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Evidence and Evolution: The Logic Behind the Science
How should the concept of evidence be understood? And how does the concept of evidence apply to the controversy about creationism as well as to work in evolutionary biology about natural selection and common ancestry? In this rich and wide-ranging book, Elliott Sober investigates general questions about probability and evidence and shows how the answers he develops to those questions apply to the specifics of evolutionary biology. Drawing on a set of fascinating examples, he analyzes whether claims about intelligent design are untestable; whether they are discredited by the fact that many adaptations are imperfect; how evidence bears on whether present species trace back to common ancestors; how hypotheses about natural selection can be tested, and many other issues. His book will interest all readers who want to understand philosophical questions about evidence and evolution, as they arise both in Darwin's work and in contemporary biological research.
412 pages, Paperback
First published January 1, 2008
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January 19, 2025
A PHILOSOPHIICAL PERSPECTIVE ON EVOLUTION AND CREATIONISM
Philosopher Elliott Sober wrote in the Preface to this 2008 book, “I am not a cynic. A better answer is that philosophers of biology, and philosophers of science generally, study science. Ours is a second-order, not a first-order, subject… Two grand ideas animate the Darwinian theory of evolution… These are the ideas of common ancestry and natural selection… we can think of Darwinian ideas as competing with alternatives. The hypothesis that the species we now observe trace back to a common ancestor competes with the hypothesis that they originated separately and independently… The two parts of the Darwinian picture are LOGICALLY independent of each other, but they are METHODOLOGICALLY interdependent… The book before you is … a work of philosophy. My goal… is not to pile up facts that support this or that proposition in evolutionary biology. Rather, I want to describe the tools that ought to be used to assess the evidence that bears on evolutionary ideas.”
He explains in Chapter 1, “This book is about the concept of evidence as it applies in evolutionary biology… I do not aim here to provide anything like a complete treatment of the debate between Bayesianism and frequentism… Rather, I hope to help the reader to understand what the shooting has been about… I will argue that Bayesianism makes excellent sense for many scientific interests. However, I do agree with frequentists that applying Bayesian methods in other contexts is highly problematic. But… I do not want to throw out the Bayesian baby with the bathwater… My approach will be ‘eclectic’; no single unified account of all scientific inference will be defended here, much as I would like there to be a grand unified theory.” (Pg. 3)
He asserts, “It is important not to lose sight of the possibilities that Darwin saw so clearly. Many creationists describe theism and evolutionary theory as if they are incompatible: that the proposition that God exists entails that evolutionary theory is untrue. Some defenders of evolutionary theory … reason from the truth of evolutionary theory to the falsehood of theism. Both parties are arguing a fake dichotomy… Theistic evolution is logically consistent; it also happens to be the viewpoint that many religious people have embraced… The real difference between creationism and theistic evolutionists is [that] Creationists hold that the evolutionary process is fundamentally incapable of producing the complex adaptations we observe; those features require God’s DIRECT intervention. For theistic evolutionists, God produces complex adaptations INDIRECTLY, by way of natural processes he put in place… The theory of evolution, which is a theory about LIVING things, not about the origin of the entire universe, is silent on the question of whether there is a God.” (Pg. 112-113)
He states, “Post-Darwinian creationists often write as if … evolution by natural selection is just like monkeys and typewriters… [or] a hurricane blowing through a junkyard assembling scattered pieces of metal into a functioning airplane. This analogy is fundamentally misleading… the essence of the process of natural selection is that some outcomes are far more probable than others… Natural selection is a 'biased’ process, not a RANDOM process… it is mutation, not natural selection, that resembles the hurricane… the two-part process of mutation + selection contains a random element and a nonrandom element.” (Pg. 122-123) He adds, “Natural selection is no more a random process than intelligent design is. As for the ‘randomness’ of variation, the point is that novel variants do not arise because they would be useful; this does not mean that they are uncaused.” (Pg. 125)
Of Stephen Jay Gould’s ‘Panda’s Thumb’ argument, he comments, “How does Gould know what God… would have wanted to achieve in building the panda? Gould is assuming that an intelligent designer would have wanted to supply pandas with a super-efficient device (like a … can opener) for preparing bamboo… Perhaps God realized that if pandas had better tools, they would eat all of the bamboo, which would cause the extinction of the bamboo forest and of pandas as well. And maybe these two extinctions would have triggered a cascade of others… what is needed is independent evidence concerning what God … would have wanted to achieve if he had built the panda. And this is something that Gould does not have. I think creationists are right to object in this way to Gould’s argument.” (Pg. 127-128)
He argues, “Atheists who agree with my criticism of the design argument should reconsider whether they think the argument from evil is convincing… how can we be so sure that… God would not have had his reasons for allowing evils to exist in the quantity that we observe? Perhaps those evils are necessarily correlates of greater goods… The problem of evil is not that evil exists, but that so much of it… even if we grant for the sake of argument that free will and soul-buildings account for SOME of the evils that there are, there still appears to be vastly more evil than we have so far explained. There are evils that don’t build souls and that aren’t due to anyone’s exercising their free will. How can this excess be reconciled with the existence of … God? … theists who reply to the argument from evil by saying that God’s goals are inscrutable should have little sympathy with the organismic argument from design.” (Pg. 165-167)
He observes, “There is also the prior question of whether you should rely exclusively on evidence to decide what your theological convictions ought to be. Must ALL your beliefs be dictated by the evidence you have and by nothing else? This is the question that William James and W.K. Clifford debated… ‘The Will to Believe’ versus ‘The Ethics of Belief.’ Just as scientific theories are silent on the question of whether God exists, they also have nothing to say about this question of ethics.” (Pg. 187-188)
He asks, “How much similarity is needed for common ancestry to be a good inference? For example, human beings and chimps are about 98.5 percent similar at the level of their DNA sequences. If this is enough to justify the inference, what is the cut-off that 98.5% is said to exceed? Fifty percent? Twenty-five? Does this mean that if we find two species that are LESS similar than this cut-off that we should conclude that they LACK a common ancestor?” (Pg. 266)
He explains, “Creationists frequently claim that the absence of intermediate fossils is evidence against evolutionary theory. Evolutionists reply by pointing to the numerous intermediate fossils that have been discovered that link dinosaurs with birds, lake tetrapods with fish, reptiles with mammals, and land animals with whales… We now can turn to the accusation that evolutionists play a game of ‘heads I win, tails you lose’ when they appeal to the imperfection of the fossil record to excuse the fact that no fossil [that] is intermediate between X and Y has yet been observed… There is an old motto that scientists often repeat: Absence of evidence is not evidence of absence… the motto embodies an exaggeration. Suppose you LOOK for intermediate fossils and fail to find them… for many values of the relevant parameters, not observing a fossil intermediate provides NEGLIGIBLE evidence… absence of evidence is ALMOST valueless… [We] find it irresistible to connect the dots… we can’t assume that the fossils we observe are ANCESTORS of present-day organisms: they might just be RELATIVES.” (Pg. 318-324)
He adds in the concluding chapter, “It is false that the only alternative to intelligent design is gradual evolution by natural selection in an infinite population… the question we need to consider is contrastive: Does the evolutionary hypothesis or the intelligent design hypothesis make the observations more probable? Intelligent design proponents can’t leave their ‘theory’ in the background in the hope that evolutionary theory will shoot itself in the foot. Rather, they need to describe what intelligent design theory asserts beyond the one-sentence slogan that an intelligent designer made this or that feature; in particular, they need to say what their ‘theory’ predicts. Precisely the same considerations apply to testing selection against drift. It is no good dismissing drift on the grounds that it says that the complex and useful trait that we are studying is impossible.” (Pg. 353)
Open-minded persons from a variety of perspectives will probably find this book stimulating and thought-provoking.
Philosopher Elliott Sober wrote in the Preface to this 2008 book, “I am not a cynic. A better answer is that philosophers of biology, and philosophers of science generally, study science. Ours is a second-order, not a first-order, subject… Two grand ideas animate the Darwinian theory of evolution… These are the ideas of common ancestry and natural selection… we can think of Darwinian ideas as competing with alternatives. The hypothesis that the species we now observe trace back to a common ancestor competes with the hypothesis that they originated separately and independently… The two parts of the Darwinian picture are LOGICALLY independent of each other, but they are METHODOLOGICALLY interdependent… The book before you is … a work of philosophy. My goal… is not to pile up facts that support this or that proposition in evolutionary biology. Rather, I want to describe the tools that ought to be used to assess the evidence that bears on evolutionary ideas.”
He explains in Chapter 1, “This book is about the concept of evidence as it applies in evolutionary biology… I do not aim here to provide anything like a complete treatment of the debate between Bayesianism and frequentism… Rather, I hope to help the reader to understand what the shooting has been about… I will argue that Bayesianism makes excellent sense for many scientific interests. However, I do agree with frequentists that applying Bayesian methods in other contexts is highly problematic. But… I do not want to throw out the Bayesian baby with the bathwater… My approach will be ‘eclectic’; no single unified account of all scientific inference will be defended here, much as I would like there to be a grand unified theory.” (Pg. 3)
He asserts, “It is important not to lose sight of the possibilities that Darwin saw so clearly. Many creationists describe theism and evolutionary theory as if they are incompatible: that the proposition that God exists entails that evolutionary theory is untrue. Some defenders of evolutionary theory … reason from the truth of evolutionary theory to the falsehood of theism. Both parties are arguing a fake dichotomy… Theistic evolution is logically consistent; it also happens to be the viewpoint that many religious people have embraced… The real difference between creationism and theistic evolutionists is [that] Creationists hold that the evolutionary process is fundamentally incapable of producing the complex adaptations we observe; those features require God’s DIRECT intervention. For theistic evolutionists, God produces complex adaptations INDIRECTLY, by way of natural processes he put in place… The theory of evolution, which is a theory about LIVING things, not about the origin of the entire universe, is silent on the question of whether there is a God.” (Pg. 112-113)
He states, “Post-Darwinian creationists often write as if … evolution by natural selection is just like monkeys and typewriters… [or] a hurricane blowing through a junkyard assembling scattered pieces of metal into a functioning airplane. This analogy is fundamentally misleading… the essence of the process of natural selection is that some outcomes are far more probable than others… Natural selection is a 'biased’ process, not a RANDOM process… it is mutation, not natural selection, that resembles the hurricane… the two-part process of mutation + selection contains a random element and a nonrandom element.” (Pg. 122-123) He adds, “Natural selection is no more a random process than intelligent design is. As for the ‘randomness’ of variation, the point is that novel variants do not arise because they would be useful; this does not mean that they are uncaused.” (Pg. 125)
Of Stephen Jay Gould’s ‘Panda’s Thumb’ argument, he comments, “How does Gould know what God… would have wanted to achieve in building the panda? Gould is assuming that an intelligent designer would have wanted to supply pandas with a super-efficient device (like a … can opener) for preparing bamboo… Perhaps God realized that if pandas had better tools, they would eat all of the bamboo, which would cause the extinction of the bamboo forest and of pandas as well. And maybe these two extinctions would have triggered a cascade of others… what is needed is independent evidence concerning what God … would have wanted to achieve if he had built the panda. And this is something that Gould does not have. I think creationists are right to object in this way to Gould’s argument.” (Pg. 127-128)
He argues, “Atheists who agree with my criticism of the design argument should reconsider whether they think the argument from evil is convincing… how can we be so sure that… God would not have had his reasons for allowing evils to exist in the quantity that we observe? Perhaps those evils are necessarily correlates of greater goods… The problem of evil is not that evil exists, but that so much of it… even if we grant for the sake of argument that free will and soul-buildings account for SOME of the evils that there are, there still appears to be vastly more evil than we have so far explained. There are evils that don’t build souls and that aren’t due to anyone’s exercising their free will. How can this excess be reconciled with the existence of … God? … theists who reply to the argument from evil by saying that God’s goals are inscrutable should have little sympathy with the organismic argument from design.” (Pg. 165-167)
He observes, “There is also the prior question of whether you should rely exclusively on evidence to decide what your theological convictions ought to be. Must ALL your beliefs be dictated by the evidence you have and by nothing else? This is the question that William James and W.K. Clifford debated… ‘The Will to Believe’ versus ‘The Ethics of Belief.’ Just as scientific theories are silent on the question of whether God exists, they also have nothing to say about this question of ethics.” (Pg. 187-188)
He asks, “How much similarity is needed for common ancestry to be a good inference? For example, human beings and chimps are about 98.5 percent similar at the level of their DNA sequences. If this is enough to justify the inference, what is the cut-off that 98.5% is said to exceed? Fifty percent? Twenty-five? Does this mean that if we find two species that are LESS similar than this cut-off that we should conclude that they LACK a common ancestor?” (Pg. 266)
He explains, “Creationists frequently claim that the absence of intermediate fossils is evidence against evolutionary theory. Evolutionists reply by pointing to the numerous intermediate fossils that have been discovered that link dinosaurs with birds, lake tetrapods with fish, reptiles with mammals, and land animals with whales… We now can turn to the accusation that evolutionists play a game of ‘heads I win, tails you lose’ when they appeal to the imperfection of the fossil record to excuse the fact that no fossil [that] is intermediate between X and Y has yet been observed… There is an old motto that scientists often repeat: Absence of evidence is not evidence of absence… the motto embodies an exaggeration. Suppose you LOOK for intermediate fossils and fail to find them… for many values of the relevant parameters, not observing a fossil intermediate provides NEGLIGIBLE evidence… absence of evidence is ALMOST valueless… [We] find it irresistible to connect the dots… we can’t assume that the fossils we observe are ANCESTORS of present-day organisms: they might just be RELATIVES.” (Pg. 318-324)
He adds in the concluding chapter, “It is false that the only alternative to intelligent design is gradual evolution by natural selection in an infinite population… the question we need to consider is contrastive: Does the evolutionary hypothesis or the intelligent design hypothesis make the observations more probable? Intelligent design proponents can’t leave their ‘theory’ in the background in the hope that evolutionary theory will shoot itself in the foot. Rather, they need to describe what intelligent design theory asserts beyond the one-sentence slogan that an intelligent designer made this or that feature; in particular, they need to say what their ‘theory’ predicts. Precisely the same considerations apply to testing selection against drift. It is no good dismissing drift on the grounds that it says that the complex and useful trait that we are studying is impossible.” (Pg. 353)
Open-minded persons from a variety of perspectives will probably find this book stimulating and thought-provoking.
August 6, 2016
Only for the evolutionary biologist, technically advanced at that. This is an academic work, that I suspect is a challenge for many even in this group. The chapter, Intelligent Design dryly demolishes any remnants of the notion.
"My goal in this chapter is to arrive at the strongest, most defensible, version of the [word removed by mgb], and to say why I think the argument is defective." p.113
A great deal of probability logic follows ...
e.g. f2=freq(an intelligent designer produced X|X is complex and useful & we observe what produced X) is high.
etc.
clap-trap statements from Plantinga and Behe are laid bare. At the end he leaves it up to individuals to decide for themselves about the existence of God, which is what most evolutionists do. It is simply an untestable hypothesis. He suggests that theists could ask "Must all [my] beliefs be dictated by the evidence you have and nothing else?"
"My goal in this chapter is to arrive at the strongest, most defensible, version of the [word removed by mgb], and to say why I think the argument is defective." p.113
A great deal of probability logic follows ...
e.g. f2=freq(an intelligent designer produced X|X is complex and useful & we observe what produced X) is high.
etc.
clap-trap statements from Plantinga and Behe are laid bare. At the end he leaves it up to individuals to decide for themselves about the existence of God, which is what most evolutionists do. It is simply an untestable hypothesis. He suggests that theists could ask "Must all [my] beliefs be dictated by the evidence you have and nothing else?"
June 2, 2012
This is a hard book to review. Excellent summary of how we reason about evolution, comprehensive and deep. It wades into strict probabilistic deconstruction of the arguments for design, natural selection, drift, common ancestry, and other popular hypotheses. Thus, it's not for the faint at heart.
shelved
September 15, 2012The evidence concept coupled with controveries of creationism and evolutinary theory.
Displaying 1 - 4 of 4 reviews