Tag Archives: evolution

July 10, 2015 · 12:13 pm

Framing Fossil Exhibits: Environmental Change

Over the past few months, I’ve been writing about the strengths and weaknesses of various large-scale paleontology exhibits from an educational standpoint. Check out the Introduction, Walk Through Time, Phylogeny, and Habitat Immersion posts if you’d like to catch up. I’ll wrap up this series for the time being with a look at two upcoming renovations of classic fossil displays, which appear to have converged on similar aesthetic, organizational, and interpretive approaches.

First up is the Peabody Museum of Natural History, where the Great Hall of Dinosaurs and adjacent Hall of Mammal Evolution have seen little modification since the 1950s. While the PMNH fossil galleries are fascinating as a time capsule of mid-century exhibit design, much of the content is rather dated and a thorough overhaul is sorely needed. PMNH staff started planning for the renovation in 2010, and I highly recommend Collections Manager Chris Norris’s blog posts on the process. Once the basic layout and concepts were in order, the museum hired the architectural firm Studio Joseph to prepare the images being used to promote the project. Fundraising is now underway, but an estimated completion date has yet to be announced.

Conceptual render of the Great Hall of Dinosaurs by Studio Joseph. Source

The big idea behind the new exhibit is the dynamic relationship between the biosphere and the Earth’s various other spheres (atmosphere, geosphere, hydrosphere, etc). The evolution of life on Earth did not occur in a vacuum, but as part of a continuously changing global system. This narrative does have a time axis – visitors will travel from the Permian at one end of the exhibit to the Quaternary at the other – but the precise divisions of geologic time are de-emphasized in favor of the broad environmental transitions that triggered evolutionary innovations. Examples might include the separation of continents during the Mesozoic, the diversification of flowering plants in the Cretaceous, or the massive climatic shift at the end of the Eocene. In this context, it’s more important that visitors understand (for example) that the Cenozoic was generally a transition from hot and wet to cold and dry (and the implications on mammalian evolution) than that they know the names and time spans of each epoch.

This approach contrasts sharply with traditional chronological exhibits, such as the Field Museum of Natural History’s “Evolving Planet.” The FMNH fossil galleries are extremely linear, and each geologic period is introduced with a set of easily-digested bullet points summarizing what happened during that time. Relatively tight spaces prevent visitors from seeing specimens from other time periods prematurely, and the galleries devoted to each period are color-coded to make them immediately distinct. According to Norris, this segmented presentation of the history of life obscures the large-scale transitions which transcend the somewhat arbitrary divisions of geologic time. As such, the new PMNH fossil halls will present the narrative holistically, encouraging visitors to track the underlying environmental trends that precipitated evolutionary change over time.

mammal hall concept art by Studio Joseph

Conceptual render of the Hall of Mammals by Studio Joseph. Source

As is immediately clear from the promotional images, the new exhibit will juxtapose a modern, wide-open aesthetic with elements of the museum’s past – specifically, the outdated but gorgeous Rudolph Zallinger murals. Both of these design elements tie directly to exhibit’s narrative themes. By breaking up the central dinosaur pedestal and eliminating the unsightly glass cases in the Mammal Hall, the exhibit designers have dramatically increased the available floor space and opened up new lines of sight. This should allow visitors to view each of the galleries comprehensively, rather than as a series of discreet segments. Meanwhile, the Zallinger murals will remain a celebrated part of the exhibits. These magnificent frescoes were painted between 1942 and 1967, and are among the most iconic images of prehistoric life ever created. Although the physiology of some of the animals is outdated, Zallinger was in other ways ahead of his time. Rather than giving the geologic periods hard borders, Zallinger artfully wove the sections together so that each one fades imperceptibly into the next. The viewer can see that the flora, fauna, and climate are changing over time, but it’s a gradient, not a ladder, which perfectly reflects the narrative of the new exhibit.

A conceptual render of Deinonychus and other Cretaceous fossils. Source

About 300 miles south of PMNH, the re-imagining of the fossil halls at the National Museum of Natural History is well underway. This building’s east wing has been home to paleontology displays since it opened in 1910 and has been updated several times, but this is the first time it has undergone a complete, wall-to-wall modernization. The old exhibits were formally closed on April 28th, 2014, and NMNH staff spent the following year removing thousands of specimens from the halls. With the fossils out of the way, the next step will be to restore the historic space to its original neoclassical glory. After that, the new exhibits and updated fossil mounts can be assembled in time for a 2019 re-opening.

Intriguingly, the planned design of the new National Fossil Hall is both thematically and aesthetically similar to the PMNH renovation, albeit on a grander scale. The National Fossil Hall’s narrative focus will be on large-scale environmental transitions over time, and how these changes drove the evolution of plants and animals. Like at PMNH, this will be accentuated by an open layout: false walls and barriers that have divided the space since the early 1960s will come down, allowing visitors to see clear across the spacious three-story hall. This airy aesthetic hearkens back to the Hall of Extinct Monsters, and like the restoration of the Zallinger murals at PMNH it represents an admirable celebration of the institution’s history.

Early conceptual render of the National Fossil Hall by Reich + Petch Source

One interpretive choice that will set the National Fossil Hall apart is the clustering of specimens on islands, or “pork chops”, as the were called early in development. Each pork chop represents North America at a particular period in time. While anchored by a few charismatic mounts, the pork chops will also include all manner of small animals, invertebrates, and plants that were part of that environment. In this way, the islands are self-contained mini exhibits, each one showing a complete ecosystem that existed at a particular time. Moving among the these displays, visitors should get a sense of how climate change and faunal interchange (among other phenomena) can completely transform an ecosystem over millions of years. They’ll also learn how certain organisms, like sauropods in the Jurassic or grass in the Neogene, can change landscapes and influence the evolution of contemporary plants and animals.

The emphasis on open spaces and freedom of movement is notable, because this is quite different from the linear exhibits of the late 20th century. In recent decades, exhibits have become increasingly structured, with specific learning goals and physical spaces designed to corral visitors through a carefully orchestrated narrative journey. Again, Evolving Planet at FMNH is an excellent example of this philosophy. The new National Fossil Hall is in some ways a push in the opposite direction – although it has a clear narrative and overarching message, visitors can roam through the exhibit as they please. I see the pork chop system as a way to have it both ways. Whether visitors work through the exhibit front to back or run straight to the T. rex in the center of the hall, then wander around at random, they’ll still be able to compare and contrast the different ecosystems and learn what the designers want them to learn.

Early concept art of the Jurassic “pork chop.” Image from The Last American Dinosaurs, NMNH.

More than anything else, what I expect to set the National Fossil Hall apart from peer exhibits will be its explicit connections to modern-day environmental crises. It’s worth quoting the Department of Paleobiology’s summary in full:

Visitors to the Museum will be able to explore how life, environments, and ecosystems have interacted to form and change our planet over billions of years. By discovering and harnessing the tools and methods paleobiologists use to study fossils, visitors will gain a deeper understanding of how the world works.

The distant past affects all of us today and will continue to do so in the future. How will climate change impact the natural world and our daily lives? How can we make informed choices about our ecosystems as individuals and as a species? How can we all become informed citizens of a changing planet?

We are in the midst of an extinction event of our own making. Anthropogenic climate change, habitat destruction, and invasive species are as dangerous as any asteroid, and will likely have profound effects on our own lives and livelihoods in the coming century. But while humans are undeniably the cause of the latest round of global changes, we also have the power to mitigate and manage their consequences. The study of fossils provides important contextual information – we can place modern organisms in an evolutionary context and understand their role in shaping the world as we know it, and we can see how organisms have responded to significant environmental overhauls in the distant past. The fossil record is in fact the only way to directly observe these things (as opposed to relying on models or actualistic experiments). As such, the new National Fossil Hall will make it clear that paleontology isn’t just about historical curiosity. The study of past life gives us a long view of the Earth’s biotic and abiotic systems, and helps us predict how they will respond to today’s environmental changes.

Concept drawing of the National Fossil Hall’s Cretaceous zone. In the old hall, the viewer would be standing at the base of the mezzanine stairs facing the rotunda. Source

With the modern climate crisis front and center, the new National Fossil Hall has the potential to be one of the most immediately relevant and important paleontology exhibits ever assembled*. This is significant, because as I lamented when I started this series, immediacy and relevance are not things that most museum visitors expect from fossil displays. While fossils, particularly the mounted skeletons of dinosaurs and other prehistoric animals, have been central to the identity of natural history museums since the late 19th century, most visitors don’t regard these exhibits as anything more than prehistoric pageantry. Visitor surveys consistently reveal that dinosaurs are seen as eye candy – monsters that might as well be from another planet. This is a shame, because dinosaurs and other prehistoric organisms were real parts of our own world, and we can learn much from them.

The new National Fossil Hall will be arranged in reverse chronological order – as visitors move accross the gallery, familiar elements of modern environments will be stripped away and the world will become an increasingly alien place. Source

And so we come full circle. What is the point of a museum exhibit**? Is it enough to provide visitors an opportunity to see cool objects and specimens? When we ask museumgoers what they want to see, they tell us “dinosaurs” or “fossils.” They don’t ask for compelling narratives or connections to big contemporary issues, and they don’t see their museum visit as an important way to bridge gaps in scientific literacy.

Still, it is of critical importance that we provide these narratives and connections. Even if we accept the fact that the very existence of a museum and the chance to see real specimens is a Good Thing, museums are still accountable to the public. Virtually all museums cite education as the primary purpose of their institution, and it’s imperative to live up to that. A museum should have a learning goal in mind, it should be able to prove that this message is coming across, and it should be able to articulate why its audience is better off for it. This is not necessarily easy – exhibits need to be relevant without being condescending or preachy. Exhibit designers need to understand their visitors as much as their content. They need to find a balance between feeding visitors information and providing a customizable experience for diverse audiences. As we have seen, not every exhibit succeeds, but my impression is that we’re getting better at it.

*It’s also notable that this climate change-focused exhibit will be on the national mall, given the ongoing politically-motivated opposition to climate science.

**Note that I’m referring specifically to public-facing exhibits. There are many good reasons why the ongoing maintenance of natural history collections is intrinsically valuable.

References

Marsh, D.E. (2014). From Extinct Monsters to Deep Time: An ethnography of fossil exhibits production at the Smithsonian’s National Museum of Natural History. http://circle.ubc.ca/handle/2429/50177

Weil, S.E. (2002). Making Musueums Matter. Washington, DC: Smithsonian Books.

Werning, S. (2013). Why Paleontology Is Relevant. The Integrative Paleontologists. http://blogs.plos.org/paleo/2013/02/19/why-paleontology-is-relevant

6 Comments

Filed under dinosaurs, education, exhibits, FMNH, museums, NMNH, opinion, PMNH, science communication

Tagged as education, evolution, exhibits, Extinct Monsters, museums, natural history museums, NMNH, paleontology, Peabody Museum, science communication, scientific literacy, Smithsonian

April 28, 2015 · 3:06 pm

Permo-Triassic Synapsids at NMNH

Click here to start the NMNH series from the beginning.

In the middle decades of the 20th century, museum theory and paleontological science were undergoing complementary revolutions. Museum workers shrugged off their “cabinet of curiosity” roots and embraced visitor-centric, education-oriented exhibits. Designers began to envision the routes visitors would travel through an exhibit space, and consider how objects on display could contribute to holistic stories. Meanwhile, paleontologists like Stephen J. Gould and David Raup moved their field away from purely descriptive natural history, exploring instead how the fossil record could inform our understanding of evolution and ecology. The common thread between both transitions was a focus on connections – bringing new meaning and relevance to disparate parts by placing them in a common narrative.

Between 1953 and 1963, the Smithsonian implemented an institution-wide modernization program, transforming virtually every exhibit in the museum complex. The National Museum of Natural History began renovations to its classic fossil halls in 1959, and the new exhibits were emblematic of contemporary trends in both museum design and paleontology. The plan, as devised by exhibit designer Ann Karras, was to do away with the loose arrangement of specimens and turn the east wing into a guided narrative of the biological and geological history of Earth. Responsibility for selecting specimens and writing label copy in each of the four halls fell to a different curator. In Hall 2, which housed dinosaurs and fossil reptiles, that curator was Nicholas Hotton.

Layout of the USNM east wing, circa 1963.

Layout of the NMNH east wing as of 1963.

Hotton joined NMNH in 1959 as an Associate Curator of Paleontology. Entirely onboard with Karras’s vision and the paleobiology movement as a whole, Hotton described the old exhibits as “crowded” and “unorganized.” He thought NMNH had plenty of dinosaurs, but “mammal-like reptiles”* were sorely needed if Hall 2 was to tell the complete story of amniote evolution. Following that, Hotton’s mission over the next several years was to assemble a respectable collection of synapsid specimens for NMNH, and to incorporate them into a well-illustrated exhibit on the origins of mammals. This post highlights just a few of the specimens featured in Hotton’s version of Hall 2.

*In Hotton’s day, early mammalian relatives were usually called “mammal-like reptiles”, hence their inclusion in the fossil reptile exhibit. Today, most specialists prefer a more precise definition of reptiles that excludes synapsid (mammal-line) animals. In this post, I will be using the modern classification wherever possible.

The Dimetrodon

Prior to 1960, the non-mammalian synapsid collections at NMNH were mostly limited to early Permian pelycosaurs. The most impressive of these was a Dimetrodon gigas collected in 1917 by independent fossil hunter Charles Sternberg. One of the best collectors of his day, Sternberg worked intermittently for E.D. Cope, O.C. Marsh, and various North American museums. In the summer of 1917, however, Sternberg was on a personal collecting trip with his son Levi. Their target was the Craddock Ranch bone bed of Baylor County, Texas, which was first explored in 1909 by a University of Chicago team. Sternberg was already quite familiar with this part of western Texas, having made some of the first thorough surveys of the Permian “red beds” in the 1880s, but the site itself was new to him. Nevertheless, Sternberg was extraordinarily successful that summer, collecting hundreds of fossils from a wide range of animals. He offered this bounty to the Smithsonian, and they purchased it from him immediately.

The Craddock Ranch fossils were particularly appealing because of their unique preservation. Buried in soft clay at the bottom of a shallow pond, the fossils could be removed from the ground with relative ease, and were largely free of encrusting matrix. Although few of the bones were articulated, many were identifiable. All told, the Sternberg collection included at least 35 skulls and partial skeletons from amphibians like Cardiocephalus, Diplocaulus, and Seymouria, plus hundreds of individual Dimetrodon bones, and a single articulated Dimetrodon specimen.

An early photograph of the Dimetrodon mount. Image from Gilmore 1919.

The Dimetrodon was first displayed on the north wall of the Hall of Extinct Monsters. Source

That Dimetrodon (USNM 8635) was the basis for a mount constructed by T.J. Horne. The articulated skeleton included a complete series of presacral vertebrae, the shoulder girdles, most of the forelimbs, and the left femur and tibia. The skull and jaw bones were found disarticulated, but bound together in the same mass of matrix as the skeleton. Horne added the pelvic bones and sacrum from smaller Dimetrodon specimens, and sculpted the rest of the missing material in plaster to complete the mount. Notably, his reconstructed tail was extremely short and stubby. Although the American Museum and Field Museum already had Dimetrodon mounts on display, the NMNH version stood out because of its open jaws, which Charles Gilmore said “gives the animal an appearance of angrily defying one who has suddenly blocked his path.”

Gilmore added the Dimetrodon to the Hall of Extinct Monsters in 1918. Like the other standing mounts constructed under Gilmore’s supervision, the skeleton was placed on a base textured and painted to resemble the rocks in which it was found. At this point in time, the NMNH fossil halls lacked any overarching organizational scheme, and interpretive content was minimal. Nevertheless, Gilmore displayed the Dimetrodon mount with both a small model and a 15-foot oil painting by Garnet Jex, which provided general audiences a better understanding of the animal’s life appearance.

Dimetrodon in the 1963 fossil reptiles exhibit. Image courtesy of the Smithsonian Institution Archives.

Dimetrodon in 2014. Photo by the author.

Dimetrodon after the 1981 renovation. Photo by the author.

During the 1962 renovation, Hotton re-contextualized the classic Dimetrodon mount as a mammal ancestor. Unmissable orange arrows pointed to the specific anatomical traits that signify the animal’s kinship with mammals, including heterodont teeth and a single temporal fenestra. By design, visitors would pass Dimetrodon before visiting the true mammals in the adjacent hall.

The Dimetrodon skeleton itself was altered during the next renovation in 1981, when it was placed on a new, untextured base and given a longer replica tail. Contemporary staff also repainted the plaster sections to more closely resemble the original fossils – a surprising reversal of Gilmore and Horne’s original intention to make the reconstructed bones obvious to viewers.

The Thrinaxodon

Pelycosaurs like Dimetrodon represent the first major synapsid radiation, but by the middle Permian they were almost entirely replaced by therapsids. A more derived group which includes modern mammals, therapsids spread across the globe and became increasingly diverse as the Permian progressed. From weasel-sized burrowers to multi-ton herbivores, non-mammalian therapsids were among the first animal groups to conquer a wide range of terrestrial niches. Hotton wanted to tell this story in the modernized fossil exhibit, but there were hardly any non-mammalian therapsids in the NMNH collections. To correct this problem, Hotton took to the field for several months in 1960, and again in 1961. He joined James Kitching in exploring the Beafort Group rocks of South Africa, which were known to produce plentiful Permian and Triassic vertebrate fossils. Hotton returned to the museum with over 200 new specimens, the best of which were used in the renovated exhibit.

Hotton’s display of South African synapsids and amphibians. Note “Baby Doll” on the far left. Photo courtesy of the Smithsonian Institution Archives.

Thrinaxodon paired with Cynognathus skull. Photo by the author.

Hotton’s most prized find from South Africa was a gorgeously preserved and nearly complete Thrinaxodon liorhinus (USNM 22812). Hotton called this specimen “Baby Doll”, and while it was not prepared in time for Hall 2’s 1963 opening, it would later earn a spot of honor in the exhibit. Before that happened, though, Baby Doll was actually stolen by an over-enthusiastic volunteer. The FBI located and returned the fossil a year and a half later.

Since the 1980s, the Thrinaxodon has been displayed alongside the skull of Cynognathus crateronotus (USNM 22813), which Hotton collected on the same expedition. Both are members of the cynodont clade, which includes some of the closest relatives of modern mammals.

The Daptocephalus

Less than a month after hall 2 reopened, Nicholas Hotton returned to South Africa. This time, he was accompanied by his spouse Ruth Hotton and their three young children. For seven months, the Hottons traveled among fossil sites on different ranches, camping most nights. They collected some 300 specimens for the Smithsonian, and Hotton’s biostratigraphic mapping of the Beaufort Group brought a measure of clarity to this region’s historically convoluted geology.

Ruth Hotton made one of the trip’s most impressive finds while prospecting in a dry riverbed with her daughter, Carol (who is now a paleobotanist at NMNH). Turning a corner, she stumbled upon a dicynodont skeleton, completely exposed and lying in the middle of the channel. One can only imagine the surprise and delight of finding an articulated fossil skeleton completely uncovered. If the Hottons had been there one season earlier or one season later, the river would have undoubtedly destroyed the fossils.

Daptocephalus on display. Photo by James Di Loreto, National Museum of Natural History.

Back at the museum, Nicholas Hotton prepared the specimen (USNM 299746) and determined it to be Daplocephalus leoniceps, one of the plethora of dicynodonts known from the Beaufort Group. Based on this classification, he reconstructed the damaged skull to resemble more complete Daplocephalus specimens, and added casts of Daplocephalus limbs.

The specimen was restored in 2019 and is now labeled Platypodosaurus. Photo by the author.

As it turns out, however, USNM 299749 is not a Daplocephalus—it is a somewhat distantly related dicynodont currently called Platypodosaurus. To varying degrees, fossil mounts are hypotheses made of bone and plaster. They are based on the best information available at the time, but sometimes they need to be corrected. The NMNH “Daplocephalus” had been mislabeled and erroneously reconstructed for many years, but the 2014 renovation of the NMNH fossil halls now presented an opportunity to deconstruct the specimen and study it up close. As of 2019, Platypodosaurus was back on display with a newly reconstructed skull and limbs.

Thanks to Christian Kammerer for kindly sharing images and insight on “Daptocephalus”!

References

Gilmore, C.W. (1919). A Mounted Skeleton of Dimetrodon gigas in the United States National Museum, with Notes on the Skeletal Anatomy. Proceedings of the United States National Museum 56:2300:525-539.

Kammerer, C. (2015). Personal communication.

Lay, M. (2013). Major Activities of the Division of Vertebrate Paleontology During the 1960s. http://paleobiology.si.edu/history/lay1960s.html

Marsh, D.E. (2014). From Extinct Monsters to Deep Time: An ethnography of fossil exhibits production at the Smithsonian’s National Museum of Natural History. http://circle.ubc.ca/handle/2429/50177

Sepkoski, D. (2012). Rereading the Fossil record: The Growth of Paleobiology as an Evolutionary Discipline. Chicago, IL: The University of Chicago Press.

4 Comments

Filed under exhibits, Extinct Monsters, field work, fossil mounts, history of science, mammals, museums, NMNH

Tagged as evolution, fossil mounts, history of science, museums, natural history museums, paleontology, Smithsonian, synapsids

April 3, 2015 · 10:20 am

History of the AMNH Fossil Halls – Part 2

Start with History of the AMNH Fossil Halls – Part 1.

During his leadership of the American Museum of Natural History’s Department of Vertebrate Paleontology and later, the museum at large, Henry Osborn oversaw an unprecedented expansion of the institution’s paleontology exhibits. As fossils poured in from the Department’s international collecting expeditions, these displays expanded into five separate galleries on the museum’s fourth floor. During the first two decades of the 20th century, AMNH staff was installing newly prepared and mounted specimens every single year, and AMNH was the undisputed center of American vertebrate paleontology. The increasingly marginal role of descriptive natural history in the greater field of biology at this time made the scale of Osborn’s program all the more impressive.

Nevertheless, this golden age of fossil exhibits would not last forever. Osborn supported the expensive expeditions and monumental displays through his personal connections with wealthy benefactors. The combination of the Great Depression and Osborn’s death in 1933 all but eliminated this source of income, and the museum had to scale back its activities considerably. In 1942, the Department of Vertebrate Paleontology was dissolved. Paleontology work continued under the Department of Geology, but with only a fraction of its former staff and budget.

Phase IV: 1940 – 1955

In the post-Osborn era, responsibility for the fourth floor exhibits deservedly transferred to Barnum Brown. Indeed, Brown’s adventures as a swashbuckling fossil hunter not only brought him personal fame, but made the museum’s world-class paleontology exhibits what they were. Of the 36 dinosaurs on display by 1939, no less than 27 had been discovered by Brown. Most of these iconic finds were made in his 20s and 30s, but Brown nevertheless remained at AMNH for most of his life. Even after officially retiring in 1943, Brown still frequented the museum, often giving spontaneous personal tours of the exhibits.

Brown’s Jurassic Hall, around 1940. Photo from Dingus 1996.

In 1932, the architectural firm Trowbridge and Livingston completed the 13th building in the AMNH complex. This meant that for the first time, the paleontology exhibits formed a complete circuit, an arrangement that persists to this day. Brown opted to spread the dinosaurs into two halls, making the new space the Jurassic Hall and converting the Osborn-era Great Hall of Dinosaurs into the Cretaceous Hall. Several existing fossil mounts had to be moved as a result, including the massive “Brontosaurus.” Eyeballing the widths of the doorways and corridors separating the present day Hall of Saurischian Dinosaurs (formerly the Jurassic Hall) and Hall of Ornithiscian Dinosaurs (formerly the Cretaceous Hall and Great Hall of Dinosaurs), it’s difficult to imagine how museum staff could have moved the 66-foot sauropod in one piece. This photograph suggests that the skeleton was divided into several sections, which then had to be brought down the freight elevator on one side of museum and carted around to an elevator on the other side. This would be the third and final position for the “Brontosaurus” – even when the mount was updated in 1995, preparators left the torso and legs in place.

Brown’s Cretaceous Hall, around 1939. Photo courtesy of the AMNH Research Library.

The 1930s and 40s saw a number of new dinosaur mounts added to the displays, nearly all of which were discovered by Brown. The new Jurassic Hall gained a Stegosaurus and Tenontosaurus (oddly, not a Jurassic dinosaur), and the Cretaceous Hall gained Brown’s astonishingly intact Centrosaurus, Corythosaurus, and Styracosaurus from Alberta.

Phase V: 1956 – 1990

Edwin Colbert joined AMNH in 1930 as Osborn’s assistant (he called this “a time of experiences and incidents,” whatever that means). Eventually rising to Curator of Vertebrate Paleontology, Colbert was one of only a handful of mid-century researchers studying dinosaurs. He is also notable for his public outreach — in collaboration with his partner, Margaret Colbert, he wrote more than 20 popular books about paleontology.

In 1953, Colbert worked with exhibit specialist Katharine Beneker to redesign the Jurassic and Cretaceous Halls. The Jurassic Hall received the most dramatic aesthetic makeover — windows were covered up to create a “black box” effect, while the dinosaur mounts were illuminated dramatically from above and below. The most significant addition to this space wasn’t a standing mount, but a trace fossil. Exhibit developers incorporated several slabs of sauropod tracks (collected at the Paluxy River in Texas by Roland T. Bird) into the central pedestal, as though left behind by the “Brontosaurus.” Cemented together, the slabs weighed 22 tons — apparently nobody expected that they would ever need to be moved. The fossil fish alcove, formerly part of the 1905 Hall of Fossil Reptiles, also found a home in this space.

In stark contrast to the Charles Knight oil and watercolor murals commissioned by Osborn, Colbert elected to decorate the Jurassic Hall with a series of understated chalk drawings. Joseph Guerry created the illustrations, which was then projected onto the walls and traced in chalk. The initial plan was to paint over the chalk outlines, but Colbert enjoyed the blackboard-like look and left them as they were. The exhibit team didn’t even add fixative, since it would have turned the lines an unpleasant yellow.

Jurassic hall colbert. Photo from Dingus 1996.

The Jurassic —or Brontosaur— Hall opened in 1953. Photo from Dingus 1996.

Architectural modifications to the Cretaceous Hall were minimal, although the standing dinosaur mounts were all clustered onto a single platform. Interestingly, both the National Museum of Natural History and the Peabody Museum of Natural History would arrange their dinosaurs in precisely the same way within the decade. While it’s possible that these museums were copying AMNH, this similarity is probably a reflection of the transition to more holistic natural history displays that was occurring in museums nationwide. Rather than displaying specimens individually, exhibit designers in the 1950s and 60s began to arrange them in meaningful ways — for example, grouping animals with a shared habitat. The Cretaceous Hall also gained some new specimens, including an array of Protoceratops skulls recovered during the Central Asiatic Expeditions. Signs and labels were updated with more approachable language, once again reflecting contemporary museum theory.

The Cretaceous —or Tyrannosaur— Hall opened in 1954. Photo courtesy of the AMNH Research Library.

Meanwhile, some of the oldest AMNH fossil exhibits were retired and replaced during this period. In 1961, the classic geology hall — the oldest exhibit on the fourth floor — became the research library and was closed to regular museum visitors. Its spiritual successor was the new Earth History exhibit, which replaced Osborn’s Hall of the Age of Man. Around the same time, George Gaylord Simpson curated what was colloquially known as the “Sloth Hall.” Occupying the space that was once the Hall of Fossil Reptiles, this exhibit featured ground sloths and glyptodonts, plus a sizable display demonstrating how fossils are collected and prepared. Only the Hall of Fossil Mammals remained ostensibly untouched during this wave of modernization.

The Hall of Advanced Mammals in 1982. Some sections were boarded up but remaining exhibits were virtually unchanged from the turn of the century. Photo courtesy of the AMNH Research Library.

The 1950s and 60s iterations of the AMNH fossil halls endured for 30 years, making them the longest-lasting versions to date. Displays like the “Brontosaurus” and Tyrannosaurus became immutable symbols for the institution, visited again and again by generations of museum-goers. However, time gradually took its toll. A large section of the Hall of Fossil Mammals was boarded up, since museum staff had removed so many specimens for study or conservation. Railings were eventually added to the Jurassic Hall, because it was too tempting for visitors to join the dinosaurs on the platform, Ke$ha-style.

The Brontosaur Hall in 1988. Photo courtesy of the AMNH Research Library.

Most importantly, the exhibit content became increasingly out-of-date with each passing year. This obsolescence permeated nearly every aspect of the exhibits, from the discussion of the dinosaurs’ extinction to the drab, earth-tone aesthetics. However, the most visibly antiquated elements were the fossil mounts themselves. A new wave of dinosaur research demonstrated that these animals had been active and socially sophisticated, a far cry from the the coldblooded tail-draggers that populated the galleries. AMNH had once been the center of American paleontology, but by the late 1980s its dated displays were lagging far behind newer museums.

Phase VI: 1995 – Present

Between 1987 and 1995, Lowell Dingus coordinated a comprehensive, $44 million renovation of the AMNH fossil exhibits (previously discussed here and here). The original plan was to renovate only the Hall of Fossil Mammals, since it had remained largely unaltered since 1895. Within a year, however, the project had expanded to encompass all six halls on the fourth floor, telling the entire story of vertebrate evolution. Two primary goals originated very early in the planning process. First, the “walk through time” layout would be replaced with one rooted in phylogenetic classification. The cladistic methodology for tracing organisms’ evolutionary history became the central theme that unified the new exhibits. This required a fairly substantial reorganization of existing specimens. The mammals could remain in the same two halls, but the denizens of the Jurassic and Cretaceous halls had to be rearranged to feature Saurischian and Ornithiscian dinosaurs, respectively. Meanwhile, the research library moved to a new location to make way for the Hall of Vertebrate Origins.

The Hall of Advanced Mammals was the first renovated exhibit opened to the public. Photo by the author.

The second major goal was to restore the original architecture in each hall, ensuring that both the historic specimens and the spaces they occupied would come “as close to their original grandeur as possible” (Dingus 2006). In many cases original architecture elements — such as the molded ceilings — were still intact behind panels that had been installed over them. These features were painstakingly restored, or when necessary, recreated. Classic decorative elements, from the colonnades to the elegant chandeliers, were reintroduced.

The updated Apatosaurus in the Hall of Saurischian Dinosaurs. Photo by the author.

The vast majority of the fossil mounts in the renovated exhibits had already been on display for years. Among the classic mounts, only the two most iconic displays were completely overhauled. The restoration of Apatosaurus (formerly “Brontosaurus“) took more than a year. A conservation team led by Jeanne Kelly worked from a temporary wooden scaffold, filling cracks in the aging fossils with epoxy and securing loose joints on the armature. The mount’s torso and legs remained in place throughout the process, but the neck and tail were dismantled and remounted by Phil Fraley’s exhibit company. In addition to a new head, the revised Apatosaurus gained several caudal and cervical vertebrae, extending its total length to 88 feet. Remounting the Tyrannosaurus rex was even more difficult, because the fossils were so fragile. Once again, Phil Fraley was responsible for disassembling and reposing the skeleton. The T. rex now sports a more accurate horizontal posture, and its weight is supported by steel cables extending from the ceiling.

The new fossil mounts are easily recognized by their dynamic poses. In the Hall of Vertebrate Origins, the amphibian “Buettneria” (now Koskinonodon) assumes a diving pose, while a Prestosuchus charges with its tail aloft. Among the dinosaurs, a new Deinonychus mount (assembled in part from previously-unidentified historic material) is posed in mid-leap. Finally, the dog-like Amphicyon chases the tiny antelope Ramoceros in the Hall of Advanced Mammals.

In the Hall of Vertebrate Origins, a new Koskinodon mount represents the vertebrates’ critical transition to terrestrial life. Photo by the author.

The AMNH fossil halls represent one of the most exhaustively complete fossil collections in the world, but these exhibits ultimately tell two stories. On one hand, we have the story represented by the fossils themselves. The exhibit is an extended genealogy, tracing our origins across 500 million years of deep time. On the other hand, we have the museum’s history, which highlights both the praiseworthy and the ugly sides of 20th century science. It reminds us where our society has been and where it needs to go. Both stories are relevant to each and every person passing through these halls, and laudably, the latest renovation highlights both.

References

Colbert, E.H. (1958). Chalk Murals. Curator 4:10-16.

Dingus, L. (1996). Next of Kin: Great Fossils at the American Museum of Natural History. New York, NY: Rizzoli International Publications, Inc.

Norell, M, Gaffney, E, and Dingus, L. (1995). Discovering Dinosaurs in the American Museum of Natural History. New York, NY: Alfred A. Knopf, Inc.

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Filed under AMNH, dinosaurs, exhibits, fossil mounts, history of science, mammals, museums, reptiles

Tagged as amnh, Barnum Brown, brontosaurus, dinosaurs, Edwin Colbert, evolution, fossil mounts, fossils, Henry Osborn, history of science, museums, natural history museums, paleontology, Tyrannosaurus

February 26, 2015 · 11:51 am

Framing Fossil Exhibits: Phylogeny

This is the third part of an on-again, off-again series about organizational and interpretive approaches in large-scale paleontology exhibits (see the introduction and walk through time entries). This time, I’ll be discussing exhibits arranged according to phylogenetics – that is, the evolutionary relationships among living things. Natural history museums have displayed specimens according to their place on the tree of life since the days of Charles Wilson Peale, and more than any other organizational scheme, phylogeny is the way biologists think about the living world. Perhaps unsurprisingly, this arrangement was more common in the past, when exhibits were typically designed by and for experts. Examples of these old-school displays include the fossil mammal gallery at the Peabody Museum of Natural History and the paleontology halls at the University of Kansas Natural History Museum (neither has been thoroughly overhauled since the 1950s).

The jargon-heavy signage in the Peabody Museum’s classic fossil mammal exhibit is probably ignored by most visitors. Photo by the author.

Modern natural history museums rarely attempt phylogenetic exhibits. In vertebrate paleontology, an understanding of the evolutionary relationships of animals as identified via minute anatomical details is fundamental to our science. However, most people simply don’t think about the world in this way. For example, I was halfway through my first semester teaching an undergraduate anatomy course when I realized that most of the class didn’t really understand what a mammal is. The students were familiar with the word “mammal” and could provide some examples, but they couldn’t articulate what sets mammals apart from other animals, and the relationship of mammals to other vertebrates within the tree of life was all new to them. It’s easy to forget that even the most basic elements of evolutionary classification are specialized knowledge, even among biology students.

Describing the history of life on Earth chronologically is relatively easy—museum visitors intuitively understand the forward progression of time. But scientific classification (as opposed to colloquial categorization) requires a lot of explanation up front, and it’s easy to overwhelm an audience with jargon. While not impossible (see Neil Shubin’s masterful Your Inner Fish), it is very difficult to explain phylogeny to a general audience in a relatable and approachable way.

In 1995, the American Museum of Natural History attempted to do just that with the most recent renovation of its historic 4th floor fossil halls. This evolutionary arrangement was a major change for AMNH, since this space had a “walk through time” layout for most of the 20th century. In the accompanying book Discovering Dinosaurs in the American Museum of Natural History, curators Norell, Gaffney, and Dingus explain that phylogenetics (and the cladistic methodology in particular) is the only way to approach the study of prehistoric life in an objective way. Patterns of evolutionary relationships revealed by cladistic analyses are hard evidence in a field of study traditionally characterized by idle speculation. Norell and colleagues argue that the new exhibit arrangement shows visitors the credibility and scientific rigor behind modern paleontology.

Map of the fossil halls on the 4th floor of AMNH. Source

Communicating the rigorous and trustworthy nature of scientific conclusions is a worthy goal, and the choice to ground the AMNH exhibit in this way seems almost prophetic given the litany of speculation-heavy paleontology “documentaries” that have proliferated in the years since it opened. Scientific rigor is definitely a running theme here – sign after sign explains that popularly depicted dinosaur behaviors like parental care and pack-hunting are largely untestable speculation. To a degree, this label copy takes the fun out of an undeniably fun subject, but I can appreciate the effort to legitimize paleontological science in the public eye. Overall, the AMNH exhibits represent an attempt to train visitors to look at fossils the way scientists do, and the phylogenetic layout is central to that goal.

In the exhibit, visitors are meant to walk through a cladogram of chordates. You’ll pass through large halls dedicated to broad groups like saurischian dinosaurs and advanced mammals, while visiting smaller cul-de-sacs that represent narrower clades like ornithomimids and testudines. A central black path guides you through the evolution of life, and centrally-situated pillars along your route identify major evolutionary innovations, such as jaws or the ability to reproduce on land. The insanely comprehensive vertebrate fossil collections at AMNH make this institution uniquely capable of putting so much diversity on display (although non-tetrapods are woefully underrepresented). Meanwhile, an open floor plan allows you to spend as much or as little time in each area as you wish, and ample natural lighting goes a long way toward making it possible to study specimens in detail.

Pillars mark major evolutionary milestones in the Hall of Vertebrate Origins. Photo by the author.

The evolutionary pathway becomes considerably less obvious among the dinosaurs. Photo by the author.

Nevertheless, I agree with Riley Black that the AMNH fossil halls don’t do the best job communicating the story of vertebrate evolution to their core audience. The underlying purpose of any exhibit structure is to provide meaning and context for objects – to help visitors see them as more than neat things to look at. According to visitor surveys, the default mode of understanding for most people passing through a paleontology exhibit is what I’ve been calling “dinosaur pageantry.” After seeing the exhibit, most visitors will recall a list of cool skeletons they saw. A few might consider which ones are meat-eaters and which ones are plant-eaters, but without further prompting that’s all we can usually expect from non-specialists. It’s the museum’s job to give visitors the intellectual tools to contextualize those fossils in a more sophisticated way, but there’s a fine line to walk. Provide too little information and nobody learns anything, but provide too much and the content is ignored. Unfortunately, the AMNH exhibits fall into the “overkill” category.

As discussed, phylogeny is complicated, often counter-intuitive, and largely unfamiliar to many visitors. To overcome this, the AMNH designers rely on a fairly long orientation film, which introduces the concept of categorizing organisms based on shared derived characteristics. There are a few problems with this. First there’s the film itself, which dives right into the traits that characterize different groups – like the stirrup-shaped stapes of derived mammals and the temporal fenestrae of archosaurs – without explaining why these traits are significant. To a layperson, these probably seem like really inconsequential things to hang a whole group on. The video also presents a cladogram of vertebrates without explaining how to read it. As Torrens and Barahona demonstrate, interpreting a phylogenetic tree is a specialized skill that many natural history museum visitors lack. Second, I saw no incentive or instruction to actually start my visit to the 4th floor in the orientation hall. There are no less than four entrances to the fossil exhibits, so many visitors won’t know there is an orientation film (I sure didn’t) until they’re halfway through the galleries. Finally, there’s the reliance on media in general: do we really want visitors to spend even a portion of their time in an exhibit full of real fossils watching a video in a darkened room? Telling visitors what to think in a narrated video is easy, but it’s not nearly as meaningful as showing them the same concept with specimens (or better yet, coaxing them to reach conclusions themselves).

Hall of Saurischian Dinosaurs, American Museum of Natural History. Photo by the author.

Iconic mounts in the Hall of Saurischian Dinosaurs are iconic. Photo by the author.

Within the actual fossil halls, interpretation remains stubbornly unapproachable. For example, the sign introducing proboscidians tells visitors that this group is defined primarily by eye sockets located near the snout. An observant visitor might wonder why scientists rely on such an obscure detail, as opposed to the obvious trunks and tusks. There’s a good teaching moment there concerning why some characteristics might face more selection pressure (and thus change more radically) than others, but instead visitors are only offered esoteric statements. Relatedly, the exhibit does little to prioritize information. Most label text is quite small, and there’s a lot of it. Compare this to Evolving Planet at the Field Museum, where there is a clear hierarchy of headings and sub-headings. Visitors can read the main point of a display without even stopping, and parents can quickly find relevant information to answer their charges’ questions (rather than making something up).

Evolving Planet also compares favorably to the AMNH fossil halls in its informative aesthetics and spatial logic. At FMNH, walls and signs in each section are distinctly color-coded, making transitions obvious and intuitive. Likewise, consistent iconography – such as the mass extinction zones – helps visitors match recurring themes and topics throughout the exhibit. AMNH, in contrast, has a uniform glass and white-walled Apple Store aesthetic. It’s visually appealing, but doesn’t do much to help visitors navigate the space in a meaningful way.

Phylogenetic interpretations change quickly – Edentata is no longer considered a natural group. Photo by the author.

The phylogenetic layout introduces a number of other unique interpretive challenges. Since there is no temporal axis, it’s often unclear whether the lineage in a particular cul-de-sac cluster went extinct, continued on, or gave rise to another group elsewhere in the exhibit. Visitors that want to know which animals lived contemporaneously are out of luck. Meanwhile, the exhibit sometimes uses modern animal skeletons to fill out displays where fossil examples are limited, such as bats and primates. While these are labeled, the text is too small to be seen from a distance. The evolutionary organization is also burdened by the fact that phylogenetics is a fast-moving and often changing field of study. While the order of geologic time periods will never change, the 20 year-old displays at AMNH are already out of date in several details. For example, there is a cul-de-sac devoted to edentates, which is now considered polyphyletic, and a cladogram in the Hall of Saurischian Dinosaurs incorrectly places tyrannosaurids among the carnosaurs.

Glass architecture lets visitors see through displays and get a sense of what lies beyond. Photo by the author.

Neat comparison of mammal teeth. Too bad there's no obvious label.

This display is a great example of the diversity in mammal teeth, but it’s a confusing centerpiece for the Hall of Primitive Mammals. Photo by the author.

The AMNH fossil exhibits excel in many respects, chiefly in the amazing diversity and quantity of specimens on display. The exhibit throws a lot of good science at visitors, but falters in explaining why it matters. The point of all this is not to nit-pick the design choices at AMNH, but to reiterate that phylogenetically-arranged fossil exhibits are really hard to pull off. This is not the most intuitive way to introduce the history of life, or even the process of evolution. With so much background to cover, perhaps a more structured and linear layout would be better. In fact, a lot of my issues with the AMNH fossil exhibits seem to stem from a disconnect between the phylogenetic interpretive content and the wide-open aesthetics. Open exhibits can be great, but in this case it hinders the learning opportunities for self-guided groups of visitors. It’s difficult to imagine a typical visitor, arriving with their family or another mixed-age group, having the patience to make sense of it all. Regrettably, such visitors default to the dinosaur pageantry level of understanding, making all the work invested in creating a meaningful exhibit space for naught.

References

Norell, M, Gaffney, E, and Dingus, L. (1995). Discovering Dinosaurs in the American Museum of Natural History. New York, NY: Alfred A. Knopf, Inc.

Torrens, E. and Barahona, A. (2012). Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted? Evolution: Education and Outreach 1-25.

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Filed under AMNH, dinosaurs, exhibits, fish, FMNH, fossil mounts, mammals, museums, opinion, reptiles, reviews, systematics

Tagged as amnh, dinosaurs, evolution, exhibit reviews, exhibits, fossil mounts, fossils, mammals, museums, natural history museums, paleontology, science communication

July 17, 2013 · 7:07 pm

The Osborn problem

In both paleontology and the museum field, we’ve long contended with what one might call “the Osborn problem.” The legacy of Henry Fairfield Osborn, paleontologist and president of the American Museum of Natural History between 1908 and 1933, is quite important to both fields. To paleontologists, he is known for accumulating at AMNH one of the largest and most exhaustive fossil collections in the world, for financing and supporting the careers of legends like Barnum Brown and Charles R. Knight, and of course for naming and describing saurian celebrities like Tyrannosaurus and Velociraptor.

Osborn is also well-regarded by museum specialists for heightening the standards for public exhibitions, investing in lifelike habitat dioramas of taxidermy animals and spectacular mounted dinosaur skeletons in order to make science exciting for a wide audience. Osborn’s devotion to storytelling and drama in the exhibits he curated brought millions of visitors to AMNH and quite literally defined public expectations for what museums should offer to this day.

Henry Fairfield Osborn.

In recent decades, however, historical interest in Osborn has been mostly focused on his disreputable personal and political beliefs: Osborn was a flagrant racist and anti-Semite, an admirer of Adolf Hitler and a strong supporter of research in eugenics. Osborn regularly used his clout to bring material harm to the American working class, lobbying for legislation including the Emergency Quota Act and the Immigration Act of 1924. For what it’s worth, Osborn was also apparently unbearably arrogant and truly dreadful to work with, going as far as to demand lower-ranked museum employees leave the elevator car when he got on.

All this puts paleontologists and museum specialists in an awkward position. Is it acceptable to admire Osborn’s positive achievements in light of his personal politics? After all, Osborn’s views were not terribly unusual among the aristocratic class of his day. Perhaps we shouldn’t condemn the man entirely for not “rising above his time and place” (as Stephen Ambrose argues regarding coming to terms with Thomas Jefferson the slave owner).

Unfortunately, Osborn’s case is complicated by the fact that his bigotry inspired (or at least contributed to) much of his work at AMNH*. To start, Osborn’s scientific work was based on an inaccurate orthogenetic interpretation of evolution. He professed that an ill-defined guiding force shaped life from lesser to greater forms, the effect of which could be seen by comparing “primitive” and “advanced” species, and of course, “primitive” and “advanced” expressions of humanity. While we cannot conclusively link Osborn’s pseudo-evolutionary ideas with his bigoted social agenda, it is certainly convenient for him that he saw people of “Nordic” descent as biologically superior.

*To clarify, none of the exhibits curated by Osborn remain on display and none of my comments here apply to the present day AMNH.

Critically, Osborn did not keep his ideas of natural hierarchy in the ivory tower. He explicitly intended that the exhibition halls of AMNH educate visitors not just about natural science but about the naturally graded order he believed to be characteristic of life on earth. Osborn thought that collections of biological specimens implicitly revealed an upward ascent of life, and that those on top had earned their place through innate superiority. Osborn pronounced that his exhibits would teach morality to new American immigrants, presumably by putting them in their place with the rather hideous racial hierarchy on display in the Hall of the Age of Man. As Donna Haraway puts it in her classic essay Teddy Bear Patriarchy, Osborn’s exhibits were a “gospel of wealth and privilege” that appropriated natural specimens to affirm the American elite’s place at the top of the pecking order.

Tyrannosaurus and others in AMNH Dinosaur Hall, 1927. Photo courtesy of AMNH Research Library.

Museums are understood to be sources of intellectual authority, and deservedly so. But exhibits have authorship, same as any other written work, and Osborn’s legacy demonstrates that the influence of authors and their worldviews can be a powerful force. For example, Osborn arranged the Hall of the Age of Man in what he saw as ascending order, from the ancient peoples of Africa, to North America, and finally Europe. Placed at the end of an exhibit series that started with Cambrian invertebrate fossils before passing through Paleozoic, Mesozoic, and Cenozoic fossil displays, the Age of Man gallery deliberately implied that European-descended humans were the culmination of the entire history of life on Earth.

Meanwhile, the exhibit on fossil horses curated by Osborn depicted small, multi-toed horses of the Eocene gradually becoming larger, losing toes and becoming better at being modern Equus. This orthegenetic representation runs counter to evolution via natural selection as originally proposed by Darwin, and as understood today. Indeed, other paleontologists, including O.C. Marsh, had established in the 19th century that horse evolution more closely resembled a tangled bush, with many overlapping morphological offshoots adapted to varying environmental circumstances. But Osborn had rejected Darwinian evolution in favor of his presumed hierarchy of life, and ensured that his inaccurate story was what was seen by millions of visitors.

So what does Osborn’s legacy mean to paleontologists and museum specialists today? Do we need to qualify every mention of his name with a denouncement of his worldview? Should we always write out “Tyrannosaurus rex Osborn, 1905″ as “Tyrannosaurus rex Osborn the racist jerk, 1905″? At minimum, Osborn’s exhibits are a sobering reminder to all us involved in science education that our field is not immune to bias. The subjectivity of cultural and historical museum exhibits has been well-explored by scholars like Ames and Weil, but comparatively little reflection has been done on the authorship of exhibits on science and natural history. We rely on the “naturalness” of the objects we display to speak for itself, and to bear the burden of proof for the statements we make. The world around us is knowable, and science is the best tool to learn about it. But explaining what we have learned in any form (books, technical journals, museum exhibits) is an avenue for personal or cultural bias to slip in, and that is why it remains important to actively and regularly check our assumptions.

References

Ames, M.M. (2004). Museums in the Age of Deconstruction. In Reinventing the Museum: Historical and Contemporary Perspectives on the Paradigm Shift. Lanham, MD: AltaMira Press.

Brinkman, P.D. (2010). The Second Jurassic Dinosaur Rush: Museums and Paleontology in America at the Turn of the Twentieth Century. Chicago, IL: University of Chicago Press.

Colbert, E.H. (1968). Men and Dinosaurs: The Search in Field and Laboratory. New York, NY: E.P. Dutton and Co., Inc.

Haraway, D. (1984). Teddy Bear Patriarchy: Taxidermy in the Garden of Eden, New York City, 1908-1936. Social Text 11:20-64.

Kohlstedt, S.G. (2005). Thoughts in Things: Modernity, History and North American Museums. Isis 96:586-601.

Osborn, H.F. (1921). The Hall of the Age of Man in the American Museum. Nature 107:236-240.

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Filed under AMNH, anthropology, history of science, mammals, museums, science communication

Tagged as anthropology, evolution, history of science, museums, natural history museums, Osborn, science education

January 1, 2013 · 4:00 pm

Beating the orthogenetic horse

According to the rad personalized 2012 review provided by WordPress, the top search engine terms leading people here over the last year were dinosours, horse evolutionary tree, horse evolution tree, horse phylogenetic tree and Daspletosaurus. It’s not too difficult to pick out the pattern there – horse evolution seems to be a major draw, even though I only mentioned it in a single post back in June. I aim to please, so I suppose a more detailed discussion of horse phylogeny is in order. First off, let me recommend Brian Switek’s thorough and thoughtful take on the subject. If you stick around here, you’re going to get more of a tirade.

Most depictions of horse evolution available online, including the one I posted a few months ago that is luring people to this site, are terrible. The typical linear presentation of horses progressively increasing in size from Eohippus to modern Equus, losing toes along the way, misrepresents not only what we know about horses as a group, but how evolution works in general.

This didn’t happen.

Evolution is, of course, neither linear nor progressive: it is primarily the result of populations adapting to thrive in their particular environments. As environments change over time species may evolve or go extinct, but there is no predetermined goal that lineages are reaching for. Modern Equus is not the most “highly evolved” horse – this is, in fact, a misleading if not meaningless concept, because a species’ success is dependent on its ability to thrive in that specific time and place. A modern horse is well adapted for grazing and running fast on open plains, but relocate one to the Eocene cloud forests where Eohippus thrived and it would do very badly.

Furthermore, it has been known for over a century that horses as a group did not consistently grow larger over time or otherwise become more Equus-like. Instead, horses diversified into a variety of forms over the group’s 55 million year existence, each group adapting to different environmental niches across the northern hemisphere. Large and small, forest-dwelling browsers and plains-dwelling grazers, these and all manner of other horses overlapped in time and space over the course of the Cenozoic. As J.W. Gidley of the American Museum of Natural History had worked out as early as 1907, horse evolution was not a linear progression but a tangled bush (just like the evolution of most other clades).

A modern horse phylogeny. From MacFadden 2005, via Laelaps.

So where did the orthogenetic depiction of horse evolution come from, and why is it still with us today? The answer highlights the importance of museum exhibits and specimen provenance in the public’s understanding of paleontology, with a dose of jealous personalities for good measure.

In 1859, Charles Darwin published On the Origin of Species, in which he articulated the process of evolution by natural selection virtually exactly as we understand it today. Darwin’s book incited a whirlwind of debate in both scientific and public circles because of its implication that the diversity of life could be attributed to natural forces, rather than an unknowable divine power. Within a decade, however, the vast majority of the scientific community was convinced by the soundness of Darwin’s theory, and to this day billions of individual observations of the natural world tell us that evolution is assuredly true.

One of the many lines of evidence covered in On the Origin of Species is the fossil record, with which we can trace the evolution and extinction of organisms over time, including the ancestors of modern life. However, Chapter 9 of Darwin’s book, “On the Imperfection of the Geological Record” (full text pdf) reads like like a lengthy apology for the incomplete nature of fossil preservation. Today, the use of organized, cladistic methodologies allow paleontologists to piece together detailed phylogenies from fossils, but in Darwin’s day, the evidence was patchier, and he opted to de-emphasise the fossil record’s usefulness to avoid such criticism. As Darwin put it, “we have no right to expect to find in our geological formations an infinite number of of those fine transitional forms.” Unfortunately for paleontology specialists, this led other biologists to believe that fossils could not make any independent contribution to the understanding of evolution. Largely shut out of the biggest biological discovery of all time, paleontologists became stewards of a “second-class discipline” (Sepkoski 2012, 9).

Paleontologists in the late 19th century.

Since biologists interested in evolution considered paleontology mostly irrelevant, late 19th-century paleontologists were left with three options. They could support evolution as best they could and accept that other biologists might not take notice, they could ignore theoretical discussion entirely and focus on purely descriptive studies of morphology, or they could be spiteful and seek alternatives to Darwinian evolution. The second course of action was the most popular well into the 20th century. E.D. Cope seems to be an example of the third approach, favoring an odd sort of neo-Lamarckism in his book The Origin of the Fittest. Such conceptions of directional change, such as Cope’s Law, are counter to evolution as proposed by Darwin and as understood today. However, a handful of paleontologists stuck with it and endeavored to provide meaningful fossil evidence for evolutionary theory.

Throughout the 1860’s, paleontologist O.C. Marsh amassed an impressive array of fossil horses from Wyoming and elsewhere in the American west. Horse fossils had been found in Europe much earlier, but Marsh’s horse collection was much more complete, and was probably the best fossil record compiled for any vertebrate group at the time. In 1870, the influential British naturalist Thomas “Darwin’s Bulldog” Huxley visited Marsh in New Haven and was suitably impressed: Marsh’s fossils ranged from the Eocene up until the Pleistocene, providing a clear picture of how the horse family had evolved over time. While Darwin had been hesitant to make too big a deal about the fossil record as evidence for evolution, the horse fossils were blatant examples of animals changing over time.

During the same visit, Huxley gave a lecture in New York in which he cited the horse fossils as a fantastic new line of evidence in support of evolution. Unfortunately, Huxley’s lecture (while admittedly aimed at a general audience) tread into some severely teleologic territory. As quoted in The Gilded Dinosaur (Jaffe 2000, 162), Huxley told his audience that “the horse is in many ways a most remarkable animal in as much as it presents us with an example of one the most perfect pieces of machinery in the animal kingdom.” He went on to explain how horse ancestors, from the little four-toed Hyracotherium in the Eocene to increasingly large horses like Merychippus and Pliohippus, gradually perfected the design of the modern horse. According to Huxley, over the course of the Cenozoic horses got bigger, faster, leggier, and generally better at being horses as we know them today. Problematically, this essentialist narrative rather misses the point of evolution as described by Darwin.

Marsh, like Huxley, was an early advocate of evolution, but his narrative of horse evolution was more on the mark. Marsh concluded that the smaller early horses with brachydont teeth were well suited for life in the rainforests that covered the western United States 50 million years ago. Horses like we know them today emerged as a direct result of the Earth getting cooler and drier over the course of the Cenozoic, and by the end of the Pleistocene the lineages of forest horses were completely extinct. Equus is with us today not because it is the best horse for any circumstance, but because it was most successful during the ice ages that shaped the modern flora and fauna (it also helped that humans figured out that horses are useful and ensured their survival through domestication).

Unfortunately, Marsh was never enthusiastic about public education, and so the progressive view of horse evolution was the one that made it into the public sphere. The history of horses remained a popular example of evidence for evolution, trotted out over the years by prominent biologists like George Simpson and Stephen Gould. Indeed, it was the first good evolutionary story known from fossils, although by no means the last or the best. In the earliest 1900s, Henry Osborn had a major role in solidifying the orthogenetic horse evolution story in the public eye when he curated the exhibit on the subject at the American Museum of Natural History. It is on the basic premise of this exhibit that the textbook, museum, and web descriptions of linear horse evolution that persist to this day are based.

The fossil horses of AMNH. Photo by the author.

After the modern biological synthesis, paleontologists realigned with the rest of biology, and the odd pseudo-evolutionary ideas that persisted in paleontological circles began to fall by the wayside. However, orthogenetic ideas remain common in natural history exhibits on horse evolution to this day (in about 62% of them, according to MacFadden et al. 2012). The reason these exhibits have stuck around isn’t entirely clear. MacFadden and colleagues suggest suggest a lack of inertia or funding for the renovation of exhibits is a factor, but they also point out that even some newer exhibits fall back on linear horse evolution.

The biggest problem is that orthogenetic evolution makes more intuitive sense to non-specialists. We often use the word “evolution” to imply improvement, so it would follow that horses should get bigger and better over time. This is an important misconception to overcome, because, as if we need a reminder, only 15% of Americans believe humans evolved from other animals via strictly natural processes, and an even smaller number can correctly articulate how evolution works. Evolution is the fundamental principle underlying everything we see in the natural world, and it is imperative that a correct understanding of how it works is the basis of any biology education. With the proper background, the real story of horse evolution is a great example of how changing climates effect organisms and ecosystems over time. This is helpful for interpreting the ever-important subject of climate change, but it won’t click until the linear horse evolution story is trampled out for good.

References

Jaffe, M. 2000. The Gilded Dinosaur: The Fossil War Between E.D. Cope and O.C. Marsh and the Rise of American Science. New York, NY: Three Rivers Press.

MacFadden, B.J., Oviedo, L.H., Seymour, G.M. and Ellis, S. 2012. “Fossil Horses, Orthogenesis and Communicating Evolution in Museums.” Evolution, Education and Outreach 5:29-37.

Sepkoski, D. 2012. Rereading the Fossil Record: The Growth of Paleobiology as an Evolutionary Discipline. Chicago, IL: University of Chicago Press.

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Filed under AMNH, history of science, mammals, museums, science communication, systematics

Tagged as Cope and Marsh, evolution, fossils, horse evolution, horses, paleontology, science communication, science education

June 20, 2012 · 9:41 am

Communicating Systematics, Part 2

In the previous post, I discussed how phylogenetic trees, while powerful and informative to trained eyes, can be misinterpreted by lay audiences. These misunderstandings are easy to diagnose, but actually finding solutions to the problem is challenging.

In a perfect world, every child would be introduced to evolutionary theory early and often in their obligatory science education, and everybody would be able to interpret phylogenetic trees the way scientists do. This is unlikely to happen anytime soon, especially in the United States, so educators are going to have to get creative. One option is to provide additional information to aid in the interpretation of the diagram. On the surface, adding more information is always an attractive prospect, but unfortunately it does not always work as intended. Attention spans are perilously short, and the goal of a visual representation should be to make the content immediately intuitive and easier to understand.

If conventional shapes and symbols in evolutionary trees are not getting the intended message across to target audiences, then perhaps we need to rethink how we are structuring these trees. I don’t have a catch-all solution, but the following might be enough to at least start a conversation.

Change the shape of the tree

Torrens and Barahona argue that many misinterpretations of trees stem from ideas of essentialism and teleology that are deeply ingrained in and continually reinforced by western culture. Likewise, equating up with good and down with bad is a recurring, internalized motif. Therefore, trees that illustrate evolution and diversification proceeding upward or to the right only encourage presuppositions of linear, goal-oriented evolution.

One solution that has been experimented with (at AMNH, for example) is to draw trees as circles (see below). This eliminates the problem of associating up with good and bad with down, or upward movement with progress. A circular “tree” has no orientation, and thus does not imply any taxa to be better than the rest. Personally, I find circle diagrams confusing to read, but I appreciate what they are intended to accomplish. A diagram of evolutionary relationships could theoretically take any shape, since the crucial information is in the branching order, not the nature of the lines.

A circular tree. From eplanetscience.com.

Be careful with representation of ancestors

Many phylogenetic diagrams place specific fossil taxa at nodes along the tree in order to illustrate the course of evolution. This is informative of general evolutionary trends, but it can also be confusing. As a case in point, I just did an image search for a horse evolution diagram to use as an example, and found that many of the top results came from creationist websites. These sites aren’t worth linking to (although they are easy enough to find), but they erroneously assume that fossil taxa are thought to be directly ancestral to modern Equus caballus. Evolutionary scientists think no such thing, but looking at the image below I can see how that conclusion could be reached.

This diagram of the evolutionary history of horses can lead to the mistaken assumption that earlier species are thought to be directly ancestral to later ones. That polytomy that leads to three unlabeled nodes doesn’t help either.

In a proper cladogram, taxa are only placed at the ends of branches. Direct ancestry is (almost) never inferred, because the scarcity of the fossil record prevents us from ever knowing exactly what evolved into what when. The cladogram below shows the relationships between the seven modern-day species of Equus. Systematists have determined a series of branching relationships based on anatomical and molecular data, and even provide a suggestion of when these divergences occurred, via the time scale. Each node represents a common ancestor that definitely existed, but we will probably never find or identify their fossils.

A cladogram of modern horse species. From Hooper Virtual Natural History Museum.

In this case, I would prefer if books or exhibits for popular audiences nixed images like the first one and instead went with cladograms that do not suggest specific ancestor-descendant relationships. Obviously the cladogram could be spiced up with colors and illustrations, but it is important to use a format that represents precisely what scientists do and do not know.

Always clarify orientation

Proboscidea phylogeny from academic.reed.edu.

Individuals well-versed in evolutionary science automatically read trees from the basal node out to the tips. Typically, and in the elephant phylogeny above, that would be from the bottom up. It can therefore come as a surprise (it certainly did for me) that non-specialists frequently attempt to read phylogenetic trees from left to right. Viewers may assume that the horizontal order of taxa across the top is significant, representing either the course of evolution or time. Neither would be correct, as Mammut on the far left and Mammuthus on the far right were roughly contemporaneous, and Loxodonta africana and Elephas maximus in the middle are the only extant elephants. Although it may not occur to specialists, it is a simple and necessary precaution to label the orientation of the tree and avoid such confusion.

Avoid calling anything “more evolved”

This is more of a nomenclature issue than a visual one, but poor graphics can exacerbate this misconception. All contemporary species, from sponges to frogs to humans, have been evolving for the same amount of time. An amphibian or reptile is not “primitive”; it is just as adapted to its environment as we are. Using this sort of terminology is attractive as a shortcut when referring to less-diverse sister groups to more-diverse clades, but it misrepresents the nature of evolution and should be discouraged.

References

MacDonald, Teresa E. “Communicating Phylogeny: Evolutionary Tree Diagrams in Museums.” 2010. Paper presented at the NARST (National Association for Research in Science Teaching).

Torrens, Erica and Barahona, Ana. “Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted?” 2012 Evolution: Education and Outreach 1-25.

Communicating Systematics

In case you forgot, only 15% of Americans polled by Gallup accept that human beings evolved from other animals through natural processes*. This statistic has not changed meaningfully since Gallup started asking this question in 1982. This fact should be in the back of the mind of every science educator, and for that matter, every scientist, each and every day we go to work. It is a scientifically well-established fact that all life has evolved over long periods of time, and that all forms of life are related to each other. This fact is fundamental to our understanding of life on Earth. The goal of both educators and scientists is to expand our knowledge and awareness of our world, and it is therefore disconcerting that so few people are willing (or have had to opportunity to) acknowledge the wealth of information that an understanding of evolution provides.

*A couple complaints about that link. First, the phrasing of the question, “human beings evolved over millions of years from less advanced forms of life” (emphasis mine) is poor, read on for reasons why. Second, belief that humans evolved “with God’s guidance” does not seem like a meaningful distinction to me, and does not suggest a proper understanding of evolution.

The overwhelming number of people who do not accept evolution is intimidating. The fact that our politicians and leaders are often among this number is even more troubling. It can be tempting to retreat into academia and whine about the problem to our peers, or perhaps ignore it entirely. However, 30 years of unchanging results on the Gallup poll indicate that the issue is not going to go away. Both educators and scientists need to take the offensive and directly address misconceptions and misunderstandings about evolution, as well as find effective means to mitigate them.

Phylogenetic Trees

In the world of science education, one of the trickiest issues is supplying appropriate context. Although all good science can be explained in clear, readily-understandable language, most research still requires some background on the Big Ideas in science. Two huge examples are evolution by natural selection and the scientific method, which I briefly discussed here and here. Without an understanding of how scientific ideas or generated or how evolution works, discussing the finer points of, say, feeding strategies of tyrannosaurs is quite pointless. Unfortunately, even among people who accept the fact that evolution is a real phenomenon, this background all too often does not exist.

Educators need to supply the public with the context they need to understand current science, and one good area to focus is the reading of phylogenetic trees. A phylogenetic tree is a branching diagram that depicts inferred evolutionary relationships among organisms. A tree implicitly shows that included organisms descended and diversified from a common ancestor. As such, phylogenetic trees are a visual embodiment of evolutionary theory, and provide an informative narrative of the history of life.

As is often the case, David Hone has already provided a wonderful explanation of how scientists construct trees and how to read them correctly, so I’ll just drop that link and move on. The problem is that although evolutionary trees are often used to convey ideas in museum displays and general interest science articles, many lay-viewers are interpreting them inaccurately. Reading a tree requires practice and expertise that shouldn’t be taken for granted, because misinterpretations only provide fodder for the anti-evolution/anti-science lobby. Let’s go through the common misinterpretations one at a time (many of these are discussed in Torrens and Barahona 2012, a few are my own additions).

Evolution is goal-oriented. In fact, evolution is not progressive, but is the product of organisms adapting to their specific environment. When that environment changes, taxa that were once well-adapted often die out. Being “well-evolved” is therefore fluid and transitory state. The misconception of directed evolution is probably related to ingrained western religious views of human superiority over nature. Rather annoyingly, cultural anthropologists often buy into the erroneous idea of progressive evolution, and attempt to use it as evidence that science is but one of many equally correct world-views.

There is a “main line” of evolution. This is largely the product of late 19th century drawings of trees of life which used literal trees as the basis of the diagram. Most famously, German natualist Ernst Haeckel illustrated the Systematischer Stammbaum des Menschen in his book Anthropogenie in 1874. In this drawing, the diversity of life is overlaid on a tree, which has a thick trunk running straight up to humans and other primates at the top. Again, this plays into concepts of human superiority and inevitability that have nothing to do with biological evolution.

Some contemporary species are more or less evolved than others. All contemporary species, from sponges to frogs to humans, have been evolving for the same amount of time, and are just as adapted to their environments as we are. Unfortunately, placing humans or mammals at the top or the right of phylogenetic trees seems to be an unshakable habit, even for systematists, which only encourages the notion that these taxa are somehow better.

Similarity among taxa always implies relatedness. Determining evolutionary relationships is a complex process. Modern systematists use huge matrices of independent characters to calculate the most parsimonious trees. Furthermore, Hennigean cladistics requires that relationships only be determined using synapomorphies (shared derived traits) rather than plesiomorphies (shared primitive conditions). Although the salmon and the lungfish below superficially appear more like one another than the cow, similarities like a fishy shape and a lack of a neck are primitive conditions, not specializations. The synapomorphies shared by the lungfish and cow, such as jointed limbs and the ability to breathe air, inform us that they shared a more recent common ancestor than either did with ray-finned fish.

A counter-intuitive cladogram. Subjective similarity does not always mean relatedness.

Change only occurs at nodes. The nodes in a phylogenetic tree do not represent literal evolutionary events. Rather, evolution is a continuous process. This is a case where I like to ask people who make this misconception, “how could we know that?” This can get people thinking about what evidence is available to scientists, what conclusions can be reached from these data, and what isn’t known.

Example taxa illustrated lower in the tree represent direct ancestors of taxa higher in the tree. It can be helpful to use fossil species to illustrate the general state of an evolutionary lineage at varying points in time (this is done all the time with diagrams of horse evolution). However, with few exceptions, the incomplete nature of the fossil record makes it impossible to know exactly which species were directly ancestral to others.

Traditional Linnean categories are directly applicable to trees. In fact, most (sensible) modern systematists prefer the cladistic methodology, which requires that all groups be monophyletic (that is, made up of all descendents of a common ancestor, with no exclusions). For example, the traditonal Linnean definition of reptiles, which includes turtles, lizards, snakes, tuataras and crocodiles, is not monophyletic, because any cladistic unification of these taxa would also have to include birds.

The traditional definition of reptiles, which excludes birds, is paraphyletic.

This went on a bit longer than I expected, so I’m going to leave these issues hanging for the time being. But do not fret, I will finish this train of thought soon with a discussion of potential solutions to these misinterpretations that have been attempted, and some that may be attempted in the future.

References

MacDonald, Teresa E. “Communicating Phylogeny: Evolutionary Tree Diagrams in Museums.” 2010. Paper presented at the NARST (National Association for Research in Science Teaching).

Torrens, Erica and Barahona, Ana. “Why are Some Evolutionary Trees in Natural History Museums Prone to Being Misinterpreted?” 2012 Evolution: Education and Outreach 1-25.

Tag Archives: evolution

Framing Fossil Exhibits: Environmental Change

References

Permo-Triassic Synapsids at NMNH

The Dimetrodon

The Thrinaxodon

The Daptocephalus

References

History of the AMNH Fossil Halls – Part 2

Phase IV: 1940 – 1955

Phase V: 1956 – 1990

Phase VI: 1995 – Present

References

Framing Fossil Exhibits: Phylogeny

References

The Osborn problem

References

Beating the orthogenetic horse

References

Communicating Systematics, Part 2

Change the shape of the tree

Be careful with representation of ancestors

Always clarify orientation

Avoid calling anything “more evolved”

References

Communicating Systematics

Phylogenetic Trees

References

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Tag Archives: evolution

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The Dimetrodon

The Thrinaxodon

The Daptocephalus

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Phase IV: 1940 – 1955

Phase V: 1956 – 1990

Phase VI: 1995 – Present

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References

References

References

Change the shape of the tree

Be careful with representation of ancestors

Always clarify orientation

Avoid calling anything “more evolved”

References

Phylogenetic Trees

References

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