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Scientists Discover Ancestors Ate Grass 3.5 Million Years Ago

Scientists Discover Ancestors Ate Grass 3.5 Million Years Ago

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When they grew tired of eating leaves and fruit, our ancestors tried grass


Fancy some grass for dinner? Why not? Our ancestors did 3.5 million years ago. This was before we began hunting, discovered how to make fire, and learned to cook meat — about 2.3 million years ago.

In four separate studies, scientists took a close look at carbon isotopes in the fossilized tooth enamel of our ancestors and baboons in Africa from four million to 10,000 years ago and found that they added grass and sedges, grass-like plants with triangular stems, to their diet of fruit and leaves, according to a news release by the University of Utah.

Why should we care? Diet is a principle driving force in human evolution, says Matt Sponheimer, a University of Colorado, Boulder anthropologist, former University of Utah postdoctoral fellow, and lead author of the fourth study. He says changes in our ancestors’ diets are linked to larger brain size and the advent of upright walking, which lead to us, modern humans.

Maybe now we’ll be more open to try new foods. Insects anyone?

Researchers find human ancestors switched to eating grasses earlier than thought

(—An international team of researchers has found evidence that suggests a human ancestor – Australopithecus bahrelghazali – was eating grass plants almost a million years earlier than most scientists had thought. In their paper published in the Proceedings of the National Academy of Sciences, the team says carbon dating of tooth fossil samples found in Chad indicate early hominins had been dining on a diet heavy in plants that contained 4 carbon atoms (C4), which are typical of grasses or sedges.

Very early human ancestors are believed to have eaten mostly fruits and insects, a trait they shared with most modern apes. At some point however, as the climate changed, our ancestors shifted their diet to include grasses and sedges. Previous evidence had shown that a Paranthropus boisei hominin had existed by eating mostly plants, but carbon dating had shown that individual to have lived approximately 2.8 million years ago. The A. bahrelghazali tooth fossils in this new study are from 3 to 3.5 million years ago, pushing back the date that our ancestors came down out of the trees and began eating C4 grasses, though it's not clear if they were eating actual grass blades or the roots and tubers that support such plants.
A. bahrelghazali stood approximately five feet tall (similar in size to modern chimpanzees) and walked on two legs. It also had a projecting jaw with powerful muscles and large teeth that enabled it to grind plant material to aid digestion. During its time, the part of African where it lived was covered with lakes, floodplains and wooded grasslands, which would lead quite naturally to a change in eating habits if a pattern of living on the ground as opposed to trees developed.

Grasses and sedges are generally high fiber foods that also have complex starches and some even have tissue that also offers nutrients, thus, A. bahrelghazali would have been able to survive on such a diet despite not having evolved a sophisticated plant processing digestive system such as that seen with modern cows.

The researchers acknowledge that because there is so little fossil evidence to work with, it is possible that the carbon levels found in the tooth fossils came from eating animals that consumed C4 plants, but thus far there is no other evidence to suggest that was the case.

Foods derived from C4 plants were important in the dietary ecology of early Pleistocene hominins in southern and eastern Africa, but the origins and geographic variability of this relationship remain unknown. Carbon isotope data show that Australopithecus bahrelghazali individuals from Koro Toro in Chad are significantly enriched in 13C, indicating a dependence on C4 resources. As these sites are over 3 million years in age, the results extend the pattern of C4 dependence seen in Paranthropus boisei in East Africa by more than 1.5 million years. The Koro Toro hominin fossils were found in argillaceous sandstone levels along with abundant grazing and aquatic faunal elements that, in combination, indicate the presence of open to wooded grasslands and stream channels associated with a greatly enlarged Lake Chad. In such an environment, the most abundant C4 plant resources available to A. bahrelghazali were grasses and sedges, neither of which is usually considered as standard great ape fare. The results suggest an early and fundamental shift in hominin dietary ecology that facilitated the exploitation of new habitats.

Our Human Ancestors Had A Diet Rich In Grass

Four new studies have taken a new look at the diets of our ancestors and have found their behavior was a “game changer” for early humans some 3.5 million years ago. An ape-like diet that included grasses and sedges paved the way for a diet rich in grains, meats and dairy from grazing animals.

In the first of the four studies, researchers from the University of Colorado Boulder conducted high-tech tests on tooth enamel of ancient remains. The tests indicate that four million years ago Africa´s hominids were eating like chimpanzees, which consisted primarily of fruits and some leaves, according to CU anthropology Professor Matt Sponheimer, the study´s lead author. Despite the fact that grasses were available, the hominids largely ignored them as a food source for some time.

“We don´t know exactly what happened,” said Sponheimer. “But we do know that after about 3.5 million years ago, some of these hominids started to eat things that they did not eat before, and it is quite possible that these changes in diet were an important step in becoming human.”

Sponheimer’s paper has been published online this week in the Proceedings of the National Academy of Sciences (PNAS), along with the three other related papers.

Prior to this ground-breaking research, scientists analyzed teeth from 87 hominids. The new paper from CU presents information on an additional 88 specimens, including five previously unanalyzed hominid species.


Sponheimer, who specializes in stable isotope analysis, compared particular forms of the same chemical element in fossilized teeth. Carbon isotopes obtained from the ancient hominids can help researchers piece together the types of plants that were being eaten way back when, he noted.

The carbon signals from the ancient teeth are derived from two distinct photosynthetic pathways, he added. C3 signals are from plants like trees and bushes, and C4 signals are from grasses and sedges. The wear of the teeth also provided more information on the type of foods these hominid specimens were eating.

After evolving from Australopithecus, the genus Homo likely looked to broaden its food choices. During this time, one short, upright hominid known as Paranthropus boisei from eastern Africa was moving toward a C4 type of diet. Originally dubbed the “Nutcracker Man” because of its large, flat teeth and powerful jaws, this species was later redefined, with scientists theorizing that the back teeth were actually used for grinding grasses and sedges, explained Sponheimer.

“We now have the first direct evidence that as the cheek teeth on hominids got bigger, their consumption of plants like grasses and sedges increased,” he said. “We also see niche differentiation between Homo and Paranthropus — it looks probable that Paranthropus boisei had a relatively restricted diet, while members of the genus Homo were eating a wider variety of things.”

“The genus Paranthropus went extinct about 1 million years ago, while the genus Homo that includes us obviously did not,” Sponheimer said.

Sponheimer noted that there still remain some puzzling differences in the evolutionary tree of hominids in eastern Africa and those of southern Africa. P. robustus of southern Africa was anatomically similar to its cousin P. boisei in eastern Africa, but the new analysis indicates the two species had very different carbon isotopic compositions in their teeth. P. robustus seems to have consumed a fair amount of C3 vegetation along with the evolved C4 diet.

“This has probably been one of the biggest surprises to us so far,” said Sponheimer. “We had generally assumed that the Paranthropus species were just variants on the same ecological theme, and that their diets would probably not differ more than those of two closely related monkeys in the same forest.”

“But we found that their diets differed as much isotopically as those of forest chimpanzees and savanna baboons, which could indicate their diets were about as different as primate diets can be,” he said. “Ancient fossils don´t always reveal what we think they will. The upside of this disconnect is that it can teach us a great deal, including the need for caution in making pronouncements about the diets of long-dead critters.”

Thure Cerling, a geochemist from University of Utah, and lead author of two of the four papers published online in PNAS, said: “At last, we have a look at 4 million years of the dietary evolution of humans and their ancestors.”

“For a long time, primates stuck by the old restaurants–leaves and fruits–but by 3.5 million years ago, they started exploring new diet possibilities–tropical grasses and sedges–that grazing animals discovered a long time before, about 10 million years ago,” Cerling said, when African savanna began expanding.

He noted that tropical grasses provided early hominids with a new food option and there is increasing evidence that our ancestors relied on this resource oddly enough, most primates today still do not eat grasses.

Between six and seven million years ago grassy savannas and grassy woodlands in East Africa were abundant. But the question that remains is why our ancestors didn´t start exploiting this resource until less than four million years ago.

The isotopic method may paint a good picture of what types of vegetation was consumed, but it cannot distinguish which parts of these plants were eaten, such as the leaves, stems, seeds, or roots. It also cannot determine exactly when our ancestors began getting much of their grass through consuming grass-eating insects or from grazing animals.

Cerling said direct evidence of meat scavenging doesn´t occur until about 2.5 million years ago, and definitive evidence of hunting only exists 500,000 years ago. The new evidence does clear up some of the mystery as to what was on our ancestors´ plates, but there does still remain uncertainties, he added.

“We don’t know if they were pure herbivores or carnivores, if they were eating fish [which leave a tooth signal that looks like grass-eating], if they were eating insects, or if they were eating mixes of all these,” he said.

The four papers appear in the journal PNAS this week.

A paper on the teeth of hominids from Ethipoia´s Hadar-Dikika area was written by lead author Jonathan Wynn, program director at NSF´s Division of Earth Sciences, on leave from University of South Florida. Other lead authors are Arizona State University‘s William Kimbel and California Academy of Sciences scientist Zeresenay Alemseged.

One of Cerling´s papers is on the teeth from the Turkana Basin in Kenya, collaborating with lead author paleoanthropologist Meave Leakey of Turkana Basin Institute and geologist Frank Brown of the University of Utah. His other paper is on baboon diets.

Sponheimer´s research paper summarizes the other three studies.


Previous research has shown that an early relative of human, Ardipithecus ramidus (“Ardi”), from Ethipoia ate mainly C3 leaves and fruits.

Between 4.2 and 4 million years ago on the Kenyan side of the Turkana Basin, Cerling suggests Aus. anamensis subsisted on at least 90 percent leaves and fruits — the same diet that modern chimps have.

By 3.4 million years ago, Wynn describes Aus. afarensis of Ethiopia´s Awash Basin living on a rich diet (22 percent on average) of C4 grasses and sedges that extended anywhere from zero to 69 percent of their diet.

The switch to C4 vegetation “documents a transformational stage in our ecological history,” said Wynn.

Many scientists previously believed Aus. afarensis had an ape-like C3 diet. It remains a mystery why Aus. afarensis expanded its menu to C4 grasses when its likely ancestor, Aus. anamensis, did not, although both inhabited savanna habitats, Wynn says.

Also, at around 3.4 million years ago, the human relative Kenyanthropus platyops moved to a highly varied diet of both C3 and C4 vegetation. The average was 40 percent grasses and sedges, but individuals varied widely, eating anywhere from 5 to 65 percent, explained Cerling.

In Cerling´s baboon study, he presented findings that two extinct Kenyan baboon species represent the only primate genus that primarily ate grasses throughout its history.

Theropithecus brumpti ate a 65 percent tropical grass-and-sedge diet when the baboons lived between four million and 2.5 million years ago, contradicting previous claims that they ate forest foods. Theropithecus oswaldi ate a 75 percent grass diet by two million years ago and a 100 percent grass diet by one million years ago. Both species went extinct, perhaps due to competition from hooved grazing animals.”

Most modern baboons eat only C3 cool-season grasses.

The research was funded by the National Science Foundation (NSF), the National Research Foundation in South Africa, the Leakey Foundation, the Wenner-Gren Foundation, Arizona State University, the CU-Boulder Dean’s Fund for Excellence, and George Washington University (GWU).

Early Human Ancestors Transformed Diet Around Lucy's Time

Early human ancestors made a drastic shift in their diet, from eating exclusively fruits and leaves to including grasses and succulents about 3.5 million years ago, new research suggests.

The new results, published in several studies today (June 3) in the journal Proceedings of the National Academy of Sciences (PNAS), were found by analyzing the fraction of different carbon isotopes, or atoms of the same chemical with different molecular weights, in tooth enamel from more than 100 fossilized teeth of several species of early human ancestors.

"Until about 4 million years ago our early hominin ancestors had diets that were, isotopically at least, very similar to chimpanzees'," said Matt Sponheimer, a paleoanthropologist at the University of Colorado at Boulder. "They started eating new things, using the landscape in new ways around 3.5 million years ago. It's very possible that it was one of the important steps in the diversification of our lineage." [The 10 Biggest Mysteries of the First Humans]

Diet insight

Because plants using different methods of photosynthesis to grow absorb different amounts of carbon isotopes, the ratio of those isotopes in dental enamel can reveal insights into the feeding habits of early human ancestors.

For instance, so called C3 plants absorb more of the heavy isotope carbon-13 into tissue than do C4 or CAM plants.

To analyze what the ancient human ancestors were eating, the team analyzed the fraction of different carbon isotopes in teeth from every early human fossil that could be sampled: 175 individuals from 11 different species dating between 4 million and 1.3 million years old. The fossils included the species Australopithecus afarensis, the species that includes the 3.2-million-year-old "Lucy," as well as early Homo species.

Prior to about 3.5 million years ago, human ancestors ate exclusively C3 plants. But after that, despite living in a very similar environment, their diet underwent a radical transformation to include C4 and CAM plants.

That signified a change from eating exclusively leaves and fruits to foods derived from grasses and succulents. That could include grass seeds and underground roots, and even termites or small, scavenged animals, although the exact composition of the diet still remains a mystery.

The findings suggest that beginning around the time of Lucy, human ancestors seem to have transitioned from a fairly restricted diet to one with more variety, and that may have led to their diversification, Sponheimer said.

"Lucy and her like, they seem to be willing to eat just about anything," Sponheimer told LiveScience.

By contrast, some species such as Paranthropus bosei, or "Nutcracker Man" were becoming more specialized, narrowing their diets and focusing on C4 foods. Though its large jaws were originally thought to be used for cracking nuts, in fact, now researchers believe they used their jaws to grind grasses and seeds.

The findings largely confirm what scientists suspected, Richard Klein, a biologist at Stanford University, wrote in an accompanying commentary article published in PNAS.

"Twenty years ago, we might have guessed, based mainly on the savanna settings in which early hominins evolved, that they depended increasingly on grassy foods or on creatures that ate grasses. The craniodental morphology of P. boisei might also have led to us to speculate that it relied on grassy foods to a particularly great extent," Klein wrote. "Now, thanks to stable-isotope analyses, we no longer have to guess, and the broad pattern of early hominin dietary evolution is established."

Change of diet may be a key to human evolution

The debate between Darwinians, Creationists and now the Panspermians to explain the origin of man has been going on for decades and every week, new evidence is presented to try to prove either one or another theory correct. In latest research, scientists have proposed the diet of our ancient ancestors may have been the key to biological evolution.

Scientists from multiple institutions have studied the enamel from the teeth of eleven different species of ancient humans (Homo, Australopithecus, Paranthropus etc) and baboons in Africa that span a 4 million years period of time. Analysing the carbon isotopes, they have discovered that the diet of our ancient ancestors changed at about 3.5 million years ago by adding grasses and grass-like plants to their regular diet which was similar to the diet of apes.

However, they have been unable to determine their exact diet because the isotope method that is used cannot distinguish between different food types but only general categories.

The meat came into our diet at about 2.5 million years ago, however evidence for hunting is found only 500,000 years ago. Of course we need to realize that what we have found is a tiny fraction of what is really out there waiting to be discovered.

What was it that made our ancestors suddenly change their diet and eat things that they didn’t eat before? Could it be climate change or changes in the environment or even observing other species having a different diet which they have tried to imitate? Well although there isn’t a definite answer, most scientists agree with the mainstream opinion that an environmental change triggered the change in the diet of our ancestors which according to this study was a step towards a biological evolution that would add to the Darwinian theory of human evolution.

John Black

Dr John (Ioannis) Syrigos initially began writing on Ancient Origins under the pen name John Black. He is both a co-owner and co-founder of Ancient Origins.

John is a computer & electrical engineer with a PhD in Artificial Intelligence, a. Read More

Ancient human ancestor's teeth reveal diverse diet

Expansion of our ancestor&rsquos diet millions of years ago may have been a transformational stage in our ecological and evolutionary history. In four related research articles, scientists argue that human ancestors living 3.5 million years ago were the first hominins &ndash species more closely related to humans than to chimpanzees &ndash to show evidence of expanded preferences in their plant diet. The addition of tropical grasses and sedges to an ape-like diet set the stage for our modern diet of grains, grasses, and meat and dairy from grazing animals. Download Full Image

Diet has long been implicated as a driving force in human evolution. Changes in the type of food consumed and the manner in which it was gathered have been linked with the growth of the brain and the emergence of bipedalism, as well as ecological, social and cultural evolution within the hominin lineage.

The papers appeared in the June 3 issue of the Proceedings of the National Academy of Sciences. Most of the funding for the research was through grants from the National Science Foundation.

Two of the papers, &ldquoIsotopic evidence of early hominin diets: Past, present, and future&rdquo and &ldquoDiet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia,&rdquo include Institute of Human Origins (IHO) director William Kimbel and research associate Kaye Reed as coauthors among a group of researchers from across the U.S.

Australopithecus afarensis was discovered and named by a team led by IHO founding director, Donald Johanson, who found the fossil skeleton "Lucy" at Hadar, Ethiopia in 1974. Kimbel and Reed are professors in the School of Human Evolution and Social Change in the College of Liberal Arts and Sciences.

In the new work, the scientists used carbon isotope analysis to extract the dietary signal from fossilized teeth of African hominin species dating from 4.5-1.5 million years ago.

Isotope analysis is based on the concept that &ldquoyou are what you eat.&rdquo The carbon isotopic composition of past meals is incorporated into the forming tooth enamel, frozen in time, yet recoverable after millions of years. Carbon isotopes are especially valuable for distinguishing diets based on &ldquoC3&rdquo or &ldquoC4&rdquo plants, which differ in how efficiently carbon is recovered during photosynthesis. C3 plants include trees, shrubs and herbs, and predominate in forested conditions or around well-watered areas. C4 plants are the grasses and sedges that inhabit primarily open environments. In living animals, carbon isotope ratios in tooth enamel readily distinguish grass feeders, like zebras and wildebeests, from fruit or leaf eaters, like chimpanzees and giraffes.

Scientists have collected carbon isotope data from 173 specimens representing 11 early hominin species ranging in age from 4.4 million years ago to 1.3 million years ago. In the new research, A. afarensis from the Hadar and Dikika sites in Ethiopia was analyzed for the first time.

The diets of the earliest hominin species, Ardipithecus ramidus and Australopithecus anamensis from 4.4 to 4 million years ago, were dominated by C3 plants. But beginning around 3.5 million years ago, data from Hadar and Dikika in Ethiopia and West Turkana in Kenya show that A. afarensis and another species called Kenyanthropus platyops consumed foods from both C4 and C3 plant communities. This expansion in dietary preference represents the first use of C4 plant foods that had been abundant in the environment for at least one million years. All subsequent hominin species were capable of consuming both C3 and C4 foods, a flexible adaptation that was inherited by modern humans.

&ldquoWe knew that before four million years ago, hominins had ape-like diets from an isotopic perspective and that after three million years ago, the diet had expanded to include a wide array of novel resources,&rdquo observed Kimbel. &ldquoThe time period of A. afarensis is key to pinning down exactly when this transition occurred.&rdquo

What environmental factors may have led A. afarensis to expand its diet, and to exploit a larger range of habitats than any human ancestor species before it, is the subject of the next stage of research.

&ldquoWe have no idea what parts of C4 plants A. afarensis was eating,&rdquo noted IHO&rsquos Kaye Reed. &ldquoWas it seeds, blades of grass or roots? The most interesting finding to me is that some A. afarensis individuals utilized C4 plants almost exclusively, while other individuals within the same time period ate mostly C3 plant species. This high degree of variation is not what one sees in populations of chimpanzees, for example, so the fact that A. afarensis individuals have different diets was not expected.&rdquo

The Institute of Human Origins is one of the preeminent research organizations in the world devoted to the science of human origins. A research center of the College of Liberal Arts and Sciences in the School of Human Evolution and Social Change, IHO pursues an integrative strategy for research and discovery central to its 30-year-old founding mission, bridging social, earth and life science approaches to the most important questions concerning the course, causes and timing of events in the human career over deep time. IHO fosters public awareness of human origins and its relevance to contemporary society through innovative outreach programs that create timely, accurate information for both education and lay communities.

Published June 3, 2013 in the Proceedings of the National Academy of Sciences:

(1) &ldquoDiet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia.&rdquo

Authors: Jonathan Wynn and Jessica N. Wilson, University of South Florida Matt Sponheimer, University of Colorado, Boulder William Kimbel and Kaye Reed, Arizona State University Zeresenay Alemseged, California Academy of Sciences and Zelalem Bedaso, Johns Hopkins University.

(2) &ldquoIsotopic evidence of early hominin diets.&rdquo

Authors: Matt Sponheimer, University of Colorado, Boulder Zeresenay Alemseged, California Academy of Sciences Thure Cerling, University of Utah Frederick Grine, Stony Brook University William Kimbel and Kaye Reed, Arizona State University Meave Leakey, Turkana Basin Institute, Kenya, and Stony Brook University Julia Lee-Thorp, Oxford University Fredrick Kyalo Manthi, National Museums of Kenya and University of Utah Bernard Wood, George Washington University and Jonathan Wynn, University of South Florida.

(3) &ldquoStable isotope-based diet reconstructions of Turkana Basin hominins.&rdquo

Authors: Thure Cerling and Frank Brown and Kevin Uno, University of Utah F. Kyalo Manthi, National Museums of Kenya and University of Utah Emma Mbua, National Museums of Kenya Louise Leakey, Meave Leakey and Richard Leakey, all of Turkana Basin Institute, Kenya, and Stony Brook University Frederick Grine, Stony Brook University John A. Hart, Lukuru Foundation, Democratic Republic of Congo Prince Kaleme, Maiko National Park Conservation Project, Frankfurt Zoological Society Helene Roche, University of Paris and Bernard Wood, George Washington University.

(4) &ldquoDiet of Theropithecus from 4 to 1 Ma in Kenya.&rdquo

Authors: Thure Cerling, University of Utah Kendra Chritz, University of Utah Nina Jablonski, Pennsylvania State University Meave Leakey, Turkana Basin Institute, Stony Brook University and National Museums of Kenya and F. Kylao Manthi, National Museums of Kenya and research faculty in geology and geophysics, University of Utah.

Why Our Ancestor’s Diets Matter

The earliest human ancestor to consume substantial amounts of grassy foods from dry, more open savannas “may signal a major and ecological and adaptive divergence from the last common ancestor we shared with African great apes, which occupy closed, wooded habitats,” writes University of South Florida geologist Jonathan Wynn, chief author of one of the new studies and a former University of Utah master’s student.

“Diet has long been implicated as a driving force in human evolution,” says Matt Sponheimer, a University of Colorado, Boulder anthropologist, former University of Utah postdoctoral fellow and lead author of the fourth study.

He notes that changes in diet have been linked to both larger brain size and the advent of upright walking in human ancestors roughly 4 million years ago. Human brains were larger than those of other primates by the time our genus, Homo, evolved 2 million years ago. (Our species, Homo sapiens, arose 200,000 years ago.)

“If diet has anything to do with the evolution of larger brain size and intelligence, then we are considering a diet that is very different than we were thinking about 15 years ago,” when it was believed human ancestors ate mostly leaves and fruits, Cerling says.

Isotopic Data Does Not Indicate Hunter-Gatherer Ancestors Consumed Grass - Rebuttal

Dr. Loren Cordain: I'm Loren Cordain, Founder of the Paleo movement.

Shelley Schlender: I'm Shelly Schlender. This is The Paleo Diet Podcast for October, 2013. Coming up Loren talks about recent archaeological findings that indicate that fossilized teeth from our ancestors three million years ago carry a lot of DNA from grass. Based on these finding many reporters have announced that early Hominids loved to eat grains and even grass. Loren has responded with a rebuttal that's been published in the Proceedings of the National Academy of Sciences. Here's more from Loren.

Dr. Loren Cordain: My colleague Matt Sponheimer from CU, University of Colorado down in Boulder, and I'm at Colorado State University 60 miles up the road in Fort Collins, we’re good friends and have known one another for quite some time. He and his colleagues published a series paper in the Proceedings of the National Academy in June, 2013. They've documented the isotopic signature of a chemical in primarily the teeth, the enamel of Hominids. Hominids are bipedal apes, over the course of the last three million years, actually about 4 million years. The isotopic signature can help us understand what these Hominids were eating.

The interesting part of these papers is that Matt came up with the notion that starting about 3.5 million years ago we see in the fossils of early Hominids, which ended up becoming humans, what see in their tissues were the signature of plants that are either grasses or sedges.

The popular press misinterpreted that and suggested that our early ancestors as far back as 3.5 million years ago, were eating grasses.

Shelley Schlender: You mean that in the popular press this was described as our ancestors from three million years ago were wandering the Savannah grabbing bunches of grass and chewing it up and eating it?

Dr. Loren Cordain: That's the ridiculousness of this whole argument by the popular press. I think my colleague Matt Sponheimer would never suggest that nor did they in any of the articles in the Proceedings of the National Academy. That was our point in our rebuttal to the Proceeding of the National Academy. Was that there's absolutely zero evidence to show that our ancestors were eating grass.

First off Shelley, grass is inedible. If it weren't, why don't we after you mow your lawn, why don't you go out and put all that grass into a bag and put it on your plate and eat it? We and all mammals lack and enzyme called cellulase. Grass is loaded with cellulose and hemicellulose, making it inedible. If we were to chew it we couldn't get any calories out of it.

Shelley Schlender: Not only do we lack cellulase, but we don't have what is it, four or five stomachs like a cow. I've seen the cow up there at your university at CSU where they have a porthole in its side. Basically if you look inside a cow that is walking around and eating hay, inside it's all hay. Being fermented by the microbes. We don't have that kind of cow gut to do that.

Dr. Loren Cordain: Ah exactly, exactly. That's the fundamental problem that the journalists that read these papers suggesting that we were eating grass three and a half million years ago, they didn't do their homework. Animals that do eat grass that are grazers, they are what are called ruminates. They develop stomachs in which they have this enormous micro flora of bacteria, and the bacteria can break it down.

There are other animals that have developed a very large hind gut. What a hind gut is, is the colon or the cecum. If you have a large hind gut you can have a huge bacterial element there, and those bacteria then ferment the grass and break the cellulose down, and they turn it into what are called short chain fatty acids. Then those can be digested.

Shelley Schlender: A horse has a hind gut, a cow has lots of guts, but how about us people, and how about our ancestors three million years ago, did we have a hind gut?

Dr. Loren Cordain: This is the argument I've made to the PNAS and also to my colleague Matt Sponheimer. There's absolutely no evidence whatsoever. The fossil record doesn't preserve soft tissue so we'll never really know how large or small the hind gut was in our ancient ancestors, but we can look at their bone structure and we can look at body to height ratios, and we can see what was going on in their mid-section. There's absolutely zero evidence to tell us that they had an incredibly large colon or cecum. That just doesn't make any sense.

As a matter of fact, the best available evidence is called the expense to tissue hypothesis. It shows exactly the opposite. Our ancestors, in order to have evolved a large brain we have an evolutionary trade off with our gut. The gut got smaller as the brain got larger. Modern humans maintain very small guts for our size compared to any other primate. The reason for that is that we're eating a lot of meat.

Shelley Schlender: Well compared to a cow, I'm thinking that a cow has a very large gut and very small brain.

Dr. Loren Cordain: Yeah exactly. That's called the encephalization index. Humans have very large encephilization indexes. We have a very large brain relative to our body size whereas a cow has a small brain relative to its body size.

Shelley Schlender: How did we end up with a big brain and cows ended up with not a big brain? What are we eating that's different than cows from three million years ago?

Dr. Loren Cordain: Well starting about three and a half million years ago for the very first time we see in the fossil record primitive stone tools. We see them more often about two and a half million years ago. These stone tools then were made by our ancestors not to whittle a piece of wood, but rather to butcher and dis-articulate carcasses of animals. At the very same time that this delta thirteen carbon signature appears in the fossil record, this is coincident with when our ancestors started making stone tools.

What our argument was in the PNAS paper, The National Academy paper, was that the delta thirteen carbon signature that suggests grain eating was not grain eating at all. Our ancestors were eating the flesh of animals that consumed grain. Just like in the 21 st century, you have the same signature in your hair because you have consumed flesh of cows which have been fed grain in a fed lot. This technique cannot distinguish whether or not you have consumed grasses themselves or the flesh of animal that ate grasses.

Shelley Schlender: Loren Cordain, I've got a question for you though. You said that there were stone tools that our ancestors were starting to make 3.5 million years ago. Have you examined them closely enough to tell whether they were stone axes or the tips of spears or were they back hoes or something?

Dr. Loren Cordain: Actually the very first stone tool technology was called the Oldowan lithic tradition. We see it most often started about 2.6 million years ago, but we think that it may have occurred earlier.

Essentially what they did is they took a round stone in one hand and then they took a hammer stone in the other, and then hit the stone with one hand, and they were interested in making sharp flakes, so they did. They made these sharp flakes and they made a core that came off of the sharp flakes.

What they did with the sharp flakes is they used those sharp flakes to take the flesh off of an animal and disarticulate the carcass where the joints go from one part to the other. They used it to chop off a leg or an arm of an animal so that they could take it away from a kill site. Then they used those sharp tools to get the flesh off because we don't have the teeth like a carnivore has to rip the flesh from an animal, so we use these sharp flakes to do that.

We know that from that archeologic record. When we dig up bones that are in that same place we find these Hominid bones, what we find are these cut marks of stone tools that appear on the prey of the animals that our ancestors were eating. That's why it's ridiculous to suggest that we were eating grass. When in reality all the triangulation records suggest, the stone tools, the extensive tissue hypothesis, suggest they were using those stone tools to cut the flesh from animals that ate grain.

Shelley Schlender: Loren Cordain, Matt Sponheimer, the researcher at CU, has told me that he agrees with a great deal of what you're saying. That you can't just look at these signatures that they got from the isotopes and the teeth, and say that doesn't mean all of ancestors ate grain. On the other hand he says that his isotopic data is not detailed enough to backup or disprove your idea that humans were eating a lot of meat at that time or early Hominids were.

Dr. Loren Cordain: I completely agree with Matt. We're on the same page. Delta thirteen carbon data cannot tell you whether you were eating grasses or the flesh of animals that ate grasses. However, we need to triangulate the information. It's myopic to look at that delta thirteen carbon data all by itself.

Shelley Schlender: Which is what the reporters did when they first reported on this story?

Dr. Loren Cordain: Exactly. What we need to look at is we need to triangulate that data. Okay? The question comes up. It's a very simple question. Were they eating grass or were they eating flesh of animals that ate grass? As I mentioned, if we look at the archeologic evidence, stone tools appear at the very same time when the delta thirteen carbon signature starts to show an increase in grass in our skeletons.

If you look at stone tool evidence, well it is suggestive that we were eating animals rather than grass, and secondly we don't have the capacity to digest grass. We lack the enzyme cellulase to breakdown grass. All mammals including our closest living ancestors chimps, great apes, they also lack that same enzyme, and most of them don't have large hind guts.

Now a gorilla does, a gorilla has a large hind gut, but a gorilla if we look at its bones or its teeth, does not have a C-4 signature. A gorilla doesn't eat grass either. A chimp doesn't eat grass, a gibbon doesn't eat grass. There's only one primate in the entire world that eats grass. This is a primate on the plains of Africa, it's a baboon species, and it has evolved a large hind gut.

If we look at the hair, the teeth, of this baboon that eats grass. Instead of having a C-3 signature which is a browsers signature. In other words, somebody that eats a lot of leaves, and berries, and roots, and whatever, it has a C-4 signature. There's absolutely no doubt that there's a single species of baboon that does eat grass, but all other large apes don't.

Any C-4 signature, any grass signature that comes through in the archaeologic record, we triangulate this from looking at other species that are primates, it tells us the same story.

Shelley Schlender: Loren Cordain, what Matt Sponheimer told me here at CU about his study, is that he feels that it's mostly an indication that our ancestors 3 million years ago used to be browsers of bushes, and fruits, and roots, and all of these things that you've described. That were more forest like kind of foods or jungle kind of foods, and that this change to the C-4 signature for grasses is certainly an indication that they were moving into the Savannah. They were moving into grasslands.

Dr. Loren Cordain: I am absolutely on board with what Matt is saying. We see a shift from a C-3 signature to a C-4 signature. The popular press has interpreted that shift from C-3 to C-4 as our ancestors were eating more grass. Yet the best available evidence tells us the shift from a C-3 to a C-4 was because we were increasingly as we moved out on the Savannah, we started scavenging the carcasses of grazers that were present on the Savannah.

Modern day studies show that if you're out on the Savannah walking around after hyenas and lions make kills, what they do, they leave the long bones and they leave the skull. The long bones are de-fleshed, the skull is de-fleshed, and if you're a clever Hominid that has stone tools you can take those long bones and you can put them on a flat stone you call an anvil and you can take another stone and hit that long bone with a hammer stone, and suddenly you have marrow. If you eat the marrow from an antelope that's been eating grain, the signature that was previously C-4 now becomes C-3.

That's all for this edition of The Paleo Diet Podcast. Visit my website for past episodes and for hotlinks to the experts and studies that we talked about today.

Shelley Schlender: Our theme music is by Chapman Stick Soloist Bob Culbertson.

Dr. Loren Cordain: If you want to send me questions or comments the place to go is

Shelley Schlender: For The Paleo Diet Podcast, I'm Shelley Schlender.

Dr. Loren Cordain: I'm Loren Cordain.

The Paleo Diet® team comprises a group of scientists, journalists, and recipe creators who stay at the forefront of nutrition science, specifically Paleolithic nutrition. Our hope is to bring you the latest news and research to help you understand how to follow the diet, optimize your health, and eat nutritious and delicious Paleo meals..

Human Ancestors Were Grass Gourmands

There's no accounting for taste—a truism that extends even to the earliest humans. By 3.5 million years ago, some early hominins in the Central African nation of Chad had already developed their own distinct tastes—literally. Three members of the genus Australopithecus—close cousins of the famed Lucy—had a yen for grass and sedges, according to a new study published online today in the Proceedings of the National Academy of Sciences. The shift suggests that hominins adapted their diet to living in more open terrain, as our ancestors did at some point, earlier than thought.

The earliest members of the human family walked upright, but they still looked more like apes than humans—with chimp-size brains and small, hairy bodies. Then, "around 3.5 million years ago, at least in Central Africa, the hominin diet shifted from an ape fruit diet to a grass/sedges diet," says paleontologist Michel Brunet of the Collège de France in Paris, whose team discovered the fossils. This diet rich in so-called C4 plants (enriched in a particular carbon isotope), such as tropical grasses, was a major shift from the customary diet of apes such as chimpanzees and gorillas, which feed on fruits, seeds, and plants found in woodlands.

Researchers have long wondered when members of the human family shifted from that fruit-rich diet favored by apes to one that relied on plants and animals found in more open grasslands. By studying the ratio of the two nonradioactive isotopes of carbon— 13 C and 12 C—in the enamel of teeth, researchers can detect whether an ancient creature ate a diet rich in woodland or grassland plants.

Three years ago, researchers used this method on the teeth of one of the earliest known hominins, the 4.4-million-year-old Ardipithecus ramidus. They found that Ar. ramidus still favored the kind of C3 plants that apes prefer, suggesting that it was still spending a lot of time in woodlands. About 4 million years ago, the teeth of hominins such as Au. anamensis began to show thicker enamel and bigger molars and premolars, suggesting a major shift in diet. But until recently, researchers were unable to test this by studying the carbon isotopes in the teeth of such old fossils because the method of removing the isotopes was too destructive. Now, with new laser ablation methods available in the last 15 years, they are able to sample the carbon isotopes without destroying the teeth.

Brunet gave Julia Lee-Thorp, an archaeologist at the University of Oxford in the United Kingdom and a specialist in isotopic analyses of fossil tooth enamel, permission to test the isotopes in three teeth from three individuals of the species Au. bahrelghazali from the Djurab Desert in Chad. This species is a close relative of the famous partial skeleton of Lucy, whose species Au. afarensis lived at the same time in east Africa. The fossil teeth of the three Au. bahrelghazali individuals ranged in age from 3 million to 3.5 million years old and were enriched in 13 C. That's the signature of a diet rich in grasses and sedges, such as reeds, grasses, and tuberous roots that would have grown around the floodplains and sub-basins of the ancient Lake Chad. "It was surprising because these guys were alive pretty early (in human evolution)," Lee-Thorp says.

The results imply that at least one species of hominin had already become a generalist that had adapted to a broader diet, foraging opportunistically in more open terrain for a wider range of foods than chimpanzees preferred, says anatomist Christopher Dean of the University College London. It would be interesting to know whether other hominins alive 3 million to 3.5 million years ago, including Au. afarensis, had also made this shift to grazing on grass.

Or, as University of Arkansas, Fayetteville, paleoanthropologist Peter Ungar puts it: "Maybe hominin cows weren't that unusual?"

The Real Caveman Diet

Did real cavemen follow the “prehistoric diet”?

Janek Skarzynski/AFP/Getty Images.

Russian scientists claim to have grown a plant from the fruit of an arctic flower that froze 32,000 years ago in the Arctic. That’s about the same time the last Neanderthals roamed the Earth. This particular plant doesn’t produce an edible fruit analogous to an apple or nectarine, but rather a dry capsule that holds its seeds. Did hominids eat fruits and veggies during the Neanderthal era?

They definitely ate fruit. Last year, paleoanthropologists found bits of date stuck in the teeth of a 40,000-year-old Neanderthal. There’s evidence that several of the fruits we enjoy eating today have been around for millennia in much the same form. For example, archaeologists have uncovered evidence of 780,000-year-old figs at a site in Northern Israel, as well as olives, plums, and pears from the paleolithic era. Researchers have also dug up grapes that appear to be 7 million years old in northeastern Tennessee (although, oddly, the grapes are morphologically more similar to today’s Asian varieties than the modern grapes considered native to North America). Apple trees blanketed Kazakhstan 30,000 years ago, oranges were common in China, and wild berries grew in Europe. None of these fruits were identical to the modern varieties, but they would have been perfectly edible.

Vegetables are a different story. Many of the ones we eat today have undergone profound changes at the hands of human farmers. Consider the brassicas: Between 8,000 and 10,000 years ago, humans took a leafy green plant and, by selecting for different characteristics, began to transform it into several different products. Modern kale, cabbage, broccoli, cauliflower, Brussels sprouts, and kohlrabi are all members of the same species, derived from a single prehistoric plant variety. Wild carrots may predate human agriculture, but they’re unpalatable and look nothing like the cultivated variety. The earliest domesticated carrots were probably purple, and the orange carrot emerged in the 17 th century. While legumes predate the dawn of man, modern green beans are a human invention.

It’s not altogether clear why fruits have changed less than vegetables, but it might have something to do with their evolutionary purpose. Plants developed sugary fruits millions of years ago so that sweet-toothed mammals would gobble them up and disseminate the seeds. By the time hominids descended from the African tree canopy, delicious fruits were widely available with no need for artificial selection. Since vegetables gain nothing from being eaten, they didn’t experience the same pressure to evolve delectable roots, stems, and leaves.

Just because there are some paleolithic fruits in production today doesn’t mean you can easily mimic the paleolithic diet. Modern apples, dates, figs, and pears aren’t necessarily nutritionally equivalent to their late Stone Age ancestors. Selection by humans has made them larger and sweeter, and may have caused other chemical changes. Ancient man also ate plants that you can’t find at a grocery store, like ferns and cattails. His relative dietary proportions of meats, nuts, fruits, and vegetables are in dispute, and probably varied significantly with location. Some paleoanthropologists also believe hunter-gatherers ate a far wider variety of foods than modern man, each in a smaller quantity, to minimize the risk of poisoning.


  1. Lawly

    It is known to you, she said in ...

  2. Esau

    Yes, it seemed like that to me too.

  3. Thomkins

    It is known to a god!

  4. Vijar

    magnificent thought

  5. Patricio

    Obviously you were mistaken...

  6. Emmett

    Mlyn, spammers have already got it freely with this primitive!

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