Some 66 million years ago, forests burned to the ground and the oceans acidified after the Chicxulub asteroid hit Earth in the Gulf of Mexico. Around the same time, on the other side of the planet, erupting volcanoes were busy covering much of the Indian subcontinent with lava, forming the Deccan Traps.

One of these forces drove all dinosaurs except for the birds extinct, and opened the evolutionary door for mammals until, eventually, humans arose. In the geologic equivalent of a murder mystery, which calamity actually did the deed is a debate that stretches back decades. Now, it seems, the case may finally be cracked.

The asteroid, according to a team of scientists, was the chief perpetrator, while the volcanism, driving climate change in the background, might have affected life’s recovery in the wake of the impact.

“A lot of people have wanted to argue that both the impact and the volcanism mattered in the extinction,” said Pincelli Hull, a paleontologist and geology professor at Yale University who led the research, which was published Thursday in Science. “And what we’re seeing is, it doesn’t look like it. It’s just the impact.”