Reconstructed maps indicate that the wild forebears of wheat, barley and rye occupied much smaller areas of West Asia 12,000 years ago than researchers had long believed.
This restricted geography reshapes the picture of early agriculture and calls into question archaeological interpretations of where domestication initially began.
Reconstructing ancient maps
Along the Mediterranean fringe of West Asia, the modelled distributions of 65 wild plant species are tightly grouped within a coastal corridor, rather than extending across the inland highlands.
Joe Roe of the University of Copenhagen (UCPH) analysed these projected habitats and found that the ancestors of numerous cereals and legumes were concentrated in the Levant during the late Ice Age.
Beyond this corridor, extensive parts of Anatolia, northern Mesopotamia and the Zagros are excluded from the predicted ranges, despite appearing broad today.
This reduction suggests that frequently used maps of crop origins may have exaggerated the availability of these species, prompting closer scrutiny of how their ancient distributions have been reconstructed.
Coastal refuges for cereal ancestors
The models concentrated numerous edible grasses in a narrow strip along West Asia’s coast.
Within this strip, a refugium – an area in which plants can endure severe climates – may have sheltered crop species during Ice Age pressures.
Cyprus and areas of western Turkey also emerged as notable locations, pointing to several secure pockets for cereal ancestors during colder periods.
Such coastal clustering would have influenced where early communities could establish themselves, as dependable harvests were not distributed evenly.
Cold conditions still influenced decisions
Colder and drier fluctuations did not merely drive these plants southwards, nor did they rapidly expand again as early warming began.
Many species were already able to cope with limited rainfall, meaning that a wetter climate did not necessarily produce additional suitable habitat.
On average, the modelled range of these plants contracted by about 25% as the region moved towards early agriculture.
That restriction may have intensified gathering pressure, since people had fewer dependable stands to revisit each season.
Models based on data
Computer models cannot travel back in time, but they can assess where a plant might have survived under particular climatic conditions.
At UCPH, Roe applied ecological niche modelling to identify the areas in which species could live according to climate, using modern observations as a framework.
Modern occurrence records were obtained from the Global Biodiversity Information Facility (GBIF), allowing the team to begin with actual locations instead of assumptions.
These layers were drawn from a dataset, enabling the researchers to run the models backwards and compare the results with plant remains recovered at excavations.
When evidence is absent
Carbonised seeds from archaeological excavations reveal which plants people used, but seldom show the complete local plant community.
“We know little about the natural background vegetation in these areas, which means that we also don’t know exactly where the Neolithic peoples found the plants that they eventually domesticated,” said Roe.
As this record is incomplete, the new maps provide an independent strand of evidence that does not rely on what happened to survive.
However, a climate-based map cannot identify the particular slopes people favoured; it can only indicate where plants could reasonably have grown.
Where the maps differ
When compared with plant remains from archaeological sites, the models often produced poorer matches than their strong results using modern data.
Limited excavation evidence and uneven modern sampling can each pull predictions away from reality in distinct ways.
Underestimation may occur when a computer model learns too narrowly from the places botanists have surveyed, particularly in regions that are difficult to access.
For the moment, the UCPH team considers its reconstructions to be conservative minimum estimates – a starting point rather than a final map of former ranges.
Testing established assumptions
For decades, many accounts of early farming assumed that wild plants now growing in particular places had occupied the same ranges thousands of years earlier.
A 2011 review portrayed cultivation as a gradual, region-wide development that allowed for many local experiments.
“Based on our new data, it looks like the ancestors of some of the plants most important to modern agriculture (wheat, rye and barley, etc.) did not grow where we expected and also that they were much less widespread than we thought,” Roe said.
Once this assumption is weakened, finding a plant far beyond its modern range can no longer be taken as evidence that people were cultivating it.
Leads for future excavations
Map layers of this kind can guide archaeologists towards valleys and coastal areas that once supported the most abundant stands of wild grain.
If an excavation produces an unexpected species, researchers can now assess whether the climate map indicates suitable habitat nearby.
Improved archaeological databases could make this test more rigorous, as the model performs better when dates and locations are more accurate.
Repeated comparisons between maps and excavations should eventually show where people transported plants and where they occurred naturally.
Wider implications of the research
Modern crop breeding continues to rely on wild relatives because they contain genes linked to drought tolerance and resistance to disease.
Identifying former refuges may also indicate where genetic diversity, meaning the range of genes within a species, remained high.
If crucial ancestors once occupied restricted areas, the loss of those landscapes today could remove possibilities for future crop improvement.
Understanding the ancient distribution further clarifies the effects of domestication by distinguishing human selection from limitations already imposed by climate.
These reconstructions define more narrowly the likely gathering areas for early cereals and provide a climate-based way to check archaeological narratives.
As archaeologists recover additional plant records and investigate more sites, this approach should develop into a useful practical tool rather than remain merely a scientific curiosity.
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