The discovery of a single grain of wheat has pushed back the date of settlement for the Italian city of Genoa some 700 years, indicating humans started farming the area in the second half of the sixth millennium BCE.
In a paper published in the journal The Holocene, a team of researchers led by Daniele Arobba from Italy’s Museo Archeologico del Finale reveals a detailed palaeobotanical analysis of seeds, pollen and other plant material unearthed from deep beneath the streets.
Establishing the foundation history of Genoa – Italy’s sixth largest city, with a population of around 600,000 – is challenging, because of intense urbanisation during the past century and the tendency for the area, a coastal plain, to periodically flood.
Settlement grew up around the mouth of the Bisagno River – a watercourse that these days flows underground through a purpose-built tunnel stretching from the central railway station to the sea.
All the activity – human and natural – has almost obliterated the environmental record of Genoa’s earliest days.
“The intense degree of urbanisation is one of the major factors in the periodic and dramatic floods that, even recently, have affected the city causing great damage, thus making extremely difficult the study of Holocene environmental change in the plain of Bisagno,” Arobba’s team notes.
For their latest study, however, the researchers were able to make use a singular artefact: the core of a borehole drilled in in 2006 in the Piazza della Vittoria, in the middle of the city.
The bore penetrated to 150 metres beneath the current ground level, well into the bedrock. For Arobba’s team, the important section of the core lay between 16 and 23 metres below ground, which dating techniques indicated had been deposited over a timespan of 1900 years between the end of the seventh and the first of the fifth millennium BCE.
Samples taken from the core contained alternating layers of gravel and clay soils, providing clear evidence of repeated flooding. More revealing, however, was the haul of plant material retrieved, dated and identified, which collectively told a story of botanical change, much of which could not be explained by climate and soil alone but instead strongly indicated human intervention.
In the oldest parts of the core, material derived from the silver fir (Abies alba) was abundant, becoming less so as the centuries rolled on. This finding agreed with previous studies conducted in nearby mountain and coastal areas, which found evidence to suggest that from 4500 BCE the firs thinned out dramatically, replaced by beech trees.
In part, the researchers say, the result can be interpreted as evidence of climate change during the period, with the beeches being favoured by the gradual advent of cooler and more humid conditions.
However, they add, the theory is not sufficient to explain the entire shift.
“Aside from climate change, the simultaneous decline in silver fir seems to be due also to human activity, which in this area is indicated by an increase in agricultural and clearance practices for the management of woodland resources and above all for wood collection,” they write.
Other evidence points to the ancient Bisagno basin featuring plenty of wetlands. The researchers found evidence for two marsh-loving plant species – Hydrocotyle vulgaris and Stratiotes aloides – that have long been extinct in the region. These marshes, the researchers suggest, “were probably grazed on by domestic herbivores”.
The samples also turned up a charred seed from a grape vine, Vitis vinifera, confirming the importance of the plant from the very start of settlement in the region. This, the researchers write, together with previous research by members of the same team, leads to the assumption of a “a special interest of the local population towards this species, to the point where a form of protection aimed at ensuring harvesting of the fruit may have been in place”.
The discovery of two wheat remnants, however, perhaps raised the most excitement among Arobba and colleagues.
One was a spikelet base probably belonging to a wheat variety identified as “Triticum new glume” and represents its earliest detection in the region. The strain is otherwise well known in parts of France, where it first appears around 5500 BCE and vanishes for good about 4000 years later.
The second remnant was a seed from the wheat variety Triticum dicoccum, commonly known as emmer, a grain cultivated widely in early Italy. The seed, and the sediments in which it was found, returned unexpectedly early dates, providing strong evidence that humans were farming the unpredictable lands around the Bisagno River 700 years earlier than thought.