Category Archives: Paleo Theory

A Brief History of Human Evolution and Migration

paleo diet, Paleolithic diet, hunter-gatherer diet

Huaorani hunter in Ecuador

Evolutionary theory holds that we humans—Homo sapiens—evolved from non-human primates (hominins) in a process that started 2.5 million years ago in Africa. Prominent ancestors include Homo habilis (2.3 million years ago) and Homo erectus (1.8 million years ago).

Homo sapiens eventually hit the scene 200,000 years ago, probably in east Africa, which is considered the cradle of humanity. (All Americans can honestly fill out forms that ask for our race as “African-American.”) The paleoanthropologists tell us we share many genetic traits with long-extinct hominins from two million years ago.

African Diaspora


The “Out of Africa” hypothesis to explain the worldwide spread of humans says that Homo sapiens arose in Africa, then began migrating out 50 or 100,000 years ago. A competing “multiregional” hypothesis involves Homo erectus dispersing to many regions throughout Africa, Europe, and Asia, then somehow interbreeding and culminating in Homo sapiens in several regions. Homo erectus may have begun to spread out of Africa as long as 1.4 million years ago. Among the experts, the Out of Africa theory is currently favored over the multiregional hypothesis.

Anyway, starting roughly 100,000 years ago, anatomically modern humans began migrating out of Africa, into the Near East. By 50,000 years ago we were into South Asia, then Australia 40 or 50,000 years ago. We spread to Europe 40,000 years ago. Northeast Asians moved into North America (Alaska) 12 to 30,000 years ago; South America followed. We have evidence of behaviorally modern humans from about 50,000 years ago, if not longer. In other words, in addition to looking like us, they acted like us. At this point, we’ve made it to every spot on Earth that can support life. Not to mention the moon.

As points of reference, the Bronze Age started 5,500 years ago in the Near East and the earliest known writing was 5,000 years ago.

I wonder if God made Adam and Eve 200,000 years ago, and Homo habilis, Homo erectus, and our other hominin “ancestors” are just extinct animals like the dodo bird and dinosaurs. Probably not.

Steve Parker, M.D.

Segmented Sleep: Our Ancestral Pattern?


Richard Wrangham estimates hominins tamed fire and started cooking with it 1.8 million years ago

I heard about segmented sleep a couple years ago. The idea is that you sleep for maybe three hours, then get up and putter around for two or three hours, then go back to sleep for another three or four hours.

The easy availability of light after sunset has changed our sleeping patterns only recently, on an evolutionary scale. Before we had electric lights, candles, oil and gas lamps, our only sources of artificial light after sundown were campfires and short-lived torches.

Karen Emslie has an article on segmented sleep at Aeon. A snippet:

Before electric lighting, night was associated with crime and fear – people stayed inside and went early to bed. The time of their first sleep varied with season and social class, but usually commenced a couple of hours after dusk and lasted for three or four hours until, in the middle of the night, people naturally woke up. Prior to electric lighting, wealthier households often had other forms of artificial light – for instance, gas lamps – and in turn went to bed later. Interestingly, Ekirch found less reference to segmented sleep in personal papers from such households.

For those who indulged, however, night-waking was used for activities such as reading, praying and writing, untangling dreams, talking to sleeping partners or making love. As Ekirch points out, after a hard day of labouring, people were often too tired for amorous activities at ‘first’ bedtime (which might strike a chord with many busy people today) but, when they woke in the night, our ancestors were refreshed and ready for action. After various nocturnal activities, people became drowsy again and slipped into their second sleep cycle (also for three or four hours) before rising to a new day. We too can imagine, for example, going to bed at 9pm on a winter night, waking at midnight, reading and chatting until around 2am, then sleeping again until 6am.

Think about this if you have insomnia that wakes you in the middle of the night and you can’t get back to sleep. It may not be a detrimental condition that requires medication or other intervention. Can you really win a fight with a million years of evolution?


Steve Parker, M.D.

Ever Heard of Paleolithic Diet Pioneer Arnold De Vries?

paleo diet, Paleolithic diet, hunter-gatherer diet

Not Arnold Paul De Vries or Don Wiss, but a Huaorani hunter in Ecuador

Don Wiss turned me on to another “modern” paleo diet pioneer, Arnold Paul De Vries, who wrote a 1952 book called Primitive Man and His Food. I even found the book on the Internet a few months ago, perhaps in violation of copyright. I can’t find it now. You can request a digital copy of the book here.

I read his thoughts on the diets of North American Indians before my other duties interrupted me.

Steve Parker, M.D.

Reference (see Comments)

Evolutionary Aspects of Obesity, Insulin Resistance, and Cardiovascular Risk

paleo diet, Paleolithic diet, hunter-gatherer diet

Huaorani hunter in Ecuador

Spreadbury and Samis have a review-type article in Current Cardiovascular Risk Reports. Here’s the abstract:

Cardiovascular disease (CVD) is still virtually absent in those rare populations with minimal Western dietary influence. To date, exercise, altered fats, fibre, anti-oxidants or Mediterranean diet do not appear to overcome the discrepancy in CVD between hunter-gatherer and Western populations. The CVD risk factors of obesity and diabetes are driven by increased caloric intake, with carbohydrates potentially implicated. Paradoxically, non-Westernized diets vary widely in macronutrients, glycemic and insulinemic indices, yet apparently produce no obesity or CVD regardless, even with abundant food. ‘Ancestral’ grain-free whole-food diet may represent the best lifestyle intervention for obesity and CVD. Such diets are composed of the cells of living organisms, while Western grains, flour and sugar are dense, acellular powders. Bacterial inflammation of the small intestine and vagal afferents appears a crucial step in leptin-resistance and obesity. Therefore it may be important that the Western diet resembles a bacterial growth medium.

You may remember Spreadbury’s name from his theory about acellular carbohydrates causing obesity via alterations in gut microorganisms. Spreadbury is with the Gastrointestinal Diseases Research Unit, Queen’s University, Kingston, Ontario, Canada.

You can read the articles for yourself. The following are a few of the authors points I found interesting or want to remember.

Does physical activity explain differences in CVD between Westernized and non-Westernized Peoples? They say “maybe.”

Throughout the article are references to aboriginals like the Hadza, Kitavans, Ache, Shuar, Australian aborigines, and Inuits. I always take comparisons of them to modern Europeans with a grain of salt, because of potential genetic differences between the populations. Moreover, diet and activity levels are only two of myriad cultural differences.

Australian Aborigine in Swamp Darwin

Australian Aborigine in Swamp Darwin

Can dietary changes reduce the incidence of CVD? They say it’s unclear.

Regarding modern paleo diet trials, “All the studies with ad libitum eating [eat all you want] have reported a spontaneous reduction in caloric intake in the order of 15-30%.” (Three references.) “The reduced food intake appeared driven by a satiety increase that was apparently not explicable by energy density, fiber or macronutrient content.” (One reference.)

“In those eating a Westernized diet, carbohydrates are increasingly recognized as being associated with poor metabolic health.” Evidence? Only one reference cited: Zienczuk’s 2012 article on high arctic Inuits.

“…non-Westernized populations with excellent metabolic and cardiovascular health almost invariably have negligible dietary contribution from grains, as well as refined sugar.” No citations.

“For ‘western-style’ diets and most obesogenic diets tested, gut microbiota appear to play a crucial role in obesity.” That’s a bold statement. References? Only one, a mouse study.

The rest of the article is about Spreadbury’s acellular carb/obesity theory. He suggests that small intestine bacteria play a more prominent role than colonic germs. Bacterial-driven inflammation….

The authors provide an example of a grain-free whole-food diet. It’s unrestricted in fruit, leafy or root vegetables, unprocessed meats, eggs, fish, nuts (except peanuts), mushrooms, herbs and spices. Occasional foods to be eaten in moderation are legumes, rice, yogurt, milk, cheeses, sweet corn, palm oil/lard/olive oil, and salt. Avoid almost all processed foods, breads, cereals, cakes/cookies/donuts etc., refined sugars, dried or processed fruits, vegetable/seed oils, and processed meats. They advise a vitamin D supplement. I’m not sure if they came up with this diet on their own, or it’s S. Lindeberg’s outline.

A final quote:

The macronutrient independence of the health from ancestral diet suggests whole foods are more important to health than their macronutrient or other chemical components, and that good health is associated with unprocessed cellular foods. Flour, sugar and processed foods appear to be important drivers of Western metabolic dysfunction, overweight and inflammation, and may prove to have a profound impact on, or even be the initiators of cardiovascular disease.

I’m sure Spreadbury and Samis would agree we need more basic science and clinical research into these issues, involving human test subjects. Maybe I’m prejudiced, but I’m more interested in Asians, Africans, and Europeans than Shuar people.

Steve Parker, M.D.

Reference: Spreadbury, Ian and Samis, Andrew J.S. Evolutionary aspects of obesity, insulin resistance, and cardiovascular risk. Current Cardiovascular Risk Reports, April 2013, vol. 7, issue 2, pp. 136-146.

Another Review Article In Favor Of Paleolithic Eating

It’s in the Annual Review of Plant Biology. The authors promote fruit and vegetable consumption. A snippet from the 2013 article:

Our Paleolithic ancestors were hunter-gatherers, consuming diets rich in lean wild meat or fish, with relatively high consumption of fruits and green leafy vegetables. Our modern diets, in contrast, are high in saturated fats and starches, added sugars with high energy load, and “unnatural fats” such as transfats. Paleolithic diets, in contrast to those of simians and present-day hunter-gatherers, are estimated to have been approximately 75% fruit [that’s news to me; reference is from S. Lindeberg]. In modern US diets, foods unavailable to Paleolithic societies—including dairy products, cereal grains, refined cereal flour, refined sugars, refined vegetable oils, and alcohol—on average make up 70% of total energy consumption. Of this, 50% is in the form of vegetable oils and refined sugars .Americans currently consume less than 60% of the US Department of Agriculture recommendations for vegetables and less than 50% of the recommendations for fruits.

h/t Bill Lagakos

Reference: Annu. Rev. Plant Biol. 2013. 64:19–46. This article’s doi:10.1146/annurev-arplant-050312-120142

The Mellberg Study: Paleo Diet and Obese Postmenopausal Women

Sweden's Flag. Most of the researchers involved with this study are in Sweden

Sweden’s Flag

Swedish researchers compared a Paleolithic-type diet against a lower-fat, higher-carb diet so often recommend in Nordic countries and in the U.S. Test subjects were obese but otherwise healthy older women. The study lasted two years. Dieters could eat as much as they wanted.

They found that the paleo-style dieters lost more weight, lost more abdominal fat, and lowered their trigyceride levels. When measured six months into the study, the paleo dieters had lost 6.5 kg (14 lb) of body fat compared to 2.6 (6 lb) kg in the other group.

Measured at two years out, the paleo dieters had lost 4.6 kg (10 lb) of body fat compared to 2.9 kg (6 lb) in the other group, but this difference wasn’t statistically significant.

The greatest weight loss was clocked at 12 months: Paleo dieters were down 8.7 (19 lb) kg compared to 4.4 kg (10 lb)  in the other group.

But this study was about more than weight loss. The investigators were also interested in cardiometabolic risk factors and overall body composition.

The Set-Up

I don’t know what the researchers told the women to get them interested. Weight loss versus healthier diet versus ?  This could have influenced the type of women who signed up, and their degree of commitment.

A newspaper ad got the attention of 210 women in Sweden; 70 met the inclusion criteria, which included a body mass index 27 or higher and generally good health. Average age was 60. Average BMI was 33. Average weight was 87 kg (192 lb). Average waist circumference was 105 cm (41 inches). The women were randomized into one of two diet groups (N=35 in each): paleolithic-type diet (PD) or Nordic Nutrition Recommendations diet (NNR). There were no limits on total caloric consumption. (Were the women told to “work on weight loss”? I have no idea.)

We don’t know the ethnicity of these women.

Here’s their version of the paleo diet:

  • 30% of energy (calories) from protein
  • 40% of energy from fat
  • 30% of energy from carbohydrate
  • high intake of mono- and polyunsaturated fatty acids
  • based on lean meat, fish, eggs, vegetables, fruits, berries, and nuts
  • additional fat sources were avocado and oils (rapeseed [canola] and olive) used in dressings and food preparation
  • cereals (grains), dairy products, added salt and refined fats and sugar were excluded
  • no mention of legumes, potatoes, or tubers

The NNR diet:

  • 15% of energy from protein
  • 25-30% of energy from fat
  • 55-60% of energy from carbohydrate
  • emphasis on high-fiber products and low-fat dairy products

Over the 24 months of the study, each cohort had 12 group meetings with a dietitian for education and support, including “dietary effects on health, behavioral changes and group discussion.”

Various blood tests and body measurements were made at baseline and periodically. Body measurements were made every six months. Body composition was measured by dual energy x-ray absorptiometry. Diet intake was measured by self-reported periodic four-day food records.

Stockholm Palace

Stockholm Palace


30% of participants (21) eventually dropped out by the end of the study and were lost to follow-up, leaving 27 in the PD group and 22 in the NNR cohort.

Food record analysis indicated the PD group indeed reduced their carb intake while increasing protein and fat over baseline. Baseline macronutrient energy percentages were about the same for both groups: 17% protein, 45% carb, 34% (I guess the percentages don’t add to 100 because of alcohol, which wads not mentioned at all in the article.) Two years out, the PD group’s energy sources were 22% protein, 34% carb, 40% fat. For the NNR group, the energy sources at two years were 17% protein, 43% carb, and 34% fat. As usual, dietary compliance was better at six months compared to 24 months. The PD group failed to reach target amounts of protein energy (30%) at six and 24 months; the NNR group didn’t reach their goal of carbohydrate energy (55-60%). The PD group ate more mono- and poly unsaturated fatty acids than the NNRs.

In contrast to the food record estimates of protein intake, the urine tests for protein indicated poor adherence to the recommended protein consumption in the PD group (30% of energy). Both groups ate the same amount of protein by this metric. (This is an issue mostly ignored by authors, who don’t say which method is usually more accurate.)

“Both groups had statistically significant weight loss during the whole study, with significantly greater weight loos in the PD group at all follow up time points except at 24 months.” Largest weight loss was measured at 12 month: 8.7 kg (19 lb) in the PD group versus 4.4 kg (10 lb) in the NNRs.

The PD group lost 6.5 kg (14 lb) of body fat by six months but the loss was only 4.6 kg (10 lb) measured at 24 months. Corresponding numbers for the NNR group were 2.6 and 2.9 kg (about 6 lb). So both groups decreased their total fat mass to a significant degree. The difference between the groups was significant (P<0.001) only at six months. The greatest weight loss was clocked at 12 months: PD dieters were down 8.7 kg (19 lb) compared to 4.4 kg (10 lb) in the NNRs. Both groups saw a significant decrease in waist circumference during the whole study, with a more pronounce decrease in the PD group at six months: 11 versus 6 cm (4.3 versus 2.4 inches).

Fasting blood sugars, fasting insulin levels, and tissue plasminogen activator activity didn’t change.

Both groups had improvements in blood pressure, heart rate, c-reactive protein, LDL cholesterol, PAI-1 activity, and total cholesterol. The PD group saw a greater drop in triglycerides (by 19% at two years, but levels were normal to start with at 108 mg/dl or 1.22 mmol/l).

Reported daily energy intake fell over time for both groups, without statistically significant differences between them.

paleo diet, Steve Parker MD, diabetic diet

Sweet potato chunks brushed with olive oil, salt, pepper, and rosemary. Ready for the oven.


As measured at six months, the paleo dieters lost 10% of their initial body weight, compared to 5% in the NNR group. That’s worth something to many folks. However, the researchers didn’t find much, if any, difference in the groups in terms of cardiometabolic risk factors. They wonder if that reflects the baseline healthiness of these women. Would a sicker study population show more improvement on one of the diets?

I’m surprised the NNR group lost any weight at all. In my experience it’s hard for most folks to lose weight and keep it off while eating as much as they want, unless they’re eating very-low-carb. We’ve seen short-term weight loss with ad libitum paleo diets before (here for example, and here, and here). I bet the women signing up for this study were highly motivated to change. 

Legumes and potatoes are a debatable part of the paleo diet. Most versions exclude legumes. We don’t know if these women ate legumes and potatoes. Other than this oversight, the study paleo diet is reasonable.

The authors noted that the paleo diet group failed to reach their protein intake goal (30% of total calories), and suggested reasons “such as protein-rich foods being more expensive, social influences on women’s food choices or a lower food preference for protein-rich food among women.”

The results of this study may or may not apply to other population subgroups and non-Swedes.

The authors write:

In conclusion, a Palaeolithic-type diet during two years with ad libitum intake of macronutrients, including an increased intake of polyunsaturated fatty acids and monounsaturated fatty acids reduces fat mass and abdominal obesity with significantly better long-term effect on triglyceride levels vs an NNR diet. Adherence to the prescribed protein intake was poor in the PD group suggesting that other component of the PD diet are of greater importance.

Does this study have anything to do with diabetes? Not directly. But it suggests that if an overweight diabetic needs to lose excess body fat without strict calorie control, a lower-carb paleo-style diet may be more effective than a low-fat, higher-carb diet. I would have liked to have seen lower fasting blood sugar and insulin levels in the paleo dieters, but wishing doesn’t make it so.

Steve Parker, M.D.

PS: Carbsane Evelyn has taken a look at this study and blogged about it here and here. I’ve not read those yet, but will now.

Reference: Mellberg, C., et al (including M. Ryberg and T Olsson). Long-term effects of a Palaeolithic-type diet in obese postmenopausal women: a 2-year randomized trial. European Journal of Clinical Nutrition, advance online publication January 29, 2014. doi: 10.1038/ejcn.2013.290

Do Intestinal Parasites Help Prevent Atherosclerosis?

A trio of Indian researchers suggest a new hypothesis to explain the modern pandemic of atherosclerosis (hardening of the arteries). They repeat the notion that atherosclerosis is uncommon in modern hunter-gatherers. But why?

Reviewing evolution-linked risk factors suggests that there are four aspects to the etiology of atherosclerosis namely, decreased intestinal parasitism, oversensitivity of evolutionarily redundant mast cells, chronic underactivation of AMPK (cellular energy sensor) and a deficiency of vitamin D. A combination of these four causes appear to have precipitated the atherosclerosis pandemic in modern times.

Click for the abstract. Pretty far out stuff. I haven’t read the full article. The authors are in the Departments of Pharmacology and Pharmacy Practice.

Have You Heard It’s Better to Squat Than Sit While Defecating?

It may prevent hemorrhoids, according to a writer at Slate.

I first heard about this debate around three years ago, probably at Mark’s Daily Apple. You don’t hear about it much now. An article at Huffington Post dredged it up recently. The Post will also tell you 14 other things you’re doing wrong in the bathroom. Take’em with a grain of salt.

I only bring this to your attention in case you’re new to the paleo lifestyle. It’s not just about food, ya know. Modern toilets haven’t been around forever. Billions of us still squat to poop, just like our ancestors.



Dr. Guyenet Makes a Case for Beans in the Paleo Diet

As an introduction, he writes…

The canonical Paleolithic diet approach excludes legumes because they were supposedly not part of our ancestral dietary pattern.  I’m going to argue here that there is good evidence of widespread legume consumption by hunter-gatherers and archaic humans, and that beans and lentils are therefore an “ancestral” food that falls within the Paleo diet rubric.  Many species of edible legumes are common around the globe, including in Africa, and the high calorie and protein content of legume seeds would have made them prime targets for exploitation by ancestral humans after the development of cooking.

Richard Wrangham thinks hominins started cooking with fire as long as 1.8 million years ago. There’s no expert consensus yet.

Read the rest.

The Argument Against Starches, Safe or Otherwise

Lifextension argues it as well as anyone I’ve read. Some quotes:

Chimpanzees produce salivary amylase to digest fruit; similarly, carnivores also possess amylase in order to process the glycogen residing in muscle meat. Moreover, animals fed alternatives to their natural diet will produce amylase in amounts corresponding to the quantity of carbohydrates consumed. Humans too have their own primordial amylase gene copy; we have possessed it ever since we were primates. The second copy mutation occurred somewhere between 100 – 200,000 years ago, however this may have resulted even more recently, as single nucleotide polymorphisms and copy number mutations can result in just thousands of years. The additional – and currently incomplete – copies occurred at the very most, around 25,000 years ago, but most plausibly they came about around 10,000 years ago, concurrent with the onset of agriculture, and confirming that high starch consumption was a historically late phenomenon. Many present day human populations from low-starch consuming ancestries still only have two copies, indicating that adaptation to high-starch consumption was not globally widespread.


Moreover, the current evidence engendered from nitrogen stable isotope analysis of hominin bone data – being studied by Professor Michael Richards and the Max Planck Institute for Evolutionary Anthropology – has confirmed that our human ancestors truly were high-level carnivores. In fact, one-hundred percent of the early hominin bones studied from Upper Palaeolithic Europe reveal an even more carnivorous stable isotope footprint than that of foxes and wolves; while, comparatively, the data from omnivores such as pigs or the Brown Bear validates that these species truly did have an omnivorous diet.

Read the whole enchilada. The debate continues.