PNAS Early Edition Isotopic Data Does Not Indicate Grass Consumption

Isotopic Data Does Not Indicate Grass Consumption | The Paleo Diet

You may remember a series of scientific papers were published in the Proceedings of the National Academy of Sciences evaluating the diet of numerous species of fossilized hominins, bipedal or upright walking apes, who lived in Africa from 4.1 to 1.4 million years ago.1234 These papers were grossly misinterpreted by the mass media, suggesting our early ancestors were regular consumers of grass and grass seeds (cereal grains).5, 6, 7

Poor research and analysis by a number of science writers have done their readers a disservice by inaccurately reporting the details of these three studies, making assumptions, and drawing conclusions that ancient hominin diets that the scientists themselves did not make.

The formal letter sent to the Proceedings of the National Academy of Sciences to address shortcomings was published in today’s Early Edition: “African hominin stable isotopic data do not necessarily indicate grass consumption.” I encourage you to read it carefully, revisit the original rebuttal published on The Paleo Diet Blog, and help guide others to make informed judgments.


Loren Cordain, Ph.D., Professor Emeritus

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1. Matt Sponheimer, Zeresenay Alemseged, Thure E. Cerling, Frederick E. Grine, William H. Kimbel, Meave G. Leakey, Julia A. Lee-Thorp, Fredrick Kyalo Manthi, Kaye E. Reed, Bernard A. Wood, and Jonathan G. Wynn. Isotopic evidence of early hominin diets. PNAS 2013 : 1222579110v1-201222579.

2. Jonathan G. Wynn, Matt Sponheimer, William H. Kimbel, Zeresenay Alemseged, Kaye Reed, Zelalem K. Bedaso, and Jessica N. Wilson. Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia. PNAS 2013 : 1222559110v1-201222559.

3. Thure E. Cerling, Fredrick Kyalo Manthi, Emma N. Mbua, Louise N. Leakey, Meave G. Leakey, Richard E. Leakey, Francis H. Brown, Frederick E. Grine, John A. Hart, Prince Kaleme, Hélène Roche, Kevin T. Uno, and Bernard A. Wood. Stable isotope-based diet reconstructions of Turkana Basin hominins. PNAS 2013 : 1222568110v1-201222568

4. Thure E. Cerling, Kendra L. Chritz, Nina G. Jablonski, Meave G. Leakey, and Fredrick Kyalo Manthi. Diet of Theropithecus from 4 to 1 Ma in Kenya. PNAS 2013 : 1222571110v1-201222571

5. Arnold, Carrie. “Even Our Ancestors Never Really Ate the “Paleo Diet” – The Crux |” DISCOVER Magazine: The Crux. Kalmbach Publishing Co., 3 June 2013.

6. Joyce, Chris. “Grass: It’s What’s For Dinner (3.5 Million Years Ago).” NPR the Salt. NPR, 3 June 2013.

7. Griffin, Catherine. “Human Ancestors’ Ape-like Diet Changed 3.5 Million Years Ago to Grass.” Science World Report: Nature & Environment. Science World Report, 4 June 2013.

About the Author:

Loren Cordain, PhD, Professor Emeritus Dr. Loren Cordain is Professor Emeritus of the Department of Health and Exercise Science at Colorado State University in Fort Collins, Colorado. His research emphasis over the past 20 years has focused upon the evolutionary and anthropological basis for diet, health and well being in modern humans. Dr. Cordain’s scientific publications have examined the nutritional characteristics of worldwide hunter-gatherer diets as well as the nutrient composition of wild plant and animal foods consumed by foraging humans. He is the world’s leading expert on Paleolithic diets and has lectured extensively on the Paleolithic nutrition worldwide. Dr. Cordain is the author of six popular bestselling books including The Real Paleo Diet Cookbook, The Paleo Diet, The Paleo Answer, and The Paleo Diet Cookbook, summarizing his research findings.

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