Writing about science is a tightrope walk. You can practice as much as you want, and during preparation you have lifelines in the form of editors and experts you can phone for answers, but in the end it’s just you out there, trying to toe the line suspended between attention and accuracy. Eyes are on you for any misstep, and even a perfect performance comes with an often-unrecognized risk. That’s because science is a process, not a static collection of facts, and in an instant a new discovery or study can make the rope vanish beneath your feet.
A few months back my Phenomena neighbor Robert Krulwich wrote a post titled “The Fantastically Strange Origin of Most Coal on Earth.” It’s a lovely little story, all about how a delay in microbial evolution allowed the vast forests of over 300-million-years-ago to become compressed into the fossil fuels we rely on. “[W]hen those trees died,” Krulwich writes, “the bacteria, fungi, and other microbes that today would have chewed the dead wood into smaller and smaller bits were missing.”
Paleontologists call this the “lag hypothesis.” And it turns out to be wrong.
Back in March, about two months after Krulwich’s post went up, Stanford University geoscientist Matthew Nelsen and colleagues published a paper in PNAS that set the record straight in the very title: “Delayed fungal evolution did not cause the Paleozoic peak in coal production.” What seemed like a neatly-solved question once again turned into a conundrum.
The key to the puzzle is lignin. This is the sturdy stuff that often gives bark, wood, and even the cell walls of many plants their resilience. And in the thick forests of the Carboniferous, over 300 million years ago, lignin was supposed to be the stuff that microoganisms and fungi just couldn’t chew up. With no decomposers up to the task, the enormous trees of the time and other plant material piled up for burial rather than breaking down.
Yet new discoveries have totally reversed what paleontologists expected of those primordial forests. The bulk of the great Carboniferous swamp biomass consisted of trees called lycopsids, Nelsen and colleagues write, but up to 80% of these plants was made of a kind of bark that has no modern equivalent. In other words, these trees did not rely on lignin to support themselves.
And it gets better. “Carboniferous fossils provide direct evidence that fungi were taxonomically and ecologically diverse,” Nelsen and coauthors point out, and paleontologists have already uncovered Carboniferous wood “infiltrated with fungi and possessing damage consistent with white rot decay or other forms of fungal degradation of lignified tissue.”
The lag was in our understanding, not fungus evolution. Lignin wasn’t as critical as had been thought, and, even then, fungus and other decomposers were still capable of busting up the material. And this makes the vast coal seams created by these forests even stranger. If not a reprieve from becoming compost, what could have made such a glut of fossil fuels? The answer, Nelsen and colleagues suggest, probably has to do more with how those forests became buried.
Carboniferous forests were incredibly productive, throwing up plant life faster than the dead plants could decay, creating a literal logjam of organic material in the hot, humid habitats. This happened in a glacial world, but as those stores of ice melted the thick tangles of slowly-decaying plants were buried and eventually compacted down. The Earth’s crust had its own role to play, too. The sweltering forests grew in areas of the planet that were shunted beneath the surface as Pangaea coalesced, the movement of the Earth providing the geological forces necessary to create the fuel for the Industrial Revolution and the climate change we’ve brought upon ourselves.
Reference:
Nelsen, M., DiMichele, W., Peters, S., Boyce, C. 2016. Delayed fungal evolution did not cause the Paleozoic peak in coal production. PNAS. doi: 10.1073/pnas.1517943113
Go Further
Animals
- This ‘saber-toothed’ salmon wasn’t quite what we thoughtThis ‘saber-toothed’ salmon wasn’t quite what we thought
- Why this rhino-zebra friendship makes perfect senseWhy this rhino-zebra friendship makes perfect sense
- When did bioluminescence evolve? It’s older than we thought.When did bioluminescence evolve? It’s older than we thought.
- Soy, skim … spider. Are any of these technically milk?Soy, skim … spider. Are any of these technically milk?
- This pristine piece of the Amazon shows nature’s resilienceThis pristine piece of the Amazon shows nature’s resilience
Environment
- This pristine piece of the Amazon shows nature’s resilienceThis pristine piece of the Amazon shows nature’s resilience
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
History & Culture
- Meet the original members of the tortured poets departmentMeet the original members of the tortured poets department
- Séances at the White House? Why these first ladies turned to the occultSéances at the White House? Why these first ladies turned to the occult
- Gambling is everywhere now. When is that a problem?Gambling is everywhere now. When is that a problem?
- Beauty is pain—at least it was in 17th-century SpainBeauty is pain—at least it was in 17th-century Spain
- The real spies who inspired ‘The Ministry of Ungentlemanly Warfare’The real spies who inspired ‘The Ministry of Ungentlemanly Warfare’
Science
- Here's how astronomers found one of the rarest phenomenons in spaceHere's how astronomers found one of the rarest phenomenons in space
- Not an extrovert or introvert? There’s a word for that.Not an extrovert or introvert? There’s a word for that.
- NASA has a plan to clean up space junk—but is going green enough?NASA has a plan to clean up space junk—but is going green enough?
- Soy, skim … spider. Are any of these technically milk?Soy, skim … spider. Are any of these technically milk?
Travel
- What it's like to hike the Camino del Mayab in MexicoWhat it's like to hike the Camino del Mayab in Mexico
- Is this small English town Yorkshire's culinary capital?Is this small English town Yorkshire's culinary capital?
- This chef is taking Indian cuisine in a bold new directionThis chef is taking Indian cuisine in a bold new direction