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There is plenty of evidence of animal protein in the diets of ancient hunter-gatherers, but little of plant foods, leading to claims that the so-called meat-based ‘Paleo diet’ best reflects our evolutionary design.
“This fallacy has health implications because a diet lacking in carbohydrates can be particularly unhealthy,” says Emanuela Cristiani, coordinator of the EU-funded HIDDEN FOODS project, supported by the European Research Council.
HIDDEN FOODS has provided the first unambiguous evidence of the processing and consumption of wild cereal-type grains and other edible plants by ancient hunter-gatherers, dating back at least 15 000 years in Italy, and around 11 500 years in the central Balkans.
Unpicking direct and indirect dietary evidence
To better understand the function of the ‘non-flaked’ (unmodified) stone tools found at these sites, HIDDEN FOODS studied the wear on these tools, and examined microscopic residues preserved on their surfaces. “We even selected a range of pebbles and then used them experimentally to process wild plant food,” recalls Cristiani from the Sapienza University of Rome, the project host.
Use-wear and residues preserved on Palaeolithic and Mesolithic stone tools from sites in both Italy and the Balkans confirmed they were used to process plant-based foods.
The project also analysed samples of microscopic food particles trapped in the matrix of the dental calculus (mineralised dental plaque) of hunter-gatherer individuals found at Palaeolithic and Mesolithic sites in Italy and the Balkans.
The evolution of oral microorganisms was also reconstructed using gene sequencing techniques, complemented with data from the study of oral pathologies, enamel defects and dental wear.
Examination of the dental calculus of Palaeolithic individuals from Italy revealed that they were consuming different plants during the end of the last ice age, around 15 000 years ago, including wild cereals, seeds and forest fruits. This data was further supported by the analysis of micro-dental wear and the recovery of plant remains from archaeological sediments.
Dental calculus also indicates that an exchange between Late Mesolithic foragers and the first Neolithic farmers in the southern Balkans may have introduced domesticated species of cereals into the Danube Gorges by 6600 BC. This challenges the established view that Neolithic communities introduced them around 6200 BC, after they had settled.
“If grains were introduced to hunter-gatherers by Neolithic communities deep in the Balkan hinterland before these farmers had settled there, it implies already established social networks,” explains Cristiani.
Tracing migratory routes through the oral microbiome
The project also investigated 44 prehistoric foragers and farmers from Southern Europe to understand how the rise of farming during the Neolithic affected the ancient oral microbiome.
Existing genetic data shows that agriculture was introduced into Europe by migrants from Anatolia. Furthermore, burial practices and biomolecular information in the central Balkans evidence contact between local foragers and farming groups from the mid 7th millennium BC.
One surprising finding was that the range of microorganisms found in the mouths of ancient hunters in the central Balkans was only slightly modified by the arrival of the first Neolithic farmers. The HIDDEN FOODS team found evidence of forager-farmer encounters by reconstructing the full genome of one particular commensal bacterium over time.
Tracing the change in the genome of this species records the spread of Neolithic people through the Balkans and Italy starting from 6500 BC.
“We revealed a Near Eastern variant of the Anaerolineaceae bacterium oral taxon 439, which arrived with the Neolithic farmers, replacing the one living in the mouths of the local forager,” adds Cristiani. “This demonstrated, for the first time, the potential of the oral microbiome to infer migratory routes and interactions in ancient human populations.”
The intimate relationship between diet and evolution
One theory is that the relatively large human brain size in relation to body size was facilitated by the energy provided by glucose from plant carbohydrates. As some plants need to be ground or cooked to unlock this energy, glucose might have driven innovations in stone technology.
If applied to different time periods or other geographic areas, the functional analysis methodology developed by HIDDEN FOODS could continue to reveal more about the health, and health remedies of our ancestors.