The Pleistocene cold storage
In the remote northeastern corner of Siberia, the permafrost acts as a vast natural freezer. At sites like the Duvanny Yar outcrop, a towering cliff of exposed permafrost on the Kolyma River, layers of silt and ice have remained frozen since the late Pleistocene. This frozen earth contains a perfectly preserved record of ancient life, from mammoth bones to the microscopic. Research in this region, often conducted by scientists from institutions like the Institute of Physicochemical and Biological Problems in Soil Science, focuses on this unique archive.
The process of revival begins with collecting samples from deep within the permafrost, sometimes from depths of 40 meters (about 130 feet). These samples are taken from features like fossilized arctic ground squirrel burrows, which contain ancient plant matter and other biological material. Back in the lab, the frozen soil is carefully thawed, and scientists search for signs of viable organisms. The goal is to understand the mechanisms of long-term preservation and the limits of life's endurance.
One of the most significant discoveries from this region is the revival of a nematode that had been frozen for approximately 46,000 years. Once thawed, these microscopic roundworms began to move, eat, and reproduce. Genetic analysis revealed it to be a previously unknown species, now named Panagrolaimus kolymaensis after the Kolyma River where it was found. This organism survived by entering a state of suspended animation called cryptobiosis, where its metabolic processes effectively stopped. This discovery extended the known limit for nematode survival in cryptobiosis from just 39 years to tens of thousands.
Resurrecting an ancient world
The successful revival of ancient life is not limited to microscopic worms. In 2012, scientists regenerated a whole, fertile plant of the species Silene stenophylla (narrow-leafed campion). They used placental tissue from an immature fruit that had been stored in a squirrel burrow and buried under 38 meters of permafrost for 31,800 years. The regenerated Pleistocene plants grew, flowered, and produced viable seeds.
Researchers isolated and revived giant viruses from the Siberian permafrost. In 2014, a team revived Pithovirus sibericum from a 30,000-year-old sample. This virus, which infects amoebas and is not harmful to humans, is one of the largest ever found, measuring about 1.5 micrometers in length. Its revival demonstrated that viruses can remain infectious after being frozen for geological timescales. These studies on ancient life forms provide a record of past ecosystems and the resilience of biology.