In 2015, a team of scientists, accompanied by yaks and yak wranglers, travelled nearly four miles above sea level to the Guliya Glacier in northwest Tibet to look back in time. They bore more than 1,000 feet into the ice to recover a sample core with 41,000 years of history. Scientists have detected ancient viruses discovered in 40000-year-old Himalayan Glacier samples, albeit they point out that these species do not infect people. Their findings, which trace how viruses respond to temperature changes, were published in Nature Geoscience last week.

“Our findings depict a novel perspective on how life, in the form of viruses, has responded to climatic changes over tens of thousands of years,” the authors wrote in the Conversation.

The researchers rebuilt the genomes of viruses frozen in the Guliya Glacier. The microbes lived in nine unique time periods, including three cold-to-warm temperature changes. According to Ohio State University, around three-quarters of ancient viruses discovered in the 40000-year-old Himalayan Glacier are new species. The study gathered 50 times more viral data from glaciers than had ever been collected before.

“These kinds of data are just so foundational for asking any questions about what Earth looked like previously,” study co-author Matthew Sullivan, a microbiologist at Ohio State, tells Lauren Leffer of Popular Science. “Collecting these 1,700 genomes now empowers scientists doing glacial work elsewhere to unlock the stories in these other ice freezers, so to speak.”

The scientists revealed that the viral populations preserved in the ice differed significantly depending on the climate conditions of the time period they came from. The most identifiable viral community emerged some 11,500 years ago when the frigid Last Glacial Stage gave way to the warmer Holocene.

This research indicates that major cold and warm climate periods affected viruses. The scientists believe that temperature variations on the glacier and the entrance of viruses from other places due to altered wind patterns impacted the local viral ecosystems through selection pressures. Approximately one-quarter of the viruses found shared characteristics with known species from other parts of the world, implying that they had travelled to Guliya from areas such as the Middle East and the Arctic.

“Before this work, how viruses linked to large-scale changes in the Earth’s climate had remained largely uninvestigated,” lead scientist Zhi-Ping Zhong, a microbiologist at Ohio State, says in the announcement. “This indicates the potential connection between viruses and climate change.”

Researchers discovered that viruses can change their hosts’ “fitness” for the environment, affecting their capacity to deal with extreme glacial conditions.

The experts say additional research is needed before drawing any definitive conclusions—but they’re running out of time to gather more glacial cores before rising temperatures caused by humans make it impossible.

Also Read: Snow Disappearing From OM Parvat Shows The Extreme Effects Of Climate Change