The presence of tiny balls of fungus and feces in materials dating over several millennia may disprove the theory that an exploding comet 12,900 years ago ignited a dramatic drop in earth temperature called the Younger Dryas.
The Younger Dryas has been associated with the extinction of mammoths and other Ice Age mammals in North America. But the theory that a comet or asteroid explosion is behind the cooling event is wrong, according to study leader Andrew C. Scott, a paleobotanist at Royal Holloway University in London.
According to National Geographic:
For years proponents of the impact theory have cited tiny spherules of carbon found in a layer of charred sediment throughout North America that dates to the Younger Dryas period. According to the theory, these spherules are organic matter subjected to intense heat after debris from an exploded meteor rained down on Earth, sparking massive wildfires.
The new research, however, detected carbon spherules in soil layers from before, during, and after the Younger Dryas, making it hard to argue that the particles are products of a sudden impact.
"All these particles are of natural biological origin and are not related to either intense wildfires or cosmic impacts," Scott said in an email. "The press and public are very interested in catastrophic explanations. But it is important that when evidence stacks up to show the theory does not work, then it should be abandoned."
Scott said fungal spores have similar microscopic features to nanodiamonds, which some researchers have cited as evidence of a massive comet explosion above the earth’s surface nearly 13,000 years ago.