July 9, 2009
Carbon Dating Shows Ancient Seeds Not Ancient
Scientists have determined that the oldest viable seeds in the world, dating from the Pleistocene era, are not as old as experts once believed, BBC News reported.
The seeds, which have been grown into live Arctic lupine plants, are not 10,000 years old as believed, according to new dating techniques.In fact, using the new methods, scientists have concluded they are actually modern seeds that contaminated ancient rodent burrows.
However, the scientist who debunked the record said it remains possible that plants may yet be grown from seeds trapped in ice age permafrost.
Canadian scientists published details in one of the world's foremost scientific journals over 40 years ago of how they discovered two dozen seeds of an Arctic lupine plant within ancient lemming burrows.
The author's wrote of how these burrows, found at Miller Creek within the Yukon Territory of western Canada, had been buried deep within frozen silt since the Pleistocene era"”putting them over 10,000 years old.
Additional finds that were thought to confirm the seeds' old age included rodent nests, fecal pellets, and an ancient lemming skull.
The scientists even managed to germinate and cultivate normal healthy Arctic lupine (Lupinus arcticus) plants from the "ancient" specimens.
Grant Zazula, a scientist working for the Yukon Paleontology Program run by the Government of Yukon, based in Whitehorse, Canada, said they were considered to be the oldest viable seeds to have ever grown.
But controversy swirled over the idea that seeds could remain viable for so long.
Zazula said the scientific community was really split by the presumed ancient viable Arctic lupine seeds.
"Some believed it, others did not," he added.
The method used at the time to date the seeds was at the center of the controversy, considering there was no way of radiocarbon dating small samples the size of seeds when the researchers published the original claim in 1967.
Therefore, the seeds, at the time, were presumed to be of the same age as the ancient frozen lemming burrows in which they were discovered.
Zazula became suspicious of the seeds' provenance through his own research into ice age fossils.
He noted that he had never found any 'ancient' Arctic lupine seeds during his studies of ancient rodent nests buried in the Yukon permafrost"”some up to 25,000 years old"”from which he had recovered seeds from around 65 different plant species.
"Also, Arctic lupine is a boreal forest understory flower, and I do not think it lived during the ice age with incredibly cold, harsh arctic conditions. The ecology does not fit," he said.
He then decided to contact Richard Harington of the Canadian Museum of Nature, one of the authors of the original 1967 Science paper about the seeds, telling him that some of the seeds still existed, though they were coated in paraffin wax to preserve them.
Along with Fiona Brock, an expert in radiocarbon dating from the University of Oxford, Zazula found a way to avoid the contamination from the paraffin and accurately radiocarbon date the seeds for the first time.
Zazula's team reported in the journal New Phytologist, that the Pleistocene seeds appear to be from between 1955 and 1957.
However, the lemming skull found alongside the seeds was confirmed to be from the Pleistocene, which validated the original researchers' claim that they had collected Pleistocene samples from deep within the permafrost.
But the seeds must have fallen into the burrows without their knowledge, just years before they were collected.
Zazula said he was excited that they were able to put such a controversy to rest.
He said it was nice to be able to conclusively demonstrate the actual age of the seeds, since the 'ancient' viable Arctic lupine seed was cited throughout seed germination textbooks, studies on permafrost and throughout the botanical literature.
Together, they concluded that any claims for ancient seed viability must be accompanied by rigorous dating methods.
"If you are going to say something is really old, the research has to effectively demonstrate their age," he said.
But ancient seeds that remain viable may someday be discovered, and live plants could still be grown from them, Zazula noted.
A 2,000-year-old date palm recovered near the Dead Sea currently holds the record for the oldest viable seeds.
Russian scientists in 2002 published a claim that they had germinated a 33,000-year-old seed of a small tundra flower (Silene stenophylla).
But Zazula said the work was published in a relatively unknown journal, and the claim has received almost no acceptance in the scientific community.
"Although we have shown that these Arctic lupines were not as old as previously thought, I still think that in the near future we will be able to grow ancient, ice age seeds that are preserved in permafrost," Zazula said.
Studies are, in fact, already underway to attempt to germinate real ancient seeds from the Yukon permafrost.
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