The origins and dispersal of the chicken (Gallus gallus) across the ancient world is one of the most enigmatic questions regarding Eurasian domesticated animals. The lack of agreement concerning timing and centers of origin is due to issues with morphological identifications, a lack of direct dating, and poor preservation of thin, brittle bird bones. In new research, archaeologists examined ancient chicken eggshells from 13 different archaeological sites, spanning a period of a millennium and a half. Their results show that chickens were widely raised across southern Central Asia from the 4th century BCE through Medieval periods, likely dispersing along the ancient Silk Road.
A compilation of evidence for ancient chickens in Central Asia: SEM images of a Bash Tepa egg shell, emphasizing morphologically distinct breathing pores at magnifications x30 (a), x150 (b), x750 (e, f); (c) a ceramic egg with clay balls from Bukhara dating between the tenth and twelfth centuries CE; (d) the Sophytes coin from Bactria in 300 BCE; (g) a fragment of an ossuary from Bash Tepa dating to the last centuries BCE, with an apparent chicken on the top; (h) a selection of eggshells from the Bukhara site, showing color (essentially all white) and burning, which was evident on many of the shells. Image credit: Peters et al., doi: 10.1038/s41467-024-46093-2.
“Debate over the origins and spread of domesticated chickens has intensified in recent years with the introduction of genetic and molecular methods, reigniting old controversies over the enigmatic bird,” said Dr. Carli Peters, a researcher at the Max Planck Institute of Geoanthropology, and colleagues.
“Historical sources attest to the prominence of chickens in southern Europe and southwest Asia by the last centuries BCE.”
“Likewise, art historical depictions of chickens and anthropomorphic rooster-human chimeras are reoccurring motifs in Central Asian prehistoric and historic traditions. However, when this ritually and economically significant bird spread along the trans-Eurasian exchange routes has remained a mystery.”
“Specialists agree that domestication traits evolved in an insular population of South Asian jungle fowl, likely the red jungle fowl (Gallus gallus ssp. spadiceus) somewhere across its expansive range from Thailand to India.”
“However, scholars have also presented widely diverging dates and routes of spread, and some of this confusion comes from unclear identifications of birds in ancient art and overlap in morphological features of chicken bones with those of certain wild avian species.”
“In addition, brittle hollow bones and eggshells are far less likely to be preserved, recovered, and identified than those of other animals.”
In their new research, the authors discovered evidence for a prominence of chicken egg production in Central Asia starting in the last centuries BCE and continuing into the Medieval period.
“We show that chickens were widely raised in Central Asia from approximately 400 BCE to 1000 CE and were likely dispersed along the ancient Silk Road,” they said.
“The abundance of eggshells further suggests that the birds were laying out of season.”
“It was this trait of prolific egg laying that made the domestic chicken so attractive to ancient peoples.”
To reach these conclusions, the researchers collected tens of thousands of eggshell fragments from 13 archaeological sites located along the main Central Asian corridor of the Silk Road.
They then used a method of biomolecular analysis called ZooMS to identify the source of the eggs.
Much like genetic analysis, ZooMS can make species identifications from animal remains such as bone, skin and shell, but it relies on protein signals rather than DNA. This makes it a faster and more cost-effective option than genetic analysis.
“Our study showcases the potential of ZooMS to shed light on human-animal interactions in the past,” Dr. Peters said.
“The identification of these shell fragments as chickens, and their abundance throughout the sediment layers at each site, led us to an important conclusion: the birds must have been laying more frequently than their wild ancestor, the red jungle fowl, which nests once per year and typically lays six eggs per clutch.”
“This is the earliest evidence for the loss of seasonal egg laying yet identified in the archaeological record,” said Dr. Robert Spengler, a researcher at the Max Planck Institute of Geoanthropology.
“This is an important clue for better understanding the mutualistic relationships between humans and animals that resulted in domestication.”
The team’s paper was published in the journal Nature Communications.
_____
C. Peters et al. 2024. Archaeological and molecular evidence for ancient chickens in Central Asia. Nat Commun 15, 2697; doi: 10.1038/s41467-024-46093-2
Source : Breaking Science News