2014-06-01 19:57:12
About seven years ago, I wrote on this page about the resolution of a mystery that had kept scientists interested in finding out the history of human migrations in check: the origin of the chicken in South America. This question may seem insignificant, but it is important if we want to better understand the history of Humanity. It turns out that the dispersion of the chicken across our planet occurs as a domestic animal that accompanies human movements, so revealing the family ties between the different chickens on Earth will provide us with valuable information about the way in which Humanity colonized it.
New genomic technologies today make it possible to relatively easily sequence DNA extracted from chickens from all over the world, compare the sequences with each other, and create a family tree that will reveal human migrations. To do this, the DNA of the mitochondria is usually used, the organelle responsible for generating energy in the cell. The mitochondria comes from an ancient cellular ancestor that entered into symbiosis with another cell. As such an independent ancestor, the mitochondria maintains its own genome which, although it is much smaller than the genome of the rest of the cell, mutates and evolves like that of other organisms. This evolution is what allows migratory changes to be followed.
Discovery in the south?
The origin of the South American chicken was, therefore, a mystery whose resolution would provide important information about human migrations to the American continent. In principle, the South American chicken seemed not to come from Europe, since when the Conquistadors conquered Peru, the Incas were already fed with domestic chickens which, consequently, must have come from another part of the world and had arrived on said continent before the Europeans. What could its origin be then?
The discovery of an archaeological site in Chile dating back to around the year 1400 and containing chicken remains in good condition allowed DNA to be extracted and analyzed from these remains. Comparison of their mitochondrial DNA sequence with sequences from chickens from other parts of the world indicated that the South American chicken probably came from Polynesia. This implied that America had been “discovered” by the Polynesians in the south, probably more than a century before the Spanish “discovered” it, and brought and raised their chickens, in the north. The year was 2007 and, finally, this chicken mystery seemed to have been solved.
DNA sequencing and analysis technology has become so powerful in recent years that, spurred by the above data, Australian and UK researchers set out to map human colonization of the Pacific Islands by studying the genealogy of the chicken. The colonization of the Pacific by humans is, without a doubt, one of the most impressive feats of humanity, begun about 3,250 years ago by the Lapita people, originally from the Bismark archipelago, northeast of the island of New Guinea.
Annoying contaminations
The researchers sequence mitochondrial DNA from 122 modern chicken specimens and 22 ancient chicken specimens from Polynesia and the Pacific Islands and obtain and analyze their data with new laboratory procedures, and new analytical and statistical methods. With this data, they are able to create a map that indicates the possible chronological and geographical order in which the Pacific islands were colonized. However, the surprise arises when, in their studies, researchers now find no genetic relationship between the South American chicken and the Polynesian chicken. What could be the reason for this discrepancy with previous studies?
And well, as extraordinary as it may seem, researchers have solid reasons to believe that the genetic relationship previously found is false due to the contamination of the reagents and laboratory materials used in these studies with DNA from modern chickens. These materials and reagents are manufactured by companies whose workers undoubtedly eat chicken and can transfer traces of chicken to the products they make. A tiny trace of external DNA is enough to ruin everything. The use of numerous precautions and new methods in this latest study neutralizes this contamination and now reveals that, most likely, Polynesian chickens never reached South America, which implies that the colonizing feat of this people was impressive, but not so impressive as to cross the entire Pacific.
These new findings, published in the journal Proceedings of the National Academy of Sciences of the United States, once again reopen the mystery of the origin of the South American chicken. Could it perhaps come from chickens transported to the continent by the ancient Vikings? It is believed that this people of warriors and explorers reached the northern coasts of the American continent back in the 10th century AD. It could be that they brought chickens with them and that they later dispersed throughout the rest of the American continent and were domesticated independently. It is a hypothesis that, like other alternatives that may be formulated, will require new studies to confirm or refute it. And science is exciting even when it studies the origin of chicken.
NEW WORK BY JORGE LABORDA.
It can be purchased here:
Chained circumstances. Ed. Lulu
Other works by Jorge Laborda
One Moon, one civilization. Why the Moon tells us that we are alone in the Universe
One Moon one civilization why the Moon tells us we are alone in the universe
The intelligence funnel and other essays
#Cienciaes.com #mystery #American #chicken #reborn