Why Did the Chicken Cross the World? Read online

  The evidence for chickens in South America before 1500 is ambiguous. When a Portuguese navigator that year bumped by accident into South America, about five hundred miles north of Rio de Janeiro, he reported many birds but no chickens. Shown a hen, some locals appeared terrified. Two decades later, an Italian adventurer named Antonio Pigafetta, who was traveling with Ferdinand Magellan on the world’s first circumnavigation, landed on the Brazilian coast and traded one fishhook for a half-dozen chickens. Pigafetta adds that for a single king of diamonds from his deck of cards, “they gave me six fowls and thought that they had even cheated me.”

  In 1527, a Spanish expedition anchored off Santa Catarina—nearly seven hundred miles south of Rio—when its crew was struck with disease. The captain sent a man more than one hundred miles into the Brazilian interior to obtain chickens and other food for the ill in exchange for fishhooks, knives, and mirrors. Whether the native chickens reported by these early European visitors were really chickens is hard to discern. The South American jungle is home to the curassow, a bird that resembles a large chicken and was at least partially domesticated. In 1848, as the biologist Alfred Russell Wallace explored the Amazon, he watched curassows come and go at will around Indian villages, since “being brought up from the nest, or even sometimes from the egg, there was little danger of their escaping to the forest.” In Venezuela, a gamecock breeder told me that curassows sometimes were bred with chickens to produce larger and tougher hybrids. Given the evolutionary distance between the two species, scientists doubt this is biologically possible.

  One intriguing report on the existence of Amazonian chickens comes from a sixteenth-century German conquistador, Nikolaus Federmann, who explored the Orinoco basin to the north in 1530 on an unauthorized expedition to find gold. In a book published a quarter century later, he claimed that he heard a rooster crow in the Venezuelan jungle. Locals explained that the bird came from the Southern Ocean in a big house. Historians interpret this to mean that the bird made its way through the jungle from Portuguese ships on the Atlantic coast, but it is possible that Federmann’s informants were referring to Polynesian canoes on the Pacific shore.

  Just two years earlier, Francisco Pizarro arrived in the Andes Mountains on the western edge of South America. A half century later, a veteran of the campaign against the Incan Empire recalled encountering “a few white chickens of Castille” in Peru. No definitive archaeological evidence of pre-Columbian chicken has been found there, however, despite a century of excavations. But the very name of the overthrown emperor, Atahuallpa, is said by some scholars to be related to the Quechuan word for chicken. A museum in Lima displays a two-thousand-year-old terra-cotta vessel that looks very much like a rooster, complete with comb and wattles and upright tail. Art historians can’t say for sure if it represents a bird that lived there at the time or was the fantasy creation of a local potter.

  What is certain is that the chicken, if it was indeed a new arrival, adapted remarkably quickly to the continent. One Jesuit in the 1580s wrote that Indians avoided sheep and cattle, but embraced dogs and chickens. Men hunted with the dogs while the chickens were treated with exquisite care. “Women carry them on their backs, and raise them as children,” he asserted, adding that the birds “were infinitely larger” than those in Portugal, a possible confusion with the curassow. Chickens soon were widespread and portable enough that they were often used as tax revenue. Some Brazilian natives were required to pay the Portuguese in the form of chickens, while hens and eggs were a regular form of tribute in Spanish-controlled areas.

  By the close of the sixteenth century, eggs brought from the lowlands were used as currency in the high mountains and plateaus of Bolivia, Peru, and Mexico. Chickens were arriving in South and Central America from Europe, Africa, and Asia. Bantu slaves from southern Africa brought their varieties to Brazil as early as 1575. This mixing of genes poses a challenge to geneticists attempting to untangle the origins of the bird in the New World, which is why the discovery and dating of the El Arenal bones caught worldwide attention.

  Those bones had gathered dust for more than two years in the Santiago house of the excavation director until a New Zealand archaeologist named Lisa Matisoo-Smith caught wind of the find while at a meeting in Chile. In January 2006, a Chilean colleague handed her a plastic Baggie containing one of the bones at the Santiago airport. Back in her lab at the University of Auckland, Matisoo-Smith turned the sample over to her PhD student Alice Storey, who broke the bone into three pieces. One piece went to an institute in Wellington for independent radiocarbon dating, which showed the chicken was alive and clucking sometime between AD 1304 and 1424. The second piece of bone went to Massey University in Auckland for DNA extraction, while Storey kept the third to do the same in her home lab. Both results then were sequenced at Massey.

  No one at that time had any idea what genetic sequences were typical of Pacific chickens, so the team collected thirty-seven other chicken bones from Polynesia dating from 1000 BC to AD 1500 to test and compare their DNA. They also plucked feathers from Araucana chickens in Chile, odd birds with ear tufts and no tail feathers that lay light-blue and light-green eggs. Some breeders think their uniqueness reflects remnants of a pre-Columbian population. About one-third of the old bones from Polynesia yielded DNA sequences, including those excavated on Easter Island, two thousand miles west of the continent’s coast and the likely stepping-stone to any South American contact by Polynesians.

  The El Arenal bone produced a sequence remarkably similar to that in ancient bones from Tonga, American Samoa, and Easter Island as well as that from the living Araucana. The Easter Island sample differed from the ancient Chilean bird by only one base pair, making it nearly an identical match. All the pieces seemed to fit. “An ancient Polynesian haplotype persists in modern populations of Chilean chickens,” the 2007 paper concluded. “In the 600 years or more since the introduction of European chicken these sequences have deviated little from their ancient Pacific ancestors.”

  A South American geneticist living in Australia, Jaime Gongora, was skeptical of the results. Gongora teaches at the University of Sydney but grew up with chickens in rural Colombia and recalls as a child wondering why Araucanas lay blue eggs. As Storey was analyzing her bone, Gongora was sequencing South American birds with hints of East Asian genetics, but concluded that the mixing could have taken place as late as the 1930s. When Matisoo-Smith and Storey shared their preliminary results with him, he was doubtful of the pre-1492 dates.

  Gongora, a thickset man who might be mistaken for a Polynesian on the streets of Sydney, meets me at a Thai restaurant near the university. During our meal, he points to a shrimp dish we share. When we eat and drink, we take in the radioisotope carbon 14—also called radiocarbon—created when cosmic rays hit the earth’s atmosphere. It pervades the sky, land, and water. Over time it loses electrons and its radioactivity. How far along organic material is in that decay process is what allows scientists to date a piece of charcoal, a seed, or a piece of bone with such accuracy. Oceans, however, mix deep waters that are very old with surface water that might be very young. Radiocarbon date yourself after eating shrimp and you might appear to have added a few years as well as ounces after the meal. Scientists call this the marine reservoir effect. Gongora assumed that if the El Arenal chickens lived close to the sea, then the birds may have feasted on seafood and therefore their bones only appeared to date to pre-­Columbian times. “If they were living with fishermen, then it is possible the chickens were eating the catch,” he says. The paper by Matisoo-Smith and Storey did not take this effect into account.

  Gongora and others, including Alan Cooper at the University of Adelaide in southern Australia, also were not persuaded by the genetic analysis. In blood samples from forty-one modern Chilean chickens, they found that the birds shared a haplotype common to European chickens. The El Arenal bone has a sequence that is the most common type found around the world. Some suspected the bone may
have been contaminated with modern genetic material during the course of Storey’s analysis, an ever-present threat in DNA sequencing. Hunt, the Hawaiian archaeologist, was on ­Matisoo-Smith’s original team but was persuaded by Gongora’s evidence.

  The battle of the bones was on. Matisoo-Smith, Storey, and Chilean colleagues used isotopic analysis to determine that the El Arenal chickens had eaten primarily land-based foods like corn and not seafood. They deny that there was contamination and reject the analysis by Gongora and his colleagues. “No one has produced any data that contradict our result,” Matisoo-Smith told me recently. But her team did back off claims linking the El Arenal birds to the modern Araucana chickens, which do appear to be largely a twentieth-century creation, as Gongora claimed. An independent team of molecular biologists has since asserted that DNA studies of modern chickens hint at two stages in their spread in the New World, supporting evidence of an early Polynesian Pacific and later Spanish Atlantic arrival of the bird.

  Whether the chicken first arrived via the Pacific or Atlantic, the controversy put a new spotlight on the possibility that Polynesians reached the New World before Columbus. Recent genetic work shows that the sweet potato passed from the peoples of the Andes highlands and into the hands of Polynesians, who spread it west all the way to New Zealand. Wind and current studies suggest that a Polynesian canoe leaving Easter Island could reach the Chilean coast, ride the current north to Ecuador, and then cycle back west on the trade winds.

  Historical records mention South Americans along the Pacific coast using sails and possibly manning floating trading stations set up just offshore. Words, tools, ritual objects, and vessels like the sewn-plank canoe used by tribes in the southern half of western South America have many similarities with those in Polynesia. And fowl have emerged as an important tool in reconstructing the audacious but poorly understood explorations of Polynesian seafarers as they settled one-third of the globe.

  Chickens have thrived on the Hawaiian archipelago as long as humans. Island myths, many centered on Kauai, are filled with stories of devious roosters and beautiful women who shape-shift between hen and human. In one tale, a virtuous hen-woman named Lepe-a-moa takes on the evil and powerful cock of the king of Maui. The ruler’s gullible opponents around the cockpit would gamble away their canoes, mats, headdresses, and even their own bones. But Lepe-a-moa slipped into the ring as the king of Oahu’s contender and defeated the Maui rooster. “She tore him to pieces, until the battle was in a thick cloud of flying feathers,” one version of the story relates.

  The bird has long had royal and magical connotations in traditional Hawaiian culture. “Hawaii is a cockpit, on the ground the well-fed cocks fight,” intones an eighteenth-century chant commemorating a victory of King Kamehameha, the cocks being the island chiefs. Archaeologists working here have uncovered remains of the bird in the houses of the ancient elite and rarely among the common people. Since the intrepid adventurers who settled the Pacific Ocean left behind no texts and few artifacts, these precious bits of cartilage provide welcome insight into an astounding era of discovery that scientists are only now starting to piece together.

  One of the richest sources of ancient Polynesian chicken bones is just above a Kauai beach. Makauwahi Cave is a limestone sinkhole wedged in a crease between high cliffs that meet the Pacific Ocean and a long stretch of sand favored by sailboarders. Looming in the distance is Mount Ha’upu, its pointy ridge home of the god Ku and the goddess Hina, who gave birth to an egg that revealed a chicken, according to one ancient creation myth.

  The cave is a giant pickling jar recording thousands of years of geological changes, biological invasions, and waves of humans that successively altered the landscape and encapsulate much of the island’s history. The archaeologist David Burney discovered what may be the richest fossil site in the entire Pacific region by accident. In 1992, he followed the tracks of tourists to a rock wall punctured by a narrow crevice and found a vast oval of rock rising sixty feet high. Ever since, he has probed the thick mud underneath, pausing to give the actor Johnny Depp a tour before Captain Jack Sparrow leaped off the cave lip in a recent Pirates of the Caribbean film.

  When I arrive at the site one breezy morning, Burney is at the bottom of a deep pit that is covered with a bright-green scum. Filling buckets with black ooze, he then hauls each by hand up the ­twenty-foot aluminum extension ladder and hands it over to a volunteer. The heavy muck is taken to the shady side of the natural coliseum and poured slowly into mesh boxes that sift for bones and shell. Burney, trim as his gray beard, invites me down the ladder. As I begin my descent, he calls up that I’m passing areas where they found a piece of glass or an iron nail bartered by the crew of a clipper ship, and then an area that was filled with large boulders deposited by a tsunami four centuries ago. These were nightmarish to remove but sealed the prehistoric layers from later disturbance. About two-thirds of the way down the ladder, he yells for me to stop. “This is where the chicken bones are,” he says from down below, pointing at a dark layer of earth in front of my nose. “And we can be pretty sure they are not mixed with modern stuff. There is not KFC chicken in here at all.”

  Finding undisturbed and uncontaminated chicken bones that are centuries old is a remarkable feat. They typically don’t last a day or two in most traditional villages. Dogs, rats, and other animals quickly devour what little is left. Insects and soil can eat up what remains of that. Burney explains that if the ground is too acidic, bone degrades although seeds fossilize. If it is too alkaline, bones will turn to fossils but vegetation degrades. Here, the alkaline limestone and the acidic groundwater cancel each other out. “This is the Goldilocks zone, perfect pH, just right,” he says. “Which means both types are preserved. Basically, everything in here is preserved. It’s like pages in a diary.”

  We clamber back up into the hot sun, which has just risen above the lip of the cliff, cross into the shade, and watch a retiree in a white tennis hat sorting through the mud in a rectangular box with ­quarter-inch mesh. “Don’t do every last little snail, but every bird bone and every seed we want to keep,” he tells her. “The biggest problem is that people try to screen too much at once,” he says, turning to me as she uses water from a garden hose to dissolve the mud. When she’s done, we hose off the thick black mud that coats our legs to the knees.

  Burney ships the chicken bones he finds to the southern Australian city of Adelaide. The five-thousand-mile trip, which required weeks on the fastest clipper ship, now takes ten hours. The bones arrive at a building set in the middle of Adelaide’s prim botanical garden. Until recently, extracting delicate strands of DNA from a long-dead sample was science fiction. Now researchers are pulling DNA from thirty-two-thousand-year-old algae dredged from the sea floor, eighty-thousand-year-old archaic humans, and horses that lived seven hundred thousand years ago. This technology makes human companions like the chicken important markers in understanding human movement around the planet.

  To see how this is done, I pay a visit to the Australian Centre for Ancient DNA. Peggy Macqueen, a youthful, round-faced woman with cropped white hair and black clothes, greets me at the entrance door. She had already told me to shower and change into clean clothes before arriving. In the foyer is a small locker room for my camera, phone, notebook, and pen. The strict protocols are designed to protect the samples from the innumerable genetic codes—not just my own—clinging to my hands, my hair, and my very breath. Microscopic leftovers of an egg sandwich could confuse analyses of Burney’s bones.

  Macqueen takes me down the hall and up a flight of stairs to a changing room where we don white all-body suits, face masks, and gloves. We sit on a knee-high bench that divides the room and swing our legs over. Then she directs me to put on a second layer of latex gloves in the final staging area. Then she has me pull on a third set of gloves.

  Finally we are ready to pass through an air lock and into the lab itself. As we enter, I feel a slight whoosh of air
against the tiny bit of skin on my face that is not covered. The air pressure inside the lab is higher than the pressure outside to limit contamination. The room we step into is spare, with white walls, a counter, and two computer terminals. There is none of the usual lab clutter of half-filled coffee cups, clipboards, and gaping backpacks.

  Macqueen guides me to a metal door in the corridor just beyond, which opens into a room the size and shape and temperature of a restaurant cooler. An entire wall of cubbyholes is filled with samples in little plastic Baggies and boxes that seem to be an inventory ­patiently waiting for a Jurassic Park–style revival of Siberian bison, Patagonian saber-toothed cats, and one of the world’s largest mammalian carnivores, the giant short-faced bear, which weighed as much as ­thirty-five hundred pounds when it prowled American woods. All went extinct, likely at the hands of humans, about twelve thousand years ago. There is a whole section of birds and, on the other side of the cooler, a corner devoted entirely to dozens of chicken-bone samples from across the Pacific—Vanuatu, Easter Island, and four from Maukauwahi Cave that made the flight from Hawaii before mine. Chickens here qualify as something apart from birds.

  Down the hall we enter a chamber of blowers, like at the tail end of a car wash. The spacious room beyond is where Macqueen cleans cartilage to remove any chemicals on the outer surface. Then she cuts a section and puts the sample in a Mikro-Dismembrator, a boxy copy-machine-sized device that, within ten seconds, pulverizes a bit of bone into less than an aspirin’s worth of powder. This she adds to a solution of enzymes designed to break down any organic material and turn the long strands of DNA into smaller and more manageable lengths. After baking it overnight at 130 degrees Fahrenheit in an incubator, Macqueen centrifuges the remaining goop at ten thousand rpm for five minutes to separate out the various components. Then she adds molecular-grade water, centrifuges the sample once again, and incubates the result for an hour or so. “You end up with nice clean DNA in nice little tiny degraded fragments,” says Macqueen, her voice slightly muffled by the mask. “And then you amplify it.”