
Finally, a discussion of the importance of mathematics to modern investigations of variation, evolution, and heredity would be incomplete without mentioning the general value of statistics and probability in the day-to-day pursuit of scientific research. In modern biological research, investigations regularly begin and end with statisticians or biostatisticians carefully assessing the methods and results of experiments. Trained in statistics and probability, these members of a research team provide guidance to laboratory scientists on how to structure their experiments so that they limit the influence of factors which might bias their outcomes. For example, a lab’s biostatistician might advise geneticists working in disease research on techniques for random sampling to ensure that they have a data set from the general population for a genetic trait that might be used comparatively to identify genetic disease markers in a population of interest. After the tests are run and the data are collected, statisticians and biometricians are also tasked with calculating the reliability of the results and assessing the data to determine whether, if any, significant patterns emerge. These duties are so important to modern genetic research that Eleanor Feingold, a quantitative geneticist at the University of Pittsburgh, explained, “a lab of any reasonable size would have a biostatistician, a quantitative geneticist, or a statistician attached to it.”
A behind-the-scenes investigation of operations of modern research into variation, evolution, and heredity reveals: (1) that these phenomena cannot reasonably be investigated without mathematics and (2) that because of the increasing size and availability of data on these phenomena, the importance of mathematics will continue to grow. For these reasons, understanding both the role of mathematical argument in science and how that role came to be established, which are the subjects of this book, should be considered important topics of exploration.
Rhetoric, Mathematics, and Science
Although modern research in variation, evolution, and heredity would be impossible without mathematics, there was a time when these phenomena were explored largely without it. The focus of this book is the one hundred-year period between the publication of The Origin of Species and the emergence of modern programs of population and quantitative genetics in the nineteen fifties and sixties. During this critical period of development, mathematics and its capacity to generate reliable knowledge about organic populations was disputed. The goal of this text is to explore some of the reasons why mathematical argument was resisted in these early periods, and how it was advocated for either successfully or unsuccessfully by natural researchers who wanted to advance its credibility and explore the possibilities for its use.
To examine the use of and debates about mathematics in this formative period, this investigation turns to the methods and tools of rhetoric, a field of research and analysis devoted to the study of human communication, argument, and persuasion. With the aid of concepts and methods from this field, the book examines choices in language, organization, and argument in discourse located within specific social, epistemological, and cultural/historical contexts. Examining these dimensions of discourse in context permits characterizations of the goals and beliefs of arguers, the perceptions they have of their audiences, and the suitability of their choices in argument and communication. By investigating these facets of argument and persuasion, this book aims to better understand mathematical argument in a scientific context as well as explore what this relationship reveals about the practical value of rhetorical tools and concepts in understanding it.
Although the text is written primarily with philosophers, historians, sociologists, and rhetoricians of science in mind, every effort has been made to accommodate a broader educated audience of readers. Non-specialist readers who follow the subjects of mathematics, genetics, and evolution will likely find their interests reflected in the choice of topics and figures being investigated in this book. Well-known researchers such as Darwin and Mendel will be discussed, and fresh perspectives on their work as mathematical argument will be examined. Chapter 3, for example, explores in detail not only Mendel’s mathematical arguments in his famous paper, “Experiments in Plant Hybridization,” but also the historical context in which he makes these arguments. Assessing these dimensions of Mendel’s work reveals his reliance on the mathematics of probability as a source of invention for his pea experiments as well as his overconfidence that by using mathematical arguments he could persuade his audience to accept the general validity of his hereditary law.
Chapter 2 looks at Darwin’s work from a seldom–examined, mathematical perspective and reveals the extent to which the self-proclaimed mathematical bumbler relied on quantitative evidence and arithmetically informed arguments to invent and support some of his central conclusions in The Origin of Species. An examination of Darwin’s letters, diaries, his “big species” book (the original manuscript from which The Origin of Species was abstracted), and his arguments in The Origin of Species reveal that Darwin hoped to place biology on par with the physical sciences by giving it a solid, mathematical foundation. Other chapters in the book are devoted to less-well-known—but no less important or interesting—figures such as Francis Galton, Karl Pearson, and R.A. Fisher, all of whom play important roles in the development of a mathematical science of variation, evolution, and heredity.
In addition to persons of interest, this book also explores topics in science and mathematics with broad appeal. For example, it engages with the perennial issue of how scientific knowledge is validated. By examining the successes and failures of the scientists featured in the text, it suggests that when a scientific paradigm cannot be relied on to establish the appropriateness of mathematical arguments, arguers can turn to beliefs and values outside of science. Further, it explores the question. “How reliable and successful are mathematics in describing real phenomena?” This query is central to our current public and scientific concerns as we turn to polls, statistics, and probabilistic assessments with increasing frequency to make decisions about products, cures, risks, and candidates. What this investigation reveals is that nineteenth and early twentieth century scientists approached new mathematical methods and their conclusions with a healthy dose of skepticism. They offered legitimate resistance to mathematically informed theories of variation, evolution, and heredity that had insufficient evidence or blatantly disregarded important aspects of biological phenomena. In a few instances, however, their rejections were premature and prejudiced by either their ignorance of mathematics or their personal commitments to other methods of analysis.
Whether you read this book for the characters or the concepts, the goal is the same: to scrutinize, using the tools of rhetoric, the texts, arguments, and contexts involved in the development of the relationship between biological investigations of variation, evolution, and heredity and mathematics from the