A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya

Abstract

One contribution of 17 to a discussion meeting issue 'Major transitions in human evolution'. Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial-lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure (ca 5-100% C 4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C 4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25-30% more C 4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C 3 -C 4 to C 4 -dominated ecosystems. The proportion of C 4 -based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C 4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61-97% C 4 vegetation on the landscape.This article is part of the themed issue 'Major transitions in human evolution'.

Neogene biomarker record of vegetation change in eastern Africa

“…2). Given that large, orbital-scale variability is observed in marine and terrestrial archives when sedimentation rates are high and sequences are adequately sampled (7,8,44), we conclude that some other factor may be smoothing or obscuring this orbital signal in our records. All of our sites were rotary drilled and, in some cases, spot cored, and coringrelated disturbance was observed in places.…”

“…Another carbon isotope archive for reconstructing eastern African paleovegetation that has emerged as a powerful tool in the past decade is terrestrial plant waxes from sediments (7,8,44). Plant wax biomarkers derive primarily from epicuticular leaf waxes that protect the leaf tissue from abrasion by dust; attack from insects, microbes, and fungi; and water loss from the leaf surface.…”

“…Paleovegetation records from terrestrial sediments are biased toward lowland vegetation simply because sediment accumulation occurs in basins. Thus, carbon isotopes in plant waxes from terrestrial sites provide a local vegetation signal (44), whereas waxes from marine sediments provide a regionally integrated signal.…”

Leaf Wax δD and δ13C in Soils Record Hydrological and Environmental Information Across a Climatic Gradient in Israel

“…Efforts have often focused on reconstructing the local climatic and environmental contexts of central locations of human evolution (d'Alpoim Guedes et al, ; deMenocal, ; National Research Council, ; e.g., Potts, ; Quade, ). Isotopic analysis of leaf wax molecules from soil horizons (paleosols) and sediments from paleontological, paleoanthropological, and archaeological sites can potentially offer climatic and landscape context directly associated with the archaeological record (e.g., Magill et al, ; Uno et al, ). Leaf wax analysis can add to the existing environmental proxies (e.g., δ 13 C and clumped isotopes in soil carbonates; Levin, ; e.g., Quade, ), pollen and phytoliths (for recent compilation see Bonnefille, ) and lignin (Magill et al, ), and assist in understanding the possible links between the environment and biological and cultural evolution.…”

Major transitions in human evolution

“…These palaeoclimatic and palaeoecological studies also allow us to explore the relationships between the environmental context and evolutionary change. Uno et al [21] highlight evidence from Turkana showing marked changes around 1.9 Ma, which, as they note, more or less coincides with the appearance of the Acheulean, as described by de la Torre [17]. Fortelius [16] also notes marked changes between 1.87 and 1.5 Ma, and this similarly coincides with a period of evolutionary dynamism.…”