Morocco Hunter-Gatherers Relied Heavily on Plants 15,000 Years Ago

Anyone following a paleo-style diet may wish to consider putting a few extra vegetables on the menu.

An analysis of teeth and bones from pre-agricultural hunter-gatherers living around 15,000 years ago in present-day Morocco indicates that their diet – traditionally believed to have contained large amounts of animal protein – leaned far more heavily towards plant foods. The findings also suggest that plants may have been used when weaning infants.

"Our results unequivocally demonstrate a substantial plant-based component in the diets of these hunter-gatherers," write a team led by anthropologist Zineb Moubtahij of the Max Planck Institute for Evolutionary Anthropology in Germany.

"This study underscores the importance of investigating dietary practices during the transition to agriculture and provides insights into the complexities of human subsistence strategies across different regions."

Hunter-gatherer diets before agriculture

It is commonly presumed that ancient people consumed considerable quantities of meat and other animal-derived foods before agriculture emerged.

There is no doubt that they ate some animal products: archaeological sites are strewn with animal remains showing signs of having been prepared for eating. However, because plant material is much less likely to survive intact for thousands of years, it has been harder to establish what proportion of ancient humans' and their relatives' diets came from roots, fruit, stems, flowers and leaves.

Modern analytical techniques can now help answer that question. Moubtahij and her colleagues applied them to human remains linked to the Iberomaurusians, a culture that occupied Taforalt Cave in Morocco towards the end of the Pleistocene, 15,000 years ago.

Even the strongest human remains generally lose all soft tissue after millennia in the ground. Dietary traces, however, can still be retrieved. Ratios between particular isotopes can, in particular, preserve remarkably detailed evidence of the foods a person ate.

Different isotope combinations in soil are absorbed by plants as they develop. Once those plants are eaten, the isotopes replace a small amount of calcium in the bones and teeth of the person who consumed them, leaving behind a distinctive ratio.

Isotope evidence from Morocco's Iberomaurusians

The team assessed 25 teeth and seven bone samples belonging to 17 Iberomaurusian people. They analysed zinc and strontium ratios in tooth enamel, carbon and nitrogen in bone collagen, and amino acids in bones from both people and animals recovered at the site.

Their results provided strong indications of substantial plant consumption. Dietary zinc, for instance, is most commonly acquired from animal sources. Zinc isotope ratios showed only a small difference between the Iberomaurusian individuals and herbivorous animals from the same area – although the difference was sufficient to establish that the Iberomaurusians did consume some meat. The researchers suggested that this population may have obtained protein from vegetables in much the same manner as Neolithic farmers.

Notably, one of the individuals studied was an infant who died at between six and 12 months old. Isotopes in the infant's bones matched a shift from the mother's milk to a diet made up largely of plant foods, the researchers concluded.

Plant foods and infant weaning at Taforalt

Further discoveries at the site support the case for a flora-rich diet. Grinding stones may have been used to prepare foods including pine nuts, acorns and legumes. The remains also have a high rate of dental cavities, consistent with starchy foods such as acorns and pine nuts. Archaeobotanical evidence likewise points to acorns, pine nuts and legumes.

Viewed together, the evidence indicates that Iberomaurusian people depended heavily on plants for survival, possibly because Barbary sheep – Taforalt's principal meat source – were available only seasonally and in fluctuating numbers.

In turn, this shows that prehistoric populations cannot always be assumed to have depended predominantly on meat, with diets differing substantially between cultures and locations.

"Our study highlights the importance of the Taforalt population's dietary reliance on plants, while animal resources were consumed in a lower proportion than at other Upper Palaeolithic sites with available isotopic data," the researchers write.

"The potential early weaning of infants at Taforalt reinforces the notion of a plant-based food focus for the population, potentially extending to the primary source of nutrition for infants."

The research was published in Nature Ecology & Evolution.