National Geographic News
A photo of a chicken in South America.

A chicken in Calana, Brazil, peeks through a hole in the henhouse wall.

PHOTOGRAPH BY LEONARDO V., NATIONAL GEOGRAPHIC YOUR SHOT

Roff Smith

for National Geographic

Published March 18, 2014

So why did the chicken cross the Pacific? Well, apparently it didn't. At least not all the way.

Scientists looking into the DNA of ancient and modern chicken breeds found throughout Micronesia and Polynesia have determined that they are genetically distinct from those found in South America. The research runs counter to a popular theory that Polynesian seafarers might have reached the coast of South America hundreds of years ago, before European explorers.

Among the intriguing indications that contact might have been made between Polynesians and the native peoples of South America was the supposed pre-Columbian presence of non-native chickens, allegedly introduced to the continent by seafarers from South Pacific islands. More evidence comes from the ubiquity of the sweet potato, a South American native, in the South Pacific—it was already widespread throughout the islands by the time James Cook sailed into the region in 1770. (See National Geographic's South Pacific photos.)

Now it appears the chicken link, at least, may be severed, according to Alan Cooper, director of the Australian Centre for Ancient DNA, a co-author of the study published this week in the Proceedings of the National Academy of Sciences.

Researchers sequenced mitochondrial DNA from 22 chicken bones found at Polynesian archaeological sites and 122 feathers from modern chickens living on islands across the South Pacific. They used an enzyme to remove any contamination by modern DNA that may have clouded the results of earlier studies. When the team compared the "cleaned-up" DNA of Polynesian chickens with that of ancient and modern South American chickens, they found the two groups were genetically distinct.

The chicken DNA does not support a connection between the peoples separated by the Pacific, Cooper said. "Indeed, the lack of the Polynesian sequences [of DNA] in modern South American chickens ... would argue against any trading contact as far as chickens go."

Cooper and his colleagues were able to trace the origins of Polynesian chickens back in time and across the Pacific, following the lines of what must rank as one of the boldest, most romantic, and least understood human migrations of all time—the peopling of the tropical islands of the South Seas.

"We can show [from chicken DNA] that the trail heads back into the Philippines," Cooper said. "We're currently working on tracing it farther northward from there. However, we're following a proxy, rather than the actual humans themselves."

An illustration of Tahitians sailing and paddling rafts.
Tahitians sail and paddle rafts in an engraving done a few years after Captain James Cook explored Polynesia and Tahiti, then called Otaheite.
ILLUSTRATION BY SSPL, GETTY

Colonizing the South Pacific

The peopling of the South Pacific happened in two stages, the first of which took place more than 3,000 years ago when mysterious seafarers known as the Lapita set off from Papua New Guinea's Bismarck Archipelago into the great blue void of the Pacific. Within a startlingly few generations they managed to find and colonize hundreds of hidden tropical paradises: Vanuatu, Fiji, Tonga, Samoa, New Caledonia.

They sailed as pioneers, not explorers, bringing their families and everything they might need to build new homes on the lands they clearly expected to find: flints for toolmaking, pottery, and foodstuffs—including their chickens.

A second, much later phase, beginning around the year A.D. 800, saw them expand into the vastness of the eastern Pacific—to Tahiti, Bora Bora, the Marquesas, Easter Island, and Hawaii. Precisely how these people accomplished such astonishing voyages, and why they attempted them, remains an intriguing mystery, for they left behind no writings and very few artifacts. (Read "Beyond the Blue Horizon" in National Geographic magazine.)

With so few clues to work from—not a single example of an early Polynesian voyaging canoe survives today—archaeologists have been forced to tease out the story of this great migration from the evidence of scattered bones and pottery shards on far-flung islands, and strands of DNA from the plants and livestock the South Seas pioneers brought with them and whose descendants live on today.

Using these bits and pieces, archaeologists have been able to put together a rough time line of the Polynesians' eastward expansion across the Pacific, and the legendary bit of southerly backtracking that led them to discover New Zealand around the year A.D. 1300. But one of the great questions remains: Did they make it all the way across the Pacific to the coast of South America? Did they beat Columbus to the New World? It is a matter of heated debate among South Pacific scholars and one unlikely to be put to rest by the latest findings on chicken DNA.

David Burley, an archaeologist at Simon Fraser University in Canada who has been working in the South Pacific for more than 25 years, has no doubt the Polynesians reached the New World, whatever the evidence from chicken DNA. "The evidence for Polynesian contact with the New World prior to Columbus is substantial," he said. "We have the sweet potato, the bottle gourd, all this New World stuff that has been firmly documented as being out here pre-Columbian. If the Polynesians could find Easter Island, which is just this tiny speck, don't you think they could have found an entire continent?"

An illustration of a house and animals in Tahiti.
This engraving of a house in Tahiti in the mid-18th century shows the household animals, including a flock of chickens.
ILLUSTRATION BY DeAGOSTINI, GETTY

Bones of Contention

The idea that Polynesians might have introduced the chicken to South America and thus left behind evidence of their seagoing feat is a fairly new one. For many years, scholars assumed that early European explorers from Portugal and Spain brought the birds to South America, along with horses, pigs, and cattle.

A 2007 study, however, announced the discovery of chicken bones found at an archaeological site near Santiago, Chile, that yielded radiocarbon dates between 1321 and 1407—long before the arrival of Europeans. The early dates, the location along the Pacific coast, and the presence in the bones of what appeared to have been a unique genetic mutation common to Polynesian chickens raised the tantalizing prospect that the meaty birds may have been introduced by South Pacific seafarers.

"It is the most likely explanation," said Alice Storey, an archaeologist with the consulting firm Archer CRM, who led the 2007 study in Chile. "I have investigated many other potential routes of introduction, and none of them are as likely as a Polynesian introduction."

Within a year, though, those results were called into question by other researchers. A subsequent analysis by Cooper and his colleagues of the DNA from the Chilean finds challenged the dates and suggested that the genetic mutation originally thought to have come from Polynesian forebears was in fact a fairly common mutation found in chickens throughout the world. That study formed the basis of the most recent research into the DNA of Polynesian chickens that appeared this week.

For her part, Storey stands by the pre-Columbian dates she and her team obtained for the chicken bones in Chile. She argues that the DNA results in the study released this week are far from conclusive.

"Indeed, the bulk of their research focuses on modern DNA," she said.  "Using modern DNA to understand what people were doing in the past is like sampling a group of commuters at a London Tube station at rush hour. The DNA you get is unlikely to provide much useful information on the pre-Roman population of London."

As humans moved around the world, they brought chickens along with them. So modern chicken populations aren't necessarily representative of past populations, Storey said. "We know from his journals [that] Cook moved chickens all over the Pacific, as did other Europeans, so DNA from chickens living on Pacific islands today has little to tell us about what people were doing in Polynesia, the Pacific, and in Southeast Asia before A.D. 1600."

The new research appears to have laid these old bones to rest, but questions remain. One thing is certain: If the dates of the 2007 study are correct and there were indeed chickens in pre-Columbian South America, they had to come from somewhere. There is also the matter of the sweet potato, a definite South American native, which had spread throughout the Pacific by the time Europeans arrived on the scene.

"The sweet potato is a good question," conceded Cooper. "The bottle gourd was recently shown to have probably crossed to South America by marine currents, not human trade, as previously assumed, so I also wonder about the potato's ability to be dispersed in that fashion."

If the presence of pre-Columbian chickens is a good indicator that Polynesians succeeded in crossing the Pacific, the absence of one of their old shipmates—Rattus exulans, the Pacific rat—makes an equally compelling case against it. The Pacific rat is known to have traveled everywhere with their Polynesian hosts, and wherever they landed they invariably established thriving local rat populations that live on to this day. There are no Pacific rats in South America.

17 comments
Douglas Cooke
Douglas Cooke

Did the Polynesians bring the rats with them deliberately, and if so, why? Did they eat them? It's hard to imagine rats stowing away in a canoe. Where would they hide?

Turo Ufi
Turo Ufi

I believe that the Polynesians brought the chickens to South America. Not the Europeans. The chickens that were used in the study belonged to breed Araucana which were kept by the Mapuche tribe. The breed is renowned for laying blue eggs which is unique just to the Araucana. No other breed lays blue eggs. The blue egg gene originates from an original cross that goes way back to Java, Indonesia, The cross was between a red junglefowl which all chickens descend from and green junglefowl which is endemic to a small number of islands in Indonesia. The green junglefowl carries the tinted egg gene which is responsible for the blue eggs in the Araucana. 

The tribes that sailed out of Java into the vast Pacific ocean brought along this hybrid chicken as a good luck charm and also a beacon for other tribe members in case they were lost, the crow of the male is distinct from the average barnyard rooster. As the other various Polynesians got ahold of this chicken they eventually hit South America which eventually got into the possession of the Mapuche. It is also noted that Mapuche men would fight the roosters as entertainment. The same practice that the Polynesian did. Go figure!

Gil Carvalho
Gil Carvalho

Doesn't explain the reverse migration of the Potato to Polynesia, with radio-carbon dating in Pacific islands to before 1000 AD. Not only did the actual potato migrate with human help, but the Polynesians used the same name as the South American natives who first cultivated it. 

Peter Al
Peter Al

how about chicken mayweather ? where he comes from?

Richmond Acosta
Richmond Acosta

I have a question. Aren't all breeds of chicken originated from Red and Grey junglefowls from Southeast and South Asia, respectively? If that is the case, doesn't all chickens trace their roots to any of these countries, including the Philippines where wild junglefowls still exist and are called Labuyo.

David Brose
David Brose

Since Tahiti was discovered by Europeans on Bougainville's 1769 voyage it's most likely the picture depicts a late 18th C view. 

Alfredo Quedi
Alfredo Quedi

Chicken DNA in Polynesia can be traced back to Philippines.  It means that Philippines fishermen have a long history of seafaring.  Bajo de Masinloc is just a backyard in comparison.  China historical claim to the whole South Pacific just got busted. 

Peter Marsh
Peter Marsh

As there is a difference between Polynesian and South American chicken DNA, further testing of fossil chicken bones from Rapa nui might show us whether the chickens there came from South America or from Polynesia. 

Kukul Khan - the Mayan emperor who is depicted as a man holding two eggs, was meant to have brought agriculture and the domestication of animals to central America from Asia - maybe he is responsible for the spread of chickens to South America.

Mioara Caragea
Mioara Caragea

Carta sobre o Descobrimento do Brasil by Pero Vaz de Caminha, written for the king of Portugal, D. Manuel, about the expedition of Pedro Alvares de Cabral to the northern of the future Brazil in 1500 tells about the choc and the fright of the indians seeing chickens on the portuguese boat. They were not afraid of the captain, clad in armour and fully armed, but took fright and ran to the shore seeing and hearing the ferocious birds pecking on the deck.

DOLORES URQUIDI
DOLORES URQUIDI

Has anyone tested Arabic chickens for DNA's?  There seeems to have been a lot of cross the ocean travels by them.  They came across on the Kamchak Current in the north and went home on the Equatorial current six months later.  Great for vacations.


Martin Zitter
Martin Zitter

Please don't mistake theory for hypothesis, conjecture, supposition, intuition, notion, and the ever popular, belief.  

Lindsay Maw
Lindsay Maw

An interesting theory on polynesian migration techniques is that explorers would set out during off-seasonal meteorologic reversals and sail more or less into what would be the prevailing breeze.  In this manner they were able to migrate from west to east with the knowledge that the returning trade wind can blow them safely home.  As they cast out in this manner they discovered polynesia.  


Migration would then follow each explorational success, the polynesians settling a vast area of the globe.  They set out looking for new lands as population and tribal pressures grew.  And the lands they found were unpopulated.


These things are important.  Explorers may not have brought chickens with them, or ate them before they hit the continent.  And full scale migration may not have followed because the great new land wasn't suitable for polynesian settlement.  There was a well established population already there.  


So no chicken.  But they grabbed some tubers and some gourds.  I for one think that it would be more amazing to think that they could make it as far as they did and not continue to the Americas.  Maybe people struggle to think that they turned their back once they found it.  "There are no islands here".

Turo Ufi
Turo Ufi

@Gil Carvalho Simple the Polynesians traded with the various tribes of South America primarily the coastal tribes like the Mapuche and Quechua. read my comment on the origin of the South American chicken, The study that was done is nonsense I sense that something to do with a pride that Europeans conquered South America is the correct one and that Polynesians having contact with natives of South America is wrong as these people are just primitive in their eyes. The people that done this study were white by the way.

Al Chock
Al Chock

So only Europeans can DISCOVER ? ?

Richmond Acosta
Richmond Acosta

@Alfredo Quedi actually, it is believed that most Pacific Islands were populated by ancient Austronesian stocks from the Philippines, who, in the first place, might have originated in present day Taiwan.


About Bajo de Masinloc; China has been trading with Filipinos eversince time immemorial. In fact, during the Ming dynasty, while China closed its doors to Japan, allowing only trade every ten years, China kept its doors open to traders from the Kingdom of Tondo (in present day Manila) who are able to make trades with the Empire every year. Therefore, their supposed "discovery of the island is ridiculous. Their maps illustrated all of China's trading partners including the chiefdoms in the present day Philippines.

Gil Carvalho
Gil Carvalho

@Jaime Pretell-Samsey but floating thousands of miles in salt water from non-human means is unlikely, considering the potato was first cultivated in a mountainous climate. Also, the Pacific Islanders called the potato the same name as the South Americans who first cultivated it. Did the name for the potato also float with it randomly across thousands of miles? Why did the potato not also float to Africa, Australia or Europe?


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