Seeds preserved for about 2,300 years in ruins of an ancient Greek farming colony in southern Italy have been found to contain intact segments of DNA, the long-chain molecule whose structure encodes the genetic programming of all living things.
Scientists are working to read the DNA's genetic message, the sequence of "letters" in the genetic alphabet that comprise a gene.
If they succeed, it should be possible to compare genes of the ancient crop varieties with those of their modern descendants and the wild ancestors of both. These are still living and presumed to be much like the wild plant that ancient farmers chose to domesticate.
The findings promise to open a new window on ancient agricultural science, giving researchers their first detailed look at the amount of plant breeding, which alters genes, that had taken place by the 4th century B.C.
The seeds, discovered by the thousands by archeologists from the University of Texas, include those of olives, grapes, figs, blackberries, peas, fava beans, chickpeas and alfalfa. They are so well preserved, archeologists said, that some of the grape seeds were inside whole grapes. Intact leaves and stems were also found.
Though older seeds -- ranging up to 44,600 years of age -- with intact DNA have been found in pack rat middens in the American West, those from Italy are believed to be the oldest DNA-bearing seeds from an agricultural village.
"We're very excited about this. The preservation is just fantastic," said Joseph C. Carter, the University of Texas archeologist who directed the excavation. "It's as spectacular in terms of plants as the bog people," he said, referring to the 2,000-year-old human bodies found undecayed in peat bogs of Denmark.
Carter attributed preservation of the seeds to the fact that they were sealed in wet clay under about 10 feet of gravel. Under such conditions, the water lacked oxygen and microbial life that can attack seeds.
Carter said the site was the source of a heavily used spring that ancient Greeks had turned into an open-air religious sanctuary. The seeds, fruits and other plant materials were brought to the site and left by the stream in terra-cotta cups as votive offerings to the spring's supposed divinities, nymphs who exercised the power of water to give life.
Erosion buried some of the offerings before they could decay and protected them from further harm.
The spring sanctuary, at a site called Pantanello, lay outside the ancient Greek colonial city of Metaponto, situated near the instep of the Italian boot.
The colony was established when agricultural productivity declined on Greece's arid and rocky slopes and farmers crossed the Ionian Sea to exploit Italy's rich soils.
Many such colonies prospered, shipping great quantities of food to Greece until the Roman Empire took over the region.
Carter, who has been leading an archeological study of Metaponto for 12 years, said the main village had about 20,000 inhabitants at its peak in the 6th century B.C. In addition, about 10,000 farmers were in outlying areas.
Genetic analysis of the seeds is being done by Franco Rollo and Lorenzo Costantini of Italy's University of Camarino. They are searching for strands of DNA that reside in the nuclei of cells within the seeds.
DNA, short for deoxyribonucleic acid, is a molecule that forms long chains composed of four different kinds of molecular subunits. Like letters of an alphabet, the subunits are linked in sequence to make up a genetic "word."
Hundreds or thousands of genetic "words" chained in sequence are a gene. Each gene contains the blueprint used by the cell to make one kind of protein molecule, typically an enzyme that plays a specific role in the cell's metabolism. Typical cells have thousands of different genes.
When the earliest farmers selected the seed to save for the next season's crop, they naturally took the sweetest berries, the plumpest grains, the fruits not felled by disease.
Without knowing that differences in genes accounted for these variations, the ancient farmers were imposing an artificial form of evolution on the plants, selecting genes that conferred desirable traits.
After countless generations of selection, the seeds would be expected to differ genetically from those of the original wild species. These differences can be measured by comparing the sequences of corresponding "words" in genes isolated from the DNA of the different varieties and counting the number of changes.
In most ancient seeds, decay causes large molecules, such as DNA, to break down into smaller components. Usually the DNA "words" are broken apart, losing any meaningful sequence.
In rare conditions, however, DNA breaks down only slightly, leaving large segments that still contain meaningful sequences thousands of "words" long.
Through genetic engineering there is hope of being able to extract the ancient DNA, make extra copies of it and read a genetic message sealed inside an otherwise dead seed cell for thousands of years.