Fossil Horses, Orthogenesis, and Communicating Evolution in Museums
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- MacFadden, B.J., Oviedo, L.H., Seymour, G.M. et al. Evo Edu Outreach (2012) 5: 29. doi:10.1007/s12052-012-0394-1
The 55-million-year fossil record of horses (Family Equidae) has been frequently cited as a prime example of long-term macroevolution. In the second half of the nineteenth century, natural history museum exhibits characteristically depicted fossil horses to be a single, straight-line (orthogenetic) progression from ancestor to descendent. By the beginning of the twentieth century, however, paleontologists realized that, rather than representing orthogenesis, the evolutionary pattern of fossil horses was more correctly characterized by a complexly branching phylogenetic tree. We conducted a systematic survey of 20 fossil horse exhibits from natural history museums in the United States. Our resulting data indicate that more than half (55%) of natural history museums today still depict horse evolution as orthogenetic, despite the fact that paleontologists have known for a century that the actual evolutionary pattern of the Family Equidae is branching. Depicting outmoded evolutionary patterns and concepts via museum exhibits, such as fossils horses exemplifying orthogenesis, not only communicates outmoded knowledge but also likely contributes to general misconceptions about evolution for natural history museum visitors.
Fifty million people visit natural history museums in the U.S. each year (MacFadden et al. 2007). These visitors expect to learn about current science and exciting discoveries and trust these institutions to communicate correct and up-to-date information (Falk and Dierking 2000; West 2005; Enseki 2006). Once inside the museum, many studies have shown that most visitors spend less than one minute at any given exhibit display (Cone and Kendall 1978; Donald 1991; Allen 2004), so museum scientists and exhibit developers are challenged to communicate science in a highly focused, engaging manner (Bell et al. 2009). This is oftentimes done with different combinations of specimens and artifacts, graphic displays, passages of text, and, more recently, multimedia technology (Hein 1998; Falk and Dierking 2000).
Many natural history museums and other informal science-learning institutions seek to communicate science content of societal relevance to the public, including current hot-button topics and of relevance to this study, evolution (NAS 2001; Diamond and Scotchmoor 2006). With regard to evolution, since the second half of the nineteenth century when many natural history museums were founded in the U.S., the fossil record of horses has frequently been depicted in exhibits communicating long-term (macro-) evolution (Gould 2002).
Evolution of Evolutionary Thought: Paleontology, Fossil Horses, and Orthogenesis
Despite this knowledge, to this day, the classic story of horse evolution in museums, books, and other media is still oftentimes depicted as orthogenetic. In addition to being factually incorrect within a modern scientific context of what we know about evolution, orthogenesis brings along with it baggage about evolution being largely progressive, deterministic, and representing improvement (MacFadden 1992; Gould 2002). These notions associated with orthogenesis therefore likely contribute to part of the general public’s misunderstanding, or incomplete knowledge, about fundamental aspects of evolution (MacFadden 1992; Diamond and Scotchmoor 2006; Spiegal et al. 2006; MacFadden et al. 2007). In Jonathan Wells’ (2000) book entitled Icons of Evolution: Science or Myth? Why much of what we teach about evolution is wrong, the author cites fossil horses as one of ten fundamental examples of evolution. He also accurately describes some of the problems associated with the miscommunication and states (Wells 2000, 195): “Since the 1950s, neo-Darwinian paleontologists have been actively campaigning to replace the old linear picture of horse evolution with the branching tree.” As we will see below, this campaign has not been particularly successful.
We assert that, despite its roots in nineteenth century evolutionary theory, the outmoded scientific concept of orthogenesis is still widely communicated to the general public through various media, including natural history museum exhibits. We use fossil horses to test this hypothesis because of their widespread use as fundamental evidence for macroevolution (e.g., Gould 2002).
Materials, Methods, and Research Design
Classification of fossil horse exhibits and museums included in the study
Number of displays
Pattern of depiction
University of Nebraska State Museum
Field Museum of Natural History
Harvard Museum of Natural History
U.S. National Museum of Natural History, Smithsonian Institution
Darwin (traveling exhibita)
Amherst College, Beneski Museum of Natural History
Kansas University Natural History Museum and Biodiversity Research Center
American Museum of Natural History
Carnegie Museum of Natural History
Natural History Museum of Los Angeles County
Peabody Museum of Natural History
International Museum of the Horse
University of Michigan Museum of Natural History
University of Oregon Museum of Natural and Cultural History
University of California Museum of Paleontology-Berkeley
Florida Museum of Natural History
Denver Museum of Nature and Science
Santa Barbara Museum of Natural History
The Horse (traveling exhibita)
Panhandle Plains Historical Museum
Total summed yearly attendance
Results and Discussion
An inability and inertia of researchers studying fossil horses to effectively communicate to other scientists (particularly outside of their discipline), museum curators, exhibit designers, text-book authors, and the public. As demonstrated above, knowledge that the evolutionary pattern of fossil horses is branching has been current for a century, but this fact has not been effectively communicated outside the narrow sphere of practicing professional paleontologists.
Museum exhibits are expensive to build, particularly in grand exhibition halls costing millions of dollars. For example, the Hall of Florida Fossils: Evolution of Life and Land at the Florida Museum of Natural History was completed in 2004 at a cost of about $2.5 million dollars, which equates to about $600 per square foot. This is fairly typical for a multimedia, specimen-rich major exhibition hall. Accordingly, and from a pragmatic point of view, after the rush of activity passes with newly opened exhibit halls, museum professionals typically move on to the next project, and therefore physical renovations and scientific updates to prior projects are slow to be implemented. It therefore is a challenge to incorporate the most current scientific concepts into physical exhibits (although with modern multimedia displays and cyberexhibits, this inertia has the potential to change in the future). Moreover, as Dyehouse (2011) has shown, even when museum curators are sensitive to the issue of public perception of orthogenesis, this pattern or schema may unintentionally become incorporated into updated physical exhibits.
With only a minute or less for learning opportunities at individual exhibits, museum interpretive content graphics are frequently presented in a simplified manner, e.g., with orthogenesis rather than a branching schema. Studies of museum visitors, however, show that, when abstract concepts are oversimplified, misconceptions can result (Bishop and Anderson 1990; Matuk and Uttal 2008). Thus, within the context of our study, we assert that orthogenetic depictions provide incorrect information for the sake of simplicity and also lead to fundamental misconceptions about the pattern of macroevolution.
Research from the cognitive and learning sciences demonstrates that common ways of visually representing evolution contribute to fundamental misconceptions, especially among people with less well-developed backgrounds in science, i.e., where intuition results in a naïve conception framework for learning. Of relevance to the current study, depictions that utilize vertical space with more recent developments placed at the top imply progress or improvement and lead individuals to conceive of evolution as a teleological (purpose-driven) process (Tversky 2011). Furthermore, linear depictions encourage anagenic (direct sequence from ancestor to descendent) interpretations of speciation (Catley et al. 2010; Novick et al. 2011).
Other research has shown that branching-tree depictions that accurately represent macroevolutionary patterns are difficult for students and museum visitors to grasp (Gregory 2008; Evans et al. 2010). The solution, we contend, is not to settle for simpler, more accessible museum displays. Inappropriate depictions of evolution in museums should be no less accurate than their textbook counterparts (Catley and Novick 2008). The 15 institutions surveyed here that depict horse evolution as either orthogenetic, primarily orthogenetic, or mixed have an estimated visitation of more than 12 million people per year (Table 1) to their physical exhibits (when cyberexhibits are added, this figure would be greater). While we do not assert that every visitor to each of these institutions saw the horse evolution exhibit, the potential exists for scientific miscommunication on a large scale, which likely contributes to the low public acceptance, and generally poor understanding, of evolutionary concepts in the U.S (Miller et al. 2006).
We have used fossil horse exhibits as an example of orthogenesis, yet the impact of this cognitive framework is pervasive and extends to other organisms, both living and extinct, including humans (Scott and Guisti 2006). The common quip among the non-believing general public, “Don’t tell me I’m descended from a monkey,” derives from an orthogenetic framework in which humans evolved directly from apes. The impact of orthogenesis also transcends museum exhibits and can be found in many other media that communicate about science, including textbooks, newspapers, magazines, documentaries, and the enormous access provided by the Web. This lack of public understanding of evolution in the U.S. has profound consequences for overall understanding within the life and natural sciences and also impacts applied aspects of society, such as human medicine.
While the scope of our study concentrated on natural history museums in the U.S., anecdotal evidence (MacFadden, personal observations; also see, e.g., Franzen 2010, but no comprehensive list is currently available) suggests that orthogenetic frameworks are widespread in museums in other countries, and this pattern is not just found in fossil horses exhibits, but in many other kinds of depictions, particularly involving evolutionary sequences and interpreted phylogenies of groups with a fossil record. The magnitude and pervasiveness of this style of content presentation thus results in a worldwide challenge for science communication and science literary.
Science evolves with the advent of new discoveries and ongoing research, as is the case for the classic story of fossil horse evolution that has developed over the past 150 years. Despite the scientific discoveries that paleontologists have made “in the trenches,” these advances in knowledge have been slow to enter into the general body of scientific knowledge about evolution. One consequence of this inertia has been that natural history museum exhibits have been slow to incorporate recent scientific advances into the content of their exhibits. Misinformation communicated in this manner likewise contributes to the museum visitors’ misunderstanding about fundamental concepts and examples of evolutionary theory. If science literacy is a priority in modern society and the public needs to make informed decisions in their everyday lives that depend upon understanding evolution, then it is incumbent on scientists and museum professionals to more effectively communicate in media such as museum exhibits.
We thank our contacts at the museums surveyed for providing exhibit photographs. This research was partially supported by U.S. National Science Foundation (NSF 09-66884, OISE, EAR, OISE), Vertebrate Paleontology Fund, Florida Museum of Natural History, and student scholarships provided by the Fossil Club of Lee County and Southwest Florida Fossil Club.
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