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Kazakhstan. Ten teeth from five horses (sets of M2 and M3 per
individual) were collected in August 2018 from the Botai field
archive and sampled for strontium, lead, carbon and oxygen stable
isotope analysis. Eight samples (four horses) were excavated in 2018
and two samples (one horse) are from the 2011 excavation. The
growing intervals of horse M2 and M3 teeth cover approximately the
first 4.5 years of the horses life. One human M3 tooth from a female
burial excavated in 2016 was also sampled,
alongside control
samples comprising of two foxes, a marmot and a ground squirrel.
Strontium (
87
Sr/
86
Sr) and lead isotopic ratios (
206
Pb/
204
Pb,
207
Pb/
204
Pb
and
208
Pb/
204
Pb) in tooth enamel are a proxy for mobility reflecting
the different surficial geologies encountered during the period of
tooth growth. These were studied as a continuous sequence using
Laser Ablation ICP-MS. Sequential enamel samples were then taken
from the same teeth and processed for carbonate isotopic analysis.
Oxygen isotope ratios (
18
O/
16
O) relate to temperature and humidity
changes experienced by the horses, revealing what time
of year the
horses moved; meanwhile, carbon isotope ratios (
13
C/
12
C) reflect
seasonal dietary change. Two further analyses were also conducted
on the same teeth sampled for isotopic analysis: microscopic analysis
of thin sections of dental cementum was used in an attempt to shed
light upon age and season of death
of the horse individuals;
meanwhile, genetic determination of animal sex was used to look for
any potential male/female differences in seasonal migration and
season of death patterns, providing information on horse
management strategies.
The strontium isotope signature of the local region near Botai
was calculated using measurements of tooth dentine and of the local
fauna (marmot and ground squirrel).
Our results indicate a
provisional estimate of around 0.712-0.713. The investigated horses
showed two main types of mobility pattern. Each investigated horse
showed periods of little change in
87
Sr/
86
Sr during the period of tooth
growth indicating they remained relatively sedentary throughout this
time. Three of the 4 horses also showed episodes with a
highly
distinctive mobility pattern, with rapid oscillations between two
different geologies. Based on horse tooth growth rates, these rapid
movements occurred regularly on a 10-14 day cycle over a period of
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several months or years. Investigations are continuing, but possible
explanations include horse mobility to different pastures, mobility to
salt/mineral licks, or mobility related to milking. The Botai human
female produced results showing a different mobility pattern
compared to the horses analysed in this study, and preliminary
indications suggest that she spent her adolescence in a geologically
distinct region elsewhere from Botai.
At the time of writing, carbon
and oxygen data are not yet available but these will be important for
placing the mobility patterns identified within a seasonal context.
Analysis of the dental cementum thin sections is also ongoing, and
results will be revealed at the conference. The results presented here
are preliminary and investigations are ongoing. Yet they clearly
provide a new view of human-animal relationships and evidence of
human subsistence practices in the early phases of horse husbandry
at Botai.
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