Around 252 million years ago, as the Permian Period transitioned into the Triassic, life on Earth waswell there wasnt much of it left, actually.

More than 80% of all species went extinct over the course of this transition, victims of the single worst mass extinction of all time the Great Dying.

And as youd expect, the fossil record of this time is full of traces of death and destruction Collapsed ecosystems, scorche landscapes, and whole branches of the tree of life that suddenly disappear entirely.

But this slice of the fossil record is full of something else, too Something much stranger, and harder to explain Its full of mutants.

The warped, fused, and malformed fossil spores and pollen of mutant plants, specifically found almost worldwide, spanning thousands of years.

But what was it about the Grea Dying that caused a global age of mutant plants?

And could figuring it out help us avoid triggering the next one?

The Great Dying was a pretty terrible time to be a plant.

Massive volcanic eruptions se in motion a runaway greenhouse effect that rapidly warmed the planet by 10 degrees celsius.

For many plants, it may have become simply too hot to photosynthesize efficiently.

They also battled relentless acid rain that ate away at their leaves and other tissues.

And rampant, ferocious globa wildfires were consuming whole forests, too.

But while mass plant death was both obvious and expected under thes conditions, mass plant mutation was not.

See, fossil spores and pollen that had strange shapes and were fused together had bee noticed in layers from the mass extinction as far back as the mid-20th century.

But for decades scientists didnt recognize them as a symptom of sudden, disruptive mutations.

Instead, they originall thought that they were possible adaptations.

Maybe these strange pollen and spores had some advantages under the specific conditions of th extinction event, so they were simply being selected for.

But in the early 2000s researchers began to argue that this malformed plant material, found on multiple continents around the world at the Permian-Triassic transition, wasnt the result of genetic adaptation It was the result of genetic damage.

See, many of the spores and pollen were fused into forms that are known as “tetrads” where four of the spores fail to separate from each other during their development.

And while this can happen occasionally under normal circumstances due to random genetic mutations, these tetrads usually make up no more than about 3% of overall spores and pollen.

But in the Permian-Triassic boundary layers, they're much more common.

At some sites, up to 19% have these malformations a sign of massive genetic stress that would have caused widespread reproductive issues.

This suggests that some plants were surviving the carnage of the Great Dying, for a while a least, but something about the event was causing a period of whats known as “mutagenesis.” Which is a sudden rise in the rate of mutations affecting their DNA, triggered somehow by the environment around them.

And its possible that this affected animals, too.

Its just that plants are much better at preserving a signal of ancient mutagenesis, thanks to all the spores and pollen they produce, giving us a larg enough sample size to detect an uptick in mutation.

But this is all extremely weird see, the Great Dying is best known for its huge amounts of lava and extreme temperature spikes, but these things alone dont always cause mutagenesis on a global scale.

And at the time, there werent any other “ages of mutants” like this known from the fossil record.

So this bizarre situation would need to have been caused by something both very rare and very powerful, such as an intense burst of radiation.

Like, for example, from supernovae explosions or gamma-ray bursts from deep space.

Both of these have bee speculated as being involved in the Great Dying, and they could probably bathe the planet in enough high-energy radiation to cause this kind of mutagenesis.

But there are a couple of problems here For one, we dont currently have any clea evidence that these things were actually involved in the extinction event.

Most scientists now pin the blame entirely on massive volcanic eruptions in Siberia instead.

And secondly, these phenomen would have been too short-lived only exposing species to radiation for years, decades, or centuries.

The mutant plant material spans millennia, so it requires a longer-lasting explanation.

Instead, the researchers who had first argued the plants were mutants suggested that th cause was much closer to home: the collapse of the ozone layer.

See, the ozone layer protects the planet from a lot of the most harmful ultraviolet radiation from th sun that damages DNA and causes mutations.

And if it collapsed around the End-Permian extinction, this would, in theory, have exposed the surface of the world to enough UV radiation to cause global mutagenesis.

Plus, we can even imagine why that radiation shield might have suddenly weakened right around this time Because the ozone layer is extremely vulnerable to the kinds of volatile gasses that were probably spewed into th atmosphere in large quantities by the eruptions.

But even though this works in theory, its hard to actually prove.

Remember, this is essentially a thin layer of gas from 252 million years ago that we're talking about here surprise surprise, it didn't fossilize.

And the lack of direct evidence for either its presence or absence means that researcher only have indirect evidence to go on.

In 2018, for example scientists published a study in which they blasted trees with high levels of UV radiation, mimicking the radiation exposure expected at the end of the Permian if the ozone layer had been depleted.

They saw a five-fold spike in pollen malformations produced by the trees afterwards, matching those seen in the fossil record.

But while a weakened ozone layer is definitely plausible albeit hard to prove it isnt the only suspect behind this age of mutant plants.

Because mutagenesis doesn't have to be a result of radiation exposure certain chemicals can cause it, too.

And we know that the volcanic eruptions of the End-Permian would have brought some o these exact chemicals from deep underground to the surface where they could suddenly wreak havoc on species DNA Like, for example, mercury.

Mercury is the mos DNA-damaging element on earth, and we see spikes of it in many Permian-Triassic boundary layers, possibly scattered there by the eruptions.

This, too, could be a pretty convenient explanation a spike in mercury that caused a spike in mutant plants.

But because of how globally widespread the mutant plant material is, mercury would have had to spike basically everywhere, coming into contac with plants all over the world.

Now, massive volcanic eruption can disperse mercury way across the globe, pretty far from the actual eruptions themselves, it's true.

But a total global dispersal, all at once, is much harder to prove rather than a bunch of localized poisonings in far flung spots.

And even if the mercury really did go global, it's hard to tell if it was the main mutagen or secondary to the potentially depleted ozone layer.

So, neither could be ruled out as the culprit behind the age of mutant plants.

For that wed need a second age of mutant plants where we can tell only one of the tw possible factors was involved.

Now, more recently, researchers have found traces of plant mutagenesis during other extinction events, too Specifically, the mass extinction events o either side of the Great Dying the end-Devonian extinctio before it, and the end-Triassic extinction after it also show sprinklings of mutant spores and pollen.

But seeing as both of these are also thought to have been driven at least in part by massive volcanic eruptions, too, the two potential culprits ozone depletion and mercury cant be ruled out for either.

So while we still dont kno for sure which of these factors was behind the age of mutant plants, the fact that global mutagenesis happened at all changes how we think about mass extinctions in general.

We often get hung-up on the so-called “kill mechanisms” behind those events the things that directly caused widespread sudden death viewing them as the be-all-and-end-all of mass extinctions.

But clearly, at least some species during these extinctions werent directly killed by the chaos of the events.

In fact, some forests might have eve appeared deceptively healthy at times on the surface, at least.

But thanks to the invisible havoc being wreaked on their DNA and their ability to reproduce, they were still doomed in the longer term.

It was mass mortality in the short term and mass reproductive issues in the longer term that, together, made up these mass extinctions.

And theres another lesson in here for us, too Both ozone layer depletion and chemical mutagen pollution are things we have been playing fast and loose with recently.

We narrowly avoided losing muc of the ozone layer in the ‘90s and early 2000s, perhaps coming dangerously close to potentially triggering another global age of mutants.

And there are several site polluted by human activity that exist today where localize mutagenesis has been recorded.

Just because we havent torn down an ecosystem and killed all the species it contains, tha doesnt always mean that weve kept it safe from harm Perhaps 250 million years from now, one of the few remaining signals of human activity on planet Earth will be a sprinkling of weird, warped, and mysterious spores.