Understanding the Science Behind Ancient Wine

Using hi-tech tools to learn about the winemaking methods of the past

fermenting wine
Photo illustration by Jeff Quinn.

For hundreds of years, questions about the origins of winemaking were answered with a pleasingly colorful mix of educated guesses, myths, and snippets of epic poetry—because after all, what other options did we have?

But new research has provided astonishing details about the distant past, from the spices that Egyptian pharaohs and ancient kings used to flavor wine, to the parents of Cabernet Sauvignon and many other grapes, to evidence of winemaking or grape harvesting from 6,000, 8,000, or even 20,000 years ago. There’s been a flood of new information, prompting curiosity about the limits of this new research.

Patrick McGovern, a pioneer in the field of ancient wine and spirits research, believes we are “just at the beginning of an ever-intensifying endeavor, as genetic, chemical, botanical, and other scientific techniques become increasingly more accurate, sensitive, and wide-ranging.” So how, exactly, are scientists able to coax detailed evidence from artifacts that are thousands of years old?

The First Foundation: Atomic Energy Research

This field, sometimes called archaeobiology, has progressed rapidly in recent decades, with indirect help from two very different types of research. In the 1940s and 1950s, huge amounts of money poured into atomic energy, yielding not just reactors and bombs, but also unbelievably precise tools for measurement and analysis. For example, McGovern and others can probe ancient samples with nuclear magnetic resonance spectroscopy to identify the structure and chemical properties of specific molecules and even atoms. It works because the protons inside the nucleus of a cell have very slightly different magnetic charges. Or as one Bryn Mawr researcher put it, think of the nuclei “as tiny, atomic, bar magnets” that point in different directions. Today, scientists can identify and analyze details about those tiny magnets.

Instrumental neutron activation analysis (INAA) is another tool. McGovern explains that researchers can take tiny pieces of ancient pottery, put them in nuclear reactors, and subject them to high-energy neutron beams. Various chemical elements in the sample become radioactive, so their gamma ray emission can be measured, resulting in a kind of “fingerprint” that can be matched to natural clay beds. So, it is now possible to determine whether an ancient wine amphora that was found in Greece was originally made from clay in a specific region of the Holy Land, where the business of amphora-making flourished 2,000 or 3,000 years ago.

There’s also gas chromatography-mass spectrometry. “[A mass spectrometer] weighs molecules, sorts them according to weight, then counts the number of each weight,” explains Harold Wiley, a pioneer who helped expand use of the tool in the 1940s. The molecular weight can reveal the exact compound present. Mass spectrometry also helps modern wine research. In 2008, Australian scientists identified the precise compound that gives Syrah its peppery taste. It’s called rotundone, a term now widely recognized in the wine community. In grapes, rotundone is only present in the skin. Some people can detect rotundone concentrations as low as two parts per billion in red wine (that’s roughly the equivalent of one drop in a 9,000-gallon liquid tanker truck).

The Beverage Alcohol Laboratory of the US Department of the Treasury also uses some of these high-tech tools to screen products for contaminants and unauthorized additives, as well as handling mislabeling and fraud investigations, smuggling and counterfeiting, and pre-import testing of foreign wines. Government lab spec sheets reveal that alcohol has a molar or atomic weight of 46.0684.

The Second Foundation: Genomics

Genomics is the second foundation of ancient wine research. Again, scientists benefited from the vast amounts of federal and private money that supported the Human Genome Project in the 1990s and early 2000s. Only a few decades ago, labs had to use a slow, labor-intensive process to isolate and analyze DNA (which looks a bit like clear taffy). Now, the process has been automated, greatly reducing costs and the time it takes to get results. These days, scientists such as McGovern, José Vouillamoz (co-author of Wine Grapes), and other experts can examine not just the DNA of living grapevines, but fragments of DNA extracted from specimens that are thousands of years old. Just as ancient pottery contains hidden clues, grape DNA (and even yeast DNA) provides a kind of ledger of past mutations, and a way to isolate specific genes that drive flavor and aroma production, growth, and even resistance to disease.

For example, more than 2,000 years ago, Egyptian, Greek, and Roman winemakers used sulfur, in the form of smoke, to disinfect clay amphora. Spanish researchers found that about 50% of wine yeast strains contain a genetic mutation that makes them better able to resist sulfur. Wild yeast strains don’t have that mutation. Thus, we can assume that early winemakers influenced yeast evolution. Many papers in the broad field of archaeobiology share a similar theme: humans have influenced grapes and wine for thousands of years. The flavors and aromas that are so beguiling to us now didn’t happen by accident, but rather through a long process of selection.

Challenges & Questions

Archaeologists, botanists, and other wine science historians have a dazzling array of new tools at their disposal, but there are still many challenges and questions. Consider the recent paper McGovern co-authored, about evidence for 8,000-year-old winemaking that took place near Tbilisi, Georgia. The team found tartaric acid and other wine-related chemicals embedded in pottery, some of which was surprisingly large (nearly three feet tall, with a 300-liter capacity) and decorated with what appears to be a grape motif. Yet despite evidence of fairly large-scale winemaking, there were no masses of grape pip or stem remains, which ruled out DNA analysis that might have provided clues about the grape species used at that early stage. Nor was there evidence of a stone depression for wine-treading. The researchers speculate that the grapes could have been harvested and pressed at a site outside of the primitive village. Some of the pottery didn’t show evidence of wine, either—it might have held oils, grains, or other food.

By themselves, says McGovern, the high-tech tools aren’t enough. “To have the researchers to apply the instrumentation and properly interpret the data in an archaeological context is very much needed. This supremely interdisciplinary field has not yet been incorporated into traditional academic disciplines, at least here in the US.”

But with robust evidence, the science can recreate entire meals. In 1999, McGovern led a team that used archaeobiology to identify the food and drink served during King Midas’ funeral feast, held in about 700 BC in what is now central Turkey. Analysis of bowls and jugs showed remains of the same mixture of grape wine, barley beer, and honey mead, and 18 food jars revealed the menu: a stew of goat or sheep meat, perhaps marinated with honey, wine, and olive oil, then cooked with lentils and spices.

DNA testing presents other challenges. Ancient samples can be contaminated or damaged, and even seemingly clear results can mask ambiguities. Last October, researchers from the University of California at Davis used genomics to suggest that that wild and cultivated grape varieties began to diverge 22,000 years ago, far earlier than any archaeological evidence of domestication.

Yongfeng Zhou and other scientists showed intriguing evidence that wine grapes, table grapes, and wild grapes spilt into different genetic pools, as shown in the following diagram. The researchers believe this could be evidence that early hunter/gatherer humans influenced grape evolution long before the formal domestication and winemaking that McGovern documented to around 8,000 years ago in Georgia.

The study has some limitations. First, a modest sample size, comparable to generalizing about the entire US wine market by sampling only San Francisco wine bars. Even more important is how the team arrived at the 22,000-year estimate of early domestication. This type of research measures time by what is often called the molecular clock—records of mutations that occur in DNA. The basic theory suggests that mutations occur at a relatively fixed rate, like a clock ticking, but some scientists say that is too simplistic. Flaws in the theory could mean the supposed 22,000-year divergence between wild and cultivated grapes happened at a different time. This is a fascinating but inconclusive study. We will probably know far more about molecular clocks—and the entire grape genome—in 10 or 20 years.

Still, the possibilities are intriguing. A 2013 paper from Chinese researchers and members of Cornell University peered far deeper into the past. They suggest that the modern Vitis grape species diverged from earlier relatives about 28 million years ago, that Eurasian grapes diverged from North American ones about 11 million years ago, and finally, that European species diverged from Asian ones about 6 million years ago.

Genomics are also starting to reveal the origins of some wine aromas and flavors, such as Muscat. A 2010 study by Italian and French researchers  found a specific area of the genome that directs production of the distinctive sweet and floral character. Not only that, the analysis suggested that the VvDXS gene sequence may have evolved in a group of Muscat vines “due to specific and intense breeding practices during grapevine domestication and post-domestication.”

The focus on the distant past may also yield modern benefits, because the team was able to identify other mutations that produce “muscat-like aromatic mutants from neutral clones of Chardonnay, Chasselas, and Savagnin rosé.” It could be possible to screen young grapevines and identify the ones with the best flavor potential.

Looking Ahead

This brings us back to a key point about all the sensational new grape research: we’re in the very early stages of unraveling this story. Some long-cherished myths about the origins of wine will be confirmed, while others will be discarded. While there has been a resurgence of interest in Georgia over the last decade, surrounding areas could hold important clues about the origins of winemaking, too. Many potential sites in Armenia, Azerbaijan, and Eastern Turkey have not been fully explored, or even discovered. “Obtaining funding for new excavations in [these countries], as well as Lebanon, Iran, [and others], is a huge challenge,” McGovern remarked.

Recent discoveries in China of ancient fermented beverages also raise an intriguing question: given the long history of trade along the Silk Road, could countries such as Afghanistan, Uzbekistan, and Kazakhstan contain evidence of early domestication? “Yes,” McGovern says. “Central Asia is crucial to understanding why the domestication of plants and making fermented beverages on a large(r) scale emerged about the same time in Western and East Asia.”

McGovern also believes that ancient wine and beverage research may have medical value. Notes one of his papers, “Biomolecular archaeological analyses of ancient organics, especially plants dissolved or decocted as fermented beverages, have begun to reveal the preliterate histories of traditional pharmacopeias, which often date back thousands of years earlier than ancient textual, ethnohistorical, and ethnological evidence. In this new approach to drug discovery, two case studies from ancient Egypt and China illustrate how ancient medicines can be reconstructed from chemical and archaeological data and their active compounds delimited for testing their anticancer and other medicinal effects.”

The Nobel Prize-winning physicist Richard Feynman suggested in the 1960s that every glass of wine holds magnificent scientific tales. “The whole universe is in a glass of wine,” Feynman remarked. Looking closely, we find “there are the things of physics: the twisting liquid, the reflections in the glass, and our imagination adds the atoms. What strange array of chemicals are in wine? How did they come to be? There are the ferments, the enzymes, the substrates, and products. And there in wine is found the great generalization: all life is fermentation… If our small minds, for some convenience, divide this glass of wine, this universe, into parts—the physics, biology, geology, astronomy, psychology, and all—remember that nature doesn’t know it.”

We’ve learned a great deal since then, but Feynman ended with advice that still holds today. This new science is fascinating, but we shouldn’t forget what wine is for. “Let it give us one final pleasure more: drink it up and forget about it all,” Feynman said.

-Written by Kevin Begos

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