Isotopic equifinality and rethinking the diet of Australopithecus anamensis

Abstract

Objectives: Australopithecus anamensis has comparable δ 13 C enamel values to Ardipithecus ramidus, and both have been characterized as C 3 feeders in open woodland habitats similar to "savanna" chimps. Unlike Ar. ramidus and "savanna" chimps, A. anamensis shows a derived dentognathic morphology for tough foods and a dental microwear pattern similar to the C 3 -C 4 -mixed-feeding A. afarensis. Here I test the hypothesis that changing the variables (ε * enamel-diet , δ 13 C C3, δ 13 C C4 values) used to calculate the percentage of dietary C 4 foods (%C 4 diet) by 1-2‰ does not make a substantial difference for hominin diet reconstructions [van der Merwe, Masao, & Bamford, 2008, South African Journal of Science 104:153-155]. Materials and Methods: I estimate vegetation structures for A. anamensis with pedogenic carbonate and faunal enamel δ 13 C values from the Pliocene Omo-Turkana Basin(4.2-3.9 Ma). I recalculate A. anamensis' %C 4 diet based on new body size-dependent estimates of the ε * enamel-diet value and alternative δ 13 C C3 and δ 13 C C4 values. Results: The Pliocene Omo-Turkana Basin shows evidence for dietary resources with a wide range of δ 13 C values including canopy-driven 13 C depleted ground C 3 foods. Alternative equation variables changed by 1-2‰ yield higher C 4 estimates forA. anamensis (15-31%) than previously thought (0-10%). The choice of δ 13 C C3 and δ 13 C C4 values for estimating %C 4 is not a perfunctory task and potentially explains the δ 13 C isotopic equifinality of A. anamensis and "savanna" chimps.Discussion: My integrative diet model reconciles the carbon isotopic data with the dentognathic and microwear evidence of A. anamensis' diet and suggests that "savanna" chimps are not proper dietary analogs of A. anamensis. A foraging strategy across heterogeneous habitats of the Pliocene Omo-Turkana Basin incorporating an array of 13 Cdepleted and 13 C-enriched C 3 foods and a portion of C 4 resources may have served as one of the selective pressures for A. anamensis, the earliest habitual biped [van der Merwe et al.

Influences of dietary niche expansion and Pliocene environmental changes on the origins of stone tool making

“…Although microwear data contrast those of dentognathic morphology and imply soft foods were regularly consumed (Grine et al, 2012), A. anamensis' dental microwear patterns are similar to those of the C3-C4 mixed feeding A. afarensis (Grine et al, 2006;Ungar et al, 2010). Quinn (2019) In a common thread, we suggest a gradual and stepwise but not necessarily abrupt behavioral shift underpins the earliest known stone tool making behaviors as represented by LOM3. Tools are used by extant chimpanzees to forage (Boesch and Boesch, 1990;Haslam, 2014;Haslam et al, 2009;Marchant and McGrew, 2005); thus tool-assisted foraging may be a shared ape-human behavioral trait also present in the earliest hominins (Toth and Schick, 2009).…”

“…Tejada-Lara et al (2018) suggested the ε*enamel-diet value of mammalian herbivores is predicted by body mass and gut physiology, producing ε*enamel-diet values ranges between +9 and +16‰. The use of specific ε*enamel-diet values can impact dietary reconstructions (Quinn, 2019).…”

Biogeochemical evidence for residence, diet, and health of theWoman in the Iron Coffin(Queens, New York City)

“…We caution the use of a linear mixing model in a geographic and temporal setting offering numerous food items and a large range in C 3 plant δ 13 C values (e.g., Kohn, ), which commonly results in isotopic equifinality (e.g., Quinn, ). Moreover, the two tissue types (i.e., enamel and hair) record different aspects of diet (Ambrose & Norr, ).…”

From the Piedmont to the Coast: LA‐ICP‐MS 87Sr/86Sr evidence for short‐term, long‐distance mobility in the American Southeast

“…Based on previously analysed bulk enamel δ 13 C values, we calculated the percentage of marine/estuarine dietary resources ('%Marine') to further differentiate dietary practices amongst the 11 Harris Creek burials. We assumed pre-industrial atmospheric CO 2 δ 13 C values and used a combination of methods of Schwarcz et al (1985) and Cerling and Harris (1999) as summarized by Quinn (2019). Diet-enamel δ 13 C spacing (ε*)=12‰ after Lee-Thorp et al (1989); C 4 range (marine/estuarine) and C 3 (terrestrial/freshwater) δ 13 C endmembers are À12‰ and À28‰, respectively (Schoeninger and DeNiro 1984;Kohn 2010).…”