House of Karls by Dr Karl Kruszelnicki – Extract


Today there are many diets available to anybody wanting to lose some weight – some might say too many. One current favourite is the so-called “Paleolithic Diet”.

In a nutshell, it claims that our Paleolithic hunter–gatherer ancestors lived in wondrous harmony with their environment, which gave them exactly the food they needed to live a long and happy life. This sweet congruence came to an unhappy end with the development of agriculture and grain-based diets. Furthermore, the Paleo Diet claims that the period of 12,000 years or so since we invented agriculture is far too short for our bodies to have evolved to cope with the new foods that agriculture has given us.

In other words, the key to a healthy and long life is to abandon our modern agricultural diets and eat what our Paleolithic ancestors ate.

But this claim is false – and has no basis in dietetic, evolutionary or archaeological reality.

What Is the Paleo Diet?

The Paleo Diet is also called the Stone Age Diet, and the Hunter–Gatherer Diet.

It was first promoted by the gastroenterologist Walter L. Voegtlin in the mid-1970s. He argued that we humans are carnivores (wrong), and that our Paleolithic ancestors ate a carnivore’s diet (wrong again). Therefore, he claimed, our diet should be meat and fat, with tiny amounts of carbohydrates.

The Diet was re-invented by S. Boyd Eaton and Melvin Konner in 1985. They called it the

“Evolutionary Discordance Hypothesis”. This Diet is based on grass-fed, pasture-raised meat and poultry, as well as seafood, along with some fruit, green vegetables, eggs, nuts, roots and fungi. Sounds quite reasonable. It also advocates excluding dairy, grains, legumes, potatoes or processed oils. Less reasonable – I love them all, especially olive oil!

It also excludes refined salt and refined sugar. It’s an excellent idea to minimise consuming lots of refined sugar, but what about the occasional birthday cake?


The Paleo Diet has major problems at every possible level – from theoretical to practical.

First, our ancestors ate many very different varieties of Paleolithic Diets. There was no one single Paleo Diet for all the humans across our planet.

Second, we humans actually have done a lot of evolving in the last 12,000 years. That includes evolution in regard to what we can eat.

Third, we can’t eat what our Paleolithic ancestors ate anyway – because most of that stuff is not around any more.

And fourth, the recommended Paleolithic Diet is way out of kilter with what dieticians currently recommend.


“Paleolithic” literally means “Stone Age”. The Paleolithic era spans a period from around 2.5 million years ago, right up until the development of agriculture some 12,000 years ago. (I discuss Agriculture in my 17th book, Flying Lasers, Robofish and Cities of Slime.)

When people started writing books about the Paleolithic Diet back in the 1970s, we had only a very vague idea of what our Stone Age ancestors ate. (Yup, the original writers advocating Paleolithic Diets were far more like “creative writers” than “factual writers”.) We did have hints of a bias towards a diet focused on meat. For example, we have found paintings, some 17,300 years old, inside the Lascaux Cave in the Dordogne region of France. They show animals, and people hunting animals. They don’t show any agricultural fields. But since then our anthropologists and archaeologists have looked at fireplaces, middens (dunghills or refuse tips), the actual teeth of t our Paleolithic ancestors, and even the tools used to prepare their meals.

It turns out that they ate a highly varied diet. Cereals and grains are forbidden in the Paleolithic Diet. But we know for sure that our ancestors ate them. The evidence for this came from examining dental plaque an wear marks on their teeth, as well as the tools they used to process food.

And was there one single Paleolithic Diet, right across the planet?

Did everyone eat the same meal in what we now call Africa and Europe, the Americas, Asia and Australia? “No” from common sense, and “no” from what our archaeologists and anthropologists have found.

We see an incredible spread in the diets of some of the so-called “primitive” peoples. The Inuit of the Arctic get 99 per cent of their calories from meat, while the !Kung people of Africa eat around 12 per cent meat. That’s a huge range. They definitely don’t eat the same identical meal.

What Do Dieticians Say?

A 2011 report involving 22 experts rated 20 diets. Based on factors such as health, ease of following and weight loss, the Paleo Diet came last. In 2012, it tied for last place with the Dukan Diet for the lowest rating – 29th out of 29 diets.

To complete its losing streak, in 2014, Paleo tied for last place (32nd out of 32) with the Dukan Diet.


Another cornerstone of the Paleolithic Diet Creed is that our bodies could not possibly have evolved fast enough in the last 12,000 years to accommodate our new foods.

We have very solid evidence (for example, from their teeth) that 30,000 years ago some of our ancestors were already eating grainsand legumes.

Indeed, the promulgators of the Diet claim that our genes haven’t changed for 50,000 years. This is so very wrong. Evolution can be quite quick on the uptake. In the last 7000 years, about one third of us have evolved to be able to drink milk when we grow into adults (see story on “Lactose Intolerance” on page 151). There are 6000-year-old rock paintings of people herding domestic cattle in the Jebel Acacus region of the Sahara Desert in Libya. Seven thousand years is definitely less than 12,000 years!

Still concentrating on food, some of us have evolved extra copies of the amylase enzyme so that we can more easily digest starches. Furthermore, some Japanese have evolved special bacteria in their guts that can digest seaweed – so sushi is no trouble at all. (See “The Stranger Within” in my 31st book, Brain Food.)

Moving away from evolution related to food, some of us have evolved blue eyes (6000 to 10,000 years ago). Others among us, in Africa, evolved resistance to malaria (5000 to 10,000 years ago).

Consider the challenge of living at high altitudes. Three separate groups of humans living in Tibet, the Andes and in Ethiopia have evolved three different methods of dealing with low oxygen. So, yes, our bodies could easily evolve fast enough in 12,000 years to accommodate new foods. In fact, they have.

Weight Loss? One of the claims of the Paleo Diet is that it triggers the production of hormones that then suppress hunger. In turn, this would produce the desired weight loss – the whole point of any Fad Diet. Researchers found this to be incorrect. The hunger-suppressing hormones are not triggered by the diet.


The third problem with the Paleolithic Diet is that the food eaten back then is simply not around any more. We have transformed the meat and plant species we eat through millennia of artificial selection and evolution.

If you look at what comes from today’s food animals, very few meats are as lean as those our Paleolithic ancestors ate. Indeed, many of the larger food animals have gone. There are no more mammoths or moas, and the last auroch (a super-large cow) died in Poland in 1627. However, kangaroo meat is pretty lean.

Today’s corn started off as a straggly skinny grass in Central America, while tomatoes used to be tiny berries. Bananas were mostly filled with seeds until a recent mutation (discussed in my 24th book, Disinformation). Consider cabbage, broccoli, Brussels sprouts, cauliflower and kale: they might look wildly different today, but they are each cultivars of one single species, Brassica oleracea.

Modern versions of the Paleo Diet recognise that foods have changed, and allow domesticated animal meat and cultivated plants. S. Boyd Eaton and Melvin Konner have recently “adjusted” their 1985 version of the Paleo Diet to allow whole grains and low-fat dairy products.


The fourth problem with the Paleolithic Diet is its nutritional aspects.

The core recommendation of the Diet is a high protein intake – 19 to 35 per cent of a person’s daily energy. This is quite a lot higher than the Australian Nutrient Reference Values suggestion of 15 to 25 per cent. Indeed, diets rich in meat are associated with higher rates of heart disease. The Paleolithic Diet also recommends a moderate to high intake of fat – again, not recommended by modern dieticians.

The Diet advises not to eat any whole grains. However, we have very solid evidence (for example, from their teeth) that 30,000 years ago some of our ancestors were already eating grains and legumes.

But, on the plus side, the Paleolithic Diet advises against eating processed foods with added salt, sugars and flavourings – entirely sensible. It also recommends fibre from vegetables and fruit – an excellent suggestion.


The Paleo Diet relies on the underlying fantasy that, if we simply follow it, we’ll change from a balding, pot-bellied man slouched in front of a computer into a tall, well-muscled man with perfect teeth, an artfully placed fur loincloth and a spear.

Sure, sitting all day is not good for you. (I recently changed over to a desk that adjusts from standing to sitting.) But our gut is perfectly adequate for many different diets. After all, meat eaters, vegetarians and vegans can all be very healthy.

Our digestive system has adapted to eat most foods. Our mouths are equipped with the teeth of both carnivores and herbivores – we can tear meat with our canines, and we can grind fibrous plants with our molars. The gut that runs between our mouth and anus is totally different from a straight line (the shortest distance between two points). Instead, it’s about 10 metres long. It’s not the short gut of a carnivore. Neither does it have the multi-stomach fermentation chambers of a grass-eating herbivore. It’s in between.

Gregor Yanega, a professor of biology at Pacific University in Oregon, has said, “Our guts are special because they are less specialised. They can accommodate so many changes in the foods that surround us, can accommodate unusual abundance and a certain amount of scarcity: we can even eat some of the world’s more difficult foodstuffs: grains, leaves and plants. Berries, nuts, meats, sugars, those are easy. Eating them together is pretty rare.”

Maybe we should forget Fad Diets, and just remember Michael Pollan’s simpler and more useful advice: “Eat food. Not too much. Mostly plants.”


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