Ancestors

Our ancestors ate far more plants than the caveman story allows

By WhyStopHarmingAnimals.com

The caveman who lived on meat alone is mostly a modern invention. Fossilized stool[1], dental plaque[9][11] and the stone tools themselves[8] show prehistoric people eating plants in quantities no modern diet comes close to, processing them with purpose-made tools[8] about 780,000 years ago, and in the case of some Neanderthals, leaving no trace of meat at all[9].

Fiber measured in fossilized stool

The most direct evidence of what people ate is what came out the other end. Leach and Sobolik (British Journal of Nutrition, 2010) analyzed coprolites, fossilized human feces, from the prehistoric northern Chihuahuan Desert[1]. They put fiber intake at about 150 to 225 grams a day[1], including about 135 grams of inulin-type prebiotics from agave, sotol, mesquite, prickly pear and onion[1]. Modern U.S. intake is about 15 grams, roughly a tenth of the low end[1].

That desert was not an outlier[2]. Coprolites from Ocampo Caves and Tehuacán in Mexico and from Huaca Prieta in Peru point to fiber intakes above 100 grams a day[2], and rural African coprolite work has been read as high as about 120 grams of prebiotic fiber a day[2]. The sites are on different continents[2] and the methods differ, so the exact figures should be held loosely, but they share an order of magnitude[2].

Reconstructions of the Paleolithic diet arrive at similar numbers by a different route[3][4][5]. Boyd Eaton and Melvin Konner's original model (New England Journal of Medicine, 1985, revisited in 1997) had late Paleolithic diets about 65% plant-derived[3], with fiber often above 100 grams a day[3] and vitamin C on the order of 392 mg[3]. In 2006 Eaton put ancestral fiber at perhaps 100 grams a day[4], with vitamin, mineral and phytochemical intakes typically several times modern levels[4]. When Konner and Eaton revisited the model 25 years on, in 2010, they did not walk the high-fiber estimate back[5].

These people ate animals too; a diet 65% plant-derived[3] still leaves a real share for meat[3]. But fiber comes only from plants, and 100 grams or more a day is only possible when plants make up the bulk of what someone eats[2][3][4].

Nearly a million years of processing plants

The plant eating goes back much further. Carbon isotope work reviewed by Sponheimer and colleagues (2013) shows that before about 3.5 million years ago, early hominins ate almost exclusively C3 plants (trees, shrubs and herbs, the diet of apes)[6]. The dietary shift that followed widened the range of plant foods, and it was more than a simple turn to hunting[6].

At Gesher Benot Ya'aqov in Israel, an Acheulean site about 780,000 years old, Melamed and colleagues (PNAS, 2016) identified 55 edible plant taxa: nuts, fruits, seeds, vegetables and underground storage organs such as tubers[7]. Ahituv and colleagues (PNAS, 2025) then found more than 650 starch grains on the site's basalt hammers and anvils, from acorns, wild grasses, legumes, water-lily roots and water chestnuts[8]. It is the earliest clear evidence of systematic plant-food processing[8], and the proof is on the tools themselves[8].

Neanderthals ate their greens, and cooked them

Neanderthals have long been cast as the ultimate meat eaters. Weyrich and colleagues sequenced DNA preserved in Neanderthal dental plaque for a 2017 paper in Nature[9]. At Spy in Belgium the plaque showed rhinoceros and sheep[9]. At El Sidrón in Spain no meat was detected, only split-gill mushrooms, pine nuts and forest moss[9]. The researchers were surprised not to find meat, though earlier work had already suggested the El Sidrón group ate little of it[10]. It is a small sample of individuals and says nothing about the whole species, which clearly ate meat in places[9]. Those individuals, though, lived in a forest and were eating plants[9].

Other Neanderthals cooked their plants[11]. Henry, Brooks and Piperno (PNAS, 2011) recovered microfossils from dental calculus at Shanidar in Iraq and Spy in Belgium: starches from date palms, legumes and grass seeds[11], some of them chemically consistent with cooking[11]. A review of Neanderthal plant use found 61 plant taxa from 26 families at 17 archaeological sites[12], used for food, medicine and more, and showed that plant use was widespread rather than limited to the south[12].

A mouth already set up for starch

Even the bacteria in our mouths remember this history. Fellows Yates and colleagues (PNAS, 2021) found that oral streptococci from Neanderthals and modern humans share adaptations for binding amylase, the starch-digesting enzyme in saliva, that are largely absent in chimpanzees[13]. The shift happened early in the genus Homo, before the Neanderthal and modern human lines split[13], which points to starch-rich foods in the diet[13] long before farming.

Put the lines of evidence side by side and they converge. Prehistoric people ate meat when they could, sometimes a lot and sometimes none[9]. The staple, across hundreds of thousands of years and several continents[2], was plants[2][6][7], and people went to real effort to crack, grind and cook them[8][11].