Tag Archives: evolution

Human Brain Size Shrinking For Last 10,000+ Years

An article at Scientific American offers some explanations, but nobody knows why with certainty. Maybe it’s simply related to the decline in average human body size that started about 10,000 years ago, the dawn of the Agricultural Revolution.

I’d credit the SciAm author but can’t figure out who it is. A quote:

The way we live may have affected brain size. For instance, domesticated animals have smaller brains than their wild counterparts probably because they do not require the extra brainpower that could help them evade predators or hunt for food. Similarly, humans have become more domesticated.

Discovery magazine looked at shrinking brains in 2010.

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.

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.

QOTD: Dobzhansky on Evolution

Nothing in biology makes sense except in the light of evolution.


Man’s Best Friend For How Long?

Dogs May Have Been Domesticated 33,000 Years Ago according to an article at Yahoo!News.  The DNA in the old skull found in Siberia was a closer match to dogs than to wolves.  Apart from the DNA evidence, the skull appeared more similar to a dog’s than an wolf’s.  Earlier evidence suggested dogs were first domesticated in the Middle East or East Asia.

Here’s the report in PLOS One.

If Teeth Are So Important For Survival…

…why do modern cultures have so many dental problems?

An oldie but goodie from Dr. Stephan Guyenet:

Our ancestors had straight teeth, and their wisdom teeth came in without any problem. The same continues to be true of a few non-industrial cultures today, but it’s becoming rare. Wild animals also rarely suffer from orthodontic problems.

Today, the majority of people in the US and other affluent nations have some type of malocclusion, whether it’s crooked teeth, overbite, open bite or a number of other possibilities.

Read the rest.

I rarely hear dentists or orthodontists talk about these ideas.  Wonder why.

Why Is Polycystic Ovary Syndrome So Common If It Impairs Fertility?

I don’t have an answer, but Corbett and Morin-Papunin have some ideas in their new article at Molecular and Cellular Endocrinology.  I’ve not read it, but here’s a quote from the abstract:

The Polycystic Ovary Syndrome (PCOS) is a complex endocrine disorder characterised both by reproductive and metabolic disturbance, and is the most common cause globally of ovarian infertility. It is also a familial polygenic condition, linked genetically to both Type 2 diabetes and the metabolic syndrome. The striking evolutionary paradox of this prominent genetically-based condition, which impairs fertility, is that not only should it have diminished in prevalence, but it should have done so rapidly – unless there has been some form of balancing selection.

PCOS affects between six and 12% of women.

A Default Position on the Omega-6/Omega-3 Debate

ASBMB Today has a well-written balanced article on the omega-6/omega-3 fatty acid ratio debate written by Rajendrani Mukhopadhyay.  A fair amount of it is understandable to non-science majors.  The main question is whether the high consumption of omega-6 fatty acids in Western societies is unhealthy.

It’s estimated that throughout most of human evolution, our dietary omega-6/omega-3 ration has been around 3:1 or 2:1.  Today, it’s about 15:1, thanks to a large increase in omega-6 consumption.  Are our bodies adapted for the lower ratio?  A hard-core paleo diet like Dr. Cordain’s aims for that lower ratio.

Both sides of the debate agree that we would probably be better off eating more omega-3 fatty acids, as found in cold-water fatty fish.

I’m an omega-6/omega-3 ratio agnostic at this point.  I’ve never studied it in depth, so I have no strong opinion either way.

Here are a couple excerpts from the article to pique your interest:

No one is disputing that we’re eating more omega-6 than our predecessors did. Over the past 100 years, consumption of linoleic acid [an omga-6] has increased dramatically in the U.S., mainly through the use of soybean oil. Soybean oil intake has gone up from being 1 percent of calories in the American diet to as much as 10 percent, according to Hibbeln. Lands, Salem and others contend that the rise, driven by the processed food and agriculture industries, has happened without anyone knowing its effects. “If I were now to try to get permission to change 10 percent of the calories in the U.S. diet, I would need a very large body of data unequivocally proving that it was safe,” says Hibbeln. “No such body of data exists for soybean oil. But it’s in our diet. We’re the experiment. It’s been a very large, uncontrolled intervention.”

Experts like Harris and Willett say this increase has been to our benefit. “We have seen a massive decline in cardiovascular disease mortality and huge increase in life expectancy,” says Willett. “Not all the benefit is due to the increase in linoleic acid, but almost certainly much of it is. It was not an absolute disaster.” But the lipid biochemists counter that it’s not just cardiovascular disease at stake. They say diabetes, obesity and even psychiatric disorders are some outcomes of a diet heavy on omega-6s.

I’ve never before heard anybody credit linoleic acid with a major role in our  “huge increase in life expectancy” over the last century.  I doubt that’s the case.  I vote more in favor of better sewage systems, cleaner water, better hygiene, antibiotics, or improvements in surgery and medical care.

Evolutionary biologist Theodosius Dobzhansky said, “Nothing in biology makes sense except in the light of evolution.”  If that’s true, the default position is that lower amounts of omega-6 fatty acid are better than our current high consumption.  It’s up to the high-consumption proponents to prove otherwise.

Steve Parker, M.D.

h/t David Despain

PS: Dobzhansky was a Christian, by the way.

PPS: A Twitter reader (@pronutritionist) suggested that the modern Western dietary omega-6/omega=3 ratio is 9.6, not 15:1, citing Amer J Clin Nutr.  My source for 15:1 is Journal of Nutrition and Metabolism, vol. 2012, article ID 539426, doi 10.1155/2912/539426, by E. Patterson et al. I admit it’s not a great reference. Cordain’s 2002 book, The Paleo Diet, says 10:1.  Maybe it is closer to 10:1.  I’m sure there’s lots of inter-person variability.

Notable Quotes From Kuipers’ “Multidisciplinary Reconstruction of Palaeolithic Nutrition”

Australian Aborigine in Swamp Darwin

I scored of copy of “A multidisciplinary reconstruction of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilisation” by RS Kuipers, JCA Joordens, and FAJ Muskiet. I’m not going to review it here. I’m just assembling some interesting “facts” for my files, so this could be boring. You won’t offend me much if you stop reading now.

This paper is from the University Medical Center Groningen and Human Origins Group (Faculty of Archaeology, Leiden University), both in The Netherlands. It’s 23 pages long, not counting the 450 references.

I’ll following the spelling conventions of the paper’s publisher.


“…our genome has remained basically unchanged since the beginning of the Palaeolithic era.”

“Since the onset of the Agricultural Revolution, some 10 thousand years ago, and notably in the last 200 years following the start of the Industrial Revolution, humans have markedly changed their dietary habits. Consequently, it has been advocated that the current pandemic of diseases of civilization results in part from the mismatch between the current diet and our Palaeolithic genome.”

These are some of the diseases that may result from the mismatch of our Palaeolithic genome and modern lifestyle (including diet): type 2 diabetes, high blood pressure, osteoporosis, fertility problems (polycystic ovary syndrome), pregnancy complications (pre-eclampsia, gestational diabetes), some cancers (colon, breast, prostate), heart disease (such as coronary artery disease), major and postpartum depression, autism, schizophrenia, some neurodegenerative diseases (Parkinsons disease, Alzheimer’s disease). [Sorry, Dr. Cordain – no mention of acne. And I wonder about dental and eye problems.]

Evolutionary Medicine

“Many, if not all, diseases can become explained [sic] by both proximate and ultimate explanations. The science searching for the late explanations has become known as ‘evolutionary medicine.’ Unfortunately, modern medicine deals mostly with proximate explanations, while ultimate explanations seem more prudent targets for long-time disease prevention.”

The term “evolutionary medicine” was coined by Randolph M. Nesse and George C. Williams in the early 1990s. It’s also called Darwinian medicine.

“…about 20% of modern hunter-gatherers reach at least the age of 60 years.”

After the transition to the Agricultural Revolution about 10,000 years ago, life expectancy fell from about 40 years to about 20 years. This is astounding news to me, assuming it’s accurate.  (Remember that for most of human existence, infant and child mortality has been very high. If an infant dies at 6 months old and an adult dies at 40 years, average life expectancy for the two would be about 20 years.)

Average life expectancy among modern hunter-gatherers is about 40 years—same as it was for students of the Harvard College class born in 1880.

Life expectancy in the Neolithic era was stable until the late 18th century, rarely exceeding 25 years in civilized nations.  At that point, life expectancy started to improve dramatically thanks to sanitation, water and food hygiene, immunizations, and quarantine practices. (Thomas Jefferson was the third president of the U.S.  His wife Martha had six children but only two survived to adulthood.)

The earliest species in the genus Homo appeared about  two million years ago.   Homo sapiens appeared about 200,000 years ago in south or east Africa. Several different hominin lines co-existed with modern humans.

The current world population of humans may be derived for only 1000 or so individuals that survived a decimating event.

The ability to store fat is one of the things that differentiate us from other primates.

Hunting and Our Ancient Diet

The composition of the early human diet is still hotly debated.

Lotta work to snag one of these

In modern hunter-gatherers, only about 30% of diet energy is derived from hunting, with the rest coming from gathering plant food and aquatic animals.

In contrast to the arid, hot, iconic savanna, “…the combined evidence strongly suggests that early hominins frequented the land-water ecosystem and thus lived there.” If rainfall and other conditions allowed, there would be wooded grasslands.

“…the proportion of the human gut dominated by the small intestine (>56%) suggests adaptation to a diet that is highly digestible, indicating a closer structural analogy with carnivores than to [animals that eat leaves and fruit].”

“The data of combined studies of early hominins and the more recent hominins suggest a gradual increase in dietary animal protein, a part of which may derive from aquatic resources. In the more recent human ancestors, a substantial part of the dietary protein was irrefutably derived from marine resources, and this habit was only abandoned in some cases after the introduction of agriculture at the onset of the Neolithic.”

Sea levels have risen over the past 17,000 years, up to 150 meters.

“In conclusion, there is ample archeological evidence for a shift from the consumption of plant towards animal foods.”

“For a long time period in hominin evolution, hominins derived large amounts of energy from (terrestrial and aquatic) animal fat and protein. This habit became reversed only by the onset of the Neolithic Revolution in the Middle East starting about 10,000 years ago.”

“The Homo genus has been on earth for at least 2.4 million years and for over 99% of this period has lived as hunter-gatherers.”

“We conclude that gathering plays, and most likely always played, the major role in food procurement of humans. Although hunting doubtlessly leaves the most prominent signature in the archaeological record, gathering of vegetables and the collection of animal, notably aquatic, resources (regardless of whether their collection is considered as either hunting or gathering), seems much easier compared with hunting on the hot and arid savanna. We suggest that it seems fair to consider these types of foods as an important part of the human diet, unless proven otherwise. Conversely, while hunting might have played a much more important role at higher latitudes, dietary resources in these ecosystems are rich in n-3-fatty acids (for example, fatty fish and large aquatic mammals), while the hominin invasion of these biomes occurred only after the development of more developed hunting skills.”

Even though traditional Maasai showed extensive atherosclerosis with fibrous changes and lipid infiltration, they had very few complicated arterial lesions and rarely had clinical cardiovascular disease events.

The Agricultural and Industrial Revolutions

“Contrary to earlier belief, the advent of agriculture coincided with an overall decline in nutrition and general health, but at the same time provided an evolutionary advantage since it increased birth rates and thereby promoted net population growth.”  [Both supporting references are from CS Larsen.]

Good news for birth rates

With the advent of the Industrial Revolution, nutritional quality and general health declined even more rapidly.

“Among the many dietary and lifestyle changes are: a grossly decreased n-3:n-6 fatty acid ratio, the combined high intakes of saturated fatty acids and carbohydrates, the introduction of industrially produced trans-fatty acids, reduced intakes of n-3 and n-6 long-chain polyunsaturated fatty acids, reduced exposure to sunlight, low intakes of vitamins D and K, disbalanced anti-oxidant status and high intakes of carbohydrates with high glycaemic indices and loads, such as sucrose and industrially produced high-fructose maize syrup.”  [Aren’t we eating more n-6 fatty acids, not less?]

Potential Benefits of a Palaeolithic Diet

The authors conclude with a review of the few medical scientific studies of Palaeolithic diets in modern humans. These are the ones by Frassetto, Osterdahl, Jönsson, and Lindeberg. I’ve already reviewed those here.  They missed O’Dea and Kerin’s study.

My Overall Impressions

This article seems very well researched.  It lays out a logical framework for the discipline of evolutionary medicine and should spur further clinical research.  It’s well worth a read if you have more than a passing interest in paleo lifestyle theory.

Bear in mind I’m not a paleontologist, anthropologist, paleo-anthropologist, or archeologist.  So caveat lector.

Steve Parker, M.D.  (B.S. degree in zoology)

Reference: Kuipers,RS; Joordens, JCA; and Muskiet, FAJ. A multidisciplinary reconstitution of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilization. Nutrition Research Reviews, 25 (2012): 96-129.  doi: 10.1017/S0954422412000017

PS: The Paleolithic diet is also called paleo, ancestral, hunter-gatherer, Stone Age,  Old Stone Age, and caveman diet.

Why Do Our Teeth Rot?

The truth is that tooth decay is a relatively new phenomenon. Until the rise of agriculture roughly 10,000 years ago, THERE WAS NO TOOTH DECAY IN HUMANS.  Let that sink in for a moment. Humanity is 2,500,000 years old.  For the fist 2,490,000 years no one ever had a cavity.  If we understand that tooth decay started when people started farming instead of hunting and gathering for a living clearly you realize that tooth decay is a disease or mismatch between what you are eating and what your body expects you to eat.  If we examine the past as prologue it becomes clear that the path to proper health starts in the mouth and the answers are so simple that not only did a Cave Man do it.  They perfected it.

John Sorrentino in a blog post August 6, 2012