The dinosaurs are the most widely recognized victims, suffering losses of one hundred percent. But the devastation went well beyond dinosaurs. Perhaps eighty-three percent of all lizards and snakes also vanished, even though they were smaller and therefore could find shelter more easily and required less food to survive. Birds went nearly extinct as well. Even mammals, the ultimate “winners” of that mass extinction, initially experienced reductions of seventy-five and up to ninety percent in some parts of North America.11
Life staged a comeback in time, but in a world far more geographically fragmented than before. A few hardy species remained viable all over the globe. Ferns, for instance, were among the first to recolonize the charred, acidic, and devastated lands. They were so successful that pollen specialists have detected a “fern spike” right after the asteroid’s impact. Other species endured in different regions but quickly diverged from one another. Mammals are the most notable case. For tens of millions of years, they had lived in the dinosaurs’ shadow. Once the great reptiles were gone, however, they experienced what some scholars have termed an “explosive” adaptive radiation. Different types of mammals—including us—emerged in some places but not in others. The same was true for many new species of plants and animals. Cacti, for example, arose exclusively in the Americas. Today about two thousand species can be found all over the continent, living in environments ranging from very dry deserts like the Atacama in northern Chile and the Baja California Desert in Mexico, to lush rain forests in southeastern Brazil and Central America, to grasslands in the United States and Canada. Yet up until five hundred years ago, when humans began dispersing them in sailing vessels, cacti did not exist anywhere outside the Americas.12
Precisely because many organisms were originally confined to one continent even though there were favorable conditions for their subsistence on other landmasses, some managed to cross the open ocean over tens of millions of years. Exactly how these “oceanic dispersals” occurred remains a matter of conjecture, but it is easy to imagine rafts of floating vegetation and animals as a mechanism. Storms cause rivers to swell and carry logs, branches, and vegetation. Sometimes a pile of debris collects behind a natural obstruction like a large rock or a tree until the storms become too strong, finally dislodging it and causing it to rush downriver and hurtle out into the ocean. British navy officers interviewed by nineteenth-century naturalist Alfred Russel Wallace reported seeing many such rafts of vegetation floating hundreds of miles from shore. They could be sizable. A British admiral recalled seeing them around the Philippines, “with trees growing on them, so that they were at first mistaken for islands.” Animals were frequently trapped on them. Witnesses mentioned monkeys, squirrels, and even large felines traveling in spinning piles of wood along the Amazon River.13
Oceanic dispersals are extremely instructive because they reveal what is biologically possible, showing what oceans could be crossed and in what direction and which ones constituted insurmountable barriers. The Atlantic, for instance, has been breached several times. One hundred million years ago, South America became something of an island unto itself, having broken off from Africa and decoupled from North America (until about three and a half million years ago, when the Isthmus of Panama finally connected the two halves of the hemisphere). South America therefore existed in “splendid isolation” for tens of millions of years, as one scholar has put it. Yet several dispersals from Africa occurred during this time. South America was originally rodent-free, but a type of rodent called caviomorphs—related to guinea pigs, chinchillas, and capybaras but different from mice and rats—irrupted into it between fifty-five and forty-one million years ago. The closest relatives to the South American caviomorph rodents live in Africa, clearly indicating the source population. Primates followed suit. Again, South America possessed no primates at first. Yet a monkey that scientists call Chilecebus carrascoensis somehow got across the Atlantic Ocean thirty-five to twenty million years ago. To succeed, any primate had to be small and extremely resilient. To judge by the extant fossils, Chilecebus carrascoensis weighed less than two pounds and had a skull barely two inches long. This intrepid voyager would give rise to all New World monkeys, including spider monkeys, capuchins, and marmosets.14
As far as we know, about a dozen species have made it across the Atlantic Ocean, including rodents, primates, bats, tortoises, a blind snake, and even a weak-flying bird called the hoatzin. Of all these creatures, geckos and skinks were particularly capable of surviving long oceanic passages, as they hid underneath branches and laid eggs resistant to desiccation and even short-term immersion in seawater. Yet, irrespective of individual capabilities, two main factors explain these successful crossings. First, the closest two points across the Atlantic (Kabrousse, Senegal, and Touros, Brazil) now lie about 1,740 miles apart and, thirty or forty million years ago, perhaps half that distance. Nine hundred miles is far but not overwhelmingly so. Second, the rivers of western Africa constitute excellent launching pads to catch western-moving Atlantic currents leading to the Americas. Although crossing the Atlantic has never been easy, the biological record shows that it has occurred from time to time, and what is true for geckos and rodents applies no less to humans. When Christopher Columbus set out to cross the Ocean Sea in 1492, he and his crew were embarking on a voyage that other species had already made successfully.15
Other oceanic paths have been less common. The reverse Atlantic passage from South America to Africa, for instance, has played a much smaller role in the dispersal of species. Negative evidence cannot settle the matter definitively. South American organisms may well have crossed but been attacked on arrival, or perhaps they survived in Africa but without leaving much of a trace. Still, it is striking that no terrestrial vertebrates are known to have made the eastward passage across the Atlantic.16
Dispersals across the Pacific are more daunting still. Some species do exist on both sides of the Pacific Ocean, as we have seen. Marsupials live in the Americas (opossums and shrews) and in Australasia (kangaroos, koalas, Tasmanian devils, etc.). Intriguingly, a tiny arboreal marsupial from South America known as the monito del monte is more closely related to Australian marsupials than to its American cousins. Could this be the first terrestrial mammal to cross the Pacific? Recent research shows that marsupials originated in South America and migrated to Australia tens of millions of years ago, when there was a land connection via Antarctica or at least great proximity among these three landmasses. The same holds true for other lineages distributed on both sides of the Pacific, including birds, frogs, and turtles.17
The only terrestrial vertebrate that seems to have survived a transpacific passage of six thousand miles is an iguana. The vast majority of iguanas are indigenous to the New World. Yet one genus called Brachylophus lives in the South Pacific islands of Fiji and Tonga. How did it get there? A passage from Central or South America would have taken a minimum of six months and more likely a year or more. Like geckos, iguanas are well suited for oceanic dispersals. They are able to obtain water from the plants they eat and possess nasal salt glands and thick skins that protect them from dehydration. Their presence not only on the American continent but also on many surrounding islands demonstrates their ability to travel across stretches of ocean. The Galápagos Islands, for instance, lie about six hundred miles away from the coast of Ecuador and are home to no fewer than three species of land iguanas as well as one marine iguana that lives on land but dives into the ocean to procure food, foraging on seaweed and reaching exposed rocks completely surrounded by water.18
Still, it is one thing to drift on logs for a couple of weeks and quite another to endure a six-thousand-mile passage. After several months adrift and no food left, any voyaging iguana would have perished. Nonetheless, some biologists have proposed a possible solution. The stowaways may have spent much of this journey as eggs. Brachylophus has an unusually long incubation period of seven, eight, or even nine months, one of the longest of any iguana. It is possible then that thirty or
forty million years ago an unsuspecting group of iguanas, some in the form of eggs, may have dispersed by means of an epic rafting passage in which everything went right. Yet even if Brachylophus was somehow able to cross much of the Pacific, few other terrestrial vertebrates ever did until humans began making inroads in far more recent times.19
Except for the Arctic and the Antarctic, the islands scattered across the Pacific constituted the last frontier of human exploration and colonization on our planet. It was only about five thousand years ago—the blink of an eye in terms of the human experience—when an island-hopping chain began forming. Over time, it would cross the great ocean. The chain started in southern China, and the first links were quite straightforward. Early seafarers from the Asian mainland explored and colonized large nearby islands such as Taiwan and the Philippines. Their descendants, however, faced a most extravagant labyrinth of islands, atolls, and stepping-stones of diminishing size and availability of food resources as they ventured deeper into the Pacific. Around 1500 BCE, these oceangoing pioneers took a major first leap, a breathtaking passage of nearly fifteen hundred miles, reaching the Mariana Islands, the archipelago containing Guam due east from the Philippines. We will never know whether this event was deliberate or accidental; it may well have involved conditions of extreme hunger and survival. Nevertheless, the fact that it happened at all, along with the existence of ancient words for nautical terms like sails, points to a culture with great navigational expertise.20
The next push required significant adaptations. Seafarers in a broad area comprising Taiwan, the Philippines, the Bismarck Archipelago, and perhaps the colonizers of the Marianas themselves came to rely less on rice and more on tropical plants such as coconuts, bananas, and breadfruit as well as pigs, chickens, and dogs. Thus transformed, they ranged deeper into the great ocean, covering altogether about twenty-five hundred miles. Their perilous movements are clear from their distinctive pottery style known as Lapita, the languages they spoke, and the foods they carried. By 900 BCE, they had reached Tonga and Samoa, roughly a third of the way toward South America.21
A hiatus of more than fifteen hundred years followed that promising start, however. A second wave of colonization did not get under way until around 900–1000 of our era. What explains this prolonged pause? And why did seafarers suddenly start exploring again? Scholars still argue whether it was innovations like the double-hull canoe, sea-level fluctuations that revealed new lands and thus smaller sea gaps, novel forms of social organization, fortuitous changes in wind patterns due to El Niño events, or sheer luck. Whatever the reason, the voyages of this second wave rank among the most extraordinary feats of maritime exploration in all of history. Polynesian seafarers first had to negotiate the fifteen-hundred-mile gap separating Samoa from the Society Islands in what is now French Polynesia. After establishing a foothold there, these intrepid colonizers seem to have solved all remaining navigational and provisioning problems and, in one extraordinary pulse around the 1100s–1200s, explored and settled all remaining islands of East Polynesia, as far east as Rapa Nui (Easter Island), as far north as Hawai‘i, and as far south as New Zealand.
These explorers also may have reached the Americas, thus completing the great human chain across the Pacific. If they had gotten four-fifths of the way across the Pacific and were capable of finding minuscule islands in the middle of the ocean, why would they have stopped short or missed an entire continent? As of this writing, DNA evidence indicating contact between Polynesians and pre-Columbian Native Americans had just become available. Polynesian populations in Palliser, the Marquesas, Mangareva, and other islands in what is now French Polynesia bear traces of Native American ancestry dating back to the twelfth and thirteenth centuries. This new genetic information jibes well with the overall timing of Polynesian colonization of the Pacific and explains the presence of food items like coconuts and sweet potatoes across Polynesia and the American continent prior to Columbus.22
Pacific Islanders picked their way across this extravagant labyrinth with traditional methods. Captain James Cook in 1769, Don José de Andía y Varela in 1774–75, and other Western explorers down through the nineteenth century heard much about these techniques. In recent decades, too, anthropologists and sailing enthusiasts have learned from Polynesians and Micronesians who still practice these way-finding procedures. In an era of satellites and global positioning systems, it is hard to grasp the raw skill involved in such methods of ocean navigation that dispense with all instrumentation and rely solely on the detailed knowledge of the stars’ movements, awareness of the winds and currents, and the uncanny ability to read a thousand clues from the skies and the water. As they could not see islands beyond ten or twelve miles distant, early Pacific navigators had to deduce their proximity by observing birds returning to their nests, paying close attention to the cloud formations, interpreting minute disruptions in the ocean swells, and catching sight of seemingly unimportant floating debris. Caroline Islanders employed a method of navigation known as the etak system. To keep track of their progress while going from one island to another, navigators visualized a third island off to one side of their canoes as a reference point. As they moved forward, the reference island changed its alignment with respect to the background stars, as the map illustrates. The passage thus became divided into stages, or etak, defined by successive alignments as Native voyagers completed one segment after another until reaching their destination.23
These navigation systems required extraordinary powers of observation and a lifetime of practice. Yet they worked well, enabling Polynesians and Micronesians to move reliably across the islands, rendering what may seem to us like dangerous passages into routine voyages. Pacific Islanders were able to make themselves at home in this perilous world. Peoples from nearby continents still visited from time to time, and so life went.
In a few tumultuous decades in the fifteenth and sixteenth centuries, however, a small community of seamen from the continents devised new technologies of navigation that came to revolutionize the world. These newfangled techniques enabled peoples from the continents not just to hop to the nearby islands but to cross entire oceans at a time, finally overcoming vast physical obstacles that had been in place for tens of millions of years.24
A stretch of Mexico’s Pacific coast in 1550. The “Puerto de Navidad” is on the bottom right, connected to a lagoon containing two small islands. North of Navidad, one can see Guadalajara, a substantial Spanish city represented with four blocks in a grid pattern. Nomadic Indians armed with bows and arrows, waging war, taking captives, and torturing them, appear at the upper-left corner.
1
A Global Race
Navidad is a small tourist town on Mexico’s Pacific coast. About a four-hour drive south from Puerto Vallarta, it is an ideal place to hide from the world. In the sixteenth century, however, it was positively remote. No proper road led into Navidad, only a dirt path that ended at a horseshoe bay. A mangrove-choked, mosquito-infested lagoon was connected to the bay; and where bay and lagoon came together, a cluster of tumbledown huts sprouted. Illness and famine visited the hamlet with frequency. Just a few years earlier, the Native peoples of the region had launched the so-called Mixtón War, a massive rebellion that had nearly dislodged the Spanish presence in all of western Mexico.1
Clearly this was no place for a major shipyard or construction project. Acapulco would have been much better. Only the need for secrecy had tipped the scales in favor of this dilapidated harbor far north of Acapulco; and thus in 1557 some of the best carpenters and blacksmiths in all of Mexico began arriving in town.
Money seemed to be no object to the Spanish crown spearheading the secret effort. Navidad offered no suitable building materials, so nearly everything had to be brought in from distant lands: nails of all sizes from Spain, rope and rigging from Nicaragua, large trees for the masts from Oaxaca, anchors and sails from Veracruz, water barrels from Acapulco. The logistical challenges were at times alarming. The artillery piece
s, for instance, had to be shipped across the Atlantic, moved on barges through the Isthmus of Tehuantepec, hauled for sixty miles on a road so rough that hundreds of Indian laborers had to rebuild portions of it to allow the carts to pass, and finally reembarked on the Pacific coast to Navidad. The cost of all this was prohibitive. Altogether the building project at Navidad ran to more than half a million pesos, or ten times the amount that the Spanish crown had invested in Columbus’s voyage of discovery seven decades earlier. Yet the money kept flowing, and the construction proceeded in spite of a work stoppage and an earthquake that brought down what few stone structures existed there.2
Conquering the Pacific Page 2
