Calcium isotopic ecology of Turkana Basin hominins

Jeremy E Martin,José Braga,Théo Tacail,Vincent Balter,Thure E Cerling

doi:10.1038/s41467-020-17427-7

Abstract

Diet is a major driver of hominin evolution, but most of the geochemical evidence relies on carbon isotopes (δ13C). Here, we report enamel stable calcium isotope (δ44/42Ca) values against δ13C values for several hominins and co-existing primates in the Turkana Basin area, circa 4 to 2 Ma. Australopithecus anamensis clusters with mammal browsers, Kenyanthropus platyops is distinct from A. anamensis in foraging into more open environments and the coexisting Theropithecus brumpti encompasses both the grazer and omnivore/carnivore domains. Early Homo is remarkable for its wide distribution in δ44/42Ca values, possibly reflecting omnivorous and opportunistic preferences. Paranthropus boisei is uniquely distributed in the δ13C versus δ44/42Ca iso-space being distinct from all other hominins from the Turkana Basin area as well as from the co-existing Theropithecus oswaldi. Several hypotheses are explored to discuss the unique δ44/42Ca values of Paranthropus boisei including significant differences observed with δ44/42Ca values recently reported for P. robustus from South Africa, questioning the monophyly of this genus.

Highlights

Diet is a major driver of hominin evolution, but most of the geochemical evidence relies on carbon isotopes (δ13C)
While non-traditional isotopes emerge as a new toolkit to paleodietary inference[11,12,13,14,15], a great deal of the geochemical evidence for early hominin diets relies on carbon isotopes[1,2,3,4,5,6,7,8,9] and to a lesser extent on trace element concentrations preserved in mineralized tissues such as fossil bone or teeth[16,17,18,19]
In East Africa, early australopithecines derived most of their food from C3 sources[1,4,6] whereas more recent forms such as Paranthropus boisei almost exclusively relied on C4 sources[3,5]

Summary

Introduction

Diet is a major driver of hominin evolution, but most of the geochemical evidence relies on carbon isotopes (δ13C). The isotopic composition of a consumer’s tissue is controlled by the mass-weighted isotopic average of all the dietary sources and in our present case, we do not include data from early forming teeth (e.g., first molars).

Results

Conclusion