Before you get too worried, it wasn't the creepy crawly kind of bug, but the microbial kind - methanogenic bacteria, to be specific. And it wasn't recently: it happened during the Great Dying, that great loss during the Permian extinction event, about 252 million years ago.
The great extinctions are all striking and puzzling: how on earth could things go so terribly wrong that 25%, 50% or even (as in the case of the Permian event) 90% of species go extinct? Most folks know now that the event at the end of the Cretaceous was triggered by an asteroid hit. The Permian, as the largest extinction, has held scientists' attention for a long time but the various hypotheses didn't add up. It's true that vast volcanic events (the Siberian Traps) contributed carbon dioxide and dust, but the amounts did not cover the magnitude of the climate changes.
A new study may have solved the puzzle by combining three different kinds of contributions. It began with the observation that the carbon isotope anomalies, which are an indirect measure of changes in the activity of organisms and the climate, didn't take the shape you would expect from an abrupt physical event. A discrete physical disaster would be expected to add a pulse of isotope and tail off.The Permian changes are the opposite; they begin slowly and increase rapidly from there. In fact they change exponentially, and the scientists began looking for the most likely kind of exponential growth, organisms.
Key suspects were the methanogens, which as the name suggest release methane as a product of metabolism. The specific group is the genus Methanosarcina. By sequencing and comparing ribosomal proteins and RNA molecules, they were able to pin down a key evolutionary event to the time of the Great Dying. A simple gene transfer gave them genes that allowed for much more efficient methane production, and they used the large reservoir of carbon in the oceans to grow, flourish, and along the way fart out vast amounts of methane (original article and supplemental info).
The Siberian Traps played a role as well, but not the one originally proposed. Methanogens require the element nickel for the key methane producing enzymes. A pulse of nickel is seen in the Permian sediments, and it came from the outpourings of the Siberian Traps. The same gene transfer happening at a different time might have had far milder consequences. As the press release from MIT says,
The researchers’ case builds upon three independent sets of evidence. First, geochemical evidence shows an exponential (or even faster) increase of carbon dioxide in the oceans at the time of the so-called end-Permian extinction. Second, genetic evidence shows a change in Methanosarcina at that time, allowing it to become a major producer of methane from an accumulation of organic carbon in the water. Finally, sediments show a sudden increase in the amount of nickel deposited at exactly this time.
This great dying in the deep past still has lessons for us today. Who could have guessed that wee microbes could change the climate with their wastes? Yet today humans are also adding methane to the atmosphere through the action of microbes, though not intentionally. Cattle release
vast quantities of methane, a very potent greenhouse gas. Giving up beef is one way to reduce our contribution to climate change.
Bug farts almost killed all of us. Bug farts today are one small piece of caring for our planet.