"Pithovirus sibericum" was discovered in a 30,000-year-old sample of Siberian permafrost. The virus was discovered buried below the surface of a late Pleistocene sediment. It was found when riverbank samples collected in 2000 were exposed to amoebae. The amoebas started dying and were found to contain giant viruses. The authors said they got the idea to probe permafrost samples for new viruses after reading about an experiment that revived a similar aged seed two years earlier.