Microbiologists at Johns Hopkins University have determined that the asteroid impact that led to the extinction of the dinosaurs triggered a significant global fungal takeover. This conclusion stems from the analysis of 66-million-year-old rock samples from Colorado’s Denver Basin, revealing a second, previously unrecognized ecological crisis.
The end-Cretaceous mass extinction was characterized by both the Chicxulub asteroid impact and the ongoing eruption of the Deccan Traps volcanoes.
“The surge in fungal growth observed in geological samples indicates significant disruptions to ecosystems,” said Johns Hopkins researchers Rosanna Baker and Arturo Casadevall.
“While global spikes in fungal proliferation have been documented during the Permian-Triassic extinction, previous findings for the end-Cretaceous extinction were limited to New Zealand,” they added.
“Our study reevaluated whether fungi proliferated globally post the end-Cretaceous mass extinction event, using samples from North America,” the researchers explained.
Focusing on rock samples collected from various paleontological sites in Colorado’s Denver Basin and North Dakota’s Williston Basin, the team processed and analyzed the material to quantify fungal microfossils, differentiating them from pollen and other plant-derived microfossils.
The results from Colorado indicated a noticeable increase in fungal microfossils compared to plant-based ones in geological layers associated with asteroid impacts.
This marks the first direct confirmation of findings from New Zealand, reinforcing the idea that the Cretaceous period concluded not just with a catastrophic explosion, but also with a global surge in fungi.
Interestingly, the samples revealed signs of fungal uplift spanning roughly 30,000 to 10,000 years before the asteroid impact.
This fluctuation coincided with a notable period of relatively low temperatures at this site, following intense volcanic activity in what is now western India.
“Fossil records indicate that some species became extinct during this timeframe,” Baker noted.
She continued, “The volcanic activity in Asia may have stressed ecosystems worldwide, effectively setting the stage for the impending asteroid impact.”
According to the analysis, early Paleocene samples (about 10,000 years post-asteroid impact) demonstrated that fungi of unknown origins thrived for approximately 2,000 years.
“Fungi are organisms that often exploit environmental hazards to flourish,” Professor Casadevall stated.
Although the North Dakota sample did not exhibit fungal overgrowth at the time of the asteroid impact, researchers suggest that this may result from differences in geological composition compared to the Colorado sample.
Their examination of North Dakota samples reaffirmed previous findings concerning late Cretaceous epochs and early Paleocene epochs, tens of thousands of years before, and roughly 10,000 years after the asteroid event.
“Our results align with the hypothesis that the growth of fungi since the Cretaceous period provided mammals with a significant advantage over reptiles, ultimately enabling them to dominate the planet,” concluded the scientists.
The detailed findings will be published in Proceedings of the National Academy of Sciences.
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Rosanna P. Baker and Arturo Casadevall. 2026. Fungal proliferation before and after the Cretaceous-Paleogene mass extinction event in North America. PNAS 123 (20): e2536899123; doi: 10.1073/pnas.2536899123
Source: www.sci.news
