Applications of biomolecules and isotopes to infer ancient human subsistence activities : Olduvai Gorge, northern Tanzania (early Pleistocene) and Valdocarros, Spain (mid-Pleistocene)
Abstract
An ongoing debate in human evolution research is whether there are connections
between eco(hydro)logic changes, and the essential resources (food, water, shade) used
by early humans (hominins) that lived in a highly competitive and biodiverse
environment. Water and its accessibility provide a direct link between climate,
landscape, and large-mammal behaviors, and therefore exerted direct influence as well
on early human activities. Additionally, in human evolution, the use of fire is
considered a technological landmark; in particular its implications as widening diets and
calories intake, defensive tool, and heat source. However, the early development of
pyro-technology remains controversial because its remains are easily reworked and their
identification in the archaeological record can be impeded.
Biomarkers are chemical ‘fossils’ that function as a foundation of high-resolution
sedimentary (paleo)climate and (paleo)environmental reconstructions, as well as
preservation of plant tissues. Such ‘fossils’ include a wide range of diagnostic organic
compounds with known origins, which – due to their relative stability during geologic
and biochemistry processes – offer uniquely quantitative insights into ancient landscape
conditions across space and through time. Furthermore, stable (lipid) biomarkers
derived from vegetation, such as leaf-waxes (i.e., n-alkyl lipids) are commonly
preserved in soils and lake sediments associated with hominin archaeological localities.
Since plant biomarkers comprise repeated hydrocarbon (–CH2–) sub-units, which differ
in atomic composition (13C/12C [δ
13C]; 2H/1H [δD]) among plant types, it is possible to
reconstruct the composition of vegetation communities using plant biomarker-specific
isotopic signatures. As such, the combination of sedimentary plant biomarker δ
13C
measurements offers remarkable insights into vegetation and hydroclimate conditions
during geologic history.
The environmental factors that drove differences in apparent behavioral development
(i.e., evolution) between hominin species during the last 2 million years remain a matter
of heated debate. This research focuses on novel biomarker-specific isotope data
acquisition to (1) resolve the importance of different dietary options and water resources
among past hominin species, and (2) improve upon our current knowledge of how
ancient humans adapted to dramatic climate change regarding their (pyro-)technological
advancements.