During the last quarter of a billion years or so, a variety of vertebrate animals have excavated deep, spiral-shaped burrows into the ground. Some of them went several feet straight down in a helix.
Extraterrestrial aliens have been given as an unscientific explanation for a variety of engineering marvels, including the Egyptian pyramids, Easter Island statues and Stonehenge. Little green men ...
During the last quarter of a billion years or so, a variety of vertebrate animals have excavated deep, spiral-shaped burrows into the ground. Some of them went several feet straight down in a helix.
Some results have been hidden because they may be inaccessible to you
Show inaccessible results
Feedback