November 25, 2019
Jacob Aguilar and Emanuel Rodriguez | MediaWise Teen Fact-Checkers

MediaWise Rating: NEEDS CONTEXT

Picture some giant mushroom trees — sounds like something from a science fiction movie, right? Well, an Instagram claim suggests massive mushrooms are more science than science fiction. 

User @sci posted this alleged fact Oct. 16: “Before trees were common, the Earth was covered in giant mushrooms.” With more than 6.8 million followers, this is one of the more popular fact pages on instagram. However, the Instagram post is of a fantasy painting, not actual evidence, which isn’t very convincing.

Do a keyword search

We did a Google search for “was the earth covered in giant mushrooms” and came across this Smithsonian article. The story says that between 350 and 420 million years ago, there were organisms with trunks up to 24 feet high and three feet wide. But were these actual mushrooms?

According to the article, “with the help of a fossil dug up in Saudi Arabia scientists finally figured out what the giant creature was: a fungus.” The organism is known as prototaxites. A Canadian first discovered prototaxites in 1859, and the science community has been debating the actual classification of the species since then. Prototaxites have also been called a lichen, a fungal hybrid.

What are other sources saying?

According to the University of Chicago Magazine — another Google result — ancient plant scientist C. Kevin Boyce tried to settle the debate in 2007. Boyce found that the prototaxites weren’t converting the air’s carbon dioxide into energy, but they were feeding on organic matter in the soil. “Meaning: fungus,” Boyce said in the interview. Despite this discovery, some researchers still refuted the claim. 

Since science claims can be complicated, I decided to head to YouTube to see if there were any videos that were easier to follow. After yet another keyword search, I came across this video from PBS “Eons,” a series on the history of life on Earth. “So far, no one’s come up with a good way to prove whether prototaxites was a pure fungus or a lichen. But either way, it was a giant in its day. And it marks the peak of fungi’s reign over life on land.

Use Wikipedia responsibly

I wanted more information about the prototaxites themselves, so I opened a Wikipedia page about the species. The Wikipedia page, which doesn’t have any warnings at the top of the page to suggest issues with sources, states that “current opinion suggests a fungal placement for the genus,” and the page lists prototaxites in the fungi kingdom. The post also states that it would have been the largest organism of its time.

Our rating

We rate this claim as NEEDS CONTEXT. While there were huge fungus-like organisms on Earth a long time ago, these structures were not literal giant mushrooms, as the Instagram post suggests. 

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Alex Mahadevan is director of MediaWise at the Poynter Institute. He has taught digital media literacy to thousands of middle and high schoolers, and has…
Alex Mahadevan

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