Isotopes and history: Tracing the links between elephants, humans, and land use in East Africa during the 19th century ivory trade

During the 19th century, East Africa became a major source of elephant
ivory for a range of rapidly expanding industries, including cutlery, comb,
piano and billiard-ball manufacturers. The scale of extraction was enormous:
between 1840 and 1875, British demand alone rose from 200,000 kg per
annum to over 800,000 kg per annum, and even the more conservative estimates
based on historical trade records suggest that as many as 12,000 elephants
a year were being killed. However, there is a problem with historical
data in that they are patchy and record only the point of export rather than
the area of extraction. Knowing the area of extraction in further detail could
shed light on historical arguments about which areas of East Africa were
considerably depleted of elephant populations, which would have had severe
impacts on trade patterns and the ecology of specific regions. Given that the
varying geology and climate of the East African region produce distinguishable
isotope signatures in the ivory (and other tissues) of elephants, it is becoming
possible to provenance ivory using a combination of isotopes including
δ13C, δ15N, δ18O, and 87/86 Sr. The results presented include isotope analyses
from museum samples of historic elephant bone, tooth, ivory, and tail
hair as well as archaeological ivory from excavations in Kenya and modern
reference samples collected in Kenya and Tanzania. The results not only
support the use of isotope analysis for provenancing historic and archaeological
ivory, but also highlight the use of isotope analysis as an ecological
tool for understanding diet and habitat changes between historic and modern
elephant populations living in the same regions. Also, this research is creating
a database of isotope values from various regions across Africa for use in
determining the provenance of ivory, which is specifically of interest to
wildlife monitoring groups attempting to control the current illegal trade of
ivory out of Africa.