Vintners age the best wines, and it seems the grape vine itself took ages to domesticate.
Genetic analysis suggests grapes were probably first cultivated in southwest Asia during the Neolithic, approximately 8,000 years ago. However, archeological evidence suggests thousands of years passed during which many cultivated grape vines in Europe still produced smaller grapes and lower yields than the thoroughly domesticated grape subspecies, Vitis vinifera vinifera.
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The remnants of grapes grown in southern France under the Roman Empire provide evidence that domestication of the plant proceeded slowly in the region between 50 BC and 500 AD. At 17 sites in two wine producing regions of ancient France, winery waste showed a mixture of wild-type and domesticated grapes. Over centuries, a greater proportion of the grape showed signs of being artificially selected for greater size and productivity. The study was published in PLOS ONE.
The archeologists used preserved grape seeds to determine the vines degree of domestication. Domesticated grapes tend to have more elongated seeds than their wild cousins, Vitis vinifera sylvestris, as well as other shape and flavor differences. Grape growers weren't breeding their grapes for seed shape, though. The shape came as a result of selectively growing vines with larger, more oval fruits, which also had elongated seeds, according to the study. However, the authors noted other unknown pressures also may have driven changes in grapes as they were domesticated.
Greeks first planted grapes in southern France around their colony named Massalia (now Marseille) in approximately 600 BC. The Greeks made a fortune trading their wine with the Celts to the north. However grape cultivation changed dramatically after Romans overtook the region and started making wine from the conquered grapes.
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Retired Roman soldiers settled down in southern France, or Gallia Narbonensis as they called it. Those soil-working soldiers developed a wine export industry that reached as far away as India, where Roman wine containers have been found.
From the first century AD until the collapse of the Roman Empire, grapes' gradual movement towards domestic characteristics may have resulted from grape growers using different propagation techniques to replant and expand their vineyards.
As opposed to starting anew from seed, farmers may have been making greater use of cuttings and grafting to preserve and reproduce a desired vine's growth habits and productivity. Grapes grown from seed don't always maintain their parents' fruit quality, since the dice roll of sexual reproduction alters their genetic composition.
The slow centuries of grape domestication may prove to be a boon for the vines, according to a study published in PNAS. During their long domestication, domesticated grapes were repeatedly fertilized by wild grapes from different regions. This resulted in a diverse set of genes in the domesticated vine. Grapes' DNA diversity could hold genetic resistance to diseases as well as give grapes the biological flexibility to be adapted to the planet's changing climate.
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Climate change is likely to shift suitable grape habitat further north, according to Stanford University researchers. While this may benefit the wines of Oregon, the famed vineyards of California may suffer. Hopefully, the slow domestication of the vine left enough genetic diversity to allow Napa Valley vintners to breed heat tolerant vines.
IMAGE: Wine grape harvest in the southern French wine region of Minervois at the end of the September in Languedoc. (Sheriff of Nothing, Wilkimedia Commons)