We have barely managed to pierce the surface to about 12 kilometers deep (there are 3,000 kilometers to the center of the Earth): an artificial hole created in Russia, on the Kola Peninsula, in 1962, whose objective was to reach a very deep layer of the earth. Thanks to this we also discover that water remains in a liquid state at such a depth, or that the temperature increases with depth in a greater proportion than previously believed.
What is under the surface of our planet, then, continues to be a mystery, as is its extraordinary ecosystem , as biodiverse as that of the Amazon. For example, almost 70% of all microbes on Earth are under our feet. And organisms underground represent between 15 and 23 billion tons of carbon, hundreds of times more than is contained in all human beings. Not surprisingly, the underground biosphere has between 2 000 and 2 300 million cubic km, almost double the volume of all oceans.
Despite everything, until a few centuries ago there was not even evidence of the existence of life underground.
Johann Weikhard von Valvasor
The first confirmed discovery of underground life was not made until 1689, thanks to explorations of the Karst, a cave-ridden region in Slovenia that were carried out by Baron Johann Weikhard von Valvasor , a nobleman from Trieste. In the historiography Valvasor published, a snake-like creature was described, about a foot in length, leaving the caves when a strong storm fell.
Valvasor christened the creature proteus ( Proteus anguinus ), and it was a salamander that lived underground, although locals who had come across it described it as a dragon offspring. As Will Hunt explains in his book Underground : “In The Origin of Species , Charles Darwin cited the proteus as an example of his theory of adaptive evolution: in its day it was part of a population that inhabited the surface, but it began to spend more time in underground environments, perhaps seeking refuge from predators, and gradually, over the course of millions of years, physical traits beneficial to life underground were transmitted. “
Due to the new ecosystem in which the proteus thrived, it lost its pigment, turning white skin, since it no longer needed protection from ultraviolet rays. His eyes also stopped seeing because he did not need vision in such darkness . It was also capable of going a whole year without feeding.
Hunt explains that, shortly after, the researchers came to identify more examples of creatures that populated the caves, which were divided into:
- Shadow animals : they inhabited the entrance of the caves.
- Twilight Animals : They lived within the reach of diffuse light.
- Animals of the dark zone or trogolobios : they could not inhabit the surface, like the proteo.
“The cave expeditions revealed a dreamlike bestiary of trogolobes: albino catfish, pearl spiders, blind beetles, transparent crabs and eyeless insects.”
Little by little, subsequent investigations revealed the enormous complexity of the underground ecosystem, discovering creatures capable of surviving in environments similar to those of an extraterrestrial planet, without oxygen, without light, under extreme heat and many other characteristics that, until recently, , they were believed incompatible with life.
