- A roundworm thawed from 46,000-year-old permafrost recently started having babies.
- Scientists have previously revived ancient bacteria and prehistoric viruses that had been trapped.
Scientists recently revived a microscopic roundworm from 46,000-year-old Siberian permafrost that was so well preserved, it started having babies.
But this isn't the first time "zombie" creatures in ice have been brought back from the dead. Scientists have a long record of resurrecting prehistoric viruses and ancient bacteria frozen in ice.
However, as the climate crisis is melting ancient ice sheets worldwide, experts are growing concerned that prehistoric viruses could pose a risk to humanity.
Prehistoric viruses in permafrost
In March, French professor Jean-Michel Claverie found strains of 48,000-year-old frozen viruses in the Siberian permafrost.
Permafrost is a layer of soil that's frozen all year round and covers about 15% of the planet. The virus, he found, was able to infect single-cell organisms called amoebas.
As Insider previously reported, the chance of it infecting animals and humans was unclear, but the researchers said at the time that permafrost viruses should be considered a public health threat.
Other research has found 28 prehistoric viruses dating back 15,000 years in frozen ice cores. Fifteen of these were unknown to science.
The scientists said the findings could teach us about the effects of the climate crisis on viruses.
"We know very little about viruses and microbes in these extreme environments," said Lonnie Thompson, an author of the study and scientist at the Byrd Polar and Climate Research Center, at the time.
"How do bacteria and viruses respond to climate change? What happens when we go from an ice age to a warm period like we're in now?" he said.
Nematodes — 46,000 years old and 24,000 years old
Nematodes are parasites that usually live inside a host. Recent reports have found that a roundworm, a type of nematode, started making babies after an estimated 46,000 years frozen in permafrost (nematodes reproduce by parthenogenesis, meaning they don't need a partner to spread).
But it's not the first time this has been seen. Previous research has found a rotifer, another type of nematode, was uncovered from Siberian permafrost after an estimated 24,000 years caught in the ice. It was also able to reproduce, and happily ate when fed.
A bacteria that may have been 8 million years old
Bacteria have also been pulled from ancient ice in the past — and in some cases, it's thought they were able to keep thriving after millions of years underground.
Scientists in the 2000s found a bacterium in ice taken from Antarctica. The tiny bug, called Arthrobacter roseus, was able to split and multiply in the lab, even though it was thought to have been taken from 8-million-year-old ice.
We need to know more about ancient frozen bugs
It's important to take the findings listed above with a pinch of salt.
It's very difficult to keep samples pristine when extracting ancient ice, and even more difficult to conclusively date the ice. So it can be challenging to be certain that the bugs are not modern microbes dropped on the ice accidentally by the scientists themselves.
Still, these findings are crucial as we're seeing more of the world's ice disappearing in the changing climate, which could uncover more of these bugs frozen in time.
It's not clear how the human body could react to these bugs, because we may never have encountered them.
"You must remember our immune defense has been developed in close contact with microbiological surroundings," Birgitta Evengård, emeritus microbiology professor from the Umea University, told CNN, Insider previously reported.
"If there is a virus hidden in the permafrost that we have not been in contact with for thousands of years, it might be that our immune defense is not sufficient," she added.
It's not just ancient bugs that have scientists worried. It's possible that bugs we've eradicated or kept under control could resurface from the melting ice.
For instance, scientists were puzzled when one child died and 20 more got sick from anthrax in Russia in 2016, although there hadn't been an outbreak in 70 years. They believe this was caused by a bug that was lurking in permafrost and that had been released in a heat wave.