Researchers have had difficulties finding a record of plant-based foods that our forebears might have been consuming. The detritus of animal-based foods are bones and stone tools that are easily preserved but plants are perishable and leave little of themselves behind. Still, evidence is adding up, with a growing amount of study exposing indicators that plants were a major source of the food that our ancestors ate.
Part 1 of this series of articles explored an investigation of fossilized plaque on the teeth of prehistoric humans. Details of the bacteria living in the microbiomes of their mouths and the presence of enzymes specialized in breaking down starches led scientists to conclude that these early humans depended on plants for much of their energy and nutrient needs.
There is also a body of other research that approaches this topic from a range of perspectives and leads to the same conclusion. Let’s have a look at some of it.
Plant-derived Foods Aplenty in Paleolithic humans from 780,000 years ago in Israel (1)
The Acheulian sites excavated at Gesher Benot Ya’aqov in Israel uncovered a rich content of well-preserved botanical remains. Deep drilling revealed 26 archaeological layers that hold a record of the lifestyle of their ancient inhabitants – a varied plant diet with staple plant foods, a knowledge of their availability and growing seasons and the use of fire in food processing. Preserved plant-sourced foods identified here include multiple species of nuts, fruits, seeds, vegetables, rhizomes, tubers and roots. The plant-derived foods appear to be an important part of a diverse diet that also included fish, amphibians, reptiles, birds and mammals. Archaeologists studying this site “propose that a wide spectrum of food plants was a permanent aspect of the preagricultural hominin economy” and the infrequent findings of plant remains is due to the fact that plants are highly perishable and do not fossilize easily.
Starch Eating by Neanderthals living in France 300,000 years ago (2)
Neanderthals have long been thought to have existed on primarily animal-sourced food. However, archaeological excavations of several Neanderthal sites, including the one detailed in Part One of this series, challenge that assumption. Moreover, digging at the Site of Payre, located in the Rhone Valley of France, revealed that the consumption of starches was likely routine as early as 250,000 to 300,000 years ago. Starch grains were found within the dental calculus (plaque) of the Neanderthals extracted from this site as well as stone tools which exposed their use as scrapers, likely used to remove the woody, inedible exterior of plant parts like tubers and rhizomes.
Note: Rhizomes and tubers are similar, being thick portions of underground stems that act as nutrient storage for a plant. Tubers are swollen areas on the tips of underground stems that contain unused nutrients for the plant. An example of a tuber is potatoes. Rhizomes are also enlarged areas of underground stems but are different in that they grow horizontally and branch out to develop new roots and shoots over a large ground area. Examples of rhizomes are ginger and turmeric.
Rhizomes from 170,000 years ago discovered in Border Cave, South Africa (3)
Around fifteen years ago, archaeological searches in Border Cave in the Lebombo Mountains on the borders of KwaZulu-Natal Province in South Africa and Eswatini (formerly Swaziland) unearthed evidence that the people inhabiting the area hundreds of thousands of years ago were cooking starchy plants. Border Cave has been explored since 1934 and has been occupied by humans for over 200,000 years.
Small, charred cylinders were uncovered at this site while shifting through the ashes of ancient cooking fires and ash dumps. They were identified as rhizomes from the plant genus, Hypoxis, commonly called Yellow Star Flower. When examined under a scanning electron microscope, modern and primeval Hypoxis rhizomes display similar cellular structures that contain microscopic crystalline particles called raphides. These characteristics are still recognizable in the charred specimens. The examples found in Border Cave were dated back to circa 170,000 years ago. The researchers believe that these small plant pieces were preserved only because they were burnt. The fossilized Hypoxis species is now extinct but its close relative, Hypoxis augustifolia, a small flowering plant, is grown in KwaZulu-Natal today and its white flesh is used for food. Hypoxis rhizomes are nutritious and rich in energy. They can be eaten raw but are tough to peel and to digest unless they are cooked.
Because the Hypoxis remnants were found mainly in fireplaces and dumps, investigators hypothesize that they were dug out of nearby soil and carried into the cave to be cooked in the ashes of fires. A carved stick that appeared to be a digging tool was also found in the cave.
Fossilized Feces Analysis
Studying the manure of prehistoric humans can reveal much about what our ancient relatives were eating. Research on coprolites (fossilized excrement) is not new. In a book called “Dietary Fiber Research Edited”, published in 1978, a detailed description of the fecal contents of early humans was included. Fecal matter from humans dating back approximately 10,000 years had been found to consist of 30 to 56% by weight of plant matter (fiber) and 10% by weight of animal matter (mostly from small fish, birds and rodents). (4)
The investigation of coprolites has taken place in many areas of the world. For example, the contents of preserved feces of Neanderthals excavated from the El Salt archaeological site, near Alicante, Spain, reveal direct evidence that Neanderthals ingested both animals and plants. These waste specimens date from 45,000 to 60,000 years ago (5). Coprolites from dry cave deposits in the northern Chihuahuan Desert show that prehistoric human populations have relied heavily on eating plants for more than 10,000 years. The fiber constituents of these feces samples indicate that these people ate an average of 150 to 225 grams of fiber daily from plants such as agave, sotol, mesquite, prickly pear, and onion. (6)
No doubt the intake of plants by ancient humans would have fluctuated over the seasons, however, evidence from their waste suggests that they were consistently eating extremely high amounts of fiber. In addition, the types of plants consumed were extraordinarily diverse. Analysis of the coprolite information available from sites around the world estimates that the amounts of plant fiber found in fossilized stools translate into an average dietary fiber intake of about 130 grams per day, amounts similar to those of traditional people of rural China and Africa. Since fiber is only found in plants, this implies that our predecessors were adapted to eating profuse amounts of plant-derived foods (7).
Today, the Institute of Medicine in the US recommends that people consume at least 19 to 38 grams of fiber per day, depending on age and gender (8). Increasing evidence points to a physiological need of at least 50 grams of fiber a day (15). The vast majority of North Americans consume less than 15 grams of fiber daily.
Neither Early nor Modern Humans have been able to manufacture their own Vitamin C (9,10,11)
The loss of the ability to produce Vitamin C occurred very early in human evolution, approximately 61 million years ago, long before the appearance of great apes as an order of primates. This modification transpired due to inactivation of a gene, the GLO gene, which results in blocking of the last step of the synthesis of vitamin C. A few other mammals are also unable to generate vitamin C. These include apes, monkeys, guinea pigs and some bats, all of which are herbivorous creatures. Most other mammals can produce their own.
Vitamin C is an essential component of the diet. Lack of vitamin C affects the health and repair of all body tissues including the skin, teeth, cartilage and connective tissues and compromises blood health and immunity. Chronic lack of vitamin C leads to scurvy with bruising, easy bleeding, brittle bones, inability to make collagen, joint and muscle pain and, if the disease is allowed to progress, death from infection or bleeding. This means that humans must acquire their Vitamin C from an outside source such as vegetables (broccoli, Brussels sprouts, snow peas, sweet peppers, and red cabbage) and fruits (citrus fruits, guava, kiwi, papaya, and strawberries) or from a supplement (12).
If Vitamin C is so important to human health, why did we lose the capacity to produce it? Scientists believe that this ability was likely left by the wayside because the plants consumed by the earliest ancestors of humans were extremely high in this vitamin. The inactivation of this gene is thought to be caused by a random mutation. However, it would have had little, if any, effect on creatures eating a diet containing copious amounts of Vitamin C. Most importantly, this gene was unnecessary for procreation. If the change in the GLO gene had resulted in reduced fertility or affected the health and longevity of offspring, natural selection would have weeded out those who could no longer manufacture the vitamin. (16)
What is the diet of our closest primate relatives? (13,14)
We humans have a long evolutionary history beginning over 20 million years ago and we have evolved with a particular set of available foods. We know that the dietary intake of our earliest human ancestors consisted of high-fiber plants, a diet virtually the same as that of the great apes of today that included large amounts of leafy vegetables, nuts and fruit. Ancestral human diets of 6 million to 2 million years ago remained overwhelmingly plant-based, with emphasis on underground storage organs (tubers, rhizomes and roots), and with some supplementation by insects and a small amount of animal flesh (17,18).
Recently the human diet has drastically changed. In what amounts to “the blink of an eye” in evolutionary terms, our dietary alterations have included increased cooking of foods, the domestication of grains, cultivation and genetic modification to “improve” fruits and vegetables, the introduction of dairy products, the creation of highly processed foods and the increase in availability and consumption of meats, sugar and saturated fats. Generally, changes in the human genome occur extremely slowly, about one alteration in 10 million years (19) Our human digestive system simply has not had enough time to adapt to these dietary transformations.
It makes sense that the diet being eaten while our digestive system developed might be the nutritional pattern that works best for our health. Humans evolved from early primates and so observing the types of food that primates eat, the nutrient composition of their food, the anatomy of their guts and the biochemistry of their digestion might help to improve our understanding of our own dietary needs.
So what do apes and monkeys feed on? Ripe fruits, young leaves from trees and vines, flowers, seeds and roots make up the vast majority of their diet. They also ingest small amounts of animal-derived foods, most of which are invertebrates (insects, spiders, worms, snails). Chimpanzees tend to eat a larger amount of animal-sourced foods than other primates. They consume fish and ants and some small vertebrate prey but even this increased rate of consumption amounts to less than 3% of their total food intake.
Data detailing the diets of wild primates show that they ingest much greater amounts of fiber, phytonutrients, vitamins, minerals and essential fatty acids than do modern human populations. In addition, the diet of our wild relatives consists solely of whole, unprocessed foods. It is now well understood that the combination of nutrients derived in whole food form have synergistic beneficial effects that far exceed any gains achieved by taking isolated ingredient supplements.
So there you have it. Multiple scientific investigations are exposing evidence that our ancestors were almost certainly not only eating plants but an abundance of them. This makes intuitive sense. To obtain all the nutrients needed for health, eating a wide variety of foods is more likely to be successful. Furthermore, the foods that are the most nutrient dense are plants. Plants are also the most available source of food in the wild. They grow through predictable seasons, they don’t run away when their harvest is attempted and they are widely varied in taste and texture. The huge amount of fiber intake in ancient diets is a testament to a diet based largely on plant matter. Surely the notion that humans evolved eating mostly meat can now be laid to rest.
1 Melamed, Y., Kislev, M.E., Geffen, E., Lev-Yadun, S., Goren-Inbar, N. The plant component of an Acheulian diet at Gesher Benot Ya‘aqov, Israel. PNAS December 20, 2016; 113 (51): 14674-14679.
2 Hardy, B.L., Moncel, M.-H. Neanderthal use of fish, mammals, birds, starchy plants and wood 125-250,000 years ago. PLoS One. 2011; 6(8): e23768. Doi: 10.1371/journal.pone.0023768.
3 Wadley, L., Backwell, L., d’Errico, F., Sievers, C. Cooked starchy rhizomes in Africa 170 thousand years ago. Science. Jan 3,2020; 367(6473): 87-91. Doi: 10.1126/science.aaz5926.
4 Spiller, Gene A. Topics in Dietary Fiber Research Edited. Plenum: New York. 1978.
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