We consider it essential to continue permafrost studies in search of an ancient genetic pool, that of pre-existing life, which hypothetically has long since vanished from the earth's surface, the scientists said in the article. Canadian researchers had earlier regenerated some significantly younger plants from seeds found in burrows. Svetlana Yashina of the Institute of Cell Biophysics of the Russian Academy Of Sciences, who led the regeneration effort, said the revived plant looked very similar to its modern version, which still grows in the same area in northeastern Siberia. The Russian research team recovered the fruit after investigating dozens of fossil burrows hidden in ice deposits on the right bank of the lower Kolyma River in northeastern Siberia. They were firmly cemented together and often totally filled with ice, making any water infiltration impossible - creating a natural freezing chamber fully isolated from the surface. The burrows were located 125ft (38m) below the present surface in layers containing bones of large mammals, such as mammoth, woolly rhinoceros, bison, horse and deer. "The squirrels dug the frozen ground to build their burrows, which are about the size of a soccer ball, putting in hay first and then animal fur for a perfect storage chamber," said Stanislav Gubin, one of the authors of the study, who spent years rummaging through the area for squirrel burrows. "It's a natural cryobank." "If we are lucky, we can find some frozen squirrel tissue," said Mr Gubin. "And this path could lead us all the way