Olives and especially olive oil were staples of ancient economies around the Mediterranean Basin: The oil was used for cooking, lighting as well as medicinal and ritual purposes. But so far there has been little agreement among researchers as to where and when people first domesticated the plant. Dating estimates have ranged from more than 6,000 to 4,000 years ago, and multiple areas of the Eastern or Central Mediterranean have been suggested as the location of the first domestication of this important crop.
The uncertainty is largely because the archaeological and genetic evidence on the olive tend to contradict each other, says Dr. Dafna Langgut, an archaeobotanist at Tel Aviv University who led the new study published in the peer-reviewed journal Holocene.
To try to resolve the conundrum, Langgut and colleagues came up with the idea of analyzing fossilized pollen samples from across the Mediterranean to look for significant increases in olive pollen in the flora of each region. Crucially, the researchers looked for spikes in olive pollen that were not accompanied by an increased presence of plants with similar habitat requirements, such as oaks and pistachios, that would have benefited from improved environmental conditions.
This allowed them to identify increases that could only be explained by sustained large-scale human cultivation of the olive. They also correlated the data from the pollen with archaeological finds from each region to map the spread of olive cultivation across the Mediterranean.
Palynology, or the study of ancient pollens, has made great strides in recent years, providing us with information on everything from which crops ancient peoples grew to the crippling effects of environmental disasters that occurred millennia ago.
For this kind of studies, researchers analyze sediment cores extracted from the bottoms of lakes, swamps or other bodies of still water. Plant pollen can travel for dozens of kilometers (miles) carried by winds before being deposited on the surface of a lake and sinking to the bottom. There, if the microscopic grains are quickly covered by silt, they are trapped in an anaerobic environment and may be preserved for thousands of years, allowing experts to reconstruct what the surrounding vegetation looked like in different periods.
In the olive domestication study, the researchers studied 23 pollen records from across the Mediterranean spanning the entire Holocene, the current geological era, which began more than 11,000 years ago.
A small percentage of olive pollen was present across the Mediterranean throughout this era. It was initially fairly stable and attributable to wild olive trees, which are native to the region. But the researchers identified a massive spike of olive pollen – uncorrelated with the growth of vegetation with similar requirements – around 7,000 years ago in the Sea of Galilee and then some 6,500 years ago in the Dead Sea.
To illustrate the magnitude of the spike: 7,300 years ago, just 3.5 percent of the pollen that fell into the Sea of Galilee came from olive trees. By 6,900 years before present it was above 17 percent.This can only mean that large-scale cultivation of olive trees had begun in the vicinity of the lake, within a maximum radius of 50 kilometers (30 miles) of the Sea of Galilee, Langgut explains. This would mark the hilly territory of the Galilee or the Golan Heights, as well as the highlands of Judea and Samaria in the West Bank, as possible wellsprings for the first domesticated olive trees.
Archaeologically, among these regions, the Galilee is particularly rich in finds that point to it as an area where olive consumption and oil production began very early, Langgut notes. In fact, there is evidence of such activity that even predates the time given for domestication by the pollen record by a few centuries.
Archaeologists have found 7,600-year-old crushed olive pits – likely a sign of olive production – in the submerged Neolithic village of Kfar Samir, just off the northern Israeli city of Haifa. Residue analysis of clay vessels found at Ein Zippori, a Neolithic and Chalcolithic site midway between Haifa and the Sea of Galilee, turned up traces of olive oil, dated to between 8,000 and 7,000 years ago.
These earliest samples of olive oil were probably produced using fruits from wild trees, Langgut says. In this phase, farmers had not yet mastered the cultivation of olives, but probably “managed” wild trees by pruning their branches in order to increase yield, she says.
Though wild olives are small and bitter, it is still possible to produce oil from them, and it makes sense that humans would have figured this out before domesticating the plant because of the complexity involved in the process.
“Domesticating a fruit tree is a huge investment: unlike grains, which mature in a few months, it takes about four or five years for an olive tree just to bear fruits, and only then can you start selecting and crossbreeding plants to improve yields or the quality of the olives,” Langgut tells Haaretz. “So they must have known there was something useful there before they embarked on such a project.”
It is not a far-fetched postulation. One might wonder how prehistoric farmers unschooled in genetics knew about artificial selection to improve their crops – but actually the process would likely have been intuitive. You would take seeds for sowing from a nice juicy plant that tastes good, not from a nasty shriveled one that you don’t like. The fact is, archaeologists have deduced that domestication resulted in genetic changes to plants such as wheat and barley from the very start of agriculture.
The start of olive cultivation in the Southern Levant highlights the transition from the Late Neolithic to the Early Chalcolithic, the researcher says. While urbanization was still a long time in coming, farmers were already creating more complex societies, moving beyond mere subsistence to produce staples that could stimulate trade and generate wealth.
“This shows that these societies had the agricultural surplus that allowed them to invest in olive cultivation and enough stability in land rights that people could pass on ownership of the orchards they must have worked on for most of their lives to the next generation,” Langgut surmises.
The recent study goes on to track the spread of olive cultivation outside of the Southern Levant, based on data collected by scientists from eight countries.
Interestingly, pollen records indicate that the second area where the tree was cultivated on a large scale was in Crete and the Aegean islands between 6,000 and 5,500 years ago. It is not clear whether this was the result of a transfer of plants or knowledge from the Southern Levant or an independent event, the study says. However it came to the Aegean islands, the ancient Greeks took a particular liking to the olive. By the 6th century B.C.E., the Athenian legislator Solon had passed laws to protect the plant, sentencing to death anyone convicted of cutting down an olive tree.
After reaching Greece, it took another few good centuries for olive cultivation to spread to the Northern Levant – reaching Syria around 4,800 years ago and Turkey 3,200 years ago. The data shows that it spread to Italy around 3,400 years before present and finally to the Iberian Peninsula some 2,500 years ago, likely travelling with Greek and Phoenician colonizers.
Since then, olive oil has continued to play a central role in Mediterranean cultures: it was given out as a prize at sports competitions, anointed kings and religious leaders, fueled international trade, preserved food and dressed salads.
If the study’s conclusions are confirmed, olives would be the second major crop recently found to have been first domesticated in what is today Israel. Back in 2015, researchers concluded that Neolithic farmers here were the first to cultivate the fava bean, still today a major staple in the Middle Eastern diet.
Scientists are often interested in pinpointing where a certain crop was first domesticated not just because this gives us interesting information about human history and the development of early sedentary societies. Such studies can also have implications for modern farming, because most species, including humans, display their greatest genetic diversity in the area where they first evolved. So locating where human farmers first started tinkering with wild plants can also lead to discovering varieties with greater resilience to parasites, diseases – and, possibly, to climate change.
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