Modern counterparts of these plants exist, but Svetlana Yashina, who regenerated the plants, took careful steps to assure the antiquity of the tissue from which they were derived.
Over millennia, the squirrel’s burrow fossilised and was buried under increasing layers of ice. The plants within were kept at a nippy -7 degrees Celsius, surrounded by permanently frozen soil and the petrifying bones of mammoths and woolly rhinos. They never thawed. They weren’t disturbed. By the time they were found and defrosted by scientists, they had been buried to a depth of 38 metres, and frozen for around 31,800 years.
The data are published in the Proceedings of the National Academy of Sciences. Additional details are offered in a report in the New York Times:
Some of the storage chambers in the burrows contain more than 600,000 seeds and fruits...The researchers suggest that special circumstances may have contributed to the remarkable longevity of the campion plant cells. Squirrels construct their larders next to permafrost to keep seeds cool during the arctic summers, so the fruits would have been chilled from the start. The fruit’s placenta contains high levels of sucrose and phenols, which are good antifreeze agents.The Russians measured the ground radioactivity at the site, which can damage DNA, and say the amount of gamma radiation the campion fruit accumulated over 30,000 years is not much higher than that reported for a 1,300-year-old sacred lotus seed, from which a plant was successfully germinated.