Ancient climate maps rewrite the origins of early farming

Reconstructed maps have shown that the wild ancestors of wheat, barley, and rye occupied far narrower territories in West Asia 12,000 years ago than scholars long assumed.

That compressed geography redraws the landscape of early farming and challenges how archaeologists interpret where domestication first took root.

Building the old maps

Across West Asia’s Mediterranean edge, the modeled ranges of 65 wild plant species cluster tightly along a coastal corridor rather than spreading across the interior uplands.

Analyzing those projected habitats, Joe Roe at the University of Copenhagen (UCPH) demonstrated that many cereal and legume ancestors were concentrated in the Levant during the late Ice Age.

Outside that corridor, large stretches of Anatolia, northern Mesopotamia, and the Zagros fall away from the predicted ranges that today seem expansive.

Such contraction means long-used maps of crop origins may have overstated how widely these species were available, setting the stage for a closer look at how those ancient distributions were reconstructed.

Coastal refuges emerge

Along West Asia’s seaward edge, the models piled many edible grasses into a thin coastal strip.

In that strip, a refugium – a place where plants can survive harsh climates – may have buffered crops during Ice Age stress.

Cyprus and parts of western Turkey also stood out, suggesting several safe pockets for cereal ancestors in colder times.

That coastal concentration would have shaped where early groups could settle, because reliable harvests were not evenly spread.

Cold still shaped choices

Colder, drier swings did not simply push these plants south, and they did not surge back with early warming.

Instead, many species already handled sparse rainfall, so a wetter climate did not automatically create more suitable habitat.

Across those plants, the average modeled range shrank about 25% as the region approached early agriculture.

That squeeze would have concentrated gathering pressure, because people had fewer reliable stands to return to each season.

Models built from data

Computer models cannot time-travel, but they can test where a plant could live under a given climate.

At UCPH, Roe used ecological niche modeling to map where species could live based on climate, drawing on modern observations as a template.

Modern occurrence points came from the Global Biodiversity Information Facility (GBIF), letting the team start with real locations rather than guesses.

Those layers came from a dataset and let the team roll models backward, then compare output with plant remains at digs.

When evidence goes missing

Charred seeds at excavations show what people handled, but they rarely reveal the full plant community nearby.

“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.

Because that record is patchy, the new maps add an independent line of evidence that does not depend on what survived.

Still, a map based on climate cannot show which hillsides people preferred, only where plants could plausibly grow.

Where maps disagree

Comparisons with plant remains from archaeological sites often showed weaker matches than the model’s strong performance on modern data.

Sparse excavation records and uneven modern sampling can both tug predictions away from reality in different directions.

Underestimates can happen when a computer learns too narrowly from where botanists have looked, especially in hard-to-reach regions.

For now, the UCPH team views their reconstructions as conservative minimum estimates – a baseline rather than a definitive map of past ranges.

Old assumptions get tested

For decades, many explanations of early farming assumed that the wild plants growing today occupied the same ranges thousands of years ago.

A 2011 review described cultivation as gradual and region-wide, leaving room 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.

With that shortcut weakened, a plant found far from its modern range stopped being evidence that people were cultivating it.

Clues for future digs

Map layers like these can direct archaeologists toward valleys and coasts that once had the richest wild grain stands.

When a site yields an unexpected species, researchers can now check whether the climate map predicts a nearby habitat.

Better archaeological databases could tighten the test, because the model improves when dates and locations become more precise.

Over time, repeated checks between maps and digs should reveal where people carried plants, and where nature placed them.

Broader implications of the research

Modern breeding still draws on wild relatives, because they carry genes for drought tolerance and disease resistance.

Pinpointing past refuges also hints where genetic diversity, the variety of genes within a species, may have stayed high.

If key ancestors once lived in small areas, losing those landscapes today could erase options for future crop improvement.

Knowing the ancient distribution also clarifies what domestication changed, separating human selection from the limits that climate already imposed.

These reconstructions narrow the likely gathering zones for early cereals and add a climate-based check on archaeological stories.

As archaeologists uncover more plant records and examine additional sites, the method should evolve into a practical tool rather than remain a scientific curiosity.

The study is published in the journal Open Quaternary.

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