O. C. Marsh was not always an easy man to love. Yes, he could be quiet, introverted, and thoughtful. But he could also be sneaky, distrustful, and quarrelsome. By the 1880s, he would nearly bankrupt himself (and find himself socially ostracized) due to his long-running feud with fellow paleontologist Edward Drinker Cope. But that was later. The horses came first.

Marsh really had three things going for him. First, he was bright. Really, stunningly, bright. He made intuitive leaps that eluded many of the 'great minds' of the day. He had a massive grasp of morphology and a nearly boundless imagination -- and he put them together in a way that few then (or now) could match. Second, he was a workaholic. Marsh was rarely happy unless he was turning a bone over in his hand or dashing off one of hundreds of articles. He eventually named 80 species of dinosaurs, knocking off new taxa with the regularity of a scientific machinegun. Third, he was the nephew of a famously wealthy philanthropist, which is very rarely a bad thing.

At Marsh's urging, uncle George Peabody founded the Peabody Museum of Natural History at Yale, ensuring that Yale would be (and still is) a center of paleontological research. Not so coincidentally, Marsh was named to America's first professorship in paleontology that same year. In a world full of amateurs, Marsh was a professional. He had brains, drive, and a steady paycheck.

By 1874, Marsh had been collecting fossils of horses for several years. He was far from the first. A book about American horses had been published in 1848. Charles Darwin himself had found the tooth of a fossil horse in Argentina (not then part of the Appalachian Trail) back in 1833 while taking part in the famous H.M.S. Beagle expedition. William Clark (the Lewis and Clark, Clark) found fossil horse bones in Kentucky as far back as 1807 and shipped a few to his friend Thomas Jefferson.

What made all these bones so significant at first was the fact that there were no horses in America. Or at least, there had not been any horses when the Spanish arrived at the end of the 15th century. Neither Clark (nor Jefferson) seemed to notice the import of that fact, but Darwin certainly did. That there had been horses in the Americas, but those horses had disappeared, was further proof that the collection of animals roaming the continents was not a constant. This was even more true when it turned out that Darwin's tooth came not from a modern horse, but from a variety no longer found anywhere in the world.

By Marsh's time, a number of different types of fossil horses had been collected in the Americas. What Marsh did next seems simple -- he put them in order. But while this may sound no more amazing than arranging the ponies on a carousel, one look at the creatures in Marsh's chart would show that it wasn't quite that simple. At the start of the line was a creature called Hyracotherium (Marsh knew it as Eohippus). The scientific name alone is enough to suggest how different this critter was from a modern horse. The name means "hyrax-like beast." Like a modern hyrax (rabbitish beasties found in Africa and the Middle East), Hyracotherium was small, about two feet long. If you were to see one of these animals crossing a field "horse" is not exactly the first idea that would cross your mind.

In addition to the size, one other very distinct difference between this 50-million-year-old creature and a modern horse was its feet. Hyracotherium had four toes on each foot. The large modern horse, Equus, has a single toe ending in a thick hoof. There are hidden, internal remnants of two other toes still present in a modern horse, but they've been reduced to tiny spurs of bone located high up on the leg (I'm tempted to say "next to the knee," but I'm sure one of our more horse-friendly Kossacks can provide the location using the proper fetlock / forelock terminology). Each step in Marsh's chart of horse ancestors follows the same trend — reduction of toes, increase in size, lengthening of the head, and more complexity of teeth. First four toes, then tree toes, then a gradual reduction of the other toes as the central toe becomes the hoof we see today. These feet are mounted on animals the size of dogs, then deer, ponies, and finally the imposing modern horse. The teeth move from small molars with nearly flat surfaces, to larger, more complex teeth set in long, well, horsey skulls. All these steps tell the same neat story. Here are animals making the transition from small forest-dwelling browsers to large wanderers of the open plains that graze on tough grass, animals that depend on speed and strength to deal with predators.

Marsh had produced not a single transitional specimen, but a whole sequence by which species moved through drastic change. Without all the intermediate stages, even an anatomist as skilled as Marsh might not have recognized the tiny Hyracotherium as even being an related to the modern horse. But by placing related species on a timeline, Marsh reduced drastic change into a series of easily understood steps. It was exactly the sort of succession of creatures that you might expect to see resulting from natural selection. Best of all, it was essentially correct — where it wasn't wholly misleading.

The sequence that Marsh produced does reveal major points along the path that horses took in going from tiny forest animal to lord of the plains, but that path wasn't taken across a blank sheet of paper. The species that appear in Marsh's paper are only a small fraction of the ancient horses that once existed — just a sampling of a variety more vast and wonderful than any A to B to C chart can reveal. Some ancient horses didn't lose those extra toes. Instead the toes grew long as the feet adapted to walk over softer ground. Some developed teeth better suited to nipping leaves off trees than grazing on grass. During the Miocene period (from about 23 to about 5 million years ago) more then a dozen species of horses roamed the Americas. Rather than a simple line marked by a few species, the horse family was a large, complex "bush" producing diverse creatures, only a few of which looked particularly horsey.



Click for higher res image

A better look at the evolution of the modern horse would be something like this. In this chart, those species in Marsh’s straight-line evolution are shown in bold. This chart shows some of the diversity that the horse family displayed during the last 50 million years. It also shows that while all the animals selected by Marsh were indeed relatives of the modern horse, they were not all in the direct path that led from Hyracotherium to Seabiscuit.

What makes it tempting to draw a simple picture of the family tree of horses is the simplicity of the situation we see around us. Starting around four million years ago, as the world grew cooler and drier, the horse family tree started to… thin out. Hipparions, very successful and wide-spread grass-eaters similar in size and build to a modern horse, gradually disappeared from Asia, Europe, Africa, and North America. As ice expanded and contracted around the northern hemisphere, the non-equus horses disappeared and even the members of that surviving genus were greatly reduced. The last of them held on until around 8,000 years ago. That’s when the pony-sized Hippidion (which recent DNA analysis reveals may actually have been a member of Equus) vanished from South America . It’s also when Equus scotti and all the other North American horses left the stage. For the next 6,500 years, there would be no horses in America. The current situation is simple, but it wasn't always that way.

Four and a half centuries after the Spanish brought horses back to America, another sort of pony was born in Detroit, Michigan.

In 1964, Ford Division general manager Lee Iacocca recognized a open space in the automotive ecosystem. At the time, Ford had successful large sedans, a popular pickup, and a newly introduced compact car, but none of these vehicles was particularly sporty. The Thunderbird had been released in 1955, intended as competition for the Chevrolet Corvette. But despite outselling the Covette by 23 to 1, Ford executives (in particular the soon to be Secretary of Defense, Robert McNamara) worried that the two-seater roadster had a limited market. By 1964 the Thunderbird had two more seats, a thousand pounds more bulk, and an upscale price tag as a “personal luxury vehicle.” It was a sales success, but it wasn’t exactly a sports car.

Ford introduced a new vehicle. Just as the bones of Equus reveal a relationship to earlier creatures, the Ford Mustang’s ancestors were not hard to see. The chassis, suspension, and drivetrain components came from parts used in the Ford Falcon and Fairlane. It wasn’t very fast. It wasn’t very sporty. It really wasn’t much of a radical departure from other Ford’s already on the market. However, it was attractive and it was cheap. Competitors dismissed the little Ford as a “secretary’s car,” but there were a lot of secretaries — and a lot of non-secretaries who liked the idea of a fun, inexpensive auto. In the world guided by a different form of selection — consumer selection — the Mustang fit a big, empty niche. Ford’s marketing department had forcast sales of 100,000 units during the Mustang’s first year, but the factories were soon working overtime as the Mustang flew off the lots. A million were sold in the first 18 months.

As with the ancient horses of the Americas, it’s tempting to group the Mustang into a neat sequence of models. After the original model came the Mustang II (which appeared very late in the Preoilcrisian epoch of the Interstatian Age), then the “Fox” platform of the 80s, The edgier design of the 90s, and the slightly “retro” model in showrooms since 2005. But just as with the flesh and blood mustangs, the picture isn’t that simple.

Ford’s Mustang showed an ability to kick off new “species” and “subspecies” that would be the envy of the natural world. By 1968, there were nine different base models of Mustang. Coupes, convertibles, and fastbacks were manufactured with a bewildering array of engines, transmissions, and extras. Over a period of just three years, thirteen different engines were available. And that’s not even counting the many semi-official models being cranked out by racing houses that modified the Mustang into more powerful machines.

Something else began happening to Ford Mustangs, something that had also happened to those other mustangs — over time they got bigger and heavier. Each revision of the car from 1965 to 1973 brought on a meatier and more expensive beast. This kind of growth is a path that’s common to both animals and to cars. The Honda Civics of the natural and automotive world move from tiny econoboxes to more substantial forms, leaving room for the next round of little Fits to take their place. It’s not a particularly poor strategy — so long as your ecology stays healthy.

As the Mustang was growing larger, it was also growing competitors. The success of the Mustang brought on a whole generation of “pony cars.” Most of these were larger and more powerful than the original Mustang as the manufacturers fought to win the consumer selection derby through providing more room and power. By 1973, there were Camaros, Javelins, Firebirds and Cougars all scrambling for the same “ecological niche” as the Mustang — just as many other forms of horse (and other grazers) had challenged Equus on the plains. And just as challenges starting in the Pliocene whittled away at the horse ranks, a disaster was on the way that would soon reshape the pony car competition.

On October 17, 1973, the members of Organization of Arab Petroleum Exporting Countries announced an embargo against western countries.The price of oil tripled almost overnight. Within a few years, it would triple again. For the pony cars, the years of easy growth had ended. The verdant fields of buyers dried up. An automotive ice age had arrived.

Many of these models disappeared. Some of them were replaced by other vehicles of the same name at a later time. Others were gone for good. But Mustangs lived on. In fact, the Ford Mustang has been in continuous production since 1964.

What made the Mustang the automotive equivalent of Equus? It was a combination of good planning and coincidence.

Oil prices had been rising for several years before the 1973 embargo. Not sharply, but enough so that Iacocca and other executives at Ford were starting to be concerned about the Mustang’s growing size, power, and thirst. In addition, they were being nudged from another direction. Fans of the original 1965 Mustang wrote to Ford complaining that by the early 70’s the car had lost the cheap, fun appeal of the original. It had become a boy racer’s car rather than a secretary’s car, and out there in the ecosystem of auto buyers, boy racers were just not that common. Ford went to work, trimming down the Mustang and designing a new car based on the Pinto subcompact. That new car, the Mustang II, premiered just weeks before the oil embargo. The new car was smaller, it was cheaper, and it was also designed to be far more reliable, as well as offer a fit and finish that was well ahead of most American cars at any price.

It’s become fashionable these days to dismiss the Mustang II. In fact, it’s often treated as a model best forgotten, not a “real Mustang” at all. With a 4-cylinder engine in the base model, the new Mustang was spurned by the audience that had come to love it’s larger and more powerful predecessor. But it got much better mileage than its competitors. It’s smaller size and reduced power made it a loser in a straight line duel with anything faster than a economy car. But its reliability and good value for the money positioned it to compete with the flood of import cars that moved into the market as oil prices rose. Those who dismiss the car today forget that in 1974, the Mustang II — the multiple award winning, Car of the Year, Mustang II, the Mustang II that outsold the previous model in the face of an auto market as shaky as any seen until 2009 — was one of Detroit’s few bright spots.

The Mustang survived. And by surviving through that tight spot, it went on to spawn new variants and expand into new niches. It got the secretaries, and the boy racers (and the girl racers, as my friend Laurell, who recently bought one of the Mustang’s more potent subspecies, will attest).

Both the Ford Mustang and the mustang mustang, are American originals. They have spread around the world, but they started here. Both started from simple beginning, spawned dozens of variations, and were pared back by calamities. Both have proven tough enough to take on a changing world.

Finally both are also examples of one of those great rules of selection — luck counts. Equus didn’t lift a hoof to the wind, sense the coming ice age, and decide it was time to leave the forest for the plains. It was already well adapted for the world that was coming. Ford didn’t launch it’s drive for a post-cheap oil Mustang in the wake of the crisis. The new car was already on the market when the gas lines appeared. Timing may not be everything, but whether it's the importance of a scientific paper or plain old survival, it means a lot.

As we look ahead and see challenges on the horizon -- including the looming threat of climate change -- we have to remember that the survivors are not those species that learn to swim after the flood arrives. You need to be lucky, or smart, enough to take steps in advance. Otherwise you'll be a Hipparion or an AMC Javelin.

Note: this diary is a trimmed down chapter (yes, I did say trimmed down) from an unfinished manuscript titled "The Evolution of Everything." If you hate it, let me know now so I can save myself another 400 pages of writing -- and save you from reading more such chapters on upcoming Sundays.

This diary is also intended to kick off a series of diaries for DK GreenRoots -- the rest of which are sure to be both more topical and shorter.