Plants have been part of our diet as long as meat has, with new evidence showing that Neanderthals, early Homo sapiens and even earlier Homo hominins were using and processing starches, grass seeds, nuts, fruits, sedges and tubers hundreds of thousands of years before the supposed “Broad Spectrum Revolution" took place.
Researchers from The Australian National University and the University of Toronto have challenged Kent V. Flannery's 1969 theory of Broad Spectrum Revolution (BSR), which stated that hunter-gatherers only expanded their diets to include small mammals, birds, fish invertebrates and plants during the Epipaleolithic, and prior to that humans and our ancestors were predominantly big-game hunters. This theory has become widely accepted – and a narrative that's reinforced by the Paleo diet movement.
“We often discuss plant use as if it only became important with the advent of agriculture,” said study co-author Dr. Anna Florin. “However, new archeological discoveries from around the world are telling us our ancestors were grinding wild seeds, pounding and cooking starchy tubers, and detoxifying bitter nuts many thousands of years before this.”
According to the BSR, early humans only diversified their diet around 20,000 to 12,000 years ago, when the seeds of agricultural practices were first planted – so to speak. But there's growing evidence that suggests this was not the case at all, and that plants were indeed integral, not peripheral, in the earliest diets. This evidence includes starch grains, phytoliths, residues, cooking damage, coarse grinding and food remains in hearths. So not only were our ancestors eating plants, but engaged in plant processing methods that go beyond foraging in a time of big-game scarcity.
The team gathered a trove of data that reshapes the existing timeline, pointing to our origins as a broad-spectrum species. Middle Paleolithic Neanderthals consumed and processed grass seeds, legumes, nuts and underground storage organs (USOs) like tubers. At Shanidar Cave, 70,000-year-old food remains include coarsely ground grass grains cooked into a kind of porridge-like mixture. Early Homo populations, more than 700,000 years ago, were already using starch-rich plant foods, as shown by residues on Acheulian stone tools. At Ohalo II in Israel, a 23,000-year-old lakeshore camp long considered the poster child of the BSR, inhabitants gathered cereals, small-seeded grasses, nuts, fruits, wetland tubers and game. What's more, there is no evidence of resource stress – so plant diversity here reflects abundance, not desperation.
In northern Australia, Madjedbebe – the continent’s oldest known archaeological site, dating back 65,000 years – there's a continuous record of plant use including yams, palm starch, pandanus kernels, fruits and possibly wild rice processed using grinding stones, pounding tools and complex roasting methods.
And there's no evidence of a sudden shift in plant use at the Epipaleolithic, as the BSR hypothesizes. There's even genetic evidence (AMY1 duplication) suggesting that starch-rich diets were common long before the Upper Paleolithic.
Overall, the researchers are not saying people only ate plants, but evidence shows that it wasn't because of a lack of game – instead, humans, and Neanderthals, were most likely flexible omnivores, not meat specialists.
"We argue that broad-spectrum plant use, including complex plant processing, is a normal characteristic of early human groups and was a critical factor in the successful peopling of new environments globally, rather than a step en route to agriculture," the researchers noted. "We are a broad-spectrum species, and the ability to process a wide range of plant foods represents a key threshold in hominin evolution."
In fact, a 2017 study detailed how starch grains, from grasses, were recovered from the dental calculus of an Early Pleistocene Homo sp. from Sima del Elefante, Spain, dating back an estimated 1.2 million years. Discoveries that piece together our timeline have continuously found evidence of not just plant eating but increasingly sophisticated processing and cooking tools designed for plants – long before the agricultural revolution.
“This ability to process plant foods allowed us to unlock key calories and nutrients, and to move into, and thrive in, a range of environments globally,” said co-author Dr. Monica Ramsey, who also emphasized the importance of “processed plant foods” to early human diets. “Our species evolved as plant-loving, tool-using foodies who could turn almost anything into dinner."
The research was published in the Journal of Archaeological Research.
Source: The Australian National University via EurekAlert!
