A recent study has revealed that infants from the Iberian culture (circa 8th to 1st centuries BCE) who were buried in domestic settings, did not fall victim to ritualistic practices, but rather died from natural causes, like complications during childbirth or premature birth. Researchers utilized a groundbreaking technique that involved examining the neonatal line in baby teeth using optical microscopy and synchrotron light microfluorescence. This method allowed them to analyze teeth from 45 infant skeletal remains and accurately pinpoint the times of both birth and death.
A research team from Universitat Autònoma de Barcelona, in partnership with the University of Vic-Central University of Catalonia and the ALBA synchrotron, has established that newborns from the Iberian culture (8th to 1st centuries BCE), interred in home environments, died due to natural occurrences, such as complications during birth or premature birth, rather than through ritualistic practices. The team employed an advanced methodology that examined the neonatal line in baby teeth using optical microscopy and synchrotron light microfluorescence, analyzing the dental remains from 45 infants to accurately discern the moments of birth and death.
The Iberian culture thrived along the eastern and southern shores of the Iberian Peninsula during the Iron Age, spanning from the 8th to the 1st centuries BCE. Usually, the Iberian funerary custom involved cremating the deceased and placing their ashes in urns, which were buried in designated necropolises. However, archaeologists have encountered burials containing the remains of uncremated infants situated in areas used for dwelling or production. The presence of these burials has sparked debate among specialists, with proposals ranging from natural causes to infanticide or ritual sacrifices.
A study featured in the Journal of Archaeological Science provides compelling evidence supporting the theory that the majority of these newborns died from natural causes, reflecting the high infant mortality rates during the first year of life in that era.
Researchers reached this conclusion after examining 45 infant skeletons found at five archaeological sites in Catalonia, associated with the Iberian period: Camp de les Lloses (Osona), Olèrdola (Alt Penedès), Puig de Sant Andreu and Illa d’en Reixac (Baix Empordà ), and Fortalesa dels Vilars d’Arbeca (Lleida).
The research was spearheaded by the Biological Anthropology Research Group (GREAB) at Universitat Autònoma de Barcelona (UAB), alongside the MECAMAT Research Group from the University of Vic-Central University of Catalonia (UVic-UCC). Additional contributions came from members from the University of Granada, the Archaeology Museum of Catalonia (MAC), the El Camp de les Lloses Interpretation Centre, the University of Lleida, and the TR2Lab Research Group of UVic-UCC.
Utilizing an innovative methodology, researchers conducted histological and elemental analysis (focusing on both tissue and chemical composition) of the primary teeth found in these infant remains. Through optical microscopy, they were able to visualize the growth lines on the dental crowns that form during intrauterine development, leading to the identification of the neonatal line that appears at birth.
This analysis enabled them to pinpoint the birth of each infant and assess their survival, while also providing a precise estimate of the age at death. This age is determined by the time elapsed since birth, rather than the skeletal development.
Nearly half of the infants died during the perinatal phase, specifically from the 27th week of pregnancy to the end of the first week of life. Most perinatal deaths occurred around birth, often due to premature delivery. “These findings support the idea that most perinatal deaths were due to natural causes, such as complications during birth or illnesses linked to prematurity, rather than through cultural actions like infanticide or ritual sacrifice, as previously suggested,” stated Xavier Jordana, Associate Professor in the Biological Anthropology Unit at UAB.
It was also observed that, among the infants who survived beyond their first week, the longest lifespan recorded was 67 days. “In the sites we studied, no burials of infants older than two months were found, which leads us to suspect that there may have been cultural practices in place that involved burying infants who died in their earliest stages within domestic spaces,” commented Assumpció Malgosa, a researcher at UAB and co-author of the study.
Innovative technique for determining birth and death times
The histological methods applied in this research signify a notable advance in accurately estimating the age of individuals at the time of death through the examination of their teeth. Since primary teeth start forming during pregnancy and complete their development shortly after birth, they reveal growth patterns through daily growth lines that can also reflect stressful events. One of these critical lines, identifiable through optical microscopy in teeth of infants that survived birth, is the neonatal line, which marks the stress of transitioning from a womb to an external environment.
“The method we implemented is distinctive, as it allows us to ascertain birth moments and calculate the actual age at death in skeletal remains. Traditional techniques estimate biological age based on skeletal growth, resulting in significant variations in age assessment, which makes identifying the exact birth moment impossible,” explained Ani Martirosyan, a predoctoral researcher at UAB and the article’s lead author.
This methodological innovation enabled researchers to distinguish between those who died at birth and those born alive who survived. They categorized the deceased into those who died at full term (between the 37th and 42nd week of gestation) and those who died prematurely (before the 37th week), and were also capable of determining the ages of surviving infants.
To validate their techniques, researchers compared results from teeth where the chronological death age was known and conducted X-ray microfluorescence analyses at ALBA Synchrotron (located in Cerdanyola del Vallès), specifically using the Xaloc beamline, to investigate the elemental makeup of the neonatal line, including the quantification of zinc in cases where histological visualization was uncertain.
“Zinc is critical at birth, especially in relation to breastfeeding onset, but its low content makes it difficult to detect concentration variances in enamel and dentin using conventional electron microscopy. The application of synchrotron light allows us to focus an X-ray beam as small as 10 microns to examine various elements in enamel and dentin at extremely low levels,” added Judit Molera, a researcher at UVIC-UCC and co-author of the study. Their experimental results showed an increase in zinc alongside a decrease in calcium, a key component of dental enamel, correlating with the neonatal line’s presence, further supporting the histological findings.
“Our study offers far more detailed and concrete insights than previously available regarding infant mortality patterns in Iberian societies and sheds light on significant aspects of their life history and cultural practices. We hope that the methodology we employed will uncover further untold stories about ancient populations,” concluded Xavier Jordana.
This research is part of a project titled “Reevaluation of Infanticide and Sex Selection in the Iberian Period,” which is funded by the Spanish Ministry for Science and Innovation and led by researchers from GREAB.
