Sometime around thirty-five thousand years ago: We who are used to the certainty of the historical age are bound to be constantly frustrated by the vague dates of prehistory. They’re just something we’re going to have to learn to live with. The age of the Vogelherd horse is hotly debated. Some researchers suggest that it may be only thirty thousand years old, while others suggest it may be older than thirty-five thousand years. This is the case with nearly all dates referring to events in prehistory. As a consequence, I have taken what I believe to be the majority consensus and then rounded off those dates.
“an abstraction of the graceful essence of the horse”: Ian Tattersall, Masters of the Planet: The Search for Our Human Origins (New York: Palgrave Macmillan, 2012), 180.
“esthetically perfect”: Harald Floss, phone conversation with author, April 22, 2014.
the lines are now well-worn: Harald Floss, phone conversation with author, April 22, 2014.
the most frequently represented animal: I first read this in Christine Desdemaines-Hugon’s Stepping-Stones: A Journey through the Ice Age Caves of the Dordogne (New Haven: Yale University Press, 2010). I admit to having been skeptical, but numerous scholarly tomes have confirmed the assertion.
On the walls of Chauvet Cave: Chauvet Cave is not open to the general public, but numerous books, videos, and photos on the Web are available to those who are interested.
a region known as: As a result of the Wild Free-Roaming Horses and Burros Act of 1971, the federal government protects wild horses as “living symbols of the historic and pioneer spirit of the West” on several hundred designated properties across the United States. Some of the horses are under the protection of the U.S. Bureau of Land Management, of the U.S. National Park Service, or of the U.S. Forest Service. For more information on the bitter politics that accompany these horses wherever they roam, see Hope Ryden’s America’s Last Wild Horses (Guilford, CT: Lyons Press, 2005). I’ve chosen not to delve into this complicated political subject but rather to focus on the science of the horse-human partnership.
mares huddling together: See H. M. Peel’s Fury, Son of the Wilds (Franklin Watts, 1959) for a classic example of this type of story. Peel relates the story of an Australian brumby stallion in these antiquated terms in great detail, but this kind of thing can also be found in numerous books published in the twentieth century for children that tell stories of individual horses living wild. In these tales, the mares are almost always helpless and the band stallions generally fairly noble and protective. I suspect the misunderstanding stems from the glamour that stallions so frequently display. While decidedly less glamorous, the mares, it seems, are the true engine of the band’s cohesiveness.
“a dominant stallion, subordinate adult males and females”: National Research Council of the National Academies, Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward (Washington, D.C.: The National Academies Press, 2013), 27. www.nap.edu/catalog.php?Record_id=13511.
The ecologist Joel Berger studied: Joel Berger, Wild Horses of the Great Basin: Social Competition and Population Size (Chicago: University of Chicago Press, 1986).
“neither the dominant nor the most aggressive animals”: Katherine A. Houpt, Ronald Keiper, “The Position of the Stallion in the Equine Dominance Hierarchy of Feral and Domestic Ponies,” Journal of Animal Science 54 (1982): 945–50.
the British researcher Deborah Goodwin: Deborah Goodwin, “The Importance of Ethology in Understanding the Behaviour of the Horse,” Equine Veterinary Journal 28 (1999): 15–19.
more than a million free-ranging horses in the Australian outback alone: These figures are hotly debated, particularly since the government-authorized culling of the horses. As with most wildlife populations, no one really knows how many of these horses, called “brumbies,” roam the island continent, but it is obvious that there are a lot. Horse-vehicle collisions are common.
white horses have an advantage: Gábor Horváth et al., “An Unexpected Advantage of Whiteness in Horses: The Most Horsefly-Proof Horse Has a Depolarizing Coat,” Proceedings of the Royal Society B 277 (2010): 1643–50.
Canada’s Sable Island: Canadian researcher Philip D. McLoughlin spoke about the Sable Island horses and evolutionary theory at the conference discussed in the text. Following his presentation, Dr. McLoughlin was kind enough to discuss his research with me in depth both at the conference and several times on the telephone. He also forwarded me a number of his research studies as well as authoritative material on the background of the horses. Most of the information on Sable Island comes from those discussions and printed research. However, the theory about the shortening of the horses’ pasterns in response to the need to climb the steep sand dunes is mine alone.
The Sable Island horses are also behaviorally unusual: Adrienne L. Contasti et al., “Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore,” PLoS One 7 (2012), www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047858.
in the Yana River region: Pitulko, V. et al., “The Yana RHS Site: Humans in the Arctic before the Last Glacial Maximum,” Science 303 (2004): 52–56.
“the best running animal on the planet”: Darrin Pagnac, personal communication.
“As long as the wild horses continue to roam”: J. Sanford Rikoon, “Wild Horses and the Political Ecology of Nature Restoration in the Missouri Ozarks,” Geoforum 37 (2006): 200–11.
2. In the Land of Butch Cassidy
“If you want to sense the evolution of the modern horse”: Richard Tedford of the American Museum of Natural History was one of a group of scientists who gathered at the museum in 1981 to discuss the phenomenal spread of Hipparion horses. An article about the conference, titled “The Hipparion Is Still an Elusive Horse,” by Bayard Webster, ran in The New York Times on November 17, 1981. It is accessible here: www.nytimes.com/1981/11/17/science/the-hipparion-is-stilll-an-elusive-horse.html.
seas covered what is now Wyoming: One of the best ways to understand how the unique topography of the American West came about is to spend a day at the Denver Museum of Nature and Science. This museum has all kinds of exhibits, including a presentation of the geological forces that over hundreds of millions of years shaped the landscape that we experience today.
continental drift, tectonic collision: For a great, accessible discussion of plate tectonics, read Simon Winchester’s A Crack in the Edge of the World: America and the Great California Earthquake of 1906 (New York: HarperCollins, 2005).
“shale so black it all but smelled of low tide”: John McPhee, Rising from the Plains (New York: Farrar, Straus and Giroux, 1986), 11.
The result is her book: Phyllis Preator, Facts and Legends: Behind the McCulloch Peaks Mustangs (self-published, 2012). ISBN 978-0-692-01509-4.
the modern horse: We can see vestiges of the common ancestry of humans and horses in our skeletons. We both have tarsals and metatarsals, fibulas and tibias, and even patellae—all evidence of our biological kinship. We also share the calcaneus bone, though the bone takes on a different form in horses than in humans. In humans it is the heel bone, but in the horse it is located in the hock joint, halfway up the horse’s hind leg.
“artful dodgers”: Christine Janis, “Victors by Default: The Mammalian Succession,” in The Book of Life: An Illustrated History of the Evolution of Life on Earth, 2nd ed., ed. Stephen Jay Gould (New York: W. W. Norton Company, 2001), 171.
Repenomamus: Yaoming Hu et al., “Large Mesozoic Mammals Fed on Young Dinosaurs,” Nature 433 (2005): 149–52.
A 2010 paper in Science: Peter Schulte et al., “The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary,” Science 327 (2010): 1214–18.
“asteroid porn”: Chris Norris, “With Neither Bang, Nor a Whimper,” blog entry, Prerogative of Harlots, April 28, 2009, http://paleocoll.blogspot.com/2009/04/with-neither-bang-nor-whimper.html.
“Don’t get me wrong”: This statement derives from
a conversation I had with Archibald, but an in-depth discussion of the early days of mammalian expansion and the paleontological point of view regarding the effect of the Chicxulub asteroid can be found in David Archibald’s book Extinction and Radiation: How the Fall of Dinosaurs Led to the Rise of Mammals (Baltimore: Johns Hopkins University Press, 2011).
“victors by default”: Janis, “Victors by Default,” 173.
For a brief period, it was very hot: Evidence for the Paleocene-Eocene Thermal Maximum is by now multitudinous. For a good basic description, read Phil Jardine’s “Patterns in Palaeontology: The Paleocene-Eocene Thermal Maximum,” Paleontology Online 1 (2011): 5, www.palaeontologyonline.com/articles/2011/the-paleocene-eocene-thermal-maximum/.
horses may well have originated right there: I first read this in Robert Kunzig’s article “World Without Ice,” National Geographic, October 2011. It’s an unusual idea, so just to be sure, I spoke to Gingerich himself and asked if he still believed this. “Why not?” he answered.
the paleontologist Ken Rose compared: Much of the background material on both these early horses and these early primates comes from Kenneth D. Rose’s comprehensive textbook, The Beginning of the Age of Mammals (Baltimore: Johns Hopkins University Press, 2006).
gave Charles Darwin a serious headache: There are, of course, numerous biographies of Darwin. My favorite, widely believed to rank among the most definitive, is Adrian Desmond and James Moore’s immense Darwin: The Life of a Tormented Evolutionist (New York: Warner Books, 1992). For the discussion of Darwin’s health during certain times in his life, as well as his proclivity for visiting health spas, I have relied on this text.
experienced an earthquake: Marcia Bjornerud, Reading the Rocks: The Autobiography of the Earth (New York: Westview Press, 2005).
when the English genius Thomas Henry Huxley: This story has been told in hundreds of books and articles. It was also related to me directly by Chris Norris when I visited the Yale Peabody Museum.
about the size of a small dog: Ross Secord et al., “Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum,” Science 335 (2012): 959–62.
horses made changes: Philip D. Gingerich, “Variation, Sexual Dimorphism, and Social Structure in the Early Eocene Horse Hyracotherium (Mammalia, Perissodactyla),” Paleobiology 7 (1981): 443–55, www.jstor.org/stable/i317541.
3. The Garden of Eden Appears, Then Vanishes
“Living horses, with their high-crowned grinding teeth”: Michael Novacek’s Dinosaurs of the Flaming Cliffs (New York: Doubleday, 1996) is a terrific adventure story that makes for fun reading, even for those who are not deeply interested in paleontology. Accessible and easy to understand, the book is more about the paleontological lifestyle than about dinosaurs themselves. Mike Novacek is not only a respected researcher, but a good writer.
Grube Messel: Anyone even remotely interested in geology, evolution, or horses would benefit greatly by a trip to Messel. There is a museum on the site, and during the warmer months guided tours are available. Unfortunately, very little information is available to visitors who do not speak German. A good introductory English-language book is Jens Lorenz Franzen’s The Rise of Horses: 55 Million Years of Evolution, translated by Kirsten M. Brown (Baltimore: Johns Hopkins University Press, 2010). This book has wonderful photos of some of the horse fossils found in the pit.
nicknamed Ida: A great deal of controversy surrounds the fossil dubbed Ida, regarding exactly where on the evolutionary bush of life the fossil belongs—whether Ida is our direct ancestor or had already taken a baby step or two down a different twig. To understand the thrill of discovering Ida, check out Colin Tudge and Josh Young, The Link: Uncovering Our Earliest Ancestor (New York: Little, Brown and Company, 2009).
the Greek tale of Orpheus and Eurydice: Eurydice, Orpheus’s wife, died from a snake bite immediately after her wedding. Orpheus, a real charmer, convinced the gods to allow him to go into Hades and bring her back to the land of the living. Unfortunately, as soon as he emerged from Hades, he turned to look at Eurydice, who vanished just as soon as he saw her.
this horse, Orohippus, still had four toes on his front feet: For a great, and authoritative, synopsis of early horse paleontology in Wyoming, including the discovery of Orohippus at Grizzly Buttes, check out the American Museum of Natural History’s extensive online information, which has both old photos of the expeditions and written text: http://research.amnh.org/paleontology/photographs/1905-wyoming-eocene/.
I had read about Epihippus once before: Tim Flannery, The Eternal Frontier: An Ecological History of North America and Its Peoples (New York: Grove Press, 2002), 100.
horses changed their diet: Matthew C. Mihlbachler et al., “Dietary Change and Evolution of Horses in North America,” Science 331 (2011): 1178–81.
“Radinsky’s brains”: Leonard Radinsky, “Oldest Horse Brains: More Advanced Than Previously Realized,” Science 194 (1976): 626–27.
“Evolution of the Horse Brain”: Tilly Edinger, “Evolution of the Horse Brain,” The Geological Society of America Memoirs 25 (1948): 1–177. For an excellent and concise overview of Edinger’s remarkable life and effect on paleontology, read Emily A. Buchholtz and Ernst-August Seyfarth, “The Study of ‘Fossil Brains’: Tilly Edinger (1897–1967) and the Beginnings of Paleoneurology,” BioScience 51 (2001). Available in full online: http://bioscience.oxfordjournals.org/content/51/8/674.full.
“considerably advanced”: Radinsky, “Oldest Horse Brains.”
4. The Triumph of Hipparion
“The history of the horse family”: George Gaylord Simpson’s book Horses: The Story of the Horse Family in the Modern World and Through Sixty Million Years of History, published in 1951, was a popular international bestseller that thoroughly explained the evolution of horses. Since then, science has of course progressed considerably, so that much of what Simpson explained is now more thoroughly understood, particularly how the evolution of horses has been driven by tectonics and climate.
about 3.6 million years ago: The information in this narrative section is derived from numerous studies of the Laetoli ecosystem of that time frame. There has been extensive documentation by a variety of researchers who have looked not only at the early horses and humans and all other animal footprints present at the site, but also at the makeup of the plants in the area and at the geology and climate. My narrative also relies on discussions with several scientists, including Andrew Hill of Yale University, who found the tracks, and with Elise Renders, retired researcher and avid equestrian, whose fabulous analysis of the tracks made by the Laetoli mare and foal revealed for the first time how Hipparion’s “extra” toes helped stabilize the horse’s gait, as well as the fact that, in at least some horses, the four-beat gait is fully natural: Elise Renders, “The Gait of Hipparion sp. from Fossil Footprints in Laetoli, Tanzania,” Nature 308 (1984): 179–81.
the clueless foal ran right in front of the mare: Remarkably, the behavior of this young animal was recorded in the ash and can still be seen today by closely studying the tracks.
a small band of our own ancestral relatives: The discovery of these footprints has been heralded worldwide. When I visited the Musée National de Préhistoire (the National Museum of Prehistory, well worth devoting at least a half day to) in Les Eyzies, France, I found that at the entrance to the exhibits lay a replica of these preserved footprints. Research analyzing these footprints is abundant, but it’s fun to look at the original publication announcing the find, now available for all to see: M. D. Leakey and R. L. Hay, “Pliocene Footprints in the Laetolil Beds at Laetoli, Northern Tanzania,” Nature 278 (1979), www.nature.com/nature/ancestor/pdf/278317.pdf.
Australopithecus afarensis: For a clear, succinct discussion—highly accessible to the lay reader—of both the importance of this ancestral relative of ours and the influence of the discoveries made at Laetoli, see Martin Meredith’s Born in Africa: The Quest for the Origins of Human Life (New York: PublicAffairs / Perse
us, 2011).
a two-volume set of papers: Mary D. Leakey and J. M. Harris, eds., Laetoli: A Pliocene Site in Northern Tanzania, Oxford Science Publications (Oxford, U.K.: Clarendon Press, 1987).
quickly multiplied into countless species: W. A. Berggren and J. A. van Couvering, “The Late Neogene, Vol. 2: Biostratigraphy, Geochronology and Paleoclimatology of the Last 15 Million Years in Marine and Continental Sequences,” Developments in Palaeontology and Stratigraphy (Amsterdam: Elsevier Scientific Publishing, 1974).
excelled at evolutionary experimentation: Countless species of these horses thrived all over the world, except for Antarctica, for more than 20 million years. To sort them all out has been an impossible task for paleontologists, but several people have tried. A heroic attempt, now rather dated, is Bruce J. McFadden’s Fossil Horses: Systematics, Paleobiology, and Evolution of the Family Equidae (Cambridge, U.K.: Cambridge University Press, 1992).
“one of the great animal travelers”: Simpson, Horses, 140.
studied leaf waxes of plants growing in Antarctica: Sarah Feakins oversees her own Leaf Wax Lab at the University of Southern California, where she specializes in studying the paleontological history of leaf waxes from all over the world. The paper discussed here is Sarah J. Feakins et al., “Hydrologic Cycling over Antarctica During the Middle Miocene Warming,” Nature Geoscience 5 (2012): 557–60, www.nature.com/ngeo/journal/v5/n8/full/ngeo1498.html.
“higgledy-piggledy”: John Herschel, astronomer, mentioned in a letter from Charles Darwin to Charles Lyell, dated December 10, 1859. Viewable online at Darwin Correspondence Project, www.darwinproject.ac.uk/letter/entry-2575.
the paleontologist Gregory Retallak: Gregory J. Retallack, “Cenozoic Expansion of Grasslands and Climatic Cooling,” The Journal of Geology 109 (2001): 407–26, www.jstor.org/discover/10.1086/320791?uid=3739696&uid=2&uid=4&uid=3739256&sid=21104007857767.
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