Once upon a time, about 420 million years ago, during the Early Devonian period, the Earth's surface was dominated by 20-foot-high cylindrical life forms called Prototaxites.
Those of you whose wits survived the weekend intact may have noted that rather ambiguous use of "life form." That's because paleobotanists have argued for more than a century about what Prototaxites actually was. A plant? Mineral? A fungus?
Actually, says the University of Chicago's Kevin Boyce, the wildly inconsistent carbon--12 and carbon-14 levels found in Prototaxites fossiles suggest that it was not photosynthetic, as plants -- which leave consistently-carbonized fossils -- are. So if Protoataxites was large, filament-based and non-photosynthetic, it must have been -- a fungus!
During the Early Devonian, the first ocean-leaving fish had taken their first flops out of the water, and terrestrial land animals were limited to insects and spiders. For a time, then, fungus ruled the earth -- and in some strange way, that's nice to know.
When Fungi Ruled the World [Astrobiology]
