Researchers have successfully grown dates from 2000-year-old seeds recovered from an ancient fortress and caves in the Middle East. The find reveals how ancient farmers were selectively breeding dates from around the region, and it could give clues to how dates can survive for millennia.
“This is an astonishing result,” says Robin Allaby, a geneticist at the University of Warwick who was not part of the research team. “It shines a light on the fact that we don’t understand long-term seed viability.”
To grow the date plants, Sarah Sallon, an ethnobotanist at the Hadassah Medical Center, and colleagues sorted through hundreds of seeds. Some were excavated from Masada, Israel—a mountaintop fortress on a plateau overlooking the Dead Sea that was partly built by the biblical King Herod; others came from caves around the Dead Sea used for storage and living quarters.
The researchers soaked 34 of the most promising specimens in warm water and liquid fertilizer, and then planted them in sterile potting soil. Six seeds germinated and sprouted into seedlings that would eventually become date palms. The successful seeds were all several centimeters long, 30% larger than modern date seeds, suggesting dates that were significantly larger than modern varieties.
To verify that the seeds were ancient—and not more recent specimens deposited amid archaeological artifacts by burrowing animals, for example—the team carbon dated seed shell fragments clinging to the roots after the seeds had successfully sprouted. The seeds were between 2200 and 1800 years old, the team reports today in Science Advances.
Initial genetic analysis of the plants grown from the ancient seeds suggests farmers in the region were growing dates that mixed traits from around the ancient world. The result, according to classical writers like Galen, Strabo, and Herodotus, was a large, sweet, shelf-stable fruit that was a prized treat throughout the Roman world. After the collapse of the Roman empire and the Arab conquest of the region, Judean date farming declined. By the time of the Crusades, around 1000 C.E., the area’s date plantations were no more.
The new plants could be the beginning of a revival—if not of the ancient dates then at least of their best features. Study co-author Frédérique Aberlenc, a biologist at the French National Institute for Sustainable Development, says the group plans to pollinate the female plants in the near future, hopefully allowing them to bear fruit. The idea is to produce fruit with traits that could be used to improve modern varieties, increasing their sweetness and size and resistance to modern pests, for example.
The plants could also provide a window into how date plants manage to protect and preserve their DNA over the course of many centuries. Although an older grass seed was successfully germinated after millennia frozen in Siberian permafrost, these dates are some of the oldest plants ever successfully germinated. That’s because DNA and RNA usually fragment over time into tiny pieces.
That may be enough for ancient DNA analysis, but not to grow a living date palm plant. “For these seeds to germinate, the DNA had to be intact, which goes against a lot of what we know about DNA preservation,” says University of York archaeogeneticist Nathan Wales, who was not involved with the study. “It’s not out of the question that there is some really cool biological system at work that preserves DNA [in dates].”
Sallon says the unusual conditions around the Dead Sea probably helped. “Low altitude, heat, dry conditions—all of those could affect the longevity of the embryo,” she says.
The seeds’ unusual size could have played a role, too. The more genetic material there is, the more is likely to remain whole, Allaby says. “But it’s still extraordinary. … It beggars belief that you would have entire chromosomes intact.”