Abstract
Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella. Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis, the early stages of agricultural development were likely to promote the exposure of humans to this pathogen.
Highlights
The shift from hunting and gathering wild food resources to the control and husbandry of domestic animals had fundamental and far-reaching repercussions for the evolution of infectious diseases in humans [1,2]
We discuss the origins of brucellosis as a zoonotic disease, a process that has been hypothesized as intensifying during the early period of animal domestication in the Near East [5,6]
A recent review of early evidence for brucellosis in human (Homo sapiens) skeletons identifies that the earliest probable cases reported come from the Bronze Age Near East [5], the region of domestication of goats and sheep, and cattle and pigs, in multiple centres during the preceding Neolithic [8,9]
Summary
The shift from hunting and gathering wild food resources to the control and husbandry of domestic animals had fundamental and far-reaching repercussions for the evolution of infectious diseases in humans [1,2]. Early managed goats are identified at the site of Ganj Dareh in the Zagros mountains of the eastern Fertile Crescent at ca 7900 BC, where the demographic profile indicates a population under human management that are morphologically unaltered from wild animals [14,15]. The spread of goat husbandry can be followed to nearby lowland zones, reaching Ali Kosh by ca 7500 BC, and Jarmo a few centuries later still where it co-occurs with domestic sheep [16] (figure 1) Examining these three populations—from Ganj Dareh, Ali Kosh and Jarmo—allows an assessment of the diversity in management strategies during earlier phases of animal husbandry [15] and the impact of these strategies on the potential maintenance of Brucella melitensis within domestic goat populations. The precise antiquity of dairying is still debated, zooarchaeological studies of herd profiles provide indirect evidence to suggest that milking may have begun in the Near East during the eight millennium BC [12,17]; whereas the earliest direct evidence comes from organic residues preserved in pottery from 7th millennium BC Anatolia [18]
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