Tag Archives: Brain Development

Big Brains Do Not Need Carbs | The Paleo Diet

Evolution. It is a complex and interesting process.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Whether you agree with Jerry Coyne or not, there is much fascination with what exactly has led us to the current bodies and brains which we inhabit.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Two weeks ago The Quarterly Review of Biology published a controversial paper entitled “The Importance of Dietary Carbohydrate in Human Evolution.”21 Its preceding press release22 added “Big Brains Needed Carbs,” ensuring the controversy-eager media would jump all over the publication, including the University of Sydney, home of the GI Foundation. Of course this media frenzy23, 24, 25 is without critical analysis, and is simply a regurgitation of the same story. So the researchers behind this paper argued that as humans evolved from our Paleolithic ancestry, we needed carbohydrates (particularly starch) in order to develop larger brains.

While certainly generating a large amount of buzz and receiving tremendous media attention, this scientific paper is severely flawed. Quite frankly, it is fairly baffling that it was able to survive the peer review process at all. There are a number of points that are incorrect, so without further ado, let’s delve into the details of exactly why we did not need starch, in order to help develop our current brains.

To start, researchers for the paper cite the use of fire as a key point in their argument. However, they incorrectly lead the reader into believing that the timeframe for humans using controlled fire was about 300,000-400,000 years ago, when they themselves contradict this with the statement that “the timing of widespread cooking is not known.” This is likely one misfire that should have been caught in the peer review process. In reality, our ancestors could only make fire in a controlled fashion, starting about 75,000 to 125,000 years ago.26, 27, 28, 29, 30, 31, 32, 33, 34 Hominid encephalization (enlargement of the brain), by contrast, began about 2 million years ago. 35, 36, 37

This is in addition to the researchers’ lack of scientific support for starch consumption compared with non-starchy vegetables, and the necessity of these foods in the human evolutionary process. And, if one were to veer to modern research, they would plainly see studies have proven a Paleo diet does not need to be high in starches or carbohydrates to vastly improve health.38, 39 Further, it is widely accepted that hepatic de novo gluconeogenesis (a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates) can provide brain and placental tissue with all the glucose required even on a carbohydrate free diet. The fact that previously published research by the paper’s author supports this,40 is a glaring inconsistency that is hard to reconcile.

Big Brains Do Not Need Carbs | The Paleo Diet

Figure 1: The Carnivore Connection hypothesis 1 and association with recent increased prevalence of insulin resistance (IR) and type 2 diabetes in susceptible (e.g., Pima Indian) and nonsusceptible (e.g., European) populations.

Suggesting early Homo acquired the capacity for endurance running as essential to exhaust prey is a weak assumption. This reference to persistence hunting, a method of hunting that utilizes the better thermoregulation of humans as compared to their prey, is only successful in a few select climates where thermoregulation is an issue. More importantly, the authors are clearly unaware of the research that measured the energetic cost of human running at different speeds.41 Researchers found, contrary to previous beliefs, individual humans do have optimal running speeds with respect to energetic cost, but it was also demonstrated “that the use of persistence hunting methods to gain access to prey at any running speed, even the optimum, would be extremely costly energetically, more so than a persistence hunt at optimal walking speed.” No starch is necessary for that. Even if the analysis on running efficiency were incorrect, and researchers proved persistence hunters did run at high intensities, the authors would need to explain the disconnect with their hypothesis with the fact that many present-day elite endurance athletes are succeeding on a low carbohydrate diet.

The fact is, our ancestors likely ate whatever they could – a fact, which is noted by modern Paleo diet researchers.42, 43 Current science supports the notion that dense acellular carbohydrates in the diet promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity.44 This is why modern Paleo diet research is conducted with the design of eliminating foods not available during the pre-agricultural period – rather than focusing on specific amounts and quantities of foods.

Big Brains Do Not Need Carbs | The  Paleo Diet

Spreadbury, Ian. “Comparison with Ancestral Diets Suggests Dense Acellular Carbohydrates Promote an Inflammatory Microbiota, and May Be the Primary Dietary Cause of Leptin Resistance and Obesity.” Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy 5 (2012): 175–189. PMC. Web. 19 Aug. 2015.

These researchers also fail to cite a very recent paper, which examined nuclear genome sequence data from Neandertals, Denisovans, and archaic anatomically modern humans.45 It was concluded “salivary amylase gene (AMY1) duplications were not observed in the Neandertal and Denisovan genomes, suggesting a relatively recent origin for the AMY1 copy number gains that are observed in modern humans. Thus, if earlier hominins were consuming large quantities of starch-rich underground storage organs, as previously hypothesized, then they were likely doing so without the digestive benefits of increased salivary amylase production.”

As you can see, there are a myriad of flaws in this paper. The conclusions reached by the authors contradict everything we know about uncooked starch metabolism in our gastrointestinal tract, the archaeological evidence for fire production, and the brain’s requirement for docosahexaenoic acid (DHA).46, 47 DHA was obtained by our ancestors, from animal foods – not starch – in order to synthesize nervous tissue.48, 49

Lastly, perhaps one of the most interesting flaws in this paper is that many scientific studies concluded chronically elevated blood sugar (which is directly influenced by carbohydrate consumption) is correlated with dementia.50 Certainly this is the exact opposite conclusion than the one reached by the paper’s authors, who would have you believe that we needed carbohydrates in order for our brains to thrive and develop.

Hopefully, it is clear we certainly did not need starch to develop our current brains, and in fact, too many carbohydrates (including starches) impair brain processes.51, 52, 53 The problem with this conclusion is not scientific – it is economic. For you see, it is quite easy to continually churn out starch-heavy foods and make a profit – as these foods are very cheap to produce. And, without an endorsement of carbohydrates, how could a company justify selling sugar water to us, en masse?54 Thanks to a diet rich in animal products and fat, you have a big enough brain to recognize the real scientific evidence and that unethical influences are at play here. Definitely some real food for thought.

Casey Thaler, B.A., NASM-CPT, FNS

Casey Thaler | The Paleo Diet TeamCasey Thaler, B.A., NASM-CPT, FNS is an NASM® certified personal trainer and NASM® certified fitness nutrition specialist. He writes for Paleo Magazine® and for PaleoHacks. He also runs his own nutrition and fitness consulting company, Eat Clean, Train Clean®. He is pursuing his Ph.D in Nutritional Biochemistry, hopefully from Harvard University.
Dr. Mark J. Smith

Dr. Mark J. Smith | The Paleo DietDr. Mark J. Smith graduated from Loughborough University of Technology, England, with a Bachelor of Science in PE & Sports Science and then obtained his teaching certificate in PE & Mathematics. As a top-level rugby player, he then moved to the United States and played for the Boston Rugby Club while searching the American college system for an opportunity to commence his Master’s degree. That search led him to Colorado State University where Dr. Smith completed his Masters degree in Exercise and Sport Science, with a specialization in Exercise Physiology. He continued his studies in the Department of Physiology, where he obtained his Doctorate. His research focused on the prevention of atherosclerosis (the build up of plaque in arteries that leads to cardiovascular disease); in particular, using low-dose aspirin and antioxidant supplementation.

Loren Cordain PhD, Professor Emeritus of Nutritional Science, Colorado State University, Fort Collins, Colorado

The Paleo Diet | Dr. Loren CordainDr. 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.


[1] Embley TM, Martin W. Eukaryotic evolution, changes and challenges. Nature. 2006;440(7084):623-30.

[2] Weinreich DM, Delaney NF, Depristo MA, Hartl DL. Darwinian evolution can follow only very few mutational paths to fitter proteins. Science. 2006;312(5770):111-4.

[3] Wang HY, Chien HC, Osada N, et al. Rate of evolution in brain-expressed genes in humans and other primates. PLoS Biol. 2007;5(2):e13.

[4] Petersen RC, Caracciolo B, Brayne C, Gauthier S, Jelic V, Fratiglioni L. Mild cognitive impairment: a concept in evolution. J Intern Med. 2014;275(3):214-28.

[5] Bramble DM, Lieberman DE. Endurance running and the evolution of Homo. Nature. 2004;432(7015):345-52.

[6] Jablonski NG, Chaplin G. The evolution of human skin coloration. J Hum Evol. 2000;39(1):57-106.

[7] Aiello L. C., Wheeler P. 1995. The expensive-tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology 36:199–221.

[8] Antón S. C., Snodgrass J. J. 2012. Origins and evolution of genus Homo: new perspectives. Current Anthropology 53:S479–S496.

[9] Crittenden A. N. 2011. The importance of honey consumption in human evolution. Food and Foodways 19:257–273.

[10] Kaplan H., Hill K., Lancaster J., Hurtado A. M. 2000. A theory of human life history evolution: diet, intelligence, and longevity. Evolutionary Anthropology 9:156–185.

[11] Wrangham R. W. 2007. The cooking enigma. Pages 308–323 in Evolution of the Human Diet: The Known, the Unknown, and the Unknowable, edited by P. S. Ungar. Oxford (United Kingdom): Oxford University Press.

[12] Wood B., Harrison T. 2011. The evolutionary context of the first hominins. Nature 470:347–352.

[13] Preuss TM, Cáceres M, Oldham MC, Geschwind DH. Human brain evolution: insights from microarrays. Nat Rev Genet. 2004;5(11):850-60.

[14] Leonard WR, Snodgrass JJ, Robertson ML. Effects of brain evolution on human nutrition and metabolism. Annu Rev Nutr. 2007;27:311-27.

[15] Northcutt RG. Changing views of brain evolution. Brain Res Bull. 2001;55(6):663-74.

[16] Hill RS, Walsh CA. Molecular insights into human brain evolution. Nature. 2005;437(7055):64-7.

[17] Cunnane SC. [Survival of the fattest: the key to human brain evolution]. Med Sci (Paris). 2006;22(6-7):659-63.

[18] Armelagos GJ. Brain evolution, the determinates of food choice, and the omnivore’s dilemma. Crit Rev Food Sci Nutr. 2014;54(10):1330-41.

[19] Gilbert SL, Dobyns WB, Lahn BT. Genetic links between brain development and brain evolution. Nat Rev Genet. 2005;6(7):581-90.

[20] Keverne EB. Epigenetics and brain evolution. Epigenomics. 2011;3(2):183-91.

[21] Karen Hardy, Jennie Brand-Miller, Katherine D. Brown, Mark G. Thomas, Les Copeland. The Importance of Dietary Carbohydrate in Human Evolution. The Quarterly Review of Biology, 2015; 90 (3): 251.

[22]Available at: http://press.uchicago.edu/pressReleases/2015/August/150806_qrb_hardy_et_al_paleo_diet.html. Accessed August 18, 2015.

[23] Available at: http://www.telegraph.co.uk/foodanddrink/foodanddrinknews/11798169/Did-cavemen-eat-carbs-Why-the-paleo-diet-could-be-wrong.html. Accessed August 16, 2015.

[24] Available at: http://www.nytimes.com/2015/08/13/science/for-evolving-brains-a-paleo-diet-full-of-carbs.html. Accessed August 16, 2015.

[25] Available at: http://www.geneticliteracyproject.org/2015/08/11/sorry-paleo-dieters-big-human-brain-needs-carbs-to-evolve/. Accessed August 16, 2015.

[26] James SR. Hominid use of fire in the Lower and Middle Pleistocene: A review of the evidence. Curr Anthropol. 1989;30:1–26.

[27] Clark JD, Harris JWK. Fire and its roles in early hominid lifeways. Afr Archaeol Rev. 1985;3:3–27.

[28] Gowlett JAJ, Harris JWK, Walton D, Wood BA. Early archaeological sites, hominid remains and traces of fire from Chesowanja, Kenya. Nature. 1981;294:125–129.

[29] Wrangham R. Catching Fire: How Cooking Made Us Human. New York: Basic Books; 2009.

[30] Wobber V, Hare B, Wrangham R. Great apes prefer cooked food. J Hum Evol. 2008;55:340–348.

[31] Karkanas P, et al. Evidence for habitual use of fire at the end of the Lower Paleolithic: Site-formation processes at Qesem Cave, Israel. J Hum Evol. 2007;53:197–212.

[32] Goren-Inbar N, et al. Evidence of hominin control of fire at Gesher Benot Ya’aqov, Israel. Science. 2004;304:725–727.

[33] Rowlett RM. Did the use of fire for cooking lead to a diet change that resulted in the expansion of brain size in Homo erectus from that of Australopithecus africanus? Science. 1999;284:741.

[34] Andre CC, Skinner AR, Schwarcz HP, Brain CK, Thackeray F. Further exploration of the first use of fire. PaleoAnthropology. 2010;2010:A1–A2.

[35] Leonard WR, Robertson ML, Snodgrass JJ, Kuzawa CW. Metabolic correlates of hominid brain evolution. Comp Biochem Physiol, Part A Mol Integr Physiol. 2003;136(1):5-15.

[36] Hofman MA. Encephalization in hominids: evidence for the model of punctuationalism. Brain Behav Evol. 1983;22(2-3):102-17.

[37] Foley RA, Lee PC. Ecology and energetics of encephalization in hominid evolution. Philos Trans R Soc Lond, B, Biol Sci. 1991;334(1270):223-31.

[38] Manheimer EW, Van zuuren EJ, Fedorowicz Z, Pijl H. Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr. 2015;

[39] Masharani U, Sherchan P, Schloetter M, et al. Metabolic and physiologic effects from consuming a hunter-gatherer (Paleolithic)-type diet in type 2 diabetes. Eur J Clin Nutr. 2015;

[40] Brand-miller JC, Griffin HJ, Colagiuri S. The carnivore connection hypothesis: revisited. J Obes. 2012;2012:258624.

[41] Steudel-Numbers KL, Wall-Scheffler CM. Optimal running speed and the evolution of hominin hunting strategies. J Hum Evol. 2009 Apr;56(4):355-60. doi: 10.1016/j.jhevol.2008.11.002. Epub 2009 Mar 18.

[42] Boers I, Muskiet FA, Berkelaar E, et al. Favourable effects of consuming a Palaeolithic-type diet on characteristics of the metabolic syndrome: a randomized controlled pilot-study. Lipids Health Dis. 2014;13:160.

[43] Spreadbury I. Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity. Diabetes Metab Syndr Obes. 2012;5:175-89.

[44] Sayers K, Lovejoy CO. Blood, bulbs, and bunodonts: on evolutionary ecology and the diets of Ardipithecus, Australopithecus, and early Homo. Q Rev Biol. 2014;89(4):319-57.

[45] Perry GH, Kistler L, Kelaita MA, Sams AJ. Insights into hominin phenotypic and dietary evolution from ancient DNA sequence data. J Hum Evol. 2015;79:55-63.

[46] Bradbury J. Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain. Nutrients. 2011;3(5):529-54.

[47] Singh M. Essential fatty acids, DHA and human brain. Indian J Pediatr. 2005;72(3):239-42.

[48] Guil-guerrero JL, Tikhonov A, Rodríguez-garcía I, Protopopov A, Grigoriev S, Ramos-bueno RP. The fat from frozen mammals reveals sources of essential fatty acids suitable for Palaeolithic and Neolithic humans. PLoS ONE. 2014;9(1):e84480.

[49] Bourre JM. [Effect of increasing the omega-3 fatty acid in the diets of animals on the animal products consumed by humans]. Med Sci (Paris). 2005;21(8-9):773-9.

[50] Crane PK, Walker R, Hubbard RA, et al. Glucose levels and risk of dementia. N Engl J Med. 2013;369(6):540-8.

[51] De la Monte, S. M., & Wands, J. R. (2008). Alzheimer’s Disease Is Type 3 Diabetes–Evidence Reviewed. Journal of Diabetes Science and Technology, 2(6), 1101–1113.

[52] Molteni R, Barnard RJ, Ying Z, Roberts CK, Gómez-pinilla F. A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience. 2002;112(4):803-14.

[53] Purnell JQ, Klopfenstein BA, Stevens AA, et al. Brain functional magnetic resonance imaging response to glucose and fructose infusions in humans. Diabetes Obes Metab. 2011;13(3):229-34.

[54] Available at: http://well.blogs.nytimes.com/2015/08/09/coca-cola-funds-scientists-who-shift-blame-for-obesity-away-from-bad-diets/. Accessed August 16, 2015.

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