A Growth Spurt at 1,500 Years Old

Signy Island, which lies 375 miles off Antarctica, has too harsh an environment to support a single tree. Its mountains are girdled instead by banks of moss.

“It’s just like a big, green, spongy expanse,” said Peter Convey, an ecologist at the British Antarctic Survey who has worked on Signy Island for 25 years.

Only the top inch of the moss banks is growing. The lack of sunlight turns the older moss brown, and eventually it becomes permanently frozen. Blankets of permafrost have grown on the island for thousands of years, since the glaciers retreated at the end of the last ice age.

But when Dr. Convey and his colleagues have drilled to the gravel bed and examined the cores they drew up, they have seen something odd.

“All the way through the core, you can see moss shoots,” Dr. Convey said.

Typically, plants break down into organic matter as they become permafrost. Looking at the ancient moss from Signy Island, however, Dr. Convey and his colleagues wondered if, after centuries of frozen darkness, it could grow again.

It was an unlikely idea. Scientists had not managed to revive moss that had been frozen for more than 20 years. Still, Dr. Convey thought it would be interesting to try. “It was just kite-flying,” he said.

The scientists put a core of Signy permafrost under a lamp in a lab in Britain and misted it from time to time with water. After a few weeks, the moss was sending up new green growth.

The deepest layer in which the resuscitated moss grew was three and a half feet below the surface. Based on radiocarbon tests, as they report in the journal Current Biology, the revived moss turned out to be more than 1,500 years old. It’s been in a state of suspended animation, in other words, since the age of King Arthur.

Dr. Convey’s study is one of a series of recent experiments in which scientists have revived organisms — viruses, bacteria, plants, animals — that have been dormant for hundreds, thousands, even millions of years. As more ancient species are revived, some scientists are using them to get glimpses of the past and hints about the future. They’ve labeled this research “resurrection ecology.”

“Who would have thought you could have done this?” asked Lawrence J. Weider, an evolutionary biologist at the University of Oklahoma and a co-author of a resurrection ecology manifesto last year in the journal Trends in Ecology and Evolution. “ ‘Jurassic Park’ was one thing, but we’re talking about real animals, real plants, real organisms that have been suspended for very long lengths of time.”

“Jurassic Park” was based on the notion that extinct animals could be cloned back into existence. That dream still endures among a few scientists. One way would be to find a viable cell in a well-preserved carcass and turn it into a clone. Another might be to insert the extinct creature’s DNA into the cell of a living organism.

Well-preserved remains of extinct animals do turn up from time to time. Last week, for example, North-Eastern Federal University in Siberia hosted a workshop at which Russian scientists reported their dissection of a 43,000-year-old mammoth discovered last year. The mammoth’s remains included trunk muscles; its liver, stomach and intestines; and perhaps even preserved blood.

While Radik Khayrullin, a professor at Ulyanovsk State University in Russia who participated in the mammoth’s dissection, doubts that it retains any viable cells, he is optimistic about finding intact DNA. “It gives great hope” for cloning a mammoth in the distant future, he said by email.

Reviving an organism is a lot easier if it never quite died in the first place. In 2012, Russian researchers reported that they found seeds preserved in 32,000-year-old permafrost. Teasing out some tissue from the seeds, the researchers coaxed it to develop into a flower. Earlier this month, French virologists discovered viruses in 30,000-year-old Siberian permafrost that could still infect amoebae.

In January, Dr. Weider and his colleagues reported reviving eggs from a Minnesota lake that had been buried for about 700 years. They hatched and grew to be adults.

The champions of resurrection ecology are bacteria, which spend much of their time in a state of dormancy.

In 2007, Paul G. Falkowski of Rutgers University and his colleagues reported reviving bacteria trapped in Antarctic ice for eight million years.

The idea that bacteria can survive for so long has inspired a lot of debate. “It gets controversial pretty quickly,” said Dr. Jay Lennon of Indiana University, who was not involved in Dr. Falkowski’s study. Over millions of years, radiation from the environment should damage essential molecules in bacteria cells.

Some studies, however, suggest that this damage may not always be lethal. In 2007, a team of Dutch and Russian researchers found that 500,000-year-old bacteria were still repairing their damaged molecules.

In some cases, organisms may naturally revive after thousands of years without scientists’ help. And it’s possible that they play an important role in their ecosystems.

At the end of each ice age, for example, retreating glaciers leave behind bare ground that develops into new ecosystems. Dr. Convey wonders if moss, and perhaps other species, may survive under the ice for thousands of years and revive when the glaciers melt. “That gives you a very different way of understanding the biodiversity of a region,” he said.

While cloning mammoths remains speculative, reviving dormant organisms is now passing out of its proof-of-concept stage. The research could lead to using revival to help bolster endangered species.

“You could use whatever is stored in ice or sediment as a sort of backup for biodiversity,” said Luisa Orsini of the University of Birmingham in England. But, she said, “one has to be really, really careful introducing something from the past.”