- Research article
- Open Access
Correcting some common misrepresentations of evolution in textbooks and the media
© Padian; licensee Springer. 2013
- Received: 31 March 2013
- Accepted: 31 March 2013
- Published: 25 June 2013
Topics related to evolution tend to generate a disproportionate amount of misunderstanding in traditional textbooks, other educational materials, and the media. This is not necessarily the fault of textbook and popular writers: many of these concepts are confusingly discussed in the scientific literature. However, faults can be corrected, and doing so makes it easier to explain related concepts. Three general areas are treated here: ideas and language about evolution, historical and philosophical aspects of evolution, and natural selection and related concepts. The aim of this paper is to produce a template for a more logical, historically and scientifically correct treatment of evolutionary terms and concepts.
- Evolution education
- History of biology
- Natural selection
- Charles Darwin
Textbook and popular writers have a difficult task. Their job is to present science to students and other members of the public who, increasingly, come from dispte cultural and economic backgrounds, live in states that have conflicting guidelines for what should be presented in science texts, and are being subjected to deteriorating state support and increasing political factionalism. With less money to spend on instructional materials, competition is tougher than ever.
It is nearly impossible for a scientist to keep up with the literature in evolutionary biology, or virtually any other scientific field. There are more journals, more online sources, more columns, stories, blogs, postings, and videos than ever before. How can professional writers (most of whom do not have advanced or even basic degrees in science), let alone biologists, keep up with this explosion of literature and judge its relevance?
The answer is, they cannot, and in practice, they do not. Teachers who compare closely the treatments of subjects in competing textbooks will notice that they promise the moon, advertising the individual and unique effectiveness of their pedagogical approach. Be that as it may, the science content is peculiarly uniform among publishing houses, although specific examples and details of concepts ‘may vary’ (to quote traditional textbook jargon). And sometimes that content is wrong, and it has been for many years. Writers are in a difficult position because, if new research seems to contradict traditional information, it is hard for them to tell whether this new finding is really legitimate or will be overturned in a matter of months. And they have been burned in the past (just look up ‘Protoavis’). But textbook writers are also reluctant to change their presentations, even when they are long outdated, because they worry about being ‘too different’ from other textbook programs and confusing some teachers who expect certain content and cannot always keep up with new developments in the field. An example is how long it is taking textbooks to get rid of the Linnean classification system and teach phylogenetic systematics (cladistics).
Because the treatment of scientific subjects is so uniform among textbooks, specific errors and misrepresentations are common to most publishing houses. These have been picked up by other media, and many of them are of longstanding. In the following suggestions I try to point out why certain conventions in science texts and popular publications are either incorrect or technically correct but could be presented better, and to suggest alternative treatments. I hope it will become clear that much of the engendered confusion is due to us scientists, who have not been as precise with their diction as we should be. Even though we often agree among each other that we know what we mean, this does not help textbook writers, reporters, teachers, or students.
The list of topics that follows is wide-ranging but necessarily incomplete; I have tried to divide them generally into ‘The ideas and language of evolution’, ‘Historical and philosophical aspects of evolution’, and ‘Natural selection and related concepts’. For related articles see Padian (1997, 1999, 2007, 2008a, b, c, 2009), and many issues of William J. Bennetta’s The Textbook Letter (see http://www.textbookleague.org/missn.htm). The goal of this paper is to stimulate awareness and discussion among scientists, educators, textbook writers, and journalists who have to interpret evolution to students and the general public. Although there is a lot of room for interpretation and debate of language and concepts, the hope is that a forthright discussion of ambiguities and infelicities should eventually improve the presentation of evolution to the public.
Distinguish evolution as fact, pattern, and process
The word ‘evolution’ has several meanings. So do lots of useful words. Let us take ‘business’. What’s my business? I’m an architect. Where’s my business? On Fourth Street. How much do I make? None of your business. Three different senses of the same word. And so it is with evolution. Evolution is a fact: science understands that life has evolved through time, and there is no reasonable doubt about this anywhere in the scientific community. It is a theory: it comprises a great many patterns, processes, observations, and hypotheses - all testable. Evolution has patterns, such as the patterns of diversity through time. It has processes, such as natural selection, sexual selection, species selection, drift, and more. Evolution is a big subject with a lot of dimensions. As long as you are clear about which dimension of evolution you mean, there’s no conflict for readers.
Following the pgraph above, how does one choose a definition of evolution to use? Because science has no catechisms, there is not a single, standard definition of evolution. But some are more and less useful. A popular one, especially among scientists who work on population biology, is ‘a change in gene frequency in a population’. This means, for example, that an allele with a frequency of 0.75 in one generation can change to 0.73 in the next, and this is evolution. Well, sort of. In the next generation, the frequency can change back to 0.75. So what has evolved? It is like defining a football game as the process of hiking the ball. This simple (or simplistic) definition gets to one level of the processes of evolution (yet it misses many processes from speciation to what causes changes in gene frequencies in populations). Other definitions, such as ‘the history of life’, get to the patterns of evolution, but do not describe their causes. So both kinds of definitions are inadequate on their own.
Avoid the term ‘modern’
Avoid the words ‘primitive’ and ‘advanced’ (See ‘modern’)
These words also carry value judgments. Remember that what we might call a ‘primitive’ characteristic of some tetrapod wanna-bes from the Devonian was not only perfectly useful to them at that point; it may have given them a considerable advantage over what their fellow wanna-bes had at the time. It does not make sense for us to judge Devonian critters by the standards of what organisms have evolved in the ensuing 350 million years.
Think of it as you would human cultures. We no longer talk of some rituals and practices as ‘primitive’ and others as ‘advanced’. It makes things clearer for readers to avoid the same terms in biology.
‘Many scientists believe’ is a phrase with three fundamental difficulties
Third, ‘believe’: saying that scientists ‘believe’ their results suggests, falsely, that their acceptance is not based on evidence, but is based somehow on faith. Yet again, it is about the quality of the evidence: scientists accept their results as the best explanation of the problem that we have at present, but we recognize that our findings are subject to re-evaluation as new evidence comes to light. This is a problem because scientists themselves often use the word ‘believe’ when discussing their results! It is just sloppy diction: they would not say that their conclusions are a matter of faith, rather than of evidence.
Instead of saying ‘many scientists believe’ or ‘some scientists think’, it is more productive to talk about the evidence. What evidence (if any) supports a certain hypothesis, and what evidence (if any) seems to contradict it? And two more things: first, discuss what else we would have to know before we can advance the question further; and second, be clear about how we would know if a hypothesis were wrong. This, more than anything else, shows students what the process of science is all about. It takes a little more work on the part of the writer, but it is worth it in raising student interest and understanding. (An indispensable reference for explaining how science actually works is at http://undsci.berkeley.edu/article/howscienceworks_01.)
For example, many texts and the vast majority of news reporters like to repeat the idea that an asteroid crashed into the Earth some 65 million years ago and destroyed the dinosaurs and a lot of other organisms. This is a complex idea, and parts of it could be wrong or right without destroying the general concept that a large asteroid impact could have created substantial environmental havoc. Scientists from many disciplines have worked on this problem for decades. No one has all pieces of the puzzle, and their individual trainings influence what they think is important and even what they understand. But none of this is a question of belief or faith.
It is accurate to say that many people accept or think that an asteroid killed the dinosaurs, and this includes a lot of scientists. But most scientists who actually work on the dinosaurs of that time period do not agree that an asteroid killed them. That by itself should be important, but it is not as important as the evidence: when various lineages of vertebrates are traced across the Cretaceous-Tertiary boundary, it turns out that some mammal lineages were affected and some were not, most vertebrates such as crocodiles, lizards, and amphibians were not severely affected, and that all but three kinds of dinosaur had disappeared during the preceding six million years - presumably not in anticipation of the great crash. So the evidence is what scientists rely on - or should. And this is true for those who report on the issues.
Do not personalize a scientific debate
Often, however, the personal aspect intervenes as scientists in a certain field will tend to favor one hypothesis over another, simply because they have been educated to understand (and therefore trust) some lines of evidence over others. The story is still usually not about individual scientists, but about standards of evidence in different fields.
For example, until about a decade ago paleontologists and molecular biologists differed on the subject of the closest relatives of whales. Geneticists had found some very unusual and diagnostic molecular sequences called SINEs in both whales and hippopotamus (Shedlock et al. 2000). They inferred that these animals were each other’s closest relatives, and that made sense, some molecular biologists said, because both groups are large, aquatic, and hairless. Paleontologists dismissed this because the earliest known whales were first found in the early Eocene, some 50 million years ago; whereas the first hippos are not known until about 15 million years ago. Where could you hide the missing hippos for 35 million years? Moreover, the first known hippos were not large, aquatic, and hairless, but small, terrestrial, and probably not hairless.
This is not a perfect system, but it is how science often works. Note that this example was not about individual scientists arguing with each other, but about the kinds of evidence that scientists in certain fields are trained to understand and preferentially accept. (For more information, visit http://evolution.berkeley.edu/evolibrary/article/evograms_03 and cited references.)
Students and other audiences will benefit more from having the evidence explained to them than from asking them to choose sides based on profiles of opposing scientists. (Textbooks often ask students to make judgments about the social implications of scientific questions such as climate change after receiving only minimal information.) In so doing, they will experience more accurately how the scientific enterprise works, which is by analyses and arguments that fit the evidence together and provide more or less inclusive explanations of that evidence (see http://undsci.berkeley.edu/article/howscienceworks_01). And, whereas it does little service to profile scientists who are on different sides of an issue, and personalize and polarize their arguments for students to choose between, it is perfectly useful to profile individual scientists who have pioneered concepts in a field, as well as including other people who have worked with them, to show how science is a cooperative enterprise. After all, most present-day scientific problems are advanced not by lone individuals but by teams of people from many institutions who take years to propose hypotheses, make research plans, and carry out interdisciplinary research.
‘Evolution’ has meant different things at different periods of history
Darwin used the root word only once in the Origin of Species (the last word of the book is ‘evolved’), because in his day ‘evolution’ denoted the gradual, predetermined unfolding of organismal development (a fiddlehead fern, for example, or the shell of a snail). He wanted to avoid the ‘predetermined’ aspect, and this is why he preferred the term ‘transmutation’ when discussing changes in species through time. But, after the publication of his book, ‘evolution’ increasingly came to mean what it does today. (See Bowler 2009 for good background on this and related topics.)
It was possible in pre-Darwinian times to accept some or most lines of evidence for what we would now encompass as ‘evolution’. For example, the sequence of fossilized life through time in the geologic record was established by the earliest stratigraphers, such as William Smith, the civil engineer who published his geological map of England in 1801. Smith was no ‘evolutionist’ in our sense of the word. But he saw that fossils and rocks succeeded each other through the rock column, what was called the progression of life through time. (Of course, in those days no one really knew how much time was involved.) This was pretty much undeniable for any scientist by the 1820s.
However, the progression of life through time could be explained in various ways. A creditable view in the 18th and early 19th centuries was that there could have been a series of events of creation, following large-scale global or regional extinctions. But where in Scripture was this view validated? Besides, long before the 19th century, natural philosophers had stopped looking to Scripture for answers about science. Alternatively, it could be proposed that species were transformed into other species through succeeding geological strata. But what would have been the mechanism of this change? That mechanism, in the end, was what Darwin hoped to provide in the Origin of Species in the form of natural selection. But he had to overcome a lot of skepticism that such an explanation was even possible. Moreover, he was providing a strictly material explanation of this transformation. In this he was departing from many of his contemporaries, including Richard Owen and Charles Lyell, who were uncomfortable with an explanation of evolutionary change that did not include some role of a Higher Power, however mechanistic (Bowler 2009).
In the Victorian Era, one could accept evolution (the ‘unfolding’ of organisms through time, like the predetermined ‘unfolding’ of a leaf or fiddlehead fern) but not transmutation (a direct change of one kind of organism into another). This seems strange to us today, but if we want to understand Victorian and pre-Victorian sensibilities to scientific explanation, we have to wrap our heads around it. (See the description of Richard Owen’s views below.)
‘Gradual’ did not always mean gradual
It is very important to explain to students that small steps (as in punctuated equilibria) and insensible changes (as in classical gradualism) are more like each other than are small steps and very large steps. The latter mechanism - sudden, great morphological changes - has never been seriously considered in evolutionary theory, and the notion that ‘large steps’ create macroevolutionary changes (for example, that a bird could have hatched from a lizard egg) is a caricature. There should not be a need to mention Richard Goldschmidt’s (1940) much-maligned, scientifically naïve ‘hopeful monster’, because hardly anyone has ever considered it seriously as a mechanism of major evolutionary change, or has uncovered any evidence for it. That said, Goldschmidt’s book is a brilliant survey of ecophenotypic variation by a first-rate laboratory geneticist and field biologist, and it should be read closely rather than dismissed.
Use care in characterizing the religious beliefs of historical figures
Like most men of the Enlightenment (including most of American’s founding fathers), Darwin (for much of his life) was a Deist: he thought there was something bigger than human consciousness, but he did not personify it (as theists do), and gradually he lost all feeling that we would call religious (as opposed to spiritual: Desmond and Moore 1992, Moore 1994). His colleague Thomas Henry Huxley coined the word ‘agnostic’, and Darwin grew more comfortable with that term as he grew older (Padian 2009). Darwin’s views on religion changed through life, from fairly conventional beliefs through doubt in Providence to the absence of all interest in the subject.
Other historical figures, respected scientists who rejected Darwin’s views, or the ideas of evolution advanced in their times, were not necessarily creationists, and not usually in the strict sense of biblical literalism that we understand it today. Cuvier, for example, was not a biblical creationist, as he is often portrayed. He was a Lutheran by birth, but he seemed to have little interest in religion, and it did not enter his scientific work. He was not a catastrophist in the conventional sense of the term, either. His studies of abrupt transitions in the rock types and fossils of the hills around the Paris Basin were observational: he reported what he saw. He knew that these transitions reflected regional environmental events, but one reason why he maintained his respected status for so long in a turbulent France was that he avoided making rash pronouncements. Cuvier did not think that these transitions were the result of divinely mandated catastrophes; and although he did not fully understand the mechanisms behind them, he hypothesized that the animals that succeeded those of earlier strata may have migrated in from elsewhere as the environments changed. He was not positing the transformation of species, but neither was he suggesting a series of divine creations of each new fauna (Rudwick 1997; Taquet 2006).
In the same way, it would be wrong to call Richard Owen, Darwin’s greatest nemesis, a creationist, or even an anti-evolutionist. Owen was likely a deist, though he assuaged the theistic views of much of his Victorian audience. He knew the fossil record well and accepted the progression of life through time. He even thought that species could arise continually through a common ancestral form, modified somehow by development and the influence of the environment; but he was shadowy on these points (Padian 1997, 2007).
Avoid pitting science against religion, even though sometimes there are real conflicts
There has always been some kind of religious opposition to any and all ideas about evolution (and other scientific concepts). Nevertheless, there has been no serious scientific opposition to evolution since the Victorian Era. Yes, scientists do disagree and debate about various evolutionary mechanisms and patterns, and their relative importance, although they do not dispute that all living things have evolved from common ancestors. But just because all is not solved does not mean that evolutionary biology is in a state of turmoil. We like to say that ‘science is open-minded, not empty-headed’: trying to advance solutions to problems, based on what we already have found and want to know next, is why scientists get up in the morning. Scientific propositions are supposed to be testable, and ‘Science’ does not equal ‘Truth’, a word that should not be used in science.
Oddly, perhaps, the very openness of science is what attracts scorn from religious fundamentalists, who build their lives on what they accept as immutable truths of faith. The principal act of faith of a scientist is accepting that the natural world is knowable, and that we can use our (however imperfect) faculties and judgment to learn about natural phenomena and trust our results, wherever our investigations lead. After that, the rules of scientific inquiry are not about faith, but about posing and testing hypotheses. But science has its limits, and the supernatural is one of them. In short, science does not deal with the supernatural. Religion has its limits too, and one of them is in making statements about the natural world. There is only conflict between science and religion if people want it; or rather, there is conflict when people want it. That conflict comes from either side saying more than it reasonably can about its domain. But the non-theistic axiom of science (see below) means that it does not favor or disfavor any particular religious or other supernatural beliefs. In return, its statements about the natural world should not be contradicted on the basis of any sectarian religious beliefs. So, regardless of what some interpretations of old writings about Scripture-professed, scientific evidence affirms that the Earth cannot be 6,000 years old. That is in direct conflict with some religious views. Contemporary evolutionary biologists hold varying religious views; contrast, for example, Gould (2002a), Miller (2007), Coyne (2009), and Asher (2012). But when they operate as scientists, they do not place religious views above empirical evidence.
In textbooks, it is appropriate to discuss why evolution or any scientific idea or hypothesis was or is controversial as science (cold fusion is an example). But it is not appropriate to pretend that well-established scientific concepts are controversial. It is also not appropriate to note that some scientific concepts were controversial in the past, without noting the present state of understanding of those concepts (a great many important scientific ideas are controversial when they are first proposed). Cultural and religious controversy about science has no place in science texts, and pedagogical activities that encourage children to have debates about evolution or global warming - in an educational system where they can have only the most rudimentary exposure to these subjects - merely amplify the prejudices of the students’ families.
Is there room to discuss cultural and social controversies over scientific ideas in textbooks? Perhaps, although the focus of a science textbook should be squarely on the science. But textbook authors who choose to discuss cultural and social controversies should be careful to ensure that they are not misrepresenting the science as controversial or offensive to the beliefs of their readers, and thus undercutting the legitimacy of the science.
Avoid giving the impression that evolution is atheistic, or that evolutionists must be atheists
Individual scientists, like accountants, plumbers, and postal employees, can be atheistic or deeply religious in any number of ways. But science places no strictures on their beliefs except to ask them to be checked at the door when it is time to test the hypotheses. This has been the case since the Enlightenment coalesced.
Furthermore, the scientific study of nature, or naturalism, has two main approaches, but only one is scientific; the other is philosophical. Philosophical naturalism says that observable nature is all there is; methodological naturalism says that there may or may not be more than the observable phenomena of nature, but science is only concerned with what can be observed.
The objective of this paper has been to identify and explore some persistent misconceptions in evolutionary biology that are broadly found not only in textbooks and popular science publications, but in scientific journals and books. I have no illusion that other scientists will be in unanimous agreement with all the points I raise here. I challenge all of us, however, to consider the points and improve upon them, so that in turn we can help journalists, textbook writers, and others to interpret our science for the public.
I thank Glenn Branch, Eugenie Scott, Brian Switek, and Judy Scotchmoor for helpful and constructive comments on the manuscript, and Bill Bennetta, Kathy diRanna, the late Tom Jukes, Lawrence Lerner, and Elizabeth Stage for decades of sage advice. Joleen Tseng drew the cartoons used in the figures. The illustration of the evogram was developed by Brian Swartz.
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