Bacterial bioerosion of bone may help identify stillborn infants from the past

New research using novel microscopic investigation of bacterial bioerosion of archaeological bone has shown that you can differentiate between stillborn and post-newborn babies. This was most exciting to me as offering a means to contribute to the debate of the interpretation of infanticide in the past, through an investigation of time of death.

Bioerosion is the removal of mineralised substrate through the action of organisms, and has been found to be the most common form of microbial attack of archaeological bone (Figure 1). The author of this new research, Tom Booth from the Natural History Museum, notes that although it was once believed that soil bacteria caused most of this bioerosion in bone, it is the gut microbia that is responsible for corpse putrification that causes this process. Based on the findings that it is the bacteria inside the body that produces this bioerosion, the author thought that this could be useful for assessing different mortuary treatments of the body.

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Figure 1: Transmitted light micrograph of a human fresh bone transverse femoral thin section (top) demonstrating perfect microstructural preservation and a typical archaeological femoral section (bottom) where the internal microstructure has been extensively altered by bacteria (from Booth et al., 2015).

To investigate if there is any relationship between bacterial bone bioerosion and funerary treatment, Booth undertook a microscopic analysis of human bones from European prehistoric (4000 B.C. – A.D. 43) and British historical (A.D. 43 – present day) sites. These two assemblages were used as they have been found to have different funerary practices, with the historic period sites practicing burial soon after death, whereas the prehistoric sites have more variable mortuary practices, sometimes including postmortem modification. E.g. Booth and colleagues’ work that found evidence for mummification in Bronze Age Britain using this microscopic method has recently received media attention.

This research shows that irrespective of burial environment, including antiquity or soil type, there was immaculate histological preservation of almost half of the neonatal samples. This is interpreted as the result of sterility of stillborn infant intestinal tracts resulting in the bones being unaffected by the process of bacterial tunneling. In addition, most (12/15) of the unbioeroded newborn samples are from historical cemeteries where most of the other samples had been extensively bioeroded. A previous experimental study by White and Booth using pigs found that bone from stillborn neonatal carcasses had immaculate histological preservation due to the intrinsic sterility of newborn infant intestinal tracts.

Booth found that the soil type had no relationship with bacterial bioerosion. There was evidence for variation in bacterial bioerosion among the later prehistoric assemblages argued to be “consistent with the knowledge that these individuals were subject to variable early post mortem treatment that exposed the bones to diverse levels of bacterial attack.” Bacterial bioerosion in the historical assemblage was high, consistent with that expected within bones of intact bodies that had been interred soon after death.

The use of this novel method to differentiate stillborn vs post-newborn infants can contribute to extending our knowledge of the cause of death during the most crucial time for mother and child in the past, and may also have useful applications for the study of cultural beliefs around stillbirth and post-neonatal death.

References:

Booth, T. J., A. T. Chamberlain and M. P. Pearson (2015). “Mummification in Bronze Age Britain.” Antiquity 89(347): 1155-1173.

Infanticide in the archaeological record: sense or sensationalism? (Or: No, I’m not an ‘over-emotional’ mother and archaeologist)

A cursory look through the bioarchaeological literature for explanations of infant death in the past may leave you with a view that infants were being purposefully killed and buried in community cemeteries or simply tossed away in high numbers (e.g. Mays 1993, Mays and Eyers, 2011, Smith and Kahila, 1992).

 

But what is the likelihood that these accounts are accurate? Here I want to take an analytical look at the bioarchaeological evidence and arguments for infanticide. Some of my views on childhood in the past have been criticised for being clouded by my status as a mother within a ‘Western’ culture. Sometimes I feel that my interpretations are dismissed and put down to my ‘personal’, ‘irrational’, ‘hyper-emotional’, ‘ethnocentric’ thoughts on infancy. One example of this type of experience was at a conference when a senior academic after viewing my poster ‘mansplained’, “you must realise that childhood wasn’t a rosy experience like it is now where you come from. They weren’t wrapped up in cotton wool!”. I wonder if he would have said that if my infant wasn’t attending the conference, the result of no childcare options for participants (dockristy touches on this issue of inclusive conferences for caregivers in her recent blog post).

 

Infanticide is the intentional killing of infants. Legally, “infanticide” can refer to the deliberate killing of any infant under the age of 12 months (Kellet, 1992). Here I use the term for intentional infant killing around the time of birth, as this is the time in which it usually occurs. Infanticide has been practised in a wide range of cultures through time, and has been argued in some anthropological texts to be an adaptive strategy to environmental, economic, and social circumstances since the Pleistocene era (Hausfater and Hrdy, 1984:xxix).

 

Common methods for disposing of unwanted children in non-Christian cultures were exposure or drowning without subsequent burial or with covert burial (reviewed in Gilmore and Halcrow, 2014). Some of the motives documented for infanticide include poverty, and if a baby was born with a physical deformity or was “weak”. The sex of infants was also an important factor in infanticide practice for many cultures.

 

What evidence are these bioarchaeological studies using to inform their interpretations of infanticide? For most papers their main evidence cited for infanticide is a peak rate of mortality around the age of full-term gestation (the perinatal period of about 38-41 weeks gestation) (e.g. Mays 1993, Mays and Eyers, 2011, Smith and Kahila, 1992).*

 

However, we know from modern age-at-death information that it is normal to see a high rate of infant death at around full-term gestation (see Halcrow et al. 2008 for a review of this evidence). Birth is the most crucial time in a baby’s and mother’s life. Birth and the first few days of life are a dangerous time for a baby with the risk of mortality being extremely high (Kelnar et al., 1995:1). Birth complications, maternal health factors and the risk of disease are likely to have increased the incidence of perinatal deaths and stillbirths in the past. Postpartum dangers include trauma, pneumonia due to infection of the amniotic cavity (Redfern, 2007:185), and respiratory distress syndrome, particularly for pre-term or low birth-weight perinates, owing to the immaturity of the lungs. Environmental hazards for the newborn include infections, bathing in contaminated water, and tetanus due to the use of dirty instruments (Kelnar et al., 1995:6-8, Redfern, 2007:185).

 

Unsurprisingly, this high rate of infant death around the time of birth has also been found in the archaeological record throughout the world and during different time periods. In the majority of the prehistoric Southeast Asian sites I have worked on we find a high peak of mortality occurring around the time of birth. Other sites with this type of age distribution include Argolid in the Aegean (Angel, 1971), Roman period Britain (Mays, 1993), Southeast Europe (Boric and Stefanovic, 2004), mediaeval and post-mediaeval England (Lewis and Gowland, 2007), post-contact indigenous populations in North America (Owsley and Jantz, 1985), Roman period Egypt (Tocheri et al., 2005), and many more. Were all these cultures at these different time periods killing their infants and then burying them overtly within community cemeteries? I think not. I am not arguing that infanticide never existed in the past. However, these were often discrete events with the dead babies disposed of covertly.

 

IMG_0879Probable mother and newborn death from the ‘Neolithic’ site of Khok Phanom Di, Southeast Thailand. This site had a infant death representation of over 40% of the cemetery sample.

P1010598A ‘foetal’ (preterm) birth from the site of Ban Non Wat, Bronze Age, Northeast Thailand. If a live birth, this baby wouldn’t have lived for long after birth because of its immaturity.

 

One of these bioarchaeological papers that has interpreted the practice of infanticide is based on the Yewden Roman villa site at Hambleden in Buckinghamshire, England, which became somewhat of an archaeological “celebrity”, showcased by the BBC in 2010 (Mays and Eyers, 2011). The Hambleden site has been identified as a sophisticated “two corridor” Roman villa (Percival, 1990:531). It was first excavated in 1912 by Alfred Heneage Cocks, who reported the discovery of 103 burials, 97 of which were small infants, buried under courtyards or walls on the north side of the site (Cocks, 1921). The infant bones were recently rediscovered in a museum archive after almost a century.

 

Mays and Eyers (2011) have compared the perinatal age-at-death distribution pattern to other sites that have been interpreted to have an ‘infanticide’ type mortality profile. Other than that there is nothing in the mortuary or archaeological information to suggest that infanticide was probable. The burials at Hambleden are inconsistent with what is known about Roman infanticide practices. As discussed, exposure or drowning were the most usual methods employed, in which case we might expect to find infant bones as haphazard scatters in middens, remote areas of the landscape, or in wells or waterways as has been the case in Scandinavia (Wicker, 1998:215).

 

An understanding of the historical and ethnographic information on infanticide practices and burial, the historical or other contextual information associated with the site, infant burial practices, and mortality pattern data information is essential for assessing the likelihood for infanticide. It remains that the most parsimonious explanation for cemeteries with a peak of infant death around full-term are the result of a normal age-at-death pattern.

 

Why then is there a preoccupation or fascination with this idea of infanticide in the past? Were people in the past seen to be of lower moral status and therefore more likely to kill their babies? Could this continued focus on arguments of infanticide stem from an anthropological legacy of the 19th century of exploring ‘dark’, ‘primitive’ cultures, who were seen to lack intelligence and emotion?

 

Certainly more critical engagement with the literature on infanticide motives, practices, contextual burial information, and medical literature on the causes and timing of normal infant death offers a good approach to review evidence of infant death in the past. Even a mother with a mind ‘clouded’ by breastfeeding hormones and a ‘rosy’ view of childhood can look at the empirical evidence.

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*Smith and Kahila (1992) also include preterm and post-perinatal infants in their “perinate” age category. The preterm infants probably died a natural death, as is likely without modern medical intervention. In historical and modern accounts, infanticide often occurs soon after birth, so the individuals who died in the post-perinatal period were also less likely to be the victims of infanticide.

 

NOTE: Part of this blog post has been taken from our work in the following papers (all references cited can be found within these publications):

Gilmore, H. and S. E. Halcrow (2014). Interpretations of infanticide in the past. J. Thompson, M.P. Alfonso-Durruty and John Crandell (eds). Tracing Childhood: Bioarchaeological investigations of early lives in antiquity. Florida: University of Florida Press. 123-138.

Halcrow, S. E., N. Tayles and V. Livingstone (2008). “Infant death in prehistoric Southeast Asia” Asian Perspectives. 48 (2): 371-404.

See also Gowland et al. (2014) who offer an excellent re-evaluation of evidence for infanticide in Roman Britain.

Gowland, R. L., A. Chamberlain, & R. C. Redfern (2014). “On the brink of being: re-evaluating infanticide and infant burial in Roman Britain” Journal of Roman Archaeology Supplementary Series 96: 69-88.

My work with babies – today and from prehistory

I often hear phrases such as: “I don’t know how you do it” and “your children must be very flexible with your job”. These well-meaning remarks often play on my anxiety as a mother and an academic who has the added challenge of having to undertake fieldwork and data collection overseas. I study human remains from archaeological sites and have worked in Thailand since 2002 and also in Laos, Cambodia and Chile. Because all the skeletal material from these projects are curated locally I do most of my fieldwork and data collection overseas.

I have just come back home to New Zealand after a stint in Northeast Thailand doing data collection from infants and children from an Iron Age site with my two children in tow, a 22-month-old and 10-year-old. Most of my research in bioarchaeology involves working with infants and children. Just as this age group are sensitive indicators of population health today, so too are they good indicators of cultural and health change in the past.

As a parent, I need to balance my professional work with childcare, which for me means packing up my two children for weeks or months on end and re-introducing them to the different languages, cultures, foods, smells, and exotic flora and fauna!

This really is a great opportunity for my children to experience other cultures and languages, but presents some rather major challenges for both me and them. This means leaving family and friends and sometimes missing school, and sporting and our own cultural events. For example, this year we spent Christmas in Thailand, which was of a non-event in a way.

Here are some photos from the early days of my fieldwork in Thailand at the archaeological site of Ban Non Wat, Non Sung Province, Northeast Thailand, which has an unusually long time span from early agricultural development through to the late metal ages (3,800-1,500BP).

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Excavation of a ‘Bronze’ Age child from Ban Non Wat, 2003

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Excavation of an ‘Iron’ Age adult burial, 2003

 

Over several excavation seasons at Ban Non Wat a total of about 700 individuals were excavated with about one-third of these aged less than 15 years. This site is very important for documenting the biological and demographic changes that were occurring in the region with the intensification of agricultural practices. The general bioarchaeological model of health change posits that with the introduction of agriculture there is a deterioration of health as a result of the increase of sedentism and population density, leading to more insanitary living conditions. However, my work and others from mainland Southeast Asia is challenging this Neolithic Transition model, which is mainly based on bioarchaeological investigation in North America and Europe. What we are finding is evidence for a very late and swift heath and demographic transition in the Iron Age. This is particularly exciting as it fits nicely with archaeological evidence at this time period for an intensification of wet rice agriculture, and changes in water management and socio-economic systems.

My recent data collection season was focused on the the site of Non Ban Jak, which is geographically very close to Ban Non Wat. This site is particularly important because it presents the best preserved collection of Iron Age burials in the region and has a very large proportion of infants represented (potentially half of the skeletal collection). At present we have over 145 individuals represented at this site, and have just secured significant funding for future excavation and analyses of the human and cultural material at this site.

The baby was petrified of the nanny for much of the time this season working on these remains, so my work plan had to be flexible. I worked solidly during her afternoon naps and the evenings, and when she was distracted by the 10 year-old. Sometimes she ‘helped’ washing stones beside me.

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The baby ‘helping’ me clean and reconstruct a late Iron Age burial of a newborn infant from the site of Non Ban Jak, Northeast Thailand. Photo by Paige Halcrow (10 years old).

With the extension of research at this site, and further research opportunities planned in the region, my fieldwork with infants and children – both past and present – will continue into the future.

Over the years I have developed a general response for when people ask me how I do it. I reply: “It is challenging, but I wouldn’t change my family or my work for the world.”