Category Archives: Scepticism

Are cancers a modern phenomenon?

Yesterday, I came across a news report on a study by Professor Rosalie David and Professor Michael Zimmerman of the University of Manchester, who postulate that cancers are in large part a modern phenomenon and are ‘man-made’. I have objections to almost all of the claims the researchers make, so I will address them one by one.

Tumours were rare until recent times when pollution and poor diet became issues, the review of mummies, fossils and classical literature found.

It is true that there are more contaminants in the environment and poor lifestyle choices has led to an increase in some types of cancers. Numerous studies have shown pollution to be a factor in cancer, albeit a minor one. Inactivity, excess body fat, heavy drinking, and smoking are well known to increase your risk of developing cancer.

However, the main reason for the rarity of cancer in the past is that people lived much shorter lives. The chances of development many forms of cancer increases with age. Improvements in healthcare mean we are living much longer than past generations. Most cancers occur in individuals over the age of 50, well beyond the expected lifespan for much of human history. The increased detection of cancer is also due to our improved capacity to diagnose cancers.

The virtual absence of malignancies in mummies must be interpreted as indicating their rarity in antiquity, indicating that cancer-causing factors are limited to societies affected by modern industrialisation.

All animals get cancer. Even sharks! There is no reason to think that our ancestors were any different.

The authors find that there is a low prevalence of cancers which are already rare for the age group under examination. In a different study, Zink and colleagues observed 4 cases of malignant tumours in a series of 325 Egyptian mummies. It is reasonable to assume that these numbers represent a minimum, given the limitations of diagnosing cancer in ancient tissues.

These and other studies show that cancers did occur in Egyptian mummies. How then do the authors get from cancers occurred in ancient populations to cancers are the product of modern industrialisation?

Dismissing the argument that the ancient Egyptians didn’t live long enough to develop cancer, the researchers pointed out that other age-related disease such as hardening of the arteries and brittle bones died [sic] occur.

The authors of this study conveniently choose to dismiss perhaps the most important predictor of most cancers – age. The study looked at mummies between the ages of 25 and 50, although people over the age of 50 are by far at greatest risk of getting cancer. According to a 2010 American Cancer Association report [pdf] around 78% of cancers are diagnosed in people 55 years and older. A primary reason many cancers are on the increase is because people are living longer. Given the short lifespan of prehistoric people it is inevitable that the occurrence of cancers will be much greater today.

Even the study of thousands of Neanderthal bones has provided only one example of a possible cancer.

The one example the authors refer to is the Stetten II skull bone, believed to date to 35,000 years BP (before present). There a tumour on the parietal bone of this specimen. However, much of the Stetten material has been redated to less than 5000 years BP, including a cranium designated Stetten II.

What’s more, the authors fail to mention the Ferrassie Neandertal, whose leg bone lesions have been interpreted as possibly being the result of lung cancer. This specimen has bilateral periostitis, which is a common manifestation of hypertrophic pulmonary osteoarthropathy (HPO). HPO is a condition associated with a number of circulatory and lung diseases. Among the most common causes of HPO are pulmonary carcinomas. Palaeopathology is a tricky business in which practitioners attempt to reconstruct past diseases and infections from often ambiguous marks left on the bones. While the Ferrassie case is open to interpretation, it should not be dismissed out of hand.

It is also worth noting that the incidence of bone cancers are incredibly low. Moreover, osteosarcomas affect mostly children. Bone cancers are among the rarest types of cancer. The number of new cases of bone cancer in the US so far this year is 2,650. To put this into perspective that’s 0.000009% of the US population that have been diagnosed with bone cancer in the last year. Other cancers may secondarily affect bony tissue but, like the Ferrassie Neandertal above, the aetiology in such cases is more equivocal.

There is nothing in the natural environment that can cause cancer. So it has to be a man-made disease, down to pollution and changes to our diet and lifestyle.

The ascertain that nothing in the environment causes cancer is demonstrably wrong. Prolonged exposure to UV rays is the chief cause of skin cancers. Human papillomaviruses and hepatitis viruses cause cervical and liver cancers respectively. Helicobacter pylori bacteria have been linked to gastric cancer. Exposure to radon is the second leading cause of lung cancer (after smoking), while carcinogenic aflatoxins are made naturally by moulds.

In conclusion, the researchers found only a few cases of cancer in a relatively small sample of mummies. These mummies were all estimated to be 50 years of age or younger – a demographic with a relatively low risk of cancer. Added to this, it is likely that the true rate of cancer was much higher than what was possible to diagnose for these ancient and somewhat degraded specimens. While it is interesting to ask how prevalent cancers were in the past, this study does little to shed light on the answer.


Fennell and Trinkaus (1997). Bilateral femoral and tibial periostitis in the La Ferrassie 1 Neanderthal. Journal of Archaeological Science. 24 (11) pp. 985-995.

Rosalie David and Zimmerman (2010). Cancer: an old disease, a new disease or something in between? Nature Reviews Cancer 10, 728-733.

Zink, Rohrbach, Szeimies, Hagedor, Haas, Weyss, Bachmeier and Nerlich (1999). Malignant tumors in an ancient Egyptian population. Anticancer research. 19 (5B):4273-7.

Why people believe in homeopathy

How long will it take mankind to learn that while they listen to “the speaking hundreds and units, who make the world ring” with the pretended triumphs they have witnessed, the “dumb millions” of deluded and injured victims are paying the daily forfeit of their misplaced confidence!

Almost 170 years after Oliver Wendell Holmes read these words to the Boston Society for the Diffusion of Useful Knowledge the pseudoscience of homeopathy continues to thrive. An EU commission statement estimates that some 30 million people in the EU use homeopathy, while the WHO estimates that around 500 million in the world use it.

Since Wendell Holmes’ time a colossal body of evidence has been amounted showing that homeopathy has no medicinal effect beyond the placebo effect. The core concepts of homeopathy fly in the face of science and logic. homeopathy uses highly dilute solutions of a substance to treat disease. Most homeopathic solutions are so dilute that there is almost no chance that they will contain even a single molecule of the original active agent. Counterintuitively, homeopathic practitioners claim that the more dilute the solution, the stronger the homeopathic remedy. This contradicts the well-known phenomenon of dose response, which says that the more of a chemical an organism is exposed to, the greater the effect. Take one sleeping pill and it will help you sleep; take two and the effect is even more powerful; take 100 sleeping pills and you are not likely to wake up … ever! On the other hand, homeopaths would suggest that the more dilute the solution, the more “powerful” the effect. But how could a solution of something that doesn’t contain even a single molecule of active ingredient have any effect? Here, things get even more bizarre. They suggest that water has memory. Seemingly, water has the ability to remember contact with certain substances, while at the same time being able to forget all the raw sewage and fecal matter that it has been in contact with. If homeopathy is nothing but water, why do so many people continue to believe it works?

Scientists and sceptics who engage with advocates of homeopathy usually end up throwing their hands up in the air in frustration. The reason is that most people who have come to believe in homeopathy do not do so based on scientific data or for particularly rational reasons. As such, it is unlikely that anyone who did not come to a particular position based on logic or reason will be argued out of that position using logic and reason. Indeed, no amount of rational argument will convince proponents of this modality that they are misguided. Holmes was well aware of the ineffectiveness such an exercise, stating that “… it is impossible not to realize the entire futility of attempting to silence this asserted science by the flattest and most peremptory results of experiment.”

It is tempting to criticise such beliefs on the grounds that the people who hold them are somehow lacking basic cognitive skills. In fact, people who believe in all kinds of strange things are often very rational in other aspects of their life. I would instead argue that the faulty thinking that many engage in is a byproduct of our mind works. The human brain evolved not only to explain the world around us; it evolved to deal with an innumerable amount of tasks. Cultural transmission does not occur by downloading information, as was once believed, but rather is based on an inferential system. We classify things in our environment into ontological categories. Most things we encounter in our environment fall into one of the following groups: person, animal, natural object, tool and plant. Each ontological category has a set of characteristics that define it and set it apart from other categories. We make certain inferences about objects based on which ontological category it belongs to. For instance, we are not surprised when a dog walks down the street but would find it strange if we saw an oak tree doing so. Locomotion is part of our mental template for people and animals but not plants. We find certain counter-intuitive notions more memorable than blander ones, a prerequisite for a successful meme. Superstitious beliefs often combine ontological beliefs with a category violation. For instance, disembodied souls and inanimate statues that can cry, hear or bleed represent category violations for a person and a natural object respectively. However, not all superstitious beliefs are equally believable. While the belief in ghosts is widespread, the belief that ghosts cannot think and have desires is virtually non-existent. Violations must allow for further inferences, otherwise they result in cognitive dead ends. Although few of my readers literally believe in superheroes and zombies, that does not stop us from making inferences about what their needs, wants and limits would be if they did exist.

The idea that water has memory is a categorical violation. Memories are characteristic of a person or animal but not a natural object. Crucially, the belief that water has memory does not block further cognitive inferences. Conversely, we would find it much more difficult to believe that water remembers the substances that other water had been in contact with. This type of belief is rare since it prevents us from making further inferences. We have experience with the concept of remembering things that we have been in contact with but don’t have experience of what it is like to remember things other people have been in contact with. People I met when I was younger — people who I have not seen for many years – still have an influence on me now. Likewise, it is not such a large cognitive leap to believe that substances that came into contact with water still have an influence over it.

Another important component of homeopathy is vitalism. The idea that we are more than just the aggregate of chemical and mechanical processes is an appealing one. Vitalism appeals to our core intuitions. Vitalists believe that the laws of science are inadequate to explain life processes. There must be something more to it – a soul or some elan vital. All of us operationally view ourselves as both body and mind, even those of us who outright reject the idea of a disembodied self or soul. The self is not something that governs the brain, rather the self is the outcomes of brain processes. However, our brain does a wonderful job of convincing us otherwise. The father of homeopathy, Samuel Hahnemann, saw the vital force as a “spirit like” force that maintained life. He believed that the inner vital force maintained the body’s internal balance. When the body became ill it would push the illness outwardly, causing the symptoms of the disease or illness to manifest. Many homeopaths believe that all disease come down to one thing — the disturbance of the vital force. They believe that only homeopathic remedies stimulate the vital force into action.

Sympathetic or imitative magic is found in cultures the world over. Sympathetic magic is based on two related concepts: the law of similarity and the law of contagion. The former states that like things produce like effects, while the latter is the idea that items that have been in contact continue to affect each other. Perhaps the best known example of sympathetic magic is the use of voodoo dolls to place a curse on a specific person. Cargo cults would also engage in sympathetic magic by building landing strips and radio towers to encourage the airplanes that delivered them precious cargo during World War II to come back again. In the past, whooping cough and a sore throat were often treated by tying knots in a piece of string and hanging it around the ill person’s neck. The knots were supposed to symbolise the tightness in the person’s throat. Liverworts have been used for hundreds of years as a cure ailments of the liver, probably because of the plant’s resemblance to the liver. A cure for pneumonia was to tie the lungs of a sheep to the soles of the feet of a patient. Golden objects and butter were commonly used as cures for jaundice. It was believed that warts could be cured by rubbing them on a frog, most likely because of the frog’s warty appearance. The use of oysters, rhinoceros horns and tiger penises as aphrodisiacs are all examples of sympathetic thinking. The list goes on and on.

In a similar vein, homeopathy uses the concept of “like cures like.” It is based on the idea that substances which produce symptoms similar to those of a particular illness can treat that illness. For instance, homeopaths may treat a person suffering from hay fever with an onion extract, since both produce watery eyes and a runny nose. The idea that water can still remember things it was previously in contact with, is an example of the “law of contagion.” In this regard, homeopathy is similar to the concept of holy water that is common to many religions.

The brain processes that lead someone to believe in homeopathy exist in all of us. Our mental capacities evolved to aid in our survival, with erroneous beliefs an emergent property of our intuitive psychology. We are all prone to cognitive dissonance aversion, memory illusion, and confirmation bias. Such cognitive traps are probably adaptive and essential to mental well-being. The biologist Lewis Wolpert suggests that scientific thinking is in fact aberrant. Science is a conscious departure from intuition and common sense. Homeopathy is parasitic upon brain processes that originally evolved for other activities. If we want to understand why people believe in homeopathy, we must first understand how such beliefs enlist our evolved mental capacities.

References and further reading

Boyer, P (2001): Religion Explained. Evolutionary Origins of Religious Thought. New York: Basic Books.

Holmes OW (1842). Homœopathy, and its kindred delusions; two lectures delivered before the Boston society for the diffusion of useful knowledge, Boston: William D. Ticknor.

Wolpert, L (1993). The unnatural nature of science. Cambridge, MA: Harvard University Press.

Above photo “Hot Raw Sewage” by Stuck in Customs is used under creative commons license.

Paleo diet

For many people the new year represents an occasion to set the clock back to zero and make a fresh start. We invariably eat too much during the festive season, only later to feel remorse for our gluttonous ways. With the new year comes the renewed goal of losing some of the extra padding. There are no end of miraculous sounding diets which promise to convert fat to flat. Among the various in vogue diets is the so-called Paleo diet (short for Paleolithic diet), also known as the caveman diet. The central premise behind the Paleo diet is that many human adaptations evolved during the Palaeolithic, and as such, we are maladapted to the modern world in which we find ourselves.

The premises of the Paleo diet raise some interesting questions that are well worth exploring. For instance, are we really better adapted to the Palaeolithic than the modern era and which aspects of the Palaeolithic does the Paleo diet reference? Many proponents ask the question “who ever heard of a fat caveman?”, as if the answer is somehow inferred. While it is seems be the case that the average Palaeolithic human had a brawnier body than the average modern human, we should not confuse correlation with causation. A better question to ask is whether the “caveman” physique is due solely to diet or are there other factors at play?

While certain human adaptations undoubtedly arose during the Palaeolithic, these are likely to be no more or less important than the adaptations of preceding and subsequent periods in our evolutionary history. Most of our genes evolved a long time before our ancestors were recognisable as primates, never mind humans. Moreover, humans continue to adapt to their diet today. Lactose tolerance is a good example of a trait that arose in many populations of humans after the Palaeolithic. Evolution exists on a continuum; it didn’t start and end sometime during the Palaeolithic.

The Palaeolithic covers a period of around 2.5 million years, as well as an immense geographic range. Moreover, many species of humans lived in very diverse environments during this time. Proponents of the Paleo diet rarely specify what period and indeed which populations or species they use as their model. Food procurement methods changed dramatically over this time period. Over the course of the Palaeolithic, humans shifted from mostly scavenging their meat to systematic hunting. Even among modern hunter-gatherers there is great dietary variation. For instance, the diets of Inuits and Aboriginal Australians couldn’t be more different. Another consideration is that humans have been selectively breeding plants and animals over many millennia. Many of the domesticated varieties we see today are unrecognisable from their wild ancestors. As such, while the Paleo diet recommends greater reliance on meats and non-cultivated plants, it should be kept in mind that these probably bear little resemblance to the wild species our ancestors ate.

The limb bones of the early Upper Palaeolithic Gravettian people are not only large but also have massive muscle attachments. Early humans were physically fit not only because of their diet but in large part due to their high mobility. Hunting and foraging expeditions would have required these groups to cover large distances. Demographic pressures impinging on these small bands of humans would also have further encouraged greater mobility.

It is not disputed that the diet of early hunter-gatherers was much more varied than that of their agricultural counterparts. Early agriculturalists often had an over reliance on few food types, leading to various nutritional deficiencies and generally poorer health. However, there is little reason why this should be the case today. Our shops and markets are packed with varieties of food that our ancestors would be only able to dream off.

Many of the recommendations of the Paleo diet are sensible, such as eating less processed foods, decreasing our sugar intake and increasing our dietary fibre. In this regard, the Paleo diet is on par with most governmental dietary recommendations. Why the need to dress it up in some romanticised account of how our ancestors ate? I will concede that versions of the Paleo diet are probably healthier than the diets most of us adhere to. However, the reasoning behind it is based on an immutable view of human prehistory, coupled with some poor evolutionary thinking.

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Above photo modified from original by Lord Jim under creative commons license.

Why the Aquatic Ape Hypothesis doesn’t hold water

Among this week’s new videos from TED, was a talk given by Elaine Morgan – the chief promoter of the Aquatic Ape Hypothesis (AAH). The AAH was first formulated by Alister Hardy and is the idea that human evolution went through an aquatic stage, which in turn explains many of the features of the human physiology. For anybody with a poor understanding of evolutionary biology the AAH arguments can seem quite compelling. Instead of repeating the numerous reasons why the AAH fails (Jim Moore has an entire website dedicated to this), I wish to address some of the specific arguments made in this video.

Morgan starts off my stating that “… there’s one aspect of this story which they [evolutionists] have thrown no light on and they seem anxious to skirt around and step over it and talk about something else. So I’m going to talk about it. It’s the question of why are we so different from the chimpanzees?”. Either Morgan has not been reading the hundreds of research papers that have addressed these important questions or she is trying to hoodwink her audience. Palaeoanthropologists and primatologists have long recognised the value of studying human and chimp differences in order to understand our shared evolutionary history. In fact, it is impossible to talk about functional anatomy and phylogenetic history in humans without reference to our closest extinct and living hominin relatives.

She continues: “Yet when you look at the phenotypes. There’s a chimp, there’s a man. They’re astoundingly different. No resemblance at all.” I am hearing this correctly? No resemblance at all? Even a five year old can see the striking similarities between chimpanzees and humans. To suggest that there is “no resemblance at all” is laughable. It was the similarities of humans to other non-human primates that led Charles Darwin to argue for common ancestry between humans and the great apes. Even without the fossil record and the unambiguous molecular evidence, the morphological similarities alone would be enough to suggest a shared common ancestry of chimps and humans.

Throughout the talk she constantly refers to humans as naked, as if to suggest we are hairless. One need only look at a shirtless Alec Baldwin, Robin Williams or Andy Garcia to know this is not the case. While it is true that humans are less hairy than the rest of our primate kin there are far more compelling hypotheses to explain our lack of hair (thermoregulation, defence against parasites or sexual selection). She claims that hairlessness is an aquatic trait when in fact most aquatic/semi-acquatic mammals are in fact hairy. Otters, polar bears, seals, and walruses are but some examples that spring to mind.

Regarding the failed savannah hypothesis of bipedalism Morgan has this to say: “What do scientists do when a paradigm fails… carry on as though nothing had ever happened… If they haven’t got a paradigm they can’t ask the questions… The only other option open to them is to stop asking the questions. So that is what they have done now. That is why you don’t hear them talking about it.”

When paradigms fail science marches on. When was the last time you heard a scientist defending the merits of Lamarckism, psychoanalysis and phrenology? Morgan is correct that the savannah hypothesis doesn’t weigh up against the evidence but she mistakenly claims that the anthropologists haven’t let go of this idea. The savannah hypothesis was formulated in a time when there was a dearth of palaeoecological data for the most important African archaeological sites. As more data came in, anthropologists changed their models correspondingly. No serious anthropologist still adheres to the savannah hypothesis. Morgan chooses to ignore this fact, instead preferring the easier route of attacking a strawman. In the references section below, you will find just a spattering of the work anthropologists have been doing on palaeoecological reconstructions of the environments occupied by our forebearers. These papers address the very questions Morgan asserts that scientists have stopped asking. Does she not read the anthropological literature or does she just choose to ignore it? She implies that because the savannah hypothesis is false it somehow offers support to the AAH. In fact, the consensus opinion suggests that neither savannah nor aquatic environments were very important in the early stages of human evolution, but rather our hominin ancestors exploited wood and forest habitats. A number of anthropologists have proposed an arboreal origin of hominin bipedality (Crompton 2008; Pickerford 2006; Senut 2003, 2006). In fact, the best known human ancestor Lucy shows clear arboreal adaptations.

Morgans proceeds by stating that “there is only one circumstance in which they always, all of them [non human primates], walk on two legs and that is when they are wading through water.” Contrary to Morgan’s claim, the data have shown apes to be bipedal more often on land than in the water.

She follows this up by saying that the fat in humans is similar to that seen in aquatic mammals. Humans have a similar number of fat cells compared with other primates. The increased subcutaneous fat seen in humans is most likely a result of diet rather than an evolutionary adaptation. Non-human primate obesity is well documented, particularly in primates kept in captivity (Videan 2007; Altmann et al 1993; Kemnitz et al 1989; Schwartz et al 1993). Moreover, the distribution of fat in humans runs contrary to need aquatic mammals have for streamlining.

Ten minutes into the talk she states that “the only creatures that have got conscious control of their breath are the diving animals and the birds”. Humans are not the only non-aquatic mammal which can hold its breath. Various monkeys, for instance, can and do hold their breath, as well as dogs.

Finally, she asserts that “we are streamlined.” Humans are anything but streamlined. Our motion in the water is generally quite wasteful. Ask any swimming coach. Fish have a fusiform shape (tapered at both ends), which is ideal for moving through the water with the least amount of resistance. Let’s put this into perspective. The sailfish records speeds of up to 116 km/hr (72 mph), while Michael Phelps can average a measly about 6.5 km/hr (4 mph) on a good day! Our body shape is a consequence of our adaptation to bipedalism, the requirements of childbirth in women, sexual dimorphism and sexual selection.

While I generally enjoy listening to the speakers at TED, I think this is an idea NOT worth spreading.


Altmann J, Alberts SC, Altmann SA, Roy SB (2002) Dramatic change in local climate patterns in the Amboseli Basin, Kenya. Afr J Ecol 40, 248–251.

Altmann J, Schoeller D, Altmann SA, Muruthi P, Sapolsky RM (1993) Body size and fatness of free-living baboons reflect food availability and activity levels. Am J Primatol 30: 149–61.

Andrews P (1996) Palaeoecology and hominoid palaeoenviron-ments. Biol Rev 71, 257–300.

Andrews P, Humphrey L (1999) African Miocene environments and the transition to early hominines. In African Biogeography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 282–300. New York: Oxford University Press.

Andrews P (2007) The biogeography of hominid evolution. J Biogeogr 34, 381–382.

Andrews P, Kelley J (2007) Middle Miocene dispersals of apes. Folia Primatol 78, 328–343.

Andrews P, Bamford M (2008) Past and present vegetation ecology of Laetoli, Tanzania. J Hum Evol 54, 78–98.

Codron D, Luyt J, Lee-Thorp JA, Sponheimer M, De Ruiter D, Codron J (2005) Utilization Of Savanna-Based Resources By Plio-Pleistocene Baboons. S Afr J Sci 101, 245–248.

Crompton RH, EE Vereecke, SKS Thorpe (2008) Locomotion and posture from the common hominoid ancestor to fully modern hominins, with special reference to the last common panin/hominin ancestor. J Anat 212, 501–543.

Demenocal PB (2004) African Climate Change And Faunal Evolution During The Pliocene-Pleistocene. Earth Planet Sci Lett 220, 3–24.

Denton G (1999) Cenozoic climate change. In African Biogeography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 94–114. New York: Oxford University Press.

Dowsett HJ, Barron JA, Poore RZ, et al. (1999) Middle Pliocene paleoenvironmental reconstruction: PRISM2. US Geol Surv, Reston, Va, Open File Rep 99–535.

Elton S (2000) Ecomorphology and evolutionary biology of African Cercopithecoids: providing an ecological context for hominin evolution. PhD dissertation, University of Cambridge.

Jacobs BF (2004) Palaeobotanical studies from tropical Africa: relevance to the evolution of forest, woodland and savannah biomes. Phil Trans R Soc Lond B359, 1573–1583.

Kemnitz JW, Goy RW, Flitsch TJ, Lohmiller JJ, Robinson JA (1989) Obesity in male and female rhesus monkeys: fat distribution, glucoregulation, and serum androgen levels. J Clin Endocrinol Metab 69:287–93.

Kingston J, Harrison T (2007) Isotopic dietary reconstructions of Pliocene herbivores at Laetoli: implications for hominin paleo- ecology. Palaeogeog Palaeoclimatol Palaeoecol 243, 272–306.

Kovarovic KM, Andrews P, Aiello L (2002). The palaeoecology of the Upper Ndolanya Beds, Laetoli, Tanzania. J Hum Evol 43, 395–418.

Pickford M (2006) Paleoenvironments, Paleoecology, Adaptations and the Origins of Bipedalism in Hominidae. In Human Origins and Environmental Backgrounds (eds Ishida H, Tuttle RH, Pick- ford M, Ogihara M, Nakatsukasa M), pp. 175–198. Heidelberg: Springer.

Schwartz SM, Kemnitz JW, Howard CF Jr (1993) Obesity in free-ranging rhesus macaques. Int J Obes 17:1–9.

Senut B (2003) Palaeontological approach to the evolution of hominid bipedalism: the evidence revisited. Cour Forsch-Inst Senkenberg 243, 125–134.

Senut B (2006) Arboreal Origins of Bipedalism. In Human Origins and Environmental Backgrounds (eds Ishida H, Tuttle RH, Pickford M, Ogihara N, Nakatsukasa M), pp. 199–208. Heidelberg: Springer.

Sikes N (1999) Plio-Pleistocene floral context and habitat prefer- ences of sympatric hominid species in East Africa. In African Bio- geography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 301–315. New York: Oxford Univer- sity Press.

Videan EN, J Fritz, J Murphy (2007) Development of guidelines for assessing obesity in captive chimpanzees (Pan troglodytes). Zoo Biology 26: 93–104.

Vincens A, Garcin Y, Buchet G. (2007) Influence of rainfall seasonality on African lowland vegetation during the Late Quaternary: pollen evidence from Lake Masoko, Tanzania. J Biogeogr 34, 1274–1288.

WoldeGabriel G, Haile-Selassie Y, Renne P, et al. (2001) Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia. Nature 412, 175–178.

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Beware the Spinal Trap

Today, numerous blogs and magazines from all around the world will publish Simon Singh’s article on chiropractic from April 2008, with the libellous part removed. The Guardian withdrew the article after the British Chiropractic Association sued for libel (please repost).


Some practitioners claim it is a cure-all, but the research suggests chiropractic therapy has mixed results – and can even be lethal, says Simon Singh.

You might be surprised to know that the founder of chiropractic therapy, Daniel David Palmer, wrote that “99% of all diseases are caused by displaced vertebrae”. In the 1860s, Palmer began to develop his theory that the spine was involved in almost every illness because the spinal cord connects the brain to the rest of the body. Therefore any misalignment could cause a problem in distant parts of the body.

In fact, Palmer’s first chiropractic intervention supposedly cured a man who had been profoundly deaf for 17 years. His second treatment was equally strange, because he claimed that he treated a patient with heart trouble by correcting a displaced vertebra.

You might think that modern chiropractors restrict themselves to treating back problems, but in fact some still possess quite wacky ideas. The fundamentalists argue that they can cure anything, including helping treat children with colic, sleeping and feeding problems, frequent ear infections, asthma and prolonged crying – even though there is not a jot of evidence.

I can confidently label these assertions as utter nonsense because I have co-authored a book about alternative medicine with the world’s first professor of complementary medicine, Edzard Ernst. He learned chiropractic techniques himself and used them as a doctor. This is when he began to see the need for some critical evaluation. Among other projects, he examined the evidence from 70 trials exploring the benefits of chiropractic therapy in conditions unrelated to the back. He found no evidence to suggest that chiropractors could treat any such conditions.

But what about chiropractic in the context of treating back problems? Manipulating the spine can cure some problems, but results are mixed. To be fair, conventional approaches, such as physiotherapy, also struggle to treat back problems with any consistency. Nevertheless, conventional therapy is still preferable because of the serious dangers associated with chiropractic.

In 2001, a systematic review of five studies revealed that roughly half of all chiropractic patients experience temporary adverse effects, such as pain, numbness, stiffness, dizziness and headaches. These are relatively minor effects, but the frequency is very high, and this has to be weighed against the limited benefit offered by chiropractors.

More worryingly, the hallmark technique of the chiropractor, known as high-velocity, low-amplitude thrust, carries much more significant risks. This involves pushing joints beyond their natural range of motion by applying a short, sharp force. Although this is a safe procedure for most patients, others can suffer dislocations and fractures.

Worse still, manipulation of the neck can damage the vertebral arteries, which supply blood to the brain. So-called vertebral dissection can ultimately cut off the blood supply, which in turn can lead to a stroke and even death. Because there is usually a delay between the vertebral dissection and the blockage of blood to the brain, the link between chiropractic and strokes went unnoticed for many years. Recently, however, it has been possible to identify cases where spinal manipulation has certainly been the cause of vertebral dissection.

Laurie Mathiason was a 20-year-old Canadian waitress who visited a chiropractor 21 times between 1997 and 1998 to relieve her low-back pain. On her penultimate visit she complained of stiffness in her neck. That evening she began dropping plates at the restaurant, so she returned to the chiropractor. As the chiropractor manipulated her neck, Mathiason began to cry, her eyes started to roll, she foamed at the mouth and her body began to convulse. She was rushed to hospital, slipped into a coma and died three days later. At the inquest, the coroner declared: “Laurie died of a ruptured vertebral artery, which occurred in association with a chiropractic manipulation of the neck.”

This case is not unique. In Canada alone there have been several other women who have died after receiving chiropractic therapy, and Edzard Ernst has identified about 700 cases of serious complications among the medical literature. This should be a major concern for health officials, particularly as under-reporting will mean that the actual number of cases is much higher.

If spinal manipulation were a drug with such serious adverse effects and so little demonstrable benefit, then it would almost certainly have been taken off the market.

Simon Singh is a science writer in London and the co-author, with Edzard Ernst, of Trick or Treatment? Alternative Medicine on Trial.

You can find this article and information about Simon Singh’s case at the Sense About Science website, as well as a petition to keep libel laws out of science.

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Above photo by jharkn under creative commons license.

Darwinism: The creationist straw man

If you visit the ironically entitled creationist website Evolution News and Views, try finding a single post that doesn’t mention the word “Darwinist” or “Darwinism”. You’ll have to dig deep… very deep. If you were completely ignorant of biology you might even be fooled into thinking that these were terms cheerfully embraced by the scientific community. After all, an evolution news outlet is hardly in the business of obfuscation, now is it?

Outside of intelligent design (i.e., creationism warmed-over), Darwinism is used primarily to refer to the theory of the evolution of species by natural selection, as formulated by Darwin, not to the modern and more complete understanding of evolution. As things tend to be in science, evolutionary theory hasn’t stood still since 1859, when Darwin communicated his ideas to the world in On the origins of species. While natural selection is indeed a principle driving force in evolution, it is not the whole story. Charles Darwin would no doubt be astonished by the such discoveries of genes and DNA, the reworking of evolutionary theory to accommodate evo-devo and the neutral theory of molecular evolution, as well as the plethora of evidence that has confirmed the basic tenets of his original ideas. To use the term Darwinism is an insult to the hard work of the thousands of scientists who have helped refine evolutionary theory. It implies that the wheels of scientific research ground to a halt some 150 years ago and serves to confuse the public’s already poor understanding of evolution.

A more menacing motivation for using the term Darwinism is to portray evolution as just another ideology, consisting of its own set of monolithic doctrines and beliefs. However, science is not based on static beliefs but is rather a ceaselessly self-correcting discipline that evolves in light of new evidence.

By misrepresenting evolution as the archaic, dogmatic ideas of one old man, creationists set up a straw man argument. It always strikes me as curious that they don’t refer to adherents of gravity as Newtonists! Judging from the overwhelming and ever-increasing evidence for evolution, creationists are given little choice but to resort to fallacious arguments.

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Above photo modified from original by Colin Purrington under creative commons license.

Is craniometry scientific?

Craniometry is the measurement of the bones of the skull. The technique is primarily used to determine ancestry, population distances and sex. It differs greatly from the psuedoscientific fields of phrenology and physiognomy, although in the general populace the distinction is not so clear. The book Postmodernism and Race has the following definition: “Craniometry is the measurement of human skulls as an indication of intelligence”, while a recent blog article on craniometry states that it “claims to be able to predict the intelligence and nature of human being.” Craniometry says nothing about intelligence or human nature.

Craniometric studies were, to a large degree, racially motivated in the early decades of the twentieth century, with anthropologists trying to validate their preconceived racial categories. In 1912, Franz Boas published a study challenging the prevailing notion that certain cranial measurements were under ironclad genetic control. He studied the head form of some 13,000 European immigrants and their American-born children. He found significant differences in the shape of the heads between parents and their children, which he interpreted as evidence for cranial plasticity. In other words, environment, not genetics, shapes cranial morphology. During the subsequent decades, Boas’ results came to be largely accepted by the anthropological community, with students of the Boasian school disregarding craniometric studies as an ill-fated enterprise. For many years, anthropologists steered clear of craniometry, instead focusing their expertise in other less stigmatised areas of physical anthropology such as palaeopathology.

Quite recently papers by Sparks et al (2002) and Gravlee et al (2003) have re-examined Boas’ original data. However, those expecting the final word on cranial plasticity were to be disappointed. The anthropologist Milford Wolpoff is quoted as saying in 1975 “The data do not speak for themselves. I have been in rooms with data and listened very carefully. They never said a word.” This is particularly true of these two papers, which use the very same data to come to divergent conclusion. While Gravlee et al believe Boas to be essential correct, Sparks et al came down firmly on the other side. The real answer, I believe, is to be found between the lines.

Boas did, in fact, find a statistically significant environmental effect in his study but this begs the question of whether it is a meaningful effect. Sparks suggests that while the effect is real, it only constitutes a tiny proportion of variation. In fact, considering the size of Boas’ sample (~13,000) it is almost impossible not to find statistically significant results; biology is, after all, intrinsically variable. It may be the case that Boas played up the importance of the environmental effects as a reaction to the racial thinking that was prevalent at that time.

Perhaps, the biggest problem with Boas’ methodology was his reliance on only a handful of measurements and particularly the use of the cephalic index (ratio of head breadth to head length). Anders Retzius introduced the cephalic index as way of classifying skulls based on their overall shape. He defined three main categories: dolichocephalic (long headed), brachycephalic (broad headed) and mesocephalic (intermediate headed).

Most modern biological anthropologists are of the opinion that the use of a couple of measurements to describe a multi-complex structure such as the skull is absurd. Today, biological anthropologist will take dozens of measurements of the skull. W. W. Howells, who measured thousands of skulls from all over the world, had the following to say about the cephalc index: “When Anders Retzius, a century and half ago, invented the cranial index, he gave us an answer for which there was no question.” Even Boas himself wrote the following in 1940: “Measurements should always have a biological significance. As soon as they lose their significance they lose also their descriptive value.”

Craniometry is used today in biological anthropology as a means of determining the relationships of peoples through their phenotype. A phenotype is the visible manifestation of a genotype. Since there is rarely a one to one relationship between the genotype and phenotype we must first demonstrate that the phenotype is an accurate reflection of the genotype. If this is not the case craniometry would be no more scientific than phrenology. Narrow-sense heritability is the proportion of phenotypic variation that arises from only the additive genetic differences among individuals and is expressed as h2 = VA/VP. Heribtaility is measured on a scale of 0 (no heritable variation) to 1 (all phenotypic variation is due to additive genetic effects). The average cranial h2 has been estimated at around 0.55 (Relethford 1994; Devor 1987). A heritability greater than 0.5 indicates that most phenotypic variation is the examined traits are attributable to genetic factors. Thus the proportionality of genotypic to phenotypic variance is a reasonable assumption. The true litmus test of any hypothesis is its predictive power. Craniometric data is used with surprising accuracy by forensic anthropologists to determine likely ancestry of unknown individual and by palaeoanthropologists to determine our relationship to other hominins. The modern scientific practice of craniometry distinguishes itself from psuedosciences like phrenology and physiognomy in that it is based on sound biological theory, it is testable, it is predictive and objective.

References cited
Boas F (1912) Changes in the bodily form of descendants of immigrants. American Anthropologist 14: 530-562.

Sparks CS, Jantz RL (2002) A reassessment of human cranial plasticity: Boas revisited. Proc. Natl. Acad. Sci. USA 99: 14636-14639.

Gravlee CC, Bernard HR, Leonard WR (2003) Heredity, Environment, and Cranial Form: A Reanalysis of Boas’s Immigrant Data. American Anthropologist.

Devor EJ (1987) Transmission of human craniofacial dimensions. J Craniofac Genet Dev Biol 7: 95-106.

Relethford JH (1994) Craniometric variation among modern human populations. Am J Phys Anthropol 95: 53-62.

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