The last time the world was ending, two cataclysms aligned. On one side of the planet, a wayward asteroid dropped like a cartoon anvil, punching through the edge of the Yucatan Peninsula and penetrating deep into Earth’s crust. Around the same time — 66 million years ago — a million cubic kilometers of lava were in the process of bubbling up to the surface, releasing climate-altering carbon dioxide and sulfur into the atmosphere and forming what would become the Deccan Traps of modern-day India.

Rock layers around the world show what happened next. No dinosaurs besides the birds made it out. Neither did the squidlike ammonites that curled like rams’ horns, or marine reptiles including the plesiosaurs (Loch Ness conspiracies notwithstanding). But because of the close timing of the asteroid and the volcanism, geologists have spent years staking out increasingly acrimonious positions on which one deserves the blame for the ensuing carnage. In 2018, The Atlantic called the debate “The Nastiest Feud in Science.”

Until recently, Pincelli Hull kept out of the fray. In her subfield, marine plankton fossils, the impact was considered the obvious sole cause of what’s called the Cretaceous-Paleogene extinction. Instead, she focused on understanding how life bounced back, not on what had almost snuffed it out. “There was a lot to be done without really ruffling any feathers,” said Hull, a paleontologist at Yale University.

That changed over time. First, a paleontologist friend who worked on other time periods argued that of course both the asteroid and volcanism were responsible. “I remember feeling so irritated,” Hull said. “This isn’t your topic of study; how do you have an opinion on this?”

But once she realized that researchers looking at other records of the extinction considered the volcanism theory an open question, not just a minority view, Hull started reaching out to them. Many of these scientists were working on more accurate ways to date when exactly the Deccan Traps erupted, and she wanted to understand their emerging evidence.

Researchers had long known that the Deccan Traps erupted within a few million years of the asteroid strike. But in 2015, a group based at Princeton University significantly narrowed the timing. They found that the lava began squishing out of the earth only 250,000 years before the impact and continued for 500,000 years afterward. Then last year, they estimated that a major pulse of lava erupted just tens of thousands of years before the strike. (At the same time, a Berkeley group argued instead that a big pulse began right after.)

It may seem like an obscure chronological feud, but this one matters: If the Deccan Traps released lava and gas just before the asteroid fell, at least some of the subsequent carnage could be attributed to climate change from the volcanoes. “It made me start to think, ‘OK, this is an open question,’” Hull said.

She didn’t think that for long. Hull went on to lead a global collaboration that, early this year, published a definitive timeline of how the mayhem played out in small ocean fossils. The team tracked changes in global temperature over time. The planet did warm up before the impact, Hull found, but then cooled back down before the asteroid arrived. And while that warming event didn’t seem to correlate to marine extinctions, over 90% of plankton species abruptly vanished after the impact. The study suggests that the major influence of the Deccan Traps was to guide the post-apocalyptic evolution of surviving species — not to drive the extinction itself.