Think your 15-year-old ficus tree is ancient? According to The Washington Post, researchers have found what might be the oldest-known land organism—an ancient fungus that could be 440 million years old. Researchers discovered pieces of the tiny, thread-like fungi called Tortotubus in fossilized rock. Each one is shorter than a human hair is wide. However, their miniscule nature belies their true importance. 

The finding, which was revealed in a recent study published in the Botanical Journal of the Linnean Society, offers new insight into Earth’s early fossil record, and into how our planet became the lush, green place it is today. Since Tortotubus  existed during a time in which Earth was transforming from a sea-filled planet into one with land (and land plants), the fungus likely played an important part in preparing the ground for colonization by other organisms, says Dr. Martin Smith, who conducted the research while at the University of Cambridge’s Department of Earth Sciences and now works at Durham University.

Since fungi have mycelium, which are filaments that extract and transport nutrients from the ground, Tortotubus  “ ... would have helped to stabilize soil, they would have helped to move nutrients around, and to transform those nutrients into a form that is accessible to what would eventually become the earliest land plants, and ultimately the earliest land animals,” Smith explained to IFLScience.

While Tortotubus is the oldest-known land organism, it likely wasn't the first, Newsweek reports. Plant-like spores came tens of millions of years before them, and there's even research suggesting that "microbial crusts" formed more than 100 million years earlier during the Precambrian Era. 

 [h/t The Washington Post]