"Inside Earth?" I exclaimed unbelievingly. "Why, not one of our biologists would agree!"
"Yet it is so," said Odin broodingly. "There are great spaces beneath the crust of the planet, mighty hollows formed by its unequal cooling. It was in one of those spaces beneath this northern part of the globe that life first began. For in those hollows are great masses of imbedded radioactive elements.
"Their radiation, powerfully drenching certain compounds of carbon, hydrogen, phosphorus, sulfur and other elements, which erosion carried down into the subterranean spaces, transformed those unstable compounds into new, complex chemical compounds. They never could have formed on the surface. Those organic compounds finally formed into cells capable of assimilation and reproduction.
"A rapid evolution of those first subterranean living cells into more complex creatures took place. It was rapid because the penetrating radiation in that subterranean space affected the genes of all living things and caused a proliferation of mutants, a constant flood of new forms. Thus, the first living things, the first plants and insects and animals, were born beneath Earth's crust.
"From there, they spread out onto Earth's surface, and soon multiplied vastly. But evolution was more rapid in the subterranean spaces. For the gene-affecting radiation was more powerful there than on the surface. Thus more mutants evolved there. So it was in the subterranean spaces that the first mammals and the first men evolved. Many of those men found their way out to the surface.
"They spread over Earth as wandering, half-animal savages who slowly developed through the ages. But the human beings who remained in the sheltered subterranean world developed far more swiftly. Those people had become intelligent when the men of the surface were still brutes. Those people in the underworld developed a great civilization and deep knowledge of science. They were my people, the Aesir.
"Generations of us lived and died in the great, hollow underground world we called Muspelheim. But then our scientific progress brought catastrophe. One of our scientists, ignoring my warnings, believed that he could enable us to live indefinitely without aging or sickening.
"His theory was that by accelerating the natural disintegration of the radioactive substances in our subterranean world, they would emit a terrific flood of radiation. It would destroy all disease bacteria and deliver us from sickness. It also would constantly renew the cells in our bodies by stimulating their unceasing regeneration."
Odin paused, and a shudder seemed to run through all the Aesir in that great hall, Valhalla.
"Against my orders, he carried out the experiment that brought catastrophe to Muspelheim. The process got beyond his control. All the radioactive matter in our subterranean world blazed up. We Aesir fled up from our underworld to the surface. We found that the mainland yonder, which we called Midgard, was populated by two of the barbarous races of the upper Earth.