Animal Board Invited Review: Sheep birth distribution in past herds: a review for prehistoric Europe (6th to 3rd millennia BC)

Abstract

In temperate latitudes sheep have a seasonal reproductive behaviour, which imposes strong constraints on husbandry in terms of work organization and availability of animal products. During the last 50 years, researchers have focused on understanding the mechanisms driving small ruminants' reproduction cycles and finding ways to control them. This characteristic is inherited from their wild ancestor. However, the history of its evolution over the 10 millennia that separates present day European sheep from their Near Eastern ancestors' remains to be written. This perspective echoes archaeologists' current attempts at reconstructing ancient pastoral societies' socio-economical organization. Information related to birth seasonality may be retrieved directly from archaeological sheep teeth. The methodology consists of reconstructing the seasonal cycle record in sheep molars, through sequential analysis of the stable oxygen isotope composition (δ 18 O) of enamel. Because the timing of tooth development is fixed within a species, inter-individual variability in this parameter reflects birth seasonality. A review of the data obtained from 10 European archaeological sites dated from the 6th to the 3rd millennia BC is provided. The results demonstrate a restricted breeding season for sheep: births occurred over a period of 3 to 4 months, from late winter to early summer at latitudes 43°N to 48°N, while a later onset was observed at a higher latitude (59°N). All conclusions concurred with currently held expectations based on present day sheep physiology, which, aside from the historical significance, contributes to the reinforcing of the methodological basis of the approach. Further study in this area will permit regional variability attributable to technical choices, within global schemes, to be fully reported.

Pioneer farming in southeast Europe during the early sixth millennium BC: Climate-related adaptations in the exploitation of plants and animals

“…Sheep and goats do not have wild relatives in the Balkans and likely experienced feeding problems in forested environments with winter snow cover. Moreover, sheep and goats are seasonal breeders having a reproductive cycle determined by photoperiod [ 63 , 64 ] and, with increasing latitude and later spring onset, they would potentially give birth too early. An early birth season not only threatens newborns’ survival, but might also decrease the productivity of herding: for modern-day sheep breeds, a 1°C decrease in mean spring temperature has been estimated to reduce lamb autumn body mass by nearly 0.4 kg [ 65 ].…”

Early evidence of sheep lambing de-seasoning in the Western Mediterranean in the sixth millennium BCE

“…The lambing season of the archaeological specimens can then be determined by comparison with modern reference sets with known dates of birth 12,52,53 . This approach has been applied successfully to sheep second (M2) and third molars (M3) in previous studies 12,53 . The δ 13 C values in tooth enamel bioapatite are derived from ingested plants 41,54 .…”

New Statistical Approaches to Intra‐individual Isotopic Analysis and Modelling of Birth Seasonality in Studies of Herd Animals

“…Nevertheless, the underlying models in both the cosine and SCEM approaches apply to seasonal variation in any temperate region and can be used to generate comparisons of birth seasonality within assemblages and regions (e.g., Balasse et al 2017b). Both of these data sets are from populations from regions at different longitudes and with different regional climates-which means that the Rousay sheep cannot be used to link birth seasonality values to specific calendar months.…”

“…Both of these data sets are from populations from regions at different longitudes and with different regional climates-which means that the Rousay sheep cannot be used to link birth seasonality values to specific calendar months. Nevertheless, the underlying models in both the cosine and SCEM approaches apply to seasonal variation in any temperate region and can be used to generate comparisons of birth seasonality within assemblages and regions (e.g., Balasse et al 2017b).…”