October 17, 2011Posted by on
By Natalie Hunter*
In the foothills of the Taurus Mountains in southeastern Turkey lies the ancient mound of Göbekli Tepe. This is the site of a Neolithic temple complex of megalithic architecture that is at least 10,000 years old. Since excavations began in 1994, the discoveries made here have fascinated the world and turned conventional theories of human prehistory and the development of civilization on its head.
The mound contains as many as 20 separate circular compounds comprised of a series of upright T-shaped stone pillars placed in ring patterns, with the spaces between closed in by stone slabs and cobbled walls of rough-cut stone. Two T-shaped pillars of enormous size stand in the central area of four of the compounds so far excavated. Many of the pillars, both the centrally located ones and those of the compound perimeter, are carved with images of various animals and petroglyphs.
Perhaps the most intriguing aspect of Göbekli Tepe is that the entire complex was intentionally backfilled and buried about 8,000 years ago. A happy fact in that the site was thus preserved, but also a tantalizing mystery because so far we have no clue as to why a complex that had been in continuous use for more than 4,000 years was suddenly buried and subsequently forgotten.
There is little debate that the complex served a ritual function of some kind. This implies that some cultural force compelled the people of the area to invest a lot of energy to construct these monuments. That cultural force clearly had to have been religious in nature, but with a level of sophistication and organizational acumen that far exceeded what had long been assumed about pre-agricultural human societies.
This failed assumption lies at the nexus of scholarly debate over Göbekli Tepe. Before Göbekli Tepe, scholars from traditional and online schools alike believed the development of agriculture had provided the impetus for humans to adopt a sedentary cultural pattern. Thus providing a reliable food source that allowed communities to grow, and freed up labor and time for the pursuit of activities beyond basic subsistence. It was only then (the previous assumptions held), after urbanization was well under way, that priestly hierarchies could develop with the level of sophistication and power to construct ritual edifices as imposing as Gobekli Tepe.
The old assumption was that first came the city, then came the temple. It was believed that nomadic hunter-gatherers had to spend most of their time and energy on subsistence, and could not possibly have had the time, leisure or organizational skill to create a sophisticated architectural achievement as that of Göbekli. This also defies the old assumption that held that no pre-agricultural, pre-urban society could muster the organizational skills or manpower necessary to build such large structures.
It was further assumed that the complex theological ideas that must have underpinned the rituals and art motifs of Göbekli could not have been possible at the pre-agricultural stage of human development. But, as the lead archeologist at Göbekli Tepe, Klaus Schmidt of the German Archeological Institute, put it: “Fist came the temple, then the city.”
So far, no evidence has been found of habitation on the site, such as cooking hearths or living areas. Nor has any evidence been found of domesticated plants or animals, which indicates that Göbekli was a pre-agricultural center throughout its existence. Intriguingly enough, the time when the complex was deliberately buried is roughly contemporaneous with the earliest developments of agriculture. As such, it remains a snapshot of a temple that stood 4,000 years before the first urban centers grew up down the rivers.
Some scholars contend that Göbekli itself may have provided the impetus that pushed mankind toward agriculture and the domestication of animals. Meanwhile, others have speculated that Göbekli Tepe represents the actual Garden of Eden and was the home to the Watchers and Nephalim of the “Book of Enoch.” Still others have found fodder to add to the many theories of ancient extraterrestrials.
This sensational discovery is perhaps one of the most important archeological finds of all time. Accordingly, the debate and speculations surrounding this mysterious place will likely be ongoing for years to come. Whatever the truth may be, what is certain is that there are more discoveries to be made at Göbekli Tepe since so far only about 5 percent of the area of the site has been excavated.
*About the author: Natalie Hunter grew up wanting to be a teacher, and is addicted to learning and research. As a result she is grateful for the invention of the internet because it allows her to spend some time outside, rather than just pouring through books in a library. She is fascinated by the different methodologies for education at large today, and particularly by the advent of online education. She also loves to travel and learn via interaction with other people and cultures.
April 29, 2011Posted by on
The Department of Archaeology, University College Cork, invites applications for a four year PhD studentships in biological anthropology as part of a new European Research Council funded project (directed by Dr R Pinhasi): “From the earliest modern humans to the onset of farming (45,000- ‐4,500 BP): the role of climate, life- ‐style, health, migration and selection in shaping European population history” (€1.088 million).
The colonisation of Europe by anatomically modern humans (AMHs) ca. 45,000 years before present (BP) and the transition to farming ca. 8,000 BP are two major events in human prehistory. Both events involved certain cultural and biological adaptations, technological innovations, and behavioural plasticity, which are unique to our species. The reconstruction of these processes and the causality between them has so far remained elusive due to technological, methodological and logistical complexities. Major developments in our understanding of the anthropology of the Upper Palaeolithic, Mesolithic and Neolithic, and advances in ancient DNA (aDNA) technology and chronometric methods now allow us to assess in sufficient resolution the interface between these evolutionary processes, and changes in human culture and behaviour.
The advertised studentship will focus on the study of cranial morphological variation among Upper Palaeolithic, Mesolithic and Neolithic skeletons using 3D morphometric methods. We are particularly interested in candidates with a strong background in morphometrics and/or statistical shape analysis.
Students will be supervised by Dr Ron Pinhasi at UCC with co- ‐supervision by Dr Jay Stock (U of Cambridge) and Dr Noreen von Cramon- ‐Taubadel (University of Kent, Canterbury) and will involve collaboration with leading geneticists, simulation specialists and anthropologists from all across Europe and with 4 appointed PhD students which are part of the project.
A full award covers fees and an annual stipend of €17, 042 (2010/2011 rates).
• A Masters degree and a first or upper second class BA/BSc degree in a relevant subject
• Background in human and/or primate osteology and the application of quantitative methods in biological anthropology or related disciplines
• Students for whom English is not their first language must meet the required minimum level of English language proficiency (IELTS 7 in all skills, or equivalent.
The starting date is September 2011.
The closing date for applications is 29th April 2011.
To apply, please send curriculum vitae (3 pages max), cover letter, and details of two academic referees by email to email@example.com.
March 30, 2011Posted by on
The site of Combe Capelle is located in the Dordogne region in the South of France. It was excavated in 1909 by Swiss archaeologist Otto Hauser. The burial was of a man who died between 40-50 years of age. He was buried in a shallow pit with numerous grave goods, including a necklace of perforated shells. The burial was believed to date to around 30,000 years ago. There is scant evidence for inhumations from this early period and the presence of grave goods is more typical of later periods.
Much of the early anthropological research was carried out under the presumption of racial types. New fossils were pigeonholed into discrete racial categories. The Grimaldi “negroid” race was readily accepted despite problems in the reconstructions of the type specimens. Similarly, the Chancelade race was believed to show strong affinities with modern Eskimos. Upon their analysis of the Combe Capelle skeleton, Hauser along with anthropologist Heinz Klaatsch gave it the designation Homo aurignacensis hauseri, a second dolichocephalic race from the Upper Palaeolithic alongside Cro-Magnon. A number of researchers drew parallels between the Combe Capelle, Galley Hill, and Brno types, which were all believed to be of great antiquity. The English Galley Hill remains were subsequently subjected to fluorine dating methods and found to be a recent intrusive burial into older geological layers. There is one direct date for the Czech Brno specimens the put it at just over 20,000 years old, although there is still some debate as to the age of the rest of the Brno material. While most researchers ended up grouping the Combe Capelle specimen in the Cro-Magnon race, i.e. Homo sapiens, other researchers continued to refer to a Combe Capelle type as late at the 1980s.
After their excavation, the Combe Capelle skeletal remains were sold to the Museum für Vor- und Frühgeschichte in Berlin, where they were lost and believed to have been destroyed since the last World War. Some of the charred postcranial remains were subsequently found among the rubble of the bombed-out museum. The skull was believed to have been lost forever until its fortuitous rediscovery in 2001.
A sample of collagen from the tooth enamel of the Combe Capelle specimen was sent to a laboratory in Kiel in 2009 for dating. The recently announced results confirm the suspicions of those who questioned the skeleton’s antiquity. The new date places the man of Combe Capelle in the Mesolithic period, around 9500 years ago. The Combe Capelle skeleton is one of many that have been redated in the past decade and have been shown to be of more recent antiquity. The redating of the Combe Capelle, Vogelherd, Velika Pećina, Hahnöfersand and many other specimens to the Holocene period means that there are now very few skeletal remains that date to the Aurignacian and makes the association of modern humans with this technology more uncertain than ever.
October 16, 2010Posted by on
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.
August 18, 2010Posted by on
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.
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.
April 15, 2010Posted by on
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.
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
April 5, 2010Posted by on
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).
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
April 1, 2010Posted by on
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.
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.
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.
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”.
De Miguel C and Henneberg M (2001) Variation in hominid brain size: how much is due to method? Homo 52: 3–58.
March 25, 2010Posted by on
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.
March 22, 2010Posted by on
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.