Tuesday, May 6, 2014

Polynesian chickens tell tales of ancient migration

European chickens were introduced into the Americas by the Spanish after their arrival in the 15th century. However, there is an ongoing debate as to the presence of pre-Columbian chickens among Amerindians in South America, particularly in relation to Chilean breeds such as the Araucana and Passion Fowl.

So did the Polynesians beat Columbus to South America? Not according to the tale of migration uncovered by analysis of ancient DNA from chicken bones recovered from archaeological excavations across the Pacific.

Research in 2008 apparently showed a pre-Columbian Chilean chicken and six pre-European Polynesian specimens clustered with the same European/Indian subcontinental/Southeast Asian sequences, providing no support for a Polynesian introduction of chickens to South America. However, sequences from two archaeological sites on Easter Island, have an uncommon haplogroup that comes from Indonesia, Japan, and China and looked as if it represented a genetic signature of an early Polynesian dispersal.

Bayesian modelling

To confirm this initial hypothesis, the team led by the University of Adelaide’s Australian Centre for Ancient DNA required more samples. They sequenced mitochondrial control region DNA from 122 modern and 22 ancient chicken specimens from Polynesia and Island Southeast Asia and used these together with Bayesian modelling methods to examine the human dispersal of chickens across this area.

Specific techniques were essential in removing contaminating modern DNA from experiments, which appear to have impacted previous studies of Pacific chickens. The results of the new examination has identified and traced a unique genetic marker of the original Polynesian chickens only present in the Pacific and Island Southeast Asia, thus reconstructing the early migrations of people and the animals they carried with them.

The research team of national and international collaborators, including Australian National University, University of Sydney, and Durham and Aberdeen Universities in the UK, used female-inherited mitochondrial DNA extracted from chicken bones excavated in archaeological digs from islands including Hawaii, Rapa Nui (Easter Island) and Niue.

“We have identified genetic signatures of the original Polynesian chickens, and used these to track early movements and trading patterns across the Pacific,” says lead author Dr Vicki Thomson of ACAD. “We were also able to trace the origins of these lineages back into the Philippines, providing clues about the source of the original Polynesian chicken populations.”

Associate Professor Jeremy Austin, ACAD Deputy Director, says: “There are still many theories about where the early human colonists of the remote Pacific came from, which routes they followed and whether they made contact with the South American mainland. Domestic animals, such as chickens, carried on these early voyages have left behind a genetic record that can solve some of these long standing mysteries.”

No evidence of any pre-Columbian contact

Professor Alan Cooper clarified the results, saying, “We were able to show that the ancient chicken DNA provided no evidence of any pre-Columbian contact between these areas.”

“Remarkably, our study also shows that the original Polynesian lineages appear to have survived on some isolated Pacific islands, despite the introduction of European domestic animals across the Pacific in the last couple of hundred years,” Professor Cooper says. “These original lineages could be of considerable importance to the poultry industry which is concerned about the lack of genetic diversity in commercial stocks.”

Past Horizons. 2014. “Polynesian chickens tell tales of ancient migration”. Past Horizons. Posted: March 19, 2014. Available online: http://www.pasthorizonspr.com/index.php/archives/03/2014/polynesian-chickens-tell-tales-of-ancient-migration

No comments: