Three fruits from 31,800 years ago flowered in a pot

Svetlana Yashina, a biologist at the Institute of Cell Biophysics in Pushchino, about a hundred kilometres from Moscow, keeps in a greenhouse some plants that flower every year and that came from three fruits a ground squirrel stored away 31,800 years ago. The fruits arrived frozen and whole. Some of their seeds put out a root and stopped there: not one of them became a plant.

Those fruits were in the lower basin of the Kolyma, in north-eastern Siberia, 38 metres down, inside the winter larder of an animal that never came back for it. Down there the permafrost — ground that never thaws — preserves fossil burrows of the Arctic ground squirrel, a rodent that fills its nest with seeds and fruits before the cold arrives. The sediment closed over that burrow and never opened again; today that ground averages seven degrees below zero.

Accelerator radiocarbon dating, which measures age by counting atoms one by one, gave 31,800 years, give or take 300. To place the number: when that squirrel sealed its nest, the first wheat harvest was still some 20,000 years away.

The plants are Silene stenophylla, a small white species of the carnation family that still grows today on the Siberian tundra. Yashina tried sowing those thirty-one-thousand-year-old seeds and got halfway: some pushed out a tiny root and then the embryo, damaged, stopped pulling.

What worked was another part of the fruit. Inside a fruit, the placenta is the inner wall the seeds are attached to, and in the three the squirrel had stored while they were still green that tissue was intact. Yashina placed it in a culture medium with sugars, vitamins and growth hormones. Out of it came shoots, then roots of their own, then whole plants that could be moved into pots. They flowered in the second year.

She pollinated them by hand, with pollen from the other ancient plants, and obtained new seeds that all germinated. The work was published in 2012 in the proceedings of the United States National Academy of Sciences.

The plant record still stands: no other plant has grown again from so far back. The animal record, on the other hand, has already fallen, and it fell on the same river. In 2023 a team pulled out of the Kolyma permafrost, at 40 metres and from another squirrel burrow, two nematodes, microscopic soil worms, dated at around 46,000 years. They woke up in the laboratory and set about having offspring; the species turned out to be new and was named Panagrolaimus kolymaensis.

The team grew modern plants of the same species alongside, collected in the same region, and they are not alike: the Pleistocene one grows and buds differently, and the paper treats it outright as a distinct phenotype from the present-day plant. Between the two lies the whole of the last glacial maximum, the harshest cold of the past 100,000 years.

The plant record, until somebody opens a deeper burrow, stands at 31,800 years. It was set by a squirrel that died with its larder full.