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  • August 17, 2011
  • 11:32 AM
  • 1,929 views

Solving the Mystery of Conjoined Twins at Angel Mound

by Kristina Killgrove in Powered By Osteons

Conjoined twinning is a rare congenital abnormality.  We know of old historical cases, of course, like Chang and Eng, whose birthplace gives us the term Siamese twins.  Going back further, Moche ceramics seem to depict conjoined twins as early as the turn of the first millennium.  But even though conjoined twins undoubtedly existed in antiquity, no conclusive bioarchaeological evidence has ever been found.

In 1941, an archaeologist named Glenn Black and his crew of WPA workers uncovered an unusual single burial of two infants, both about three months old, at a Middle Mississippian site (11th-15th c AD) called Angel Mounds near Evansville, Indiana.  Because of the positioning of the skeletons, Black suggested the burial might be that of conjoined twins.




Diagram of skeletons W11A60 and W11A61 from Angel Mounds



In order to shed light on this mystery, Charla Marshall, Patricia Tench, Della Collins Cook, and Frederika Kaestle undertook aDNA analysis, with the idea that conjoined twins would share mitochondrial genotypes because they have the same mother.  In a brief communication to AJPA, Marshall and colleagues (2011) report that their DNA sequencing clearly showed no maternal relationship.  It is still possible the infants were related, but they were not twins, conjoined or otherwise.  The question remains: why were these two infants buried in this manner?

This study, of course, would have been more interesting had the authors found conjoined twins, but they showed that certain interpretations about burials are now better made in a laboratory setting through the addition of chemical analysis of osteological data.
Reference:

Marshall C, Tench PA, Cook DC, & Kaestle FA (2011). Brief communication: Conjoined twins at Angel Mounds? An ancient DNA perspective. American Journal of Physical Anthropology, Early View. PMID: 21834072.... Read more »

  • August 16, 2011
  • 08:10 AM
  • 1,706 views

Free language choice?

by Ingrid Piller in Language on the Move

Pretty much everyone I know wants to learn English or improve their English – with the exception of those who consider themselves native speakers, obviously. What is more, everyone I know knows that everyone else wants to learn English (the … Continue reading →... Read more »

  • August 15, 2011
  • 05:28 PM
  • 1,963 views

The Hidden Advantage of Twins

by Elizabeth Preston in Inkfish

For humans and other animals that traditionally have just one baby at a time, twins are a gamble. Pregnancy is riskier for the mother and the fetuses. If the twins make it to birth, they're likely to be undersized. And even if she has two healthy babies, a mother must find twice as much food as usual to keep them that way--and must keep twice as many helpless, chubby morsels away from the lions. But if both kids survive to adulthood, the parents will have doubled their genetic contribution to the next generation.Presumably because it's an evolutionary trade-off with so many variables, the rate of twinning has evolved differently across human populations. This variation applies only to "dizygotic," or fraternal, twins. Identical (or "monozygotic") twins are more rare, and their frequency of about 0.4% stays fairly constant across populations. One embryo splitting into two seems to be a random accident. Dizygotic twinning, though, seem to result from genetic tendencies; some mothers are more likely to release two eggs simultaneously.One potential explanation involves hormones called insulin-like growth factors (IGFs). The IGF system may affect a mother's chances of releasing multiple eggs. It's been linked to twinning in a study of cattle (another mammal that usually sticks to one calf at a time). IGF hormones have also been linked to the growth of a fetus. This led a group of researchers in the UK to ask whether mothers who give birth to twins, thanks to the effect of IGF hormones, also give birth to larger non-twin babies.The researchers, led by Ian Rickard, used data collected from Gambian women between 1978 and 2009. These women had an average of about 7 children each. Researchers divided the women into those who gave birth to twins at some point, and those who never had twins. They found that "singleton" (non-twin) babies born to twinning mothers were significantly larger, on average, than babies born to non-twinning mothers. In other words, twinning mothers--when they're not having twins, which are usually small--give birth to heavier babies. This effect was independent of the mothers' BMI or height. It even held true for singleton babies that were born before their twin siblings: these babies were heavier at birth than singleton babies born to mothers who never had twins.The only time the effect didn't appear was when mothers were exposed to the "hungry season," the furthest time from the harvest, during their third trimester. With more limited resources during their pregnancies, twinning mothers gave birth to babies that were roughly as small as non-twinning mothers' babies.Though the dataset doesn't include information on IGFs or other hormones, it seems that some underlying factor causes mothers both to have twins (because they release two eggs at once) and to have large singleton babies. The researchers also don't know how many of these sets of twins were actually identical, or monozygotic (the less-common variety). But since monozygotic twinning seems to happen randomly, mothers of identical twins would presumably dilute the effect seen here. So if anything, the birthweight advantage in twinning mothers might be even greater than it seems.Whatever is underlying it, the study shows that there's an advantage to twinning--or, at least, that twinning is a side effect of an advantageous trait that makes for sturdier singleton babies. This might help to explain why twinning has evolved to be more common in some human populations than in others. Each population has its own pressures, and must strike its own balance between factors such as birthweight and survivorship. Thanks to the intricate mathematics of natural selection, twins are never just a twofer.Rickard, I., Prentice, A., Fulford, A., & Lummaa, V. (2011). Twinning propensity and offspring in utero growth covary in rural African women Biology Letters DOI: 10.1098/rsbl.2011.0598... Read more »

  • August 15, 2011
  • 12:13 AM
  • 1,015 views

Scent of a Woman

by Krystal D'Costa in Anthropology in Practice

At seventeen I discovered the perfume that would become my signature scent. It’s a warm, rich, inviting fragrance[i] that reminds me (and hopefully others) of a rose garden in full bloom. Despite this fullness, it’s light enough to wear all day and it’s been in the background of many of my life experiences. It announces [...]









... Read more »

  • August 12, 2011
  • 11:17 AM
  • 2,015 views

Weaning and Freshwater Fish Consumption in Roman Britain

by Kristina Killgrove in Powered By Osteons

In the September issue of Geochimica et Cosmochimica Acta, O. Nehlich and colleagues use sulphur isotope analysis to investigate the diet of 83 individuals from three Roman-era sites in Oxfordshire, England.  Their hypothesis was that sulphur isotopes, in combination with carbon and nitrogen isotopes, would reveal an additional facet of the diets of people in the area.  Sulphur isotopes have started to gain in popularity, as they're useful for separating marine and terrestrial protein (much like nitrogen isotopes are), for indicating freshwater resource consumption (which C/N isotope analysis can miss), and for tracking migration (in a similar manner as oxygen isotope analysis).  Nehlich and colleagues also wanted to apply sulphur isotope analysis to infants.  It is well known that nursing infants have dramatically different nitrogen isotopes than adults, and there is growing evidence that carbon, oxygen, and strontium isotopes are also affected by nursing.

The carbon and nitrogen isotope data from these Roman Oxfordshire populations were previously reported by Fuller and colleagues (2006), showing that the people got most of their protein from herbivores and possibly also from freshwater resources, and their carbohydrates from C3 plants (e.g., wheat).  Nehlich and colleagues perform a sulphur isotope analysis on the same individuals Fuller and colleagues used, and they find that sulphur can indeed distinguish between terrestrial and freshwater aquatic resource consumption:



d34S values of bone collagen of animals and humans from Oxfordshire
(credit: Nehlich et al. 2011, Fig. 3)
It's not a particularly surprising result, since some of these individuals lived along the Thames River, but sulphur provided the researchers additional information about diet that the carbon and nitrogen isotopes couldn't tease out.



While the C and N data show a linear
pattern with age, the S data don't; they
may, however, be more like a curve.
(credit: Nehlich et al., 2011, Fig. 5)
The really interesting finding in this article, though, is that sulphur isotopes can provide additional information about patterns of breastfeeding and weaning.  The original study by Fuller and colleagues had found 13C-depleted values for infants in the range of 2-4 years, which the authors interpreted as a unique weaning diet composed mostly of C3 plants and terrestrial meat, and surprisingly variable d15N values suggesting weaning was a gradual process.  Sulphur, like nitrogen, has a small trophic effect, meaning infants consuming their mothers' tissues (in the form of breastmilk) typically have higher isotope values than the adult population.  However, Nehlich and colleagues didn't observe any striking patterns in 34S enrichment.  They conclude that the pattern Fuller and colleagues saw is actually the result of consumption of freshwater fish or other foods influenced by freshwater hydrology - such as grains that grew near freshwater sources.  Nevertheless, they also found that kids 8 years and older have more 34S-enriched values, suggesting they were eating mostly terrestrial protein.

As I just finished up the (hopefully) final draft of my article on carbon and nitrogen isotope analyses of the Imperial Roman diet, this sulphur study has been on my mind.  I've written before about the problem of aquatic resource consumption in the Roman diet - sometimes fish were seen as the lowest form of food, and sometimes they were highly prized (e.g., in the form of garum, a fish sauce).  Neither of my populations lived particularly near the Tiber River, but the people buried in the St. Callixtus catacombs also weren't that close.  The Callixtus palaeodiet reconstruction by Rutgers and colleagues (2009), though, suggests freshwater resource consumption because of the comparatively low carbon and high nitrogen isotope values.  The Callixtus skeletons would therefore be an ideal place to start a sulphur isotope study in Rome.  It might also be useful to do a sulphur isotope study on the infants buried in Isola Sacra, whose skeletons gave Prowse and colleagues (2004) quite a bit of information about weaning and diet.  Interestingly, the ages at weaning in Roman Oxfordshire and in Portus Romae seem to differ a bit: while Fuller and colleagues think weaning took place from 2-4 years old, Prowse and colleagues found that kids were fully weaned by 2.5-3 years of age.  Analyses of carbon and nitrogen isotopes are increasingly showing us that there was no monolithic Roman diet, and that consumption of resources varied by age, location, time period, and (probably) status and religious/ethnic group.

Isotope analysis isn't perfect, but it is a powerful technique for looking at palaeodiet, and I hope that these bioarchaeological findings start being incorporated into general treatises on the ancient Roman diet.  For example, the recent book Taste or Taboo (Beer, 2010) is excellent but mentions no biochemical analyses of the Roman diet.  Part of this disconnect between anthropology and classics is the fault of bioarchaeologists.  After all, we publish in journals that further our careers, like the American Journal of Physical Anthropology, Journal of Archaeological Science, and Geochimica et Cosmochimica Acta.  These aren't top on the list of journals that classicists want to read, and the language of the latter two is generally highly technical, which can be problematic when a classicist does attempt to delve into the scientific data (as I've written about here in the Journal of Roman Archaeology).  One of my goals for this blog is to widely disseminate bioarchaeological work and get it noticed by classicists, anthropologists, and the public alike.  But the classicists interested in diet, migration, and burial would also do well to start perusing anthropology journals, contacting article authors if the paper is too technical, to really understand what we can contribute to the study of the ancient Romans.

References:

Beer, M.  (2010).  Taste or Taboo: Dietary Choices in Antiquity.  Prospect Books.


Fuller BT, Molleson TI, Harris DA, Gilmour LT, & Hedges RE (2006). Isotopic evidence for breastfeeding and possible adult dietary differences from Late/Sub-Roman Britain. American Journal of Physical Anthropology, 129 (1), 45-54. PMID: 16229026.

Killgrove, K.  (2010).  Migration and mobility in ... Read more »

O. Nehlich, B. Fuller, M. Jay, A. Mora, R. Nicholson, C. Smith, & M. Richards. (2011) Application of sulphur isotope ratios to examine weaning patterns and freshwater fish consumption in Roman Oxfordshire, UK. Geochimica et Cosmochimica Acta, 75(17), 4963-4977. info:/10.1016/j.gca.2011.06.009

  • August 12, 2011
  • 12:02 AM
  • 2,130 views

Ancient Remnants: Biomolecules in Paleomicrobiology

by Michelle Ziegler in Contagions

Ancient DNA is not the only method of detecting and identifying ancient pathogens. Survival challenges for ancient DNA place very real limitations on its usefulness and sensitivity as a detection method. The main advantage of aDNA is that it can be genotyped to compare with modern species. For archaeological purposes, other biomolecules may be detected [...]... Read more »

  • August 11, 2011
  • 03:36 PM
  • 980 views

Equality in the Bedroom (and why it matters)

by eHarmony Labs in eHarmony Labs Blog

In the second of the female sexuality series, I ask, what part does equality play when it comes to a satisfying sex life? Read on to find out about the importance of equality with your partner and 7 Do's and Dont's to making the bedroom more harmonious.... Read more »

  • August 10, 2011
  • 10:59 PM
  • 1,799 views

iBoyfriend

by Lachlan Jackson in Language on the Move

Having lived and taught English in Japan for more than fifteen years, until last night I’d thought I’d seen it all. That was until I stumbled across the もし彼氏が外国人だったら英会話 (What if my Boyfriend was a Foreigner English Conversation [my translation]) … Continue reading →... Read more »

Takahashi, Kimie. (2010) Multilingual couple talk: Romance,identity, and the political economy of language. D. Nunan , 199-207. info:/

  • August 10, 2011
  • 02:34 PM
  • 1,725 views

1st Installment of the Roman Bioarchaeology Carnival

by Kristina Killgrove in Powered By Osteons

Since I'm gearing up for a new semester (finishing up syllabi, packing for a move, etc.), I haven't had as much time as I'd like to blog about the interesting reports and publications that have come out recently on the topic of Roman-era skeletons.  So here's a carnival or round-up of links from the past few weeks, things I've wanted to talk about but haven't had the time to craft full posts about.

Skeletons

Roman Child Skeleton from Durnovaria
(credit: DorsetECHO)
August 10 - Today's news brought a brief story about the discovery of a skeleton of a Roman child from what used to be Durnovaria (modern-day Dorchester, England).  There's no osteological information in the report, but there is a nice little history of Durnovaria and this photo of the skeleton, which was found within the settlement (unclear if it was in a house).  It's not unusual to find children buried outside of cemeteries - within houses, near walls, etc.
August 8 - On Monday, the BBC gave a bit more coverage to the discovery of nearly 100 infant skeletons in a Roman-era villa in Britain.  Jill Eyers, who rediscovered the skeletons in a storeroom, put forth the idea last year that these infants were killed on purpose and that the villa was in use as a brothel.  [Original BBC report here, bit of video here.]  Dr. Eyers remains convinced of her theory, but scholars in both the classical and anthropological blogospheres are questioning that.  Most notable are the posts by archaeologist Rosemary Joyce, who wrote a critique of the theory last year and wrote an updated post yesterday continuing to cast doubt on the whole brothel idea.  Dr. Joyce's posts are well worth a read, as she delves into the historical and archaeological evidence of Roman brothels to bring a counter-point to the discussion of this interesting discovery.
August 8 - The American Journal of Physical Anthropology published an interesting paper on Monday by Becky Redfern and Sharon DeWitt (2011) on the effect of status on mortality risk in Roman-era Dorset, England.  The authors looked at nearly 300 individuals dating to the 1st to 5th centuries AD and assigned them a status level based on burial type.  Using models of mortality, they found that indeed higher-status individuals had lower mortality risk.  This was especially true for children and for people who were buried (and presumably lived in) an urban environment.  Interestingly, male mortality risk was higher than female mortality risk (I presume owing to warfare and other job hazards).  Redfern and DeWitt conclude that, "...the cultural buffering afforded by being of high status enabled people to more effectively deal with urban environments and migration, with lower-status individuals having greater risk because of their forms of employment and living conditions."  We can, of course, assume that individuals with higher status had better diets and overall health, and therefore lower mortality risk. But it's great to see researchers actually test that hypothesis.  It's also interesting to see that urban denizens had lower risk of mortality; in many ancient societies, urbanism meant dramatic changes to health and wellbeing, but I've also been finding with my Romans that those who lived in or near the city were generally healthier than those from the suburbs and countryside.

Mummies

Mummies arranged by age, sex, and occupation.
(credit: Panzer et al. 2010, Fig. 2)
Not Roman and not recent news, but still neat: last summer, S. Panzer and colleagues published a study of late 19th/early 20th century mummies from the Capuchin Catacombs in Palermo, Sicily.  The pictures in the article are astounding: the mummies are excellently preserved, and the radiographs show a variety of minor pathological conditions (e.g., healed fractures) in some of the mummies.  The authors were able to learn a lot about embalming techniques and about the health of the people who were given this treatment after death.

Interactive Teaching ToolsAnd finally, this link has been sitting in my bookmarks for a while.  I discovered the BBC's online video game Dig It Up: Romans through Katy Meyers' blog post (July 14, at Play the Past).  It's cute, fun, and educational.  Katy writes that, "not only does the game allow payers to see the different stages of archaeology, but it is all done in a cultural resource management with the threat of construction setting time limits."  Unfortunately, I didn't find a skeleton when I played... just a lamp and an amphora.  But the game shows that archaeologists need sampling strategies, that we don't always find every piece of an artifact, and that we don't always find anything of interest (ah, memories of Spam cans from my days excavating at Monticello).  Go play it now!  You know you need a break from work.
References:
Panzer S, Zink AR, & Piombino-Mascali D (2010). Scenes from the past: radiologic evidence of anthropogenic mummification in the Capuchin Catacombs of Palermo, Sicily. Radiographics 30 (4), 1123-32. PMID: 20631372.

Redfern RC, & Dewitte SN (2011). Status and health in Roman Dorset: The effect of status on risk of mortality in post-conquest populations. American Journal of Physical Anthropology PMID: 21826637.... Read more »

  • August 9, 2011
  • 02:30 PM
  • 1,514 views

Telesphorus, a cult hymn from Epidaurus

by Nikolaos Markoulakis in Tropaion



Frieze from Roman Philippopolis (3rd AD),
from left to right: Luna, Iaso, Telesphorus, Asclepius,
Panacea, Epione, Machaion, Padaleirios.
© Archaeological Museum in Plovdiv,
Bulgaria (RAM – Plovdiv)
Hellenic Polytheism is not just about the worship of the Twelve Olympians, but, on the contrary of a great number of divinities capable to have a straightforward and personal contact with the

... Read more »

Martin P. Nilsson. (1945) Pagan Divine Service in Late Antiquity. The Harvard Theological Review, 63-69. info:/

Wiseman, J., & Mano-Zissi, D. (1976) Stobi: A City of Ancient Macedonia. Journal of Field Archaeology, 3(3), 269. DOI: 10.2307/529437  

  • August 9, 2011
  • 10:30 AM
  • 2,757 views

Getting "Mean Girled" in the Baboon World: The Price of Being Sexy.

by Serious Monkey Business in This is Serious Monkey Business

What do female baboons have in common with the Plastics from Mean Girls? A lot of aggression towards attractive female baboons that might pose a threat to their resources--but not in the typical way you might think.... Read more »

  • August 8, 2011
  • 03:00 PM
  • 1,587 views

On the Origin of Cooperative Species: New study reverses a decade of research claiming chimpanzee selfishness

by Eric Michael Johnson in The Primate Diaries

Charles Darwin had more in common with chimpanzees than even he realized. Before he was universally known for his theory of natural selection, the young naturalist was faced with one of the great moral choices in the history of science. The decision he made has long been hailed as the type of behavior that fundamentally [...]









... Read more »

Victoria Hornera,J. Devyn Cartera, Malini Suchaka, and Frans B. M. de Waal. (2011) Spontaneous prosocial choice by chimpanzees. Proceedings of the National Academy of Sciences. info:/10.1073/pnas.1111088108

  • August 5, 2011
  • 01:36 PM
  • 1,355 views

The curious relationship between place names and population density

by Tim De Chant in Per Square Mile

Giving a name to a place is an important act. It says a place has meaning, that it should be remembered. For thousands of years, the way we kept track of place names—or toponyms—was by using our memory. Today, we’re not nearly so limited, and the number of toponyms seems to have exploded. Yet oddly [...]... Read more »

  • August 3, 2011
  • 03:48 PM
  • 1,019 views

Antipsychotics - The New Valium?

by Neuroskeptic in Neuroskeptic

Antipsychotics, originally designed to control the hallucinations and delusions seen in schizophrenia, have been expanding their domain in recent years. Nowadays, they're widely used in bipolar disorder, depression, and as a new paper reveals, increasingly in anxiety disorders as well.The authors, Comer et al, looked at the NAMCS survey, which provides yearly data on the use of medications in visits to office-based doctors across the USA.Back in 1996, just 10% of visits in which an anxiety disorder was diagnosed ended in a prescription for an antipsychotic. By 2007 it was over 20%. No atypical is licensed for use in anxiety disorders in the USA, so all of these prescriptions are off-label.Not all of these prescriptions will have been for anxiety. They may have been prescribed to treat psychosis, in people who also happened to be anxious. However, the increase was accounted for by the rise in non-psychotic patients, and there was a rise in the rate of people with only anxiety disorders.The increase was driven by the newer, "atypical" antipsychotics.Whether the modern trend for prescribing antipsychotics for anxiety is a good or a bad thing, is not for us to say. The authors discuss various concerns ranging from the side effects (obesity, diabetes and more), to the fact that there have only been a few clinical trials of these drugs in anxiety.But what's really disturbing about these results, to me, is how fast the change happened. Between 2000 and 2004, use doubled from 10% to 20% of anxiety visits. That's an astonishingly fast change in medical practice.Why? It wasn't because that period saw the publication of a load of large, well-designed clinical trials demonstrating that these drugs work wonders in anxiety disorders. It didn't.But as Comer et al put it:An increasing number of office-based psychiatrists are specializing in pharmacotherapy to the exclusion of psychotherapy. Limitations in the availability of psychosocial interventions may place heavy clinical demands on the pharmacological dimensions of mental health care for anxiety disorder patients. In other words, antipsychotics may have become popular because they're the treatment for people who can't afford anything better.These data show that antipsychotics were over twice as likely to be prescribed to African American patients; the poor i.e. patients with public health insurance; and children under 18.Comer JS, Mojtabai R, & Olfson M (2011). National Trends in the Antipsychotic Treatment of Psychiatric Outpatients With Anxiety Disorders. The American journal of psychiatry PMID: 21799067... Read more »

  • August 3, 2011
  • 01:56 PM
  • 1,975 views

Hunting Pathogens in Siberian Permafrost Graves

by Michelle Ziegler in Contagions

The Yakut community of Eastern Siberia has gained some attention from anthropologists because it culturally stands out from other Siberian populations. Their Turkic language, unique burial practices, and horse-breeding culture is not native to Siberia. Recent genetic analysis of 58 bodies preserved in permafrost from the last five centuries and 166 current members of the [...]... Read more »

Crubézy E, Amory S, Keyser C, Bouakaze C, Bodner M, Gibert M, Röck A, Parson W, Alexeev A, & Ludes B. (2010) Human evolution in Siberia: from frozen bodies to ancient DNA. BMC evolutionary biology, 25. PMID: 20100333  

  • August 1, 2011
  • 11:54 AM
  • 1,836 views

Live in ancient Peru? You'll want to be Wari...

by Kristina Killgrove in Powered By Osteons

My colleague Tiffiny Tung, whose courses I'll be teaching in a few short weeks at Vanderbilt while she's on leave, has a new article out today in the Journal of Anthropological Archaeology with archaeochemist Kelly Knudson called "Identifying locals, migrants, and captives in the Wari heartland."  They studied the strontium ratios from 31 burials and 18 trophy heads found at the site of Conchopata in the central Peruvian Andes (600-1000 AD).  Out of the 31 proper burials, they found only two with non-local strontium signatures (an adult female and an infant), but out of the 18 trophy heads, 14 of them were from somewhere outside of Conchopata.  Wari iconography suggests that they raided other peoples, captured individuals, and brought them back home, to be sacrificed and made into trophies.  They conclude (Tung & Knudson, 2011, p. 259):
...not only was human sacrifice part of the Wari ritual repertoire, it appears that Wari state structures were used to facilitate and promote this ritual production and destruction of human bodies and trophy heads. These acts of violence against the body were not random or unplanned. Rather, they seem to have been well orchestrated acts that brought together military elites who obtained prisoners and heads, ritual specialists with supernatural and technical skills to transform humans into trophy heads, and master artisans that could portray elaborately dressed warriors and deities with prisoners and trophy heads on large, state-produced urns.

Adult female cranium covered in cinnabar.
From the Wari site of Conchopata.
(Credit: T. Tung's webpage)
Not only do Tung and Knudson engage in an excellent discussion of violence and warfare in ancient Peru, but they lay out a new technique for analyzing strontium isotope values.  Now, strontium hasn't been as widely used by bioarchaeologists as, say, carbon and nitrogen isotope analyses, which means that in most areas of the world, we don't quite understand the relationship between human strontium ratios and the strontium ratios of the local geology and water.  The Peruvian Andes, though, have been very well studied compared to other parts of the world (Germany and England are other areas of pretty good coverage).  Still, there are overlapping strontium ranges for different sites in Peru, meaning it can be difficult to discriminate among the homelands of the non-locals, and sometimes to even tell whether a person was non-local or local.

To deal with this, Tung and Knudson use three techniques.  First, they calculate a two sigma local range from the strontium values of small animals.  Second, they look at the descriptive statistics (mean, median, standard deviation, etc.) and assume that those individuals on the tail ends of the normal distribution were likely foreigners.  They then calculate the mean and range of strontium isotopes based on the trimmed data (Wright, 2005).  And third, the authors introduce a new technique to identify outliers, wherein they basically zoom in on the spacing of the data to find a sectioning point between locals and nonlocals.  In essence, when a gap between samples (arrayed in increasing value) gets large, it's possible that the people on either side of the gap were from different places.  The authors note that this technique isn't absolute and therefore can't be used in isolation.

It's interesting to see their third technique in print, as it's what I had been doing visually in my strontium data from Roman sites:



(From Killgrove 2010)

You may expect to see a range of strontium values, as people living in the same place may have used slightly different water sources and had slightly different soil contents.  In the graph of my Romans, there are very clear outliers on either end of the graph.  The question that Tung and Knudson try to answer with their Wari data is, How do we find the hidden variation within a large data set?

This is a question that I am quite interested in answering as well, since Roman strontium ratios are greatly affected by the fact that there was a massive and intricate aqueduct system in the city and suburbs.  Importantly, the aqueducts brought low-Sr water from the Monti Simbruini to the suburbs and city of Rome, which was built on the volcanic (high-Sr) soils of the Colli Albani.  When you have two major strontium sources like this, another way of finding hidden variation is to plot the strontium isotope ratios versus the inverse of the strontium concentration (Montgomery et al. 2007):



(From Killgrove 2010)
From the above graph, you can see that the outliers are still outliers (T36 and F12A).  And you can see a linear relationship in Line A, which I interpret as indicative of local Roman geology, with end-members of more or less seawater (.7092) and the volcanic geology of the Colli Albani (.710).  I've created a line B with only three data points, so this may not be a valid relationship (although I hope to eventually get more data), but I interpret this as showing the people who lived on low-Sr geology - which could have been people living to the east in the Monti Simbruini or could have been people who, as children, consumed the majority (at least 70%) of their water from an aqueduct that was fed by springs in the Monti Simbruini.

Tung and Knudson's article gave me a lot to think about in terms of my own research - I'm excited to look into their new technique and apply it to the Romans as I write up my Sr/O isotope migration research as a journal article.  But it also got me thinking about trophy heads in the Roman world.  We know the Romans did this - Cicero was quite famously beheaded and impaled on the Rostrum, in the tradition of Marius and Sulla, who displayed their dead captives in the Forum.  But I don't know the whole tradition of Roman trophy heads: were they usually foreign captives, much as they were with the Wari, or were locals (aside from Cicero) also given this treatment?

References:

K. Killgrove (2010).  Migration and mobility in Imperial Rome.  PhD dissertation, University of North Carolina at Chapel Hill.

... Read more »

T. Tung, & K. Knudson. (2011) Identifying locals, migrants, and captives in the Wari heartland: a bioarchaeological and biogeochemical study of human remains from Conchopata, Peru. Journal of Archaeological Anthropology, 30(3), 247-261. info:/10.1016/j.jaa.2011.06.005

  • August 1, 2011
  • 11:17 AM
  • 1,221 views

Sonority and Sex: Why smaller communities are louder

by Sean Roberts in A Replicated Typo 2.0

Ember & Ember show that the degree of sonority in a language is related to the frequency of extramarital sex in its community. Could this be linked to why smaller communities have a smaller phoneme inventory?... Read more »

  • August 1, 2011
  • 06:49 AM
  • 1,676 views

More to rice intensification than meets the SRI.

by Jeremy in Agricultural Biodiversity Weblog

We’ve written a fair bit about the System of Rice Intensification, or SRI, and our most recent little piece sparked what passes for a vociferous debate over at Facebook (which of course I cannot now link to). As I recall it all seemed to hinge on whether there was one SRI or several different systems, [...]... Read more »

  • July 30, 2011
  • 12:44 PM
  • 1,244 views

Contra Deus ex Machina

by Cris Campbell in Genealogy of Religion

In Ars Poetica (“The Art of Poetry”), the great Roman lyricist Horace counsels against using gods to resolve thorny plots. The deus ex machina is simply too tidy and unbelievable. When gods swoop in to save the day, the mundane becomes sacred. Metaphysics to the rescue.

I was reminded of Horace’s enduring wisdom by two recent [...]... Read more »

Delton AW, Krasnow MM, Cosmides L, & Tooby J. (2011) Evolution of direct reciprocity under uncertainty can explain human generosity in one-shot encounters. Proceedings of the National Academy of Sciences of the United States of America. PMID: 21788489  

Mathew S, & Boyd R. (2011) Punishment sustains large-scale cooperation in prestate warfare. Proceedings of the National Academy of Sciences of the United States of America, 108(28), 11375-80. PMID: 21670285  

  • July 29, 2011
  • 12:18 PM
  • 1,834 views

Friday Weird Science: Knights in Shining Armor, Not as sexy as you might think

by Scicurious in Neurotic Physiology

This new article has gained substantial attention on the interwebs, and who can blame us? After all, knights, shining armor, it's what lots of people like to pretend to be (or pretend to be rescued by, goes both ways). Picture it if you would: a damsel in distress, inches from death in the maw of [...]... Read more »

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