In the Shadow of Knight
THE STORY OF LIFE ON EARTH IS HARDLY A NEW TOPIC FOR AUthors and illustrators. Popular books on this subject have existed since Franz Unger’s 1851 Die Urwelt in ihren verschiedenen Bildungsperioden (The primitive world in its different periods of formation), a landmark work that described and illustrated (courtesy of artist Josef Juwasseg) the changing environments and inhabitants of our planet for the very first time. Countless examples of the same concept have appeared since then, created by authors and illustrators of varying backgrounds and levels of expertise. Most have largely been forgotten, but the 1946 book Life through the Ages is fondly remembered and, thanks to modern commemorative editions, it remains in print well over 70 years since its first publication. The ongoing popularity of Life through the Ages has almost certainly been helped by the fact that its author/illustrator is one of the most celebrated and influential artists of extinct animals to have ever lived: Charles Robert Knight (1874–1953).
Nowadays, we consider Knight a paleoartist: an individual who restores the life appearance of fossil animals and ancient environments using paleontological and geological data, supplemented by a firm understanding of modern natural history to fill in our knowledge gaps about prehistoric worlds. Although Knight’s career saw him capture many natural history subjects, he is probably most famous and fondly remembered for his depictions of prehistory. The discipline of paleoart is as old as paleontological science, stretching back to at least the year 1800, and we can view Knight’s professional life, which ran from the 1890s to the early 1950s, as bridging the nineteenth-century foundation of paleoart with a more modern, established period characterizing the mid-twentieth century. Much of the contrast between these eras reflects the rapid accumulation of paleontological knowledge that occurred in the late nineteenth century. Paleoartists working in the early 1800s often had only scrappy fossils to work from, resulting in reconstructions that, though sometimes surprisingly insightful considering the material they were based on, were not close approximations of their subject species. The discovery of superior fossils in the latter half of the 1800s allowed for new reconstructions that eclipsed the scientific merit of their predecessors. For dinosaurs, in particular, many of these discoveries were being made in the western United States by museum teams from the northeast of the country. As a young and talented natural history artist situated around New York City in the 1890s, Knight was in a prime position to capitalize on these new discoveries. By 1894, his habit of sketching animals and specimens in the American Museum of Natural History (AMNH) was recognized by museum staff, and he was asked to restore the life appearance of the extinct piglike mammal Elotherium (now Entelodon). Knight’s career as a paleoartist was thus launched, and thereafter he spent much of his professional life recreating extinct animals in various artforms.
For two decades Knight worked closely with the director of the AMNH, Henry Fairfield Osborn, who promoted Knight’s work heavily. Osborn seems to have regarded Knight as a museum “brand” and pushed his work both to advertise the museum and to spread AMNH influence to other institutions. Knight’s work became such a beloved component of the museum’s exhibits that installations were eventually designed with his artwork in mind: it was important for fossil specimens to be associated with, but not to obscure, his murals and illustrations. Still, Osborn also saw Knight primarily as an artist, not an independent scientific intellect. He referred to Knight’s AMNH works as “Osborn–Knight restorations,” and in some instances he used Knight’s work to visualize his idiosyncratic and infamous ideas on human evolution. Though they developed a productive and successful partnership, Knight and Osborn did not always work in harmony; the two men often disagreed on matters of artistry, science, and artistic ownership. Their working relationship came to an end in 1928, when Knight agreed to a commission from the Field Museum in Chicago. For Knight, distancing himself from Osborn was probably to his benefit, as it demonstrated that he could produce excellent paleoartworks without Osborn’s direction. Osborn, however, thought Knight would flounder without his support and was critical of his later work, including his iconic murals for the Field Museum and the Los Angeles County Museum. Despite their less-than-amicable professional split, Osborn and Knight remained friends until Osborn died in 1935, with Knight writing fondly of his colleague after his passing.
Knight’s fame and reputation among scholars meant his work became a stamp of quality for any paleontological product from the late nineteenth and early twentieth centuries, almost as if he were somehow the official, licensed artist of extinct life. Knight was just one of many paleoartists working in the late nineteenth and early twentieth centuries, but he dominates histories of the discipline at this time. Indeed, his reputation is so grand that it often eclipses the nineteenth-century artists who created and shaped paleoart in the first place. To some people, Knight is the early history of paleoart, or at least the only history worth knowing. He is unprecedented among early paleoartists for his posthumous documentation, making him more than just a name associated with a few paintings: he is a fleshed-out historical figure. In addition to an abridged, posthumously published autobiography (Knight 2005), his work and life have been celebrated through collections of his artwork, correspondence, and biographical accounts (e.g., Czerkas and Glut 1982; Paul 1996; Stout 2002; Berman 2003; Milner 2012; Lescaze and Ford 2017). He is also a recurring character in accounts of the history of American science (e.g., Davidson 2008; Clark 2010; Sommer 2016), as well as those about influential figures such as Osborn (e.g., Regal 2002). He is, by far, the best-documented paleoartist of all time, and other individuals just as important to early paleoartistry as Knight—such as Benjamin Waterhouse Hawkins, Josef Juwasseg, Edouard Riou, and Zdeněk Burian—are dwarfed by the continued attention and accolade that he receives. (I stress that this comment is not an argument for less attention on Knight, but a reflection on the need for increased scholarly interest in the history of paleoart in general. Knight’s documentation is relatively modest in the grand scheme of historical figures, and he is exceptional primarily because other paleoartists receive so little popular and academic interest.)
Knight’s paleoartworks have a high level of technical proficiency and obvious influence from his skills as a traditional natural history and animal artist. His ability to composite exotic extinct species into believable landscapes makes his work as enjoyable today as it was a century ago, even if some of his scientific details have become dated. The fact that his work remains on display in Chicago, New York, and Los Angeles long after the work of other artists has been replaced by newer, more contemporary works is testament to his talent and vision. His artwork is all the more remarkable because his eyesight was extremely poor, the combined result of a severe astigmatism and a childhood accident. He was considered legally blind, and it was only through the aid of special glasses that he was able to see. His famous AMNH murals were completed with the aid of assistants, reproducing paintings Knight executed at much smaller size.
Knight is generally not remembered for what seem to be his personally favored subjects or scientifically best work. He is mostly discussed in the context of his dinosaur art, but his real affinity and sharpest scientific insight was for mammals. His writings make no effort to hide his enjoyment of capturing mammals in art, especially elephants, cats, and early humans, whereas he often belittles nonmammalian subjects. In Life through the Ages, Knight describes an Asian elephant as “magnificent” and (referring to one individual he knew well) “thoroughly lady-like” (1946, 36), while Stegosaurus is “the stupidest member of a very moronic family” (14) (presumptions about animal intelligence are common in Knight’s writings, and are often so glib as to be humorous, whether intentionally or not). His other books show similar biases. Before the Dawn of History (1935) leans toward mammal evolution and human prehistory in both text and illustrative coverage, and his 1947 Animal Anatomy and Psychology for Artists and Laymen (titled since 1959 as Animal Drawing: Anatomy and Action for Artists) devotes 82 pages to mammal anatomy, poses, and behavior, and just 14 pages for birds, reptiles, and invertebrates. His final book—Prehistoric Man: The Great Adventurer (1949)—is a 330-page summary of hominid evolution, showing his keen academic interest in human origins. This was his most scholarly tome, featuring very little artwork alongside the extensive text. Further evidence of Knight’s zeal for mammalian subjects is found in his autobiography (Knight 2005), where he remarks favorably about drawing mammals at zoos and describes his travels to Europe to see early human fossil sites.
Knight’s Brontosaurus illustration from Life through the Ages (1946). Knight is perhaps best-known for his dinosaur art, though dinosaurs do not seem to be his favorite art subjects, nor are they—scientifically speaking—his best work.
The combination of Knight’s talent and keen interest in mammals explains his terrific artistic and scientific successes with portraying these creatures. His scenes of fossil reptiles however, while just as well composed as those of his mammals, are anatomically peculiar to modern eyes. The detailed diagrams of mammalian anatomy showcased in his 1947 Animal Anatomy for Artists and Laymen leave no doubt that Knight knew how animal bodies were put together—how muscle shape and size are determined by skeletal landmarks, where shapes of the face and body conform to underlying bones, and so on—but his nonmammal works sometimes translate skeletal anatomy into restored forms only loosely. For instance, his dinosaurs have thighs that are far too slim relative to the massive pelvic bones they were attached to; have proportions that are peculiar even when compared to fossils known at that time; and have faces that sometimes deviate from their skull contours, particularly in carnivorous species. His reptiles also often lack the dynamism and nuance evident in his mammal art, mostly having relatively static poses and only rarely showing complex behavior, such as parenting or herding, despite these being commonplace in his prehistoric mammal art.
What makes this discrepancy fascinating to scholars of paleoart is its indication of cultural attitudes overriding an otherwise well-honed scientific eye. Though continued publication has given Knight’s work an ageless quality, like any scientific artwork it was informed by the ideologies and theory of its time. It’s worth highlighting the context Knight was creating his artwork in, and how he—even working with leading scientists and advisers—would have understood the prehistoric world. Many ideas and concepts about extinct life that we now take as established fact were uncertain, or even entirely unimagined, to people of Knight’s day and age. For example, Knight would never have had a firm idea of how old his paleoart subjects were, the age of Earth and its geological periods being very poorly constrained until the mid-1940s. He would have known continental drift only as a controversial theory favored by a few geologists. He died the same year that DNA was discovered, and thus he missed out on many fundamental revelations about evolutionary processes. He also shared the misunderstood view of evolution as a continued optimization of nature toward the modern day, where older creatures were inferior to newer ones. Mammals, for example, must be smarter, more behaviorally complex, and physically superior to dinosaurs because they outlasted them. In Before the Dawn of History, Knight describes mammals as “leaders among the created things” (1935, 8) while dinosaurs are “weird, monstrous and bizarre” (7). Knight (with a small handful of famous artistic exceptions) thus followed the twentieth-century idea that dinosaurs were slow, sluggish creatures ill-suited to any strenuous activity or complex behavior, despite osteological evidence to the contrary. We can only wonder how Knight’s extinct reptiles might have looked if he had been as anatomically objective in their reconstruction as he was with his mammals, and if his attitudes toward nonmammalian subjects had been a little more forward-thinking. Sadly, Knight seems to have never written about dinosaur anatomy in as much detail as he gave to mammals and we can only speculate on how he rationalized his reconstructions. He certainly had strong opinions on their portrayal, however. Records of his correspondence include a 1937 letter to a newspaper about (admittedly rather rudimentary) dinosaur sculptures in a park in Rapid City, South Dakota, in which he berated the sculptures as “amateur and foolish” (Milner 2012, 148). We have to wonder how he viewed the work of such contemporary artists as Gerhard Heilmann (1859–1946) and Harry Govier Seeley (1839–1909), who envisaged dinosaurs and flying reptiles in more anatomically correct and progressive ways. Ultimately, Knight’s talent, prestige, and association with top academic institutions gave his reptile reconstructions greater cultural weight than was given to scientifically superior contemporary work, and he went on to have a huge influence on popular culture.
The high quality and continued use of Knight’s work have seen him become one of the most copied and referenced paleoartists of all time. Perhaps only the Czech artist Zdeněk Burian (1905–1981), in many respects Knight’s successor in paleoart mastery, can claim similar treatment. Countless artists have used Knight’s portfolio as inspiration for original works or produced thinly disguised reworkings of his compositions. Decades of replicating Knight’s takes on prehistoric life place him as the source for several long-standing paleoart tropes and clichés. Some Knightian conventions—such as the establishment of Triceratops and Tyrannosaurus as enemies set to battle each other across generations of artwork (the first portrait of Tyrannosaurus, which Knight drew in 1905, featured this animal lurking close to a group of Triceratops; he revisited this theme more dramatically in his 1930 Field Museum mural)—are understandably artistically appealing for their heroic, almost legendary quality, but other Knightian memes are far more idiosyncratic. Examples include his bird-chasing Ornitholestes and stooping Allosaurus scavenging a dinosaur tail, both of which have been replicated over and over by artists despite their specificity and, in some cases, problematic science.
A modern take on a sauropod dinosaur, Diplodocus carnegii, to compare with Knight’s 1946 example. Note the powerful musculature around the top of the hindlimb and tail base, a reality of dinosaur anatomy that Knight mysteriously overlooked despite his expertise in restoring extinct animals. Some aspects of Knight’s dinosaurs reflect the culture of his time more than the objective nature of their anatomy. © Mark Witton
But it was not only illustrators who felt Knight’s influence. Early filmmakers also referenced his paintings, most famously to create prehistoric animals for The Lost World (1925), King Kong (1933), and the Rite of Spring sequence in Disney’s Fantasia (1940). Over a decade after his death, One Million Years BC (1966) and Valley of Gwangi (1969) still used his work as a reference for their prehistoric creatures. While most of the filmmakers behind these projects openly acknowledge Knight as their source (e.g., Harryhausen and Dalton 2003; Harryhausen’s foreword in Knight 2005), his name is entirely absent from anything to do with Fantasia, a curious circumstance given the film’s prehistoric animal sequence featuring numerous Knightian reconstructions and callbacks—far more than would be expected by chance (Davidson 2008). This may not reflect a simple lack of documentation about the making of Disney’s animation, either. A short article about the production of the Rite of Spring sequence, published in 1941 by the AMNH paleontologist who consulted on the film, Barnum Brown, mentions passing AMNH-endorsed prehistoric animal restorations to Disney as a basis for their creature designs. Given the historic context, Brown was surely supplying Disney with Knight’s work, but the artist curiously gets no mention. Was this an oversight, or might Knight’s departure from the AMNH diminished their desire to promote him as part of their “brand”? In any case, Knight has been more readily namechecked in fiction, such as in Ray Bradbury’s 1983 story Besides a Dinosaur, Whatta Ya Wanna Be When You Grow Up? Knight is mentioned twice in this short story, once as “a poet with a brush… Shakespeare on a wall” and later as “the man who sees through time, and paints it!” Bradbury would go on to write a short forward to Knight’s autobiography (Knight 2005).
It was only toward the end of the twentieth century that Knight’s influence began to wane, perhaps because new fossil discoveries and theories were modifying our concepts of some prehistoric animals beyond the point where his depictions were usable, because new cultural touchstones (such as the 1993 film Jurassic Park) redefined expectations for paleoart, and because novel paleoartistic methods were being established by a new generation of artists. But his legacy remained as strong as ever, as evidenced by the continued publication of books and articles about his work. Even today, it’s a challenge for professional paleoartists to be seen outside of the shadow cast by one of the giants of the discipline, and perhaps justifiably so.
A LIFE THROUGH THE AGES SEQUEL SEVEN DECADES ON
Life through the Ages is perhaps the best known and most accessible of Knight’s books. Its structure—a series of plates, each mirrored by a single page of descriptive text—is similar to the earlier Before the Dawn of History, but it lacks the expanded introduction, has fewer plates, and contains illustrations of living species to place his fossil subjects in context. It also omits the ordering of subjects by geological age that was used in Before the Dawn of History, which in addition compiles many of Knight’s famous murals. The art of Life through the Ages instead comprises original charcoal sketches and a few Knight artworks borrowed from museum libraries and magazines. It remains highly readable even today and is a terrific way to sample our understanding of animal life, both prehistoric and modern, from the early twentieth century. As in all of Knight’s written work, his text is confident, lively, and charismatic, perhaps even more to modern readers armed with seven decades of scientific hindsight.
Life through the Ages has been continually reprinted since 1946 (most recently in a commemorative edition by Indiana University Press [Knight 2001]), making it a consistently available opportunity to appreciate early twentieth-century views on animal biology and evolution. It’s this quality that makes Life through the Ages a perfect book to write a sequel to. It would have been easy to produce another book outlining the marvels of evolution under a different title, but writing a companion piece to Life through the Ages allows for direct comparison of modern ideas with those of several decades ago. I hope readers of this book will track down a copy of the original for this purpose. Both books are designed for general audiences and are illustration-heavy, so this exercise can be performed by readers of any age. Bear in mind that the artistic differences between these books reflect not just the whims of their authors, but also several generations of scientific discovery and research, as well as the distinct cultures of the mid-1940s compared to the late 2010s. Some content of this book is specifically referential to the original Life through the Ages to aid this comparison, showing Knight’s subjects revisited as we understand them today. In several cases, Knight’s original images provided compositional foundations for these new artworks, while others contain subtler homages to Knightian conventions and tone. Where our understanding has moved on too far, the new illustrations share subject matter only. But when looking at these modern visions of prehistory, remember that they too will become dated. All books on science, and the art they contain, are products of their time—mere snapshots of understanding. Perhaps in another seventy to eighty years, another entry in the Life through the Ages canon will give a new generation a chance to see how science has advanced since today, and how much further our understanding of prehistory has moved on.
As in the original book, this sequel explores ancient and modern life in the tradition of illustrations and descriptive text, foregoing diagrams and infographics in favor of life and landscape reconstructions. I have taken the opportunity not only to replicate Knight’s format but also to enhance it, using full-color images and sixty-two rather than thirty-three illustrations in the main portion of the book. Our discussions of the paintings can also be more factual and detailed, thanks not only to our improved knowledge of fossil life but also to the greater availability of scientific literature to modern authors. In the interest of transparency about the scientific content of the book, I have added an appendix with notes about the paleontological data used in each image. These are comments that would derail the narrative of the book if they were included in the main text, but they serve to establish which aspects of the animal restorations are based on facts, which are informed guesswork, and which are pure speculation. All paleoart has a blend of these components, but without notes from the creators of the images, we are often left to figure out their proportions ourselves.
An attempt has also been made to balance this sequel fairly to different geological divisions. It would be impossible to cover the evolution of life entirely in a book of any practical size, but we can at least recognize that the story of life is not simply the story of humanity. The evolution of land animals did not mark the cessation of fish evolution, just as the rise of mammals did not prohibit innovations in plant and insect lineages. We must also recognize the role that extinction has had in shaping life on Earth; to that end, several of the most dramatic extinction events in history are the focus of four paintings. Some grounding in the theories behind geological time, the relationships of organisms, and the paleoartistic process has also been added as a primer for readers who are less familiar with these concepts, as well as to establish how the disciplines of geology, evolutionary biology, and paleoart have moved on since 1946. I have given less emphasis to living species than Knight did, because, in our modern age, popular documentation of living forms has increased markedly over that of fossil animals. The 1940s was a different age not only for photography but also for photographic reproduction in books. We now enjoy spectacular images of animals and plants wherever we look, as well as greater availability of facts about these species. Many fossil animals, in contrast, remain poorly represented in art, and their paleobiology is rarely discussed outside of academic papers. I thus feel that readers will benefit more from their coverage here than from greater documentation of living species.
A final, and perhaps most important, distinction in this sequel is a subtle change of tone. The early and mid-twentieth century had a vastly different view of human development, population, and our relationship with wildlife and natural environments. Growing realization about our shrinking, weakening biosphere necessitates a greater reverence for the natural world than was generally held in the 1940s, and this underscores the urgent need for its preservation. More than ever, we need wider understanding of concepts like ecology, extinction, biodiversity, the reality of geological time, and the way that living beings influence global habitats. We must appreciate that populations of organisms—whether they are the first plants on land, herds of megaherbivores converting leaves into greenhouse gases, or primates driving motorcars—can cause planetary changes that affect life for millions of years, a scale of time that we cannot easily comprehend. Our current concept of humanity’s impact on Earth is dangerously short-sighted compared to the vastness and complexities of planetary ecology and geological time, and we must respond to overwhelming data indicating that we stand on the brink of environmental and climatic catastrophe. There has never been a more important time for understanding our place in the natural world, the evolutionary history that we are part of, and the way that organisms—including ourselves—shape the future of planet Earth.
The Antiquity of Earth, and Its Geological Divisions
THE AGE OF EARTH HAS FASCINATED SCHOLARS FOR MILLENNIA, but for most of civilized history our best guesses of its age were rough calculations based on historical records or biblical texts. Most of these early estimates were relatively low: a planet Earth, thought to be just a few thousand years old. It was not until scientific processes started to dominate scholarly thinking in the seventeenth and eighteenth centuries that we began to fathom the true enormity of Deep Time. Pioneering geologists were unable to provide a specific figure for the age of Earth, but their appreciation for how long it took sedimentary rocks to form indicated an Earth that was far, far older than anyone had previously anticipated. By the late nineteenth century, estimates of the time needed to accumulate modern rock layers and seawater salinity pointed to an Earth age of at least one hundred million years. But our best estimate, developed during pioneering work on radioactive decay rates in the 1950s, raised the predicted age much further: 4.55 billion years. This figure has since stood as a robust calculation of Earth’s age, correlating with our geological record (the oldest rocks on Earth are about 4.4 billion years old) and estimates of the age of our solar system (4.6 billion years old).
Many of Earth’s rocks are deposited in layers, stacked atop one another in order of age: the oldest at the bottom, and the most recent at the top. Because the properties of rocks are highly characteristic of the conditions in which they were created, this layering system allows us not only to date rocks based on their relationships to one another but also to track changes in environment and climate through time. This provides temporal and environmental context for the fossils contained in each rock layer and permits reconstruction of changes in Earth’s biosphere throughout history. We use widespread characteristic rock horizons or fossils to correlate geological events (and thus time) in outcrops found far away from one another, and we can precisely date some rock layers using radiometric dating techniques. These measure the amount of “decayed” atomic matter in certain minerals against their undecayed variants, allowing us to compute their age from the known decay rates of those elements. Collectively, these dating and correlating techniques have led to the creation of the geological timescale, a chronology of Earth’s history as told by the rock record. The timescale continues to be updated with new dates and divisions as new data becomes available, although modern revisions generally represent fine-tuning of a robust and mature scientific model rather than textbook-shattering rebuilding of the entire system.
Many readers will be familiar with the fact that geological time is divided into categories of time: terms like Jurassic and Pleistocene are familiar examples of the names given to geological eons, eras, periods, epochs, and so on. These divisions are not arbitrarily assigned to ancient dates but are contingent on widely mapped geological or biological events, such as a major turnover in the biosphere (perhaps reflecting a mass extinction), or the appearance of a specific type of fossil or a geographically widespread and characteristic rock layer. The result is a system that reflects major developments in the history of the planet, and one that provides more precise characterization of environmental, climatic, and biological conditions as we move from broad to fine divisions within the timescale.
As is evident from the geological timescale opposite, our ability to tease apart significant periods of Earth’s history improves in younger rocks. This reflects the fact that older rocks are rarer—having had longer to be buried, deformed, or destroyed by geological action and erosion—and the related improved quality of the fossil record in younger strata.
The Relationships of Earth’s Inhabitants
EVERYTHING LIVING ON OUR PLANET IS A DESCENDENT OF Earth’s first microbial lifeforms, linked to them through an unbroken chain of genetic material passed down through billions of years by reproducing organisms. It’s sobering to consider this long, unifying link among all life on Earth—which, of course, includes you and me. We tend to limit our gaze to our immediate ape ancestors when pondering our relationships with other species, but this is just the start of our connectedness to other life. Go back further and we share ancestry with countless other species: other mammals, egg-laying land vertebrates, fish, marine organisms like sea squirts and echinoderms, early animals like corals and sponges, and then on to fungi, plants, and many different types of microbes. We are shoots on an evolutionary tree that has, over the course of Earth’s history, grown billions of branches from roots buried at the very origin of our planet.
The tremendous biodiversity of our planet is owed to two phenomena: (1) the reproduction and recombination of RNA and DNA (ribonucleic acid and deoxyribonucleic acid, respectively, the molecules that make up the genes of different organisms) and (2) the optimizing process of natural selection. RNA and DNA are the molecular codes that tell organisms how to build cells and tissues, and any changes to them (deliberately, such as combining DNA of two individuals in sexual reproduction, or accidentally, through gene replication errors—otherwise known as mutations) introduces slight differences in how our anatomy is created or how it functions. These changes mostly have no significant effect, but they sometimes influence an organism’s ability to survive in its respective environment. Individuals that receive an advantageous change stand a better chance of reproducing and thus passing on their genes, while those that inherit a deleterious genetic alteration have lessened reproductive probability. This is “natural selection” in action. As organisms spread into different habitats or environmental conditions change over time, either natural selection modifies organisms into species that are well suited for the conditions they live in, or their lineage struggles to adapt and ultimately perishes. Because organisms must be well-rounded entities, capable of performing many actions (e.g., obtaining food, avoiding predation, protecting our tissues against harmful environmental conditions), they can never be “perfected” to one task. Our bodies are adaptive compromises, proficient enough at everything we need to do to survive and pass on our genetic material, but are never so dedicated to one task that other crucial functions are impeded.
Evolutionary relationships between organisms are revealed through shared anatomical and developmental characteristics. Greater similarity indicates a relatively close ancestry, and fewer shared features indicate a more distant relationship. Humans, for example, are so anatomically and genetically like chimpanzees and gorillas that our close and geologically recent ancestry is in no doubt. But our similarity to plants is expressed in only some aspects of our cellular anatomy and genetic makeup, indicating that our respective evolutionary branches have been developing separately for a very long time. We can use genetic data to determine evolutionary relationships among living species, but for fossil organisms we largely rely on anatomical features—the shapes and characteristics of bones, shells, and other tissues. Our record of the history of life is imperfect and we do not understand where all living organisms belong in our evolutionary tree, but the general picture of life’s evolution and the relationships of species on many specific branches are increasingly well understood.
As our grip on evolutionary theory has developed, traditional schemes for classifying life—ranking it within categories like kingdoms, orders, and families—have become misleading and arbitrary. Many biologists and paleontologists now refer to groups or clades of animals, collectives of species united by shared features without a set “rank” in the grand order of life. This reflects the true continuum of evolution better than assigning arbitrary significance to certain groups of species, and it is the approach used throughout this book.
How Prehistoric Animals Are Reconstructed in Art
THE PALEOART PROCESS IS NOT WELL KNOWN OUTSIDE OF A sphere of individuals with a keen interest in fossil animals, so it is worth outlining here to put the following illustrations in context. I stress the use of the word process in that sentence: paleoartworks are not just loosely inspired by fossils, but are the result of research into the anatomy, evolutionary relationships, and geological context of an extinct subject species. Well-researched paleoart is a visual hypothesis of the life appearance of a fossil organism and its environment. The incompleteness of the fossil record means that speculation and reasoned prediction have a role in this process, and this prevents paleoart from being a fully scientific process, but the percentage of unknown data varies from species to species. Some extinct organisms are known in enough detail for us to assume that our reconstructions are reasonable approximates of their actual appearance (even aspects of color can now be predicted for animals that lived over one hundred million years ago, so long as we have sufficiently high-quality fossils), while others can be sketched only vaguely from scant remains. It can be hard to ascertain the reliability of a reconstruction at face value, and for this reason the appendix at the back of this book clarifies certain decisions and data used in each of these paintings.
The basic steps of reconstructing a fossil animal are as Knight described them in his 1935 book Before the Dawn of History, but palaeoartistry has become much more technical since his time. In recent decades, paleontological science has adopted increasingly rigorous scientific practices to produce more robust and detailed understandings of evolution, the history of our planet, and the paleobiology of fossil species. Modern paleoart has to reflect these advances to create scientifically credible artworks. We rarely know everything about the life appearance of extinct animals, but we increasingly know what not to portray in our artworks, and this narrowing of our reconstruction options moves our visual hypotheses in more credible directions.
Beyond information gathering, the first step in many paleoartworks is a skeletal reconstruction: a process where the artist arranges fossil bones in a lifelike pose to fully understand the basic proportions of a fossil species. Where bones are missing or damaged, information from other individuals of that species or a close relative are used to fill the gaps. Information from fossil trackways can help determine aspects of pose and gait. With an understanding of the skeleton in place, the artist can add musculature over the top. This is performed in the anatomical context of close living species, transferring landmarks of muscle position to the extinct animal to create a defensible muscle reconstruction across the entire skeleton. Fatty tissues are virtually unrepresented in the fossil record, but an artist may speculatively add them at this stage, typically by considering where closely related living animals store their fat, or where fat storage would be effectively placed in the subject animal (e.g., would it be localized somewhere to minimize inconvenience, or would it be distributed across the body as insulation?). Details of skin—anatomies like scales, feathers, and fur—are either based on direct fossil evidence (features like scales and feathers are rare in fossils, but are preserved more often than might be intuitively assumed) or predicted using close relatives (even living species, in some cases). There is a lot of uncertainty about the skin types of certain extinct clades because, as plainly demonstrated by modern species, even closely related animals can differ markedly in attributes like fur or feather length, scale size, and so on. Colors and patterning can be determined (partly or completely) for fossil species in a variety of ways, but they are unknown for over 99 percent of extinct animals. Artists therefore mostly create color schemes that suit the predicted lifestyle and habitat of the subject animal. This process completes a model of the appearance of a living animal, but to give it a home among an appropriate landscape, climate, and flora, we must further consult geological and paleobotanical data. So begins another round of research and injection of science into the paleoartwork, each bringing its own challenges and surprises to visualizing prehistory.
