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.


References

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.


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Australopithecus habilis!

12tool1_ready-articleLarge
The oldest known human tool technology is known as Oldowan. These tools were originally thought to have been the handiwork of an early member of our genus, Homo. In fact, Louis Leakey and colleagues named the species Homo habilis (literally "handy man") because of its association with Oldowan stone tools. There is an almost doubling in brain volume and expansion of the frontal lobes in habilines compared to their australopithecine antecedents, which some have attributed to the formers use of stone tools.

Stone tools found during excavations in the early 1990s in the Afar region of Ethiopia have been dated to between 2.5 and 2.6 million years. However, H. habilis does not first appear on the scene until around 2.3 million years ago, which would make australopithecines or paranthropines the most likely authors of this assemblage. Even these earliest stone tools have been deemed too advanced for our first foray into stone tool making and many researchers predicted that even earlier tools were awaiting discovery.

Researchers working in the Dikika region of Ethiopia have recently uncovered bones dating to between 3.2 and 3.4 million years ago that show all the hallmarks of butchering. The cut marks and percussion marks are suggestive of defleshing and the removal of bone marrow. From a behavioural aspect, it is unclear whether this represents hunting or the scavenging of recently dead animals.

Bone trauma can be an incredible tricky thing to interpret. Trampling, tooth marks from scavenging, direct contact with rocks, among other agents can leave pseudo-cut marks on a bone. The bones were analysed under scanning electron microscope, with the researchers concluding that stone tools were most likely responsible for the cut marks and fracture patterns.

Australopithecus afarensis is the only known hominin to date from this time period and is, for the time being, the best candidate for making these marks. Tool use is seen in both our ape and monkey cousins and it seems likely that A. afarensis also utilised tools. Researchers have shown that A. afarensis would have been capable of the manual dexterity needed to manipulate tools. What is less clear is whether these cut marks were made by stone tools specifically fashioned for butchering or whether these hominins used sharp-edged natural stones. Whether these were fabricated or natural they were still used as tools. However, the dentition of A. afarensis suggests that meat constituted a negligible part of their diet. The large molars and thick enamel of this hominin point to a diet rich in tubers and other vegetation.

The elephant in the room is the absence of any tools at the Dikka site. This is unusual since tools, which ordinarily preserve better, typically outnumber bones at butchering sites. It is also unclear how many bones were collected at the site and why none of these show tool marks. Indeed, the entire evidence consists of only two small fragments of fossilised bone. The authors suggest that the lack of additional bones with cut marks could indicate that the bones were processed off-site, where better quality tools were available.

The evidence is tantalising but more is needed. Hopefully, further excavations at Dikka will uncover the missing stone tools and the humans who made them.

References
Alba DM, Moyà-Solà S, Köhler M. 2003. Morphological affinities of the Australopithecus afarensis hand on the basis of manual proportions and relative thumb length. Journal of Human Evolution 44: 225–254.

McPherron SP, Alemseged Z, Marean CW, Wynn JG, Reed D, Geraads D, Bobe R, Bearat HA. 2010. Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikka, Ethiopia. Nature 466:857-860.

Semaw, S., Renne, P., Harris, J.W.K., Feibel, C., Bernor, R., Fesseha, N. and Mowbray, K. 1997. 2. 5 million-year-old Stone tools from Gona, Ethiopia. Nature, 385:333-338.


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Australopithecus sediba: an evolutionary mosaic

Science 2010 Balter-2
The skull of MH1, a juvenile member of the species Australopithecus sediba.

Two beautifully preserved partial skeletons of a new species of human are described in the current issue of Science magazine. The new species has been given the taxonomic name Australopithecus sediba. The remains were discovered in Malapa, South Africa, located a mere 15km from the famous Sterkfontein caves. The site preservation is incredible, especially considering its great antiquity. The specimens themselves are relatively free from distortion and show few signs of taphonomic modification.

The fossils are around 2 million years old based on a combination of radiometric and palaeomagnetic dating, as well as the associated animal remains found at the site. The skeletal remains are those of an adult female and a boy of between 9 and 13 years. A. sediba would have stood at about 1.3 metres tall and had relatively long arms like those seen in other australopithecines.

Palaeoanthropologists are split on whether these fossils are members of our genus, Homo, or the earlier Australopithecus. The boy's brain, which is estimated to be around 95% its projected adult size is only 420 cc, some 90 cc below the smallest brain known for early Homo (with a brain case of only 510 cc, KNM-ER 1813 itself is considerably smaller than other Homo specimens). It is on a par with the cranial capacity of the diminutive species Homo floresiensis.

The Malapa hominins have a mix of both australopithecine and Homo traits, with the authors of the paper suggesting greatest specific affinities to A. africanus. The small body, long arms and small brain case are indeed more suggestive of australopithecines. A. africanus, itself is a very variable species and it would not be absurd to suggest that the Malapa hominins represent one tail of the bell curve of variation within that species. The biggest difference between the Malapa hominins and A. africanus is the small dental dimensions of the former. Other traits are more typically associated with Homo, such as long legs, short hands, a derived pelvic configuration, gracile jaw with a weakly developed chin, small teeth, a flat face and a projecting nose. This mosaic anatomy should be a warning to palaeoanthropologists wishing to identify species based on a single anatomical feature.

It has been suggested that A. sediba could be a candidate ancestor for Homo, based on the number of derived traits it share with early representatives of that genus (more than any other known australopithecine). While the site is too late to be ancestral to Homo, the species may not be.

So should sediba be classified in the genus Australopithecus or Homo? The traditional way of distinguishing Australopithecus from Homo was the larger brain size of the latter (with a cutoff point of around 600 cc) and its use of stone tools. Using of a trait like brain size is highly problematic, since it is strongly correlated with body size and there is not a one-to-one correspondence between brain size and brain function. The recent discovery of H. floresiensis, with its small but derived brain, was found together with sophisticated stone tools. Similarly, a preliminary analysis of A. sediba suggests that its brain is more derived than its size would suggest. The first unambiguous appearance of stone tools in the palaeoanthropological record are attributed to H. habilis. Stone tools have not been recovered from Malapa but formal excavations have yet to get underway there. If stone tools are recovered it will require a rethinking about how we define our genus. While brain size is not the only distinguishing characteristic palaeoanthropologists use to separate Homo and Australopithecus, the dividing line is nonetheless an arbitrary one. For the moment, I think Australopithecus is a reasonable preliminary designation for this material, particularly considering our incomplete knowledge of the fossil record.

News headlines touting A. sediba as the "missing link" between humans and apes is misguided on multiple levels. The term "missing link" comes from an outmoded understanding of evolution. Moreover, humans did not suddenly appear with Homo. This is a gross over-simplification of how evolution works. We should not expect to see a momentous change between the first members of a new species or genus and their parent population. Indeed, there is considerable debate as to whether members of the species H. rudolfensis (e.g. KNM-ER 1470) and H. habilis (e.g. OH 24 a.k.a. "Twiggy"), which lie on the generic dividing line, would actually be more accurately classified as australopithecines. I've seen grown men (it seems to be men that get most bent out of shape about such technicalities) argue vehemently over such taxonomic subtleties. Evolutionary theory would dictate that the line between Homo and Australopithecines be a fuzzy one. In fact, if we had a complete fossil record it would be near impossible to know where to draw the line between different genera and species.

In the meantime, more individuals are being slowly uncovered at Malapa. Among these finds, are the arms bones of a 12 – 18 months old infant uncovered metres away from the two published specimens. Whether A. sediba maintains it australopithecine designation or not, is much less interesting than what this population tells us about hominin variation circa 2 million years ago.

References
Lee R. Berger, Darryl J. de Ruiter, Steven E. Churchill, Peter Schmid, Kristian J. Carlson, Paul H. G. M. Dirks, Job M. Kibii (2010). Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa Science, 328, 195-204: 10.1126/science.1184944


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Taking a walk along our evolutionary trail

Gait_keepers
As the rain began to clear over the region a couple of hominins could be seen walking across the blackened earth. The sun was beginning to break through the mist, exploding in a rainbow of colours. The volcano had been making periodic muffled groans since the last eruption…

Some 3.6 million years ago the now extinct Sadiman volcano erupted in Laetoli, Tanzania. It released a plume of ash into the atmosphere. This was the rainy season and the rains changed ash into mud. Elephants, antelopes, hares, giraffes, pigs, rhinos, as well as some bird species walked over the muddied terrain. Among the footprints were those from a pair of (and perhaps even three) hominins, walking side-by-side. A second eruption released more ash into the air covering over the footprints, preserving them as a layer of tuff.

And so the it remained for more than three-and-a-half million years.

Mary Leakey sent an expedition to investigate Laetoli in 1974. One afternoon in 1976, a group of paleontologists were passing the time by throwing elephant dung at each other. Admidst the mud flinging, palaeontologist Andrew Hill found himself standing atop the now eroded ash layer. Archaeologists set about painstakingly excavating the footprints. The layer was friable and crumbled easily. After years of meticulous excavation, the footprints were exposed in all their glory; the grand prize being the fifty metre trail left by the hominins.

They are perhaps the clearest evidence for the early adoption of bipedal walking in our lineage. The footprints are thought to belong to Australopithecus afarensis, the species which included the famous fossil Lucy. However, there has been some debate as to whether these tracks represent fully bipedal locomotion or were more similar to the bent-knee, bent-hip gait seen when modern chimpanzees adopt a bipedal locomotion.

In a study that recently appeared in the journal PLoS ONE, human subjects were asked to walk over a specially constructed walkway. The surface of the track was covered with a damp sand, to mimic the soft underfoot condition that existed at Laetoli when the footprints were laid-down. The subjects walked twice across the trackway and then a further two times assuming a bent-knee, bent-hip gait. Walking with a normal modern human gait produced foot impressions with nearly equal heel and toe depths. In contrast, the bent knee gait resulted in footprints with deeper toe impressions than heel impressions. When non-human apes walk bipedally, weight is transmitted from the heel, along the outside of the foot, with toe-off occurring around the middle of the foot. We on the other transmit weight along the heel to the ball of the foot, finally toeing-off with the big toe. This is the more efficient way to walk bipedally. The impressions from Laetoli best match the pattern made by modern humans.

However I would be cautious about drawing too many conclusions from this study. One major drawback of this study is that walking with a bent-knee, bent-hip gait is not a natural gait for us. The impressions left by modern humans walking with this posture are probably not exactly the same as the footprints that a chimpanzee would leave when walking upright. While this study suggests that these hominins walked with a gait similar to our own, there is still room for debate as to exactly how similar the footprints are to our own. Regardless of these drawback, this study is a step in the right direction (no pun intended).

References
Raichlen, D., Gordon, A., Harcourt-Smith, W., Foster, A., & Haas, W. (2010). Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009769


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The abrupt increase in brain size that wasn't?

In an interview that recently appeared in the Guardian, neurobiologist Colin Blakemore has overstepped the mark in his discussion of the evolution of the human brain. There are a number of problems with Blakemore's thesis that have been covered more than adequately by Jerry Coyne and John Hawks. I wish to focus on the claim that there was an "abrupt" increase in brain size in hominins around 200,000 years ago. Blakemore presents his argument as follows:

The question is: why is [our brain] so big compared to the brains of our predecessors, such as Homo erectus? Until 200,000 years ago, there had been a gradual increase in brain size among hominins, starting three million years ago. Then, abruptly, there was a remarkable increase of about 30% or so.

pleistocene_brain_size-1

John Hawks is not convinced that there is any abrupt change in cranial capacity. Referring to the above graph showing endocranial volume against time he writes:
As you can see, there's no sudden jump 200,000 years ago, or at any other time. The data, such as they are, are consistent with a single pattern of increase over time, as pointed out by Sang-Hee Lee and Milford Wolpoff (2003).

Heck, it's the
lack of a sudden jump that has gotten all the attention. Because if "modern" humans suddenly showed up in Africa 200,000 years ago, and all of a sudden had vastly larger brains than any other hominins, wouldn't that be a simple and tidy story? Don't you think we'd all be talking about the sudden origin of modern humans as reflected by their larger brains?

It just didn't happen.

I decided to take the data from the Lee and Wolpoff paper and compare the periods prior and subsequent to 200,000 years ago. As Hawks eluded to, the data can be explained by a linear model. However, this is not very helpful since we can easily fit a line or curve to just about any data. More to the point, a single fitted line doesn't tell us much about any changes in the data. The red line in the graph below corresponds to the best fit line for the entire dataset (r = 0.81). The green and orange lines are the best fit lines for the two time periods we are considering. We can see that slopes of all three lines differ appreciably from one another. An analysis of covariance test confirms that there is a significant difference in cranial capacity between the two time periods, after we control for time. The model is statistically significant: F(1, 84) = 107, p < 0.001.
brain_size
Another way to consider our data is to look at the residuals. The residuals are simply the difference between our true values and the best fit line of our model. A good way to think about residuals is to imagine rotating our data above anticlockwise until the best fit line is horizontal. Since a horizontal line has a slope of zero, it also has a zero correlation with the x-variable, in our example time. In so doing, we can consider the differences in the residuals, having controlled for time. When we compare the residuals using the best fit line the means for the two time periods (separated by a grey dashed line) are significantly different. The model is also statistically significant: t(84) = -3.9994, p < 0.001. The mean difference in cranial capacity between the two periods is 122 cc; a difference of 31%. This corresponds well with Blakemore's figure. However, it is important to note that this is the mean difference between the two periods and does not necessarily indicate an abrupt change at 200,000 years ago.
residuals
While the numbers seem to agree with the hypothesis of a marked increase in cranial size for the later period, I think the weight Blakemore gives it is rather foolish. The fossil record is patchy and likely unrepresentative of the true cranial variation of past hominins. As Jerry Coyne rightfully points out, a geologically sudden change in the fossil record may simply reflection how erratic it is. We already saw how cranial size can change markedly in 30,000 years – little more than a blip on the time scale that we are considering here. The gradual decrease in cranial capacity since the early Upper Palaeolithic would seem geologically sudden when considered on the above timescale. The size of the fossil record is small enough that the discovery of five or six new specimens could mean having to revise our figures once again.

Another problem is that calculating cranial capacity is not an exact science. While advances have been made in calculating cranial capacity, in many cases it should still be considered a best guess (de Miguel and Henneberg, 2001). This is particularly the case for palaeoanthropological material which tends to come out of the ground fragmented and deformed. With all its drawbacks, the fossil record is often all we have to answer some of our most pressing questions. At the same time, we need to always be conscious of what the record can and cannot tell us, and avoid the temptation to tell "fanciful tales".

References

De Miguel C and Henneberg M (2001) Variation in hominid brain size: how much is due to method? Homo 52: 3–58.

Lee S-H and Wolpoff MH (2003) The pattern of evolution in Pleistocene human brain size. Paleobiology 29:186-196.
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Finger points to new human

dn18699-1_1-thumb

A team of archaeologists have found the bone of a little finger while digging at Denisova Cave in the Altai Mountain, located in southern Siberia. The size of the bone suggests that it came from a child between five and seven years of age. It is difficult to distinguish between different species of humans based solely on the morphology of a single finger bone. However, the tentative dates put the age of the bone at between 30,000 and 50,000 years ago; a window of time when both Neandertals and modern humans coexisted in Eurasia.

In order to determine which species the little finger came from, Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany sequenced the complete mitochondrial DNA (mtDNA) from the finger bone and compared its DNA with that of modern humans and Neandertals. What they found surprised everyone involved in the project. The mtDNA of Denisova did not match that of modern humans or Neandertals. In fact it last shared a common ancestor with us and Neandertals in Africa around a million years ago.

We know of three major hominin migrations out of Africa. The first occurred with Homo erectus around 1.9 million years ago, followed by the ancestors of Neandertals sometime between 500,000 and 300,000 years ago, and finally modern humans around 50,000 years ago. This makes the Denisova specimen too late to be part of the Homo erectus exodus and too early to part of the other two.

However, it may be a little premature to declare this a new species of human. Svante Pääbo's team is already busy sequencing the nuclear DNA of the Denisova specimen. One, albeit unlikely, possibility is that this will turn out to be a representative of an outlier Neandertal population. Previous studies have found a wide diversity in both the morphology and mitochondria of geographically separated Neandertal populations. Until the nuclear DNA has been mapped it is not possible to definitively say if we are really dealing with a new species of human. However, if this does turn out to be the case, it would mean that we shared the globe with at least three other species of humans as late as 40,000 years ago.


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Why people believe in homeopathy

sewage
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.
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Changes to commenting service

I have received notification that my comment service Haloscan will be closing. Unfortunately, there is no way to export older comments. Since my blog is relatively new and only gets a few comments, I think the move to a new comments system should be a minor inconvenience. With that said it hasn't been an easy decision. I will be migrating the comments to the Disqus service. Thanks to everybody who has commented on my past posts. Your feedback and comments are very important to me.

The upside of these changes means that I can use a plugin called RapidBlog that allows me to use the Google Blogger service to write and publish blog posts. Migrating to Blogger means that I'm no longer tied to my machine and can post while on the road. The main reason I didn't use this earlier was that it meant losing comments, which is now inevitable. Hopefully the move to Google Blogger will be invisible for you the reader. Thank you for your understanding and continued support.
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Four Stone Hearth 88

four-stone-hearth

Welcome to the St. Patrick’s Day special edition of Four Stone Hearth 88. Four Stone Hearth is a fortnightly anthropology blog carnival. Topics covered span the four major fields of anthropology: archaeology, socio-cultural anthropology, bio-physical anthropology and linguistic anthropology. If you would like to host the carnival, please write to . The next issue will be hosted at the Greg Laden’s blog on 31 March.

Online Degrees.net has posted their 100 best blogs for anthropology students. It is a wonderful resource that I recommend checking out. Now on with this round of carnival posts.

Archaeology
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Luis over at the blog Leherensuge reports on the alleged archaeological forgery at Glozel. The controversy revolves around a hoard of objects that appear to date from different time periods. The death of the principle protagonist, Emile Fradin, has renewed interest in these alleged artefacts. Are these the genuine article or just another Piltdown. Decide for yourself.

Over at Testimony of the spade, Magnus Reuterdahl reflects on how extant abbeys can give us a greater appreciation for those which over time have falling into ruin.

Martin Rundkvist over at Aardvarchaeology, has mixed feelings about his Magnum opus entitled "Domed oblong brooches of Vendel Period Scandinavia.” Martin relays how sticking to your “scholarly ideals” is not always the easiest road to career advancement.


Biological anthropology
In a recent post, I discuss the trend towards decreased head size starting around 30,000 years ago, which continues today.

Carl Feagans at ahotcupofjoe looks at the dispersal of early Homo out of Africa.

Last year, amidst much media fanfare everybody came to know about our 47 million year old purported ancestor “Ida”. This was indeed a spectacularly preserved fossil specimen, which preserved the outline of the body as well as the stomach contents. However, the scientific community at the time aired scepticism about the claim that it was on the evolutionary line that led to us. Many palaeontologists and primatologists were quick to point out that this primate looked more lemur-like. Well, it turns out that they were right. In a paper published in the Journal of Human Evolution shows that this species, Darwinius masillae, belonged to an extinct branch of primates, most closely related to lemurs and lorises. Brian Switek of the Laelaps gives a synopsis of the paper, while Eric Michael Johnson at Primate Diaries gives a very accessible account of the whole affair.

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John Hawks is a fly on the wall at a symposium on genetics and genealogy of the African Diaspora. He reports on Fatimah Jackson’s genetic work in Africa and African-Americans, in particular the idea of "ethnogenetic layering”.

Raymond Ho at the Prancing Papio blog has a review of a paper on the changing mating systems in Sichuan snub-nosed monkeys. The pieces offers some plausible evolutionary reasons for the shift from polygynous to polygamous mating systems.


Linguistic anthropology
Valerie Williamson writes about Siberian languages, which are on the verge of extinction. The race is on for linguists to document these languages before they disappear completely.


Socio-cultural anthropology
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In the spirit of the occasion, anthropologyworks has compiled a bibliography of social anthropology articles on Ireland and the Irish.

Krystal, over at Anthropology in Practice, talks about a street vendor in her city that has started to take coffee orders via text message. Is this merely a fad or society simply adapting to our greater reliance on digital media?

Ronald Kephart a.k.a. the Cranky Linguist reports on the educational malpractice of teaching religion as science at Liberty University.

CocaColaIndia
Eric Michael Johnson reports on the Itineraries of Exchange symposium. This piece gives us an insight how indigenous groups have managed to maintain traditions and self-determination in the face persecution, racism, and exploitation.

Also check out Eric’s article on Coca Cola’s over-exploitation of water resources in India. It seems that the slogan “Good Till the Last Drop" has a more pernicious meaning.

A Very Remote Period Indeed has a wonderfully titled piece “Mad Neanderthals, peer review and scholarly publication”. Controversy has surrounded the journal Medical Hypotheses since its very conception. This journal is unique in that it doesn’t have a peer review system, while promoting controversial and thought-provoking ideas. However, Julien Riel-Salvatore tells of the comment he published in this journal in response to an article that proposed that Spongiform Encephalopathies may have led to the demise of the Neanderthals. Julien does not think the biggest problem is with the journal’s incredibly low standards but rather with the academic publishing house Elsevier, who by purchasing Medical Hypotheses has given it an air of legitimacy.

That’s it for another edition of Four Stone Hearth. Happy St. Patrick’s Day to one and all!

Image Credits
Golden snub nosed monkey from artsonearth,
CocaColaIndia by Carlos Latuff under the Wikimedia Commons licence.
Marilyn Monroe reading James Joyce. Flickr creative commons licensed content by user I, Puzzled.


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