High-tech detective work solves an old puzzle
In 1954, placer miner Harold Schmidt discovered rodent burrows preserved in the frozen muck of his claim on Miller Creek in the Klondike. The burrows were several metres below the ground surface and clearly very old. Several contained nests, fecal pellets, skulls, and other evidence of their former inhabitants.
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The Miller Creek seeds came from arctic lupine like this plant, which grows in Whitehorse.
(photo: Claire Eamer)
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Like many placer miners, Schmidt was interested in the traces of ancient life that sometimes turn up in the Klondike permafrost. He collected a small skull and a number of seeds from one of the burrows before washing away the muck to get on with the business of mining gold.
The story picks up more than a decade later, in 1966, when well-known Canadian palaeontologist Richard Harington visited the Klondike. Schmidt told him about the rodent burrows, and gave him the skull and about 30 seeds to study at the National Museum of Canada in Ottawa.
Now, the scientists at the National Museum already knew quite a bit about the muck in which Schmidt found the burrows. Previous studies had shown that it was deposited at least 10,000 years ago, during a time called the Pleistocene. That meant that bones and other material found in it must be equally old.
The little skull was identified as that of a collared lemming, a tundra animal no longer found near Miller Creek. The seeds belonged to the arctic lupine, a common plant in today's boreal forest. Despite their apparent age, the seeds were biologically identical with modern arctic lupine.
Several of the seeds were in good condition, so the scientists tried germinating them. Some of the seeds germinated and eventually grew into normal plants, with one of them producing flowers 11 months later. In what became a very famous scientific paper, the research team reported the successful germination of 10,000-year-old seeds – the oldest fossil seeds ever germinated.
The record stood for more than 40 years, but it has always been controversial. At the time that Harington received the seeds, there was no technology that could establish a radiocarbon date from material as small as a seed. The only evidence of the seeds' age was the age of the ground in which they were found.
And the fact that they were found in Pleistocene sediments has been bothering Yukon palaeontologist Grant Zazula. That's where the story picks up again.
"I've looked at hundreds of these small mammal nests and never found lupine before, and it doesn't make sense for them to be there in the Pleistocene anyway," Zazula says.
During the Pleistocene, the Klondike region was dominated by open, treeless tundra, just the sort of place to find a collared lemming. But arctic lupine grows in the cold, shaded understory of the boreal forest. Something didn't fit.
New technology might provide an answer. Today it's possible to get a radiocarbon date from material even smaller than a seed. Zazula approached Harington a couple of years ago to ask if any of the seeds had survived and if Harington would mind a new attempt at dating them.
"He was fine with re-examining the seeds," Zazula says. "He just likes to see the evidence presented and the truth prevail."
Unfortunately, only two of the original seeds survived, and they had been embedded in paraffin wax for a display at the National Museum, now the Canadian Museum of Nature. Would the wax contaminate any radiocarbon reading from the seeds and make it useless?
The seeds were turned over to a specialist lab in Oxford, England, for decontamination and dating. The lab tested several other seeds to make sure the decontamination worked, and also a small sample from the Miller Creek lemming skull.
The results were published this spring in a scientific journal called the New Phytologist. And they will, as Harington wished, let the truth prevail.
The lemming skull is indeed Pleistocene. The little animal lived and died more than 23,000 years ago. But the lupine seeds are modern, from about 1955-1957. Somehow – no one is sure what happened – they got mixed with the material from the muck. Zazula thinks it might be as simple as a modern rodent finding the old bits of nest and deciding they made a good food cache.
The end of the story, so far, means that the Klondike has lost its place in the oldest-seed record book. Currently, the oldest fossil seeds with confirmed dates and germination records are only about 2000 years old.
But this might not, after all, be the end of the story for ancient Yukon seeds, says Zazula. The lupine seeds were modern, but there are lots of other seeds frozen in the permafrost that underlies much of the territory. As the climate warms and the permafrost deteriorates, some of those seeds could come back to life.
"There could be some really interesting ecosystems," Zazula says. "There might even be some extinct plant species coming back."
For more information, contact Grant Zazula of the Yukon Palaeontology Program at (867) 667-8089 or .
