Russian scientists in Siberia have brought a 24,000-year-old microscopic animal back to life — a tiny creature called a bdelloid rotifer, frozen in Arctic permafrost since the last Ice Age — and after thawing, it began moving, eating, and reproducing as if no time had passed, in research suggesting that some forms of life can survive in a kind of suspended animation for tens of thousands of years

Somewhere in the soil of northeastern Yakutia, about 3.5 metres below the present-day surface and trapped in permafrost so old it dates from the height of the last Ice Age, a small multicellular animal had been waiting for a very long time. Its biological clock had effectively stopped 24,000 years ago, when the soil around it froze permanently.

Its cells had not divided since. Its metabolism had been reduced to a level barely detectable by any physical measurement. By any conventional definition of “alive,” it was not — but by any conventional definition of “dead,” it was not that either. It was in a third state, called cryptobiosis, that some hardy organisms can enter under extreme stress and remain in for periods that turn out to be much longer than biologists had previously believed possible.

In June 2021, a team of researchers at the Soil Cryology Laboratory at the Pushchino Institute of Physicochemical and Biological Problems in Soil Science, in Russia, published a paper in Current Biology reporting that they had drilled a core sample from the Alazeya River region of Yakutia, isolated the rotifer from the permafrost, thawed it in their laboratory, and observed it return to apparent normal function. According to the original paper, led by Lyubov Shmakova and her colleagues, the radiocarbon date for the sediment from which the rotifer was recovered placed its last active period between approximately 23,960 and 24,485 years ago. After thawing, the animal began moving normally, feeding on the bacteria and algae offered to it in laboratory cultures, and reproducing through parthenogenesis — the form of asexual cloning that bdelloid rotifers have been using exclusively for approximately 40 million years.

What a bdelloid rotifer is

Bdelloid rotifers are microscopic multicellular animals, generally between 0.1 and 0.5 millimetres long, that live in freshwater and moist soils essentially everywhere on Earth. They have approximately a thousand cells each, organised into a body with a head, a foot, and the characteristic ciliated “corona” — a crown of beating cilia that gives the group its name (rotifer means “wheel-bearer”). They have been around as a distinct lineage for approximately 25 million years and, unusually among multicellular animals, reproduce exclusively by parthenogenesis — there are no males in any bdelloid species. The entire class is functionally female-only and has been for tens of millions of years, which has made them a long-standing puzzle in evolutionary biology: how does a lineage avoid the genetic deterioration that asexual reproduction usually produces?

Bdelloids have also long been known for their extraordinary tolerance of environmental stress. According to Smithsonian Magazine’s coverage of the 2021 paper, they can survive drying out completely, being exposed to high doses of radiation, low or no oxygen, extreme cold, and now — based on the Russian work — being frozen in permafrost for tens of thousands of years. Each of these stresses normally produces immediate damage to cells: drying disrupts membranes, radiation breaks DNA, freezing forms ice crystals that puncture cellular structures. Bdelloids tolerate all of them. Before the 2021 paper, the longest documented bdelloid survival in frozen conditions had been approximately 10 years. The new finding extended that figure by a factor of approximately 2,400, putting the bdelloid rotifer in a small category of multicellular organisms that can be considered, in practical terms, indefinitely revivable.

How the cryptobiosis works

The technical name for the suspended state these rotifers enter is cryptobiosis, from the Greek for “hidden life.” According to ScienceDaily’s summary of the research, cryptobiosis is a state of almost completely arrested metabolism — the organism’s biological processes slow to a level that approaches zero, while the cellular structures remain in a configuration that can resume normal function when conditions improve. The mechanisms by which this is achieved are not fully understood, but a few components are well-characterised. Bdelloid rotifers produce protective sugars, particularly trehalose, that substitute for water in cellular structures and prevent the lipid membranes from collapsing when the cell desiccates or freezes. They also produce specialised proteins that protect membranes and DNA from damage during the cryptobiotic period.

The most striking feature of bdelloid survival is their extraordinary capacity for DNA repair after revival. The DNA in a frozen or desiccated cell accumulates damage over time, regardless of whether the cell is metabolising — natural background radiation alone produces a steady rate of double-strand breaks in DNA. Bdelloid rotifers, on revival, are able to repair extensive DNA damage that would kill most other multicellular organisms. The molecular mechanisms involved are now an active area of research, in part because of their possible relevance to human cryopreservation. If the repair pathways used by bdelloids could be transferred to or simulated in human cells, the prospects for long-term storage of human tissues — for transplantation, for fertility preservation, possibly eventually for whole-organ banking — would be substantially improved.

Where this fits in the broader literature

The 2021 bdelloid result is one of several recent findings that have established multi-millennial cryptobiosis as a real and increasingly well-documented biological phenomenon. According to CNN’s coverage of the study, the previous most-cited example of a multicellular organism revived from ancient ice was a campion plant whose seed tissue, recovered from 32,000-year-old Siberian permafrost in 2012, was successfully regenerated into living plants. In 2023, the same Russian laboratory that produced the 2021 bdelloid paper published a follow-up paper describing the revival of nematode roundworms from 46,000-year-old Siberian permafrost — a new species named Panagrolaimus kolymaensis — extending the known limits of multicellular cryptobiosis by a further 22,000 years.

The cumulative weight of these findings suggests that the permafrost regions of the Earth contain a substantial population of latent organisms that have been waiting, for periods ranging from thousands to potentially hundreds of thousands of years, for the conditions to revive them. Most are microscopic — bacteria, archaea, viruses, microscopic animals — but some, like the rotifers and nematodes, are multicellular. The 2021 paper noted that the longer survival times appear to be possible specifically in permafrost, which combines several preservative conditions: stable low temperature, low oxygen, low radiation exposure, and physical immobilisation that prevents physical damage from movement or expansion.

What this means in 2026

The bdelloid result has both pure-science and applied implications that are continuing to develop. On the pure-science side, the question of why bdelloids and a few other organisms can survive extreme cryptobiosis while most multicellular life cannot has become an active area of research, with potential consequences for understanding the limits of metabolic suspension as a biological strategy. On the applied side, the implications for human cryopreservation, for the storage of biological samples for medical and conservation purposes, and for long-duration space travel are all being actively explored. Whether the mechanisms used by bdelloids can be transferred to human cells is currently unknown, but the existence proof — that some multicellular animals can in fact survive 24,000 years in suspended animation — has shifted the conversation from “is this physically possible?” to “how exactly does it work?”

The permafrost from which the rotifer was recovered is, separately, of growing concern in the context of climate change. As Arctic permafrost thaws under rising temperatures, ancient organisms — including some that may be pathogenic to modern humans, animals, or plants — are being released back into the biosphere. Several 30,000-year-old viruses have been recovered from Siberian permafrost in the past decade. The bdelloid rotifer is benign in this respect; it eats algae and bacteria, not people. But it is part of a broader rediscovery of how much life Earth’s frozen latitudes have been quietly storing, for how long, and what the implications might be when the freezer that has held them stable for 25,000 years begins, finally, to fail.