Scientists don’t have an exact date for when life from the sea made its way onto land. But the consensus is it happened sometime between 500 and 450 million years ago. Fungi played a pivotal role in life’s transition from water to solid ground.
“During the period when this organism existed, life was almost entirely restricted to the oceans: nothing more complex than simple mossy and lichen-like plants had yet evolved on the land. But before there could be flowering plants or trees, or the animals that depend on them, the process of rot and soil formation needed to be established.”
“This organism” is called Tortotubus, an ancient fungus. And a fossil of it identified in the 1980s dates back 440 million years ago. We’ll never know if Tortotubus was the first organism to live on land, but it is the oldest fossil of a land organism discovered so far.
The new research tackled several small microfossils from Sweden and Scotland. ‘Small’ doesn’t do these microfossils justice. Take the width of a human hair. These fossils were shorter than that.
Smith’s main goal was to try to reconstruct the method of growth for two different types of fossils. When they were first identified more than 30 years ago, scientists thought they were parts of two different organisms. Smith found that was not the case. The fossils were part of a single organism at different stages of growth. His analysis showed the fossils were part of a root-like system fungi use to grab nutrients from the soil.
Check out the ‘root’ system below.
“What we see in this fossil is complex fungal ‘behaviour’ in some of the earliest terrestrial ecosystems – contributing to soil formation and kick-starting the process of rotting on land,” said Smith.
Cool, but the press release asks an interesting question. If Tortotubus was one of the first land organisms, exactly what was it decomposing? Smith points to bacteria or algae as the likely source for initial decomposing. Plus, this process took time. It’s not like Tortotubus shows up and boom, you have pine trees.
Dating the Tortotubus fossil is a big deal in understanding how life flourished on land. “It fills an important gap in the evolution of life on land,” says Smith.
Tortotubus (and other fungi) paved the way for life on land. Its first meal was likely bacteria or algae. By decomposing them, fungi pumped nitrates back into the soil which provides the nutrients needed for the first plants, which are then eaten by the first land animals.