Tiny balls of fungus and feces may disprove the theory that a huge space rock exploded over North America about 12,900 years ago, triggering a thousand-year cold snap, according to a new study.

The ancient temperature drop, called the Younger Dryas, has been well documented in the geologic record, including soil and ice core samples.

The cool-down also coincides with the extinction of mammoths and other Ice Age mammals in North America, and it’s thought to have spurred our hunter-gatherer ancestors in the Middle East to adopt an agricultural lifestyle.