(CNN)Scientists have grown six date palm plants from 2,000-year-old seeds found in ancient palaces and settlements in the Judean Desert in southern Israel.
Date plants grown from 2,000-year-old seeds
The seeds are thought to be the oldest ever grown naturally and shed light on one of the world's earliest tree crops.
According to historical documents, the Kingdom of Judea was renowned for its large, sweet dates that could be stored and exported throughout the Roman Empire.
"They were incredibly sought after. They were given as a gift to the Roman Emperor on his birthday, and many ancient historians and geographers wrote about them," said Sarah Sallon, director of the Louis L. Borick Natural Medicine Research Center, who led the study published Wednesday in the journal Science Advances.
However, the last remains of the region's date plantations were wiped out by the 19th century, and this particular variety is now extinct, Sallon said.
To grow the trees, the researchers soaked 33 ancient seeds found by archaeologists in water for 24 hours and then treated them with hormones and organic fertilizer to encourage rooting.
After discarding one seed that was damaged, they planted the rest in potting soil and used desalinated water enriched with iron and fertilizer to water them.
Eventually, six of the seeds sprouted: "Some of them took a few weeks but others took months," said Sallon, who gave the plants names.
Three of the plants have now been replanted outside the greenhouse. Sallon is hopeful that Hannah, a female date tree, will flower this year and the plant could be pollinated by Methuselah -- a tree the team grew from a 1,900-year-old Judean date palm seed in 2008.
However, Sallon says it's impossible to know if the female tree will bear fruit.
"We hope that the pollen and the flower are compatible and that she will respond to it. We'll come back to you if she starts producing dates."
These date trees aren't the oldest plants to be brought back to life. Scientists in Russia have grown plants from fruit stored away by squirrels in permafrost 30,000 years ago. However, the seeds from the Silene stenophylla plant weren't grown naturally. Instead, scientists propagated them in lab dishes from fruit tissue.
The authors said that low rain and humidity around the Dead Sea, a salt lake near where the seeds were found, could be one reason for their durability.
They also suggested it could connected to the extreme conditions in the area. At 415 meters below sea level, the Dead Sea and its surroundings have the thickest atmosphere on Earth and a layer of haze linked to the chemical composition of the water.
"Nature can preserve DNA inside seeds for thousands of years that could then wake up under the right circumstances," Sallon explained.
"But these trees are also a cautionary tale in a changing climate. The original plantations were wiped out; there's no trees left," she said.
The ancient seeds were significantly longer and wider than both modern date varieties and wild date palms, which suggested the seeds had been cultivated, perhaps for their large fruit size. Typically, larger seeds produce larger fruit.
Genetic information gathered from the seeds showed the plants were blends of different tree varieties, perhaps selected to produce bigger fruit, providing insight into how the dates would have been grown 2,000 years ago.
This corroborates "the historical descriptions of the large fruits grown in this region," and that local farmers at that time used "highly sophisticated" methods in their date plantations, the authors wrote.
The seeds were found between 1963 and 1991 at six archeological sites. This includes Masada, an ancient fortress and palace built by King Herod the Great, and Qumran, an ancient settlement at the northern end of the Red Sea that's associated with the discovery of the Dead Sea Scrolls.