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Palm tree (REUTERS)
Palm tree (REUTERS)

A date nearly two millennia in the making

Judean dates grown by researchers is a remarkable model for seed longevity study

Stephen Colbert, of all people. In the years I’ve written this column, I never thought I might start one with the famous late-night talk show host. Yet here we are. This is prompted by a conversation he had a few weeks ago with Laura Linney, star of the hit series Ozark.

Colbert tells Linney that he has a present for her: a loaf of bread that he has baked. But not just any loaf. This is sourdough bread, baked using a blend of flour, water and bacteria known as a “starter". The blend is “alive" — like yogurt cultures are alive — and that’s why it acts as a catalyst for baking the bread. Nothing particularly out of the ordinary so far. But the sourdough starter Colbert used, he tells a visibly moved Linney, is 150 years old.

What can this possibly mean? You create a sourdough starter typically by mixing whole wheat (atta) and water, then letting it stand for some days so that bacteria can settle into it. Then you use a bit of it — as you would yeast — when you want to bake. You replace that in your starter with more flour and water. This is why the stuff is “alive"—because it grows and is regularly fed water and flour. You do the same every time you bake—and pretty soon, 150 years have gone by.

But is this stuff in your fridge actually 150 years old? It traces its origin back that long, sure. There’s an unbroken thread of life in it that goes back that long, sure. But consider you, meaning the human being you are. You owe your existence to your parents, who owe theirs to theirs, and on and on in an unbroken thread of life stretching back to the dawn of human history itself. Now that is a humbling, awe-inspiring thought. But would anyone say you are several million years old? Probably not.

And yet there is still charm and nostalgia, in assigning an age to a sourdough starter. A San Francisco bakery called Boudin’s is “still using the same yeast culture that Isidore Boudin collected 160 years ago", said one breathless report. A Canadian woman uses homegrown sourdough that, another report told me, “at 120 years …is much older" than she herself is.

And there’s a physicist called Seamus Blackley. Last year, from some samples of ancient Egyptian pottery in two Boston museums, he collected some 4,500-year-old yeast. He wrote: “Using careful technique... and sterilized, freshly milled Barley and Einkorn flour, I awoke and fed the sample organisms. Although this sample surely contains contaminants, it also likely contains actual ancient yeast strains." A week later, he had a starter that was “bubbly and ready to try baking with". About the loaf he baked, he said: “The aroma is amazing and new. It’s much sweeter and more rich than the sourdough we are used to."

Now there’s something astonishing. Who would expect to breathe life into organisms that you’d think, after 4,500 years, would in all respects be dead? Also, is this reference to yeast that’s 4,500 years old more or less reasonable than saying your sourdough starter is 150 years old?

But wait: in a similar vein, researchers in Israel have grown dates from 2,000-year-old seeds. Edible and delicious dates.

Some quick history: In the 1st century AD, the occupying Romans faced fierce Jewish resistance in what is modern-day Israel. But the Romans proved too powerful for the Jewish fighters. Their last hold out was the desert fortress of Masada, on a plateau 400 metres above the nearby Dead Sea. By 73 AD, Roman forces had surrounded Masada and were building a massive ramp for a final assault. When they eventually swarmed into Masada, they found everyone dead. These last 1,000 Jewish rebels had preferred suicide to capture by Rome.

Masada was excavated in the 1960s. Today, it is a spectacular, profoundly moving place, and a popular tourist attraction. In 1998, a special someone and I camped below, and hiked up the hill early one morning. From the top, the old Roman encampments are still visible. So is the ramp. Looking at it all, you feel an involuntary frisson of the same sense of doom the rebels must have felt. Masada is so remote that hardly any humans came up here between 73 AD and the excavation. For that reason and because of the dry climate, most artefacts had survived in remarkable shape for nearly 2,000 years.

As for dates: they are among the earliest fruits mankind domesticated. Date palms once grew all over the arid lands that stretch from North Africa in the west, through the Middle East to the Indus Valley in the east. Dates from what’s now Israel — “Judean dates" — were celebrated even two millennia ago for their taste, size and medicinal properties. But pitched warfare destroyed the Judean date plantations. By the 19th century, none remained. But the excavation of Masada in the 1960s turned up several date seeds. In 2005, Dr Sarah Sallon from the Hadassah Hospital in Jerusalem got herself a few of them. She and Dr Elaine Solowey, an expert in agriculture in arid conditions, planted some of them at a kibbutz in southern Israel. Dr Solowey told The New York Times that she wasn’t really expecting them to germinate, but she did use a few “horticultural tricks" anyway: “Warming, careful hydration, a plant hormone and enzymatic fertilizer."

Miraculously, and in just weeks, one had germinated. However, it was a male, and male date palms don’t produce much and need to be mated with female palms. So these seed enthusiasts got themselves 32 more date seeds from Masada and other archaeological sites in the area, including Qumran, where the Dead Sea Scrolls were found in 1946. More miracles: after those 32 were planted, six germinated, and two were female.

Six years after they germinated, one of the female palms produced yet another miracle: flowers. An excited Dr Solowey took some pollen from the male palm and spread it on the flowers of this female. This mating-by-hand was successful: flowers turned into dates. A few months later — and only a few days ago — they were ready to be picked. Dr Sallon called the dates “beautiful", and as The New York Times reported: “The honey-blonde, semi-dry flesh had a fibrous, chewy texture and a subtle sweetness." They were not as sweet as the popular “medjoul" variety, from Morocco, but reminiscent of a less-sweet Iraqi date called “zahidi". All that, from seeds nearly two millennia old. To my mind certainly, and unlike sourdough starters, there is a real sense in which these dates are really that old.

How did the seeds retain some spark of life for that long? In a paper about their findings, Solowey, Sallon and several colleagues write that seed longevity “has been related to the ability to remain in a dry quiescent state [and] low precipitation and very low humidity around the Dead Sea could have contributed (too)." They also speculate that “other extreme environmental conditions" in the area might have helped: “At 415 m below mean sea level, the Dead Sea and its surroundings have the thickest atmosphere on Earth, leading to… a complex haze layer associated with the composition of the Dead Sea water."

We will need plenty more investigation to understand why the seeds survived so long. Still, “the date palm is a remarkable model for seed longevity research", they write. What’s more, the sheer quality of the fruit they produced suggests that “aspects of ancient cultivation (are) of potential relevance to the agronomic improvement of modern dates". History coming to the aid of modern science: what a thought.

As Dr Sallon remarked: “To pollinate and produce these incredible dates is like a beam of light in a dark time."

Quotes from “Origins and insights into the historic Judean date palm based on genetic analysis of germinated ancient seeds and morphometric studies", Sarah Sallon, Elaine Solowey et al, Science Advances, 5 February 2020.

Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. His Twitter handle is @DeathEndsFun

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