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Eastern Africa is home to the largest terrestrial migrations on Earth. Though these migratory systems have been well studied for decades, little is known of their antiquity and evolutionary history. Serially sampled strontium stable isotopes ( 87 Sr/ 86 Sr) from tooth enamel can be used to track migration in mammals. Here we analyse 87 Sr/ 86 Sr for 79 bovid and equid individuals representing 18 species from four localities in Kenya to characterize prehistoric migratory systems during the Last Glacial Period (115-11.7 ka). Of the species analysed, 16 lack definitive evidence for migration, including blue wildebeest (Connochaetes taurinus), Thomson's gazelle (Eudorcas thomsonii) and plains zebra (Equus quagga), which are long-distance migrants today in the Greater Serengeti Ecosystem and historically in the Athi-Kapiti Plains. Only two species, the extinct wildebeests Rusingoryx atopocranion and Megalotragus sp., were migratory. These findings suggest a possible alternative narrative about ecosystem dynamics during the Last Glacial Period and shed light on the behaviour of both extant and extinct species at this time. In particular, these results indicate that migratory behaviour in extant species either emerged during the Holocene or was more spatiotemporally constrained in the past. Our results contribute to a growing body of evidence suggesting that the structure and function of geologically recent large mammal communities in eastern Africa differed considerably from those observed in the present day., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Although modern humans left Africa multiple times over 100,000 years ago, those broadly ancestral to non-Africans dispersed less than 100,000 years ago 1 . Most models hold that these events occurred through green corridors created during humid periods because arid intervals constrained population movements 2 . Here we report an archaeological site-Shinfa-Metema 1, in the lowlands of northwest Ethiopia, with Youngest Toba Tuff cryptotephra dated to around 74,000 years ago-that provides early and rare evidence of intensive riverine-based foraging aided by the likely adoption of the bow and arrow. The diet included a wide range of terrestrial and aquatic animals. Stable oxygen isotopes from fossil mammal teeth and ostrich eggshell show that the site was occupied during a period of high seasonal aridity. The unusual abundance of fish suggests that capture occurred in the ever smaller and shallower waterholes of a seasonal river during a long dry season, revealing flexible adaptations to challenging climatic conditions during the Middle Stone Age. Adaptive foraging along dry-season waterholes would have transformed seasonal rivers into 'blue highway' corridors, potentially facilitating an out-of-Africa dispersal and suggesting that the event was not restricted to times of humid climates. The behavioural flexibility required to survive seasonally arid conditions in general, and the apparent short-term effects of the Toba supereruption in particular were probably key to the most recent dispersal and subsequent worldwide expansion of modern humans., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

We explored whether isotope ratio mass spectrometry (IRMS) is useful to investigate the origin of falsified antimalarials. Forty-four falsified and genuine antimalarial samples (artesunate, artemether-lumefantrine, dihydroartemisinin-piperaquine and sulphamethopyrazine-pyrimethamine) were analyzed in bulk for carbon (C), nitrogen (N), and oxygen (O) element concentrations and stable isotope ratios. The insoluble fraction ("starch") was extracted from 26 samples and analyzed. Samples of known geographical origin maize, a common source of excipient starch, were used to produce a comparison dataset to predict starch source. In both an initial (n = 18) and a follow-on set of samples that contained/claimed to contain artesunate/artemether (n = 26), falsified antimalarials had a range of C concentrations less than genuine comparator antimalarials and δ 13 C values higher than genuine comparators. The δ 13 C values of falsified antimalarials suggested that C 4 plant-based organic material (e.g., starch derived from maize) had been included. Using the known-origin maize samples, predictions for growth water δ 18 O values for the extracted "starch" ranged from - 6.10 to - 1.62‰. These findings suggest that IRMS may be a useful tool for profiling falsified antimalarials. We found that C 4 ingredients were exclusively used in falsified antimalarials versus genuine antimalarials, and that it may be possible to predict potential growth water δ 18 O values for the starch present in falsified antimalarials., (© 2024. The Author(s).)

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO 2 ) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO 2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO 2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO 2 thresholds in biological and cryosphere evolution.

Individual animals should adjust diets according to food availability. We used DNA metabarcoding to construct individual-level dietary timeseries for elephants from two family groups in Kenya varying in habitat use, social position and reproductive status. We detected at least 367 dietary plant taxa, with up to 137 unique plant sequences in one fecal sample. Results matched well-established trends: elephants tended to eat more grass when it rained and other plants when dry. Nested within these switches from 'grazing' to 'browsing' strategies, dietary DNA revealed seasonal shifts in food richness, composition and overlap between individuals. Elephants of both families converged on relatively cohesive diets in dry seasons but varied in their maintenance of cohesion during wet seasons. Dietary cohesion throughout the timeseries of the subdominant 'Artists' family was stronger and more consistently positive compared to the dominant 'Royals' family. The greater degree of individuality within the dominant family's timeseries could reflect more divergent nutritional requirements associated with calf dependency and/or priority access to preferred habitats. Whereas theory predicts that individuals should specialize on different foods under resource scarcity, our data suggest family bonds may promote cohesion and foster the emergence of diverse feeding cultures reflecting links between social behaviour and nutrition., Competing Interests: We declare we have no competing interests., (© 2023 The Authors.)

The 14-carbon in animal tissues records the time that the tissues are formed; since the 1960s, using the "bomb curve" for 14 C, the age of animal death can be determined accurately. Using animal tissue samples of known collection and formation dates for calibration, we determine the age of ivory samples from four ivory seizures made by law enforcement agencies between 2017 and 2019. The 14 C measurements from these seizures show that most ivory in the illegal wildlife trade is from animals from recent poaching activities. However, one seizure has a large fraction of ivory that is more than 30 y old, consistent with markings on the tusks indicating they were derived from a government stockpile.

Fossil sloths are regarded as obligate herbivores for reasons including peculiarities of their craniodental morphology and that all living sloths feed exclusively on plants. We challenge this view based on isotopic analyses of nitrogen of specific amino acids, which show that Darwin's ground sloth Mylodon darwinii was an opportunistic omnivore. This direct evidence of omnivory in an ancient sloth requires reevaluation of the ecological structure of South American Cenozoic mammalian communities, as sloths represented a major component of these ecosystems across the past 34 Myr. Furthermore, by analyzing modern mammals with known diets, we provide a basis for reliable interpretation of nitrogen isotopes of amino acids of fossils. We argue that a widely used equation to determine trophic position is unnecessary, and that the relative isotopic values of the amino acids glutamate and phenylalanine alone permit reliable reconstructions of trophic positions of extant and extinct mammals., (© 2021. The Author(s).)

Closed-canopy rainforests are important for climate (influencing atmospheric circulation, albedo, carbon storage, etc.) and ecology (harboring the highest biodiversity of continental regions). Of all rainforests, Amazonia is the world's most diverse, including the highest mammalian species richness. However, little is known about niche structure, ecological roles, and food resource partitioning of Amazonian mammalian communities over time. Through analyses of δ 13 C bioapatite , δ 13 C hair , and δ 15 N hair , we isotopically characterized aspects of feeding ecology in a modern western Amazonian mammalian community in Peru, serving as a baseline for understanding the evolution of Neotropical rainforest ecosystems. By comparing these results with data from equatorial Africa, we evaluated the potential influences of distinct phylogenetic and biogeographic histories on the isotopic niches occupied by mammals in analogous tropical ecosystems. Our results indicate that, despite their geographical and taxonomic differences, median δ 13 C diet values from closed-canopy rainforests in Amazonia (-27.4‰) and equatorial Africa (-26.9‰) are not significantly different, and that the median δ 13 C diet expected for mammalian herbivores in any closed-canopy rainforest is -27.2‰. Amazonian mammals seem to exploit a narrower spectrum of dietary resources than equatorial African mammals, however, as depicted by the absence of highly negative δ 13 C diet values previously proposed as indicative of rainforests (<-31‰). Finally, results of keratin and bioapatite δ 13 C indicate that the predictive power of trophic relationships, and traditional dietary ecological classifications in bioapatite-protein isotopic offset expectations, must be reconsidered., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Carbon and nitrogen isotope ratios in hair sampled from 65 communities across the central and intermountain regions of the United States and more intensively throughout 29 ZIP codes in the Salt Lake Valley, Utah, revealed a dietary divergence related to socioeconomic status as measured by cost of living, household income, and adjusted gross income. Corn-fed, animal-derived proteins were more common in the diets of lower socioeconomic status populations than were plant-derived proteins, with individual estimates of animal-derived protein diets as high as 75%; United States towns and cities averaged 57%. Similar patterns were seen across the socioeconomic status spectrum in the Salt Lake Valley. It is likely that corn-fed animal proteins were associated with concentrated animal-feeding operations, a common practice for industrial animal production in the United States today. Given recent studies highlighting the negative impacts of animal-derived proteins in our diets, hair carbon isotope ratios could provide an approach for scaling assessments of animal-sourced foods and health risks in communities across the United States., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Diet is a major driver of hominin evolution, but most of the geochemical evidence relies on carbon isotopes (δ 13 C). Here, we report enamel stable calcium isotope (δ 44/42 Ca) values against δ 13 C 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 δ 44/42 Ca values, possibly reflecting omnivorous and opportunistic preferences. Paranthropus boisei is uniquely distributed in the δ 13 C versus δ 44/42 Ca 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 δ 44/42 Ca values of Paranthropus boisei including significant differences observed with δ 44/42 Ca values recently reported for P. robustus from South Africa, questioning the monophyly of this genus.

Trace elements in hair originate from intake (e.g., diet, inhalation, skin absorption), are transported in the bloodstream, and then incorporated during hair formation. However, the trace element abundance and isotopic compositions may be altered by post-eruption environmental processes. Such alterations must be addressed to obtain a meaningful interpretation of hair analysis for biomonitoring. In this study, we used strontium (Sr) isotopic analysis together with sorption kinetics of ionic Sr to quantify the rate and extent of replacement of endogenous Sr in hair by exogenous Sr from ambient water. We found that with only 10 minutes of exposure at room temperature (22°C), more than 30% of original endogenous Sr in hair was replaced with exogenous Sr from the solution. After 16 days of exposure to the solution, more than 90% of endogenous Sr was replaced, with a warmer temperature (60°C) accelerating the exchange substantially. We also found that acid leaching of exposed hair did not remove or isolate the exogenous Sr; therefore, neither the original endogenous nor the exogenous 87Sr/86Sr signal could be separated. Nonetheless, these findings illustrated that the quantitative correlation between the fraction of exogenous Sr and the soaking time, if established, could be used to estimate the length of water contact time for hair in forensic studies. Even if such time since initial contact cannot be established, the combination of acid leaching and 87Sr/86Sr analysis of hair samples may still be valuable in provenance studies to identify recent changes in the exogenous Sr pool, including movements or changes in water source., Competing Interests: The authors have declared that no competing interests exist.

Carbon isotope ratios of mammalian teeth from the Kanapoi site in northern Kenya are interpreted in the context of C 3 and C 4 derived resources to investigate the paleoecology of Australopithecus anamensis. δ 13 C values of large mammals, when compared at the taxon level, show an ecosystem that is strongly biased towards mixed feeders and browsers. However, sufficient C 4 resources were present such that some C 4 dominated grazers were also present in the large mammal fauna. Analyses of micromammals shows that their diets were C 3 dominated or C 3 -C 4 mixed. Carbon isotope studies of primates shows that the major primate tribes-Colobini, Papioini, Hominini-all made some use of C 4 resources in their respective diets; the Hominini had a higher fraction of C 3 diet resources than the other primate tribes represented in the fossil record., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth ( 87 Sr/ 86 Sr, 13 C/ 12 C, and 18 O/ 16 O) to examine lifelong movement and resource-use patterns of a unique freshwater population of a wide-ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.S.A.). This population's potentially unique migratory behavior and use of different trophic resources are unknown. The isotope ratios we measured in teeth showed that seals were born in the lake, remained lifelong residents, and relied principally on resources produced from in the lake, even when seasonally abundant and nutrient-dense spawning anadromous fish (i.e., sockeye salmon [Oncorhynchus nerka]) were available in the lake. Our results illustrate how serial isotope records in teeth, particularly 87 Sr/ 86 Sr ratios, can be used to quantify how coastal mammal populations exploit both freshwater and marine ecosystems. Understanding lifelong patterns of habitat and resource use is essential information when designing effective conservation plans for threatened coastal mammals. We present the Iliamna Lake harbor seals as a unique case study into how isotope records within teeth can help reveal the cryptic ecology of such a population residing in an intact ecosystem. The results also provide critical baseline information for the Kvichak River system, which is facing an uncertain future due to proposed large-scale industrial development and a rapidly changing climate., (© 2019 Society for Conservation Biology.)

As a recorder containing both physiological and environmental information, keratinized tissues, such as hair and feather, can be used to reveal geographical information, to monitor the exposure to pollutants, and to reconstruct dietary history. However, trace element analysis of keratinized tissues is complicated by the lack of reference endogenous ranges of trace element and the lack of understanding of the susceptibility of each element to exogenous contamination. The interior of animal horn is the cleanest of all keratinized tissues with minimum exogenous contamination because of its large size. Thus, the trace element concentrations in horn interior samples can provide reliable endogenous concentration ranges. Here we measured the concentrations of trace elements in horn interior samples of cattle and wild animals, which we propose to be used as the reference ranges for endogenous levels of trace elements in keratin. We calculated the enrichment factors of 30 trace elements in horn interior samples relative to the continental crust, which we considered the average exogenous contamination. We compared the ranges of elemental concentrations measured in horn interior samples, in the order of decreasing enrichment factor, to their reference ranges in hair, fingernails, and toenails, as well as their concentrations in caprine horns. Such comparison validates the use of the enrichment factor as an indicator of the susceptibility of an element to contamination: an element with a high enrichment factor is generally less likely to be affected by contamination and vice versa., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Nursing is pivotal in the social and biological evolution of hominins, but to date, early-life behavior among hominin lineages is a matter of debate. The calcium isotopic compositions (δ 44/42 Ca) of tooth enamel can provide dietary information on this period. Here, we measure the δ 44/42 Ca values in spatially located microsized regions in tooth enamel of 37 South African hominins to reconstruct early-life dietary-specific variability in Australopithecus africanus , Paranthropus robustus , and early Homo. Very low δ 44/42 Ca values (<-1.4‰), indicative of milk consumption, are measured in early Homo but not in A. africanus and P. robustus . In these latter taxa, transitional or adult nonmilk foods must have been provided in substantial quantities relative to breast milk rapidly after birth. The results suggest that early Homo have continued a predominantly breast milk-based nursing period for longer than A. africanus and P. robustus and have consequently more prolonged interbirth interval.

The fossils preserved in the Rancho La Brea "tar" seeps in southern California span the past ∼50,000 years and provide a rare opportunity to assess the ecology of predators (e.g., the American lion, sabertooth cats, cougars, dire wolves, gray wolves, and coyotes), including clarifying the causes and consequences of the terminal Pleistocene extinction event. Here, a multi-proxy approach elucidates dietary responses of carnivorans to changing climates and megafaunal extinctions. Using sample sizes that are unavailable anywhere else in the world, including hundreds of carnivoran and herbivore specimens, we clarify the paleobiology of the extinct sabertooth cats and dire wolves-overturning the idea that they heavily competed for similar prey. Canids (especially the dire wolf) consumed prey from more open environments than felids, demonstrating minimal competition for prey throughout the latest Pleistocene and largely irrespective of changing climates, including just prior to their extinction. Coyotes experienced a dramatic shift in dietary behavior toward increased carcass utilization and the consumption of forest resources (prey and/or plant resources) after the terminal Pleistocene megafaunal extinction. Extant predators' ability to effectively hunt smaller prey and/or utilize carcasses may have been a key to their survival, especially after a significant reduction in megafaunal prey resources. Collectively, these data suggest that dietary niches of carnivorans are not always static and can instead be substantially affected by the removal of top predators and abundant prey resources., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The spatial distribution of trace elements in hair is highly heterogeneous at the microscale. The relatively mild spatial variation of endogenous signal incorporated during hair growth may be amplified by orders of magnitude due to later exogenous contaminations. Here, we studied the longitudinal and transverse distributions of trace elements in elephant and giraffe hair and discussed the possible endogenous and exogenous contributions. Laser ablation ICP-MS analyses were performed on cross sections of hair to assess the surface contamination and transverse variation. We also removed the contaminated surface layer at various distances from hair root of single hair strands using physical abrasion and measured the concentrations by microwave digestion followed by ICP-MS. By comparing the concentrations of 11 trace elements between the intact and abraded hair segments as a function of distance from root and their laser ablation profiles, we rationalized the endogenous and exogenous contributions: Al and Ti concentrations are dominated by the exogenous contamination on the elephant hair surface, probably in the form of insoluble particles, but not in the giraffe hair; Mg, Ca, Sr, Ba, and Mn are enhanced on the elephant hair surface by exogenous contaminations, but a comparable amount was found in the hair interior suggesting migration of these elements from the surface towards the core; Cu, Zn, Se, and Pb did not have surface accumulation and thus were dominated by the endogenous signal. Overall, giraffe hair had minimal surficial contamination, suggesting the origin of its trace elements is predominantly endogenous, except for Mn, which might get contaminated with airborne particles. We thus demonstrate that contamination of hair may be strongly related to behavioral traits and that the interpretation of trace elemental analyses in hair as a biomonitor or for provenance studies would be highly dependent on the species considered.

Stable isotope and elemental ratios in hair are influenced by the environment, including both climate and geology. Stable carbon isotopes can be used to give estimates of the C 4 /CAM fraction of diets of herbivorous mammals; stable nitrogen isotopes are related to the local water deficit; strontium isotopes are determined by the local geology. We studied hair from rhinos in Kenya to determine spatial patterns in δ 13 C, δ 15 N, and 87 Sr/ 86 Sr ratios. The samples of rhino hair were collected during Kenya Wildlife Service translocation or veterinary activities. δ 13 C values showed diets dominated by C 3 foods, but in some regions the diet, at least seasonally, contained significant quantities (i.e., > ca. 20%) of C 4 /CAM foods. δ 15 N values were related to water deficit, with higher δ 15 N values in regions with high water deficit. 87 Sr/ 86 Sr isotope ratios were found to be related to the local geological substrate suggesting that 87 Sr/ 86 Sr isotope ratios are provisionally useful for determining the origins of illegal wildlife materials in Kenya and elsewhere in Africa.

The heart of forensic science is application of the scientific method and analytical approaches to answer questions central to solving a crime: Who, What, When, Where, and How. Forensic practitioners use fundamentals of chemistry and physics to examine evidence and infer its origin. In this regard, ecological researchers have had a significant impact on forensic science through the development and application of a specialized measurement technique-isotope analysis-for examining evidence. Here, we review the utility of isotope analysis in forensic settings from an ecological perspective, concentrating on work from the Americas completed within the last three decades. Our primary focus is on combining plant and animal physiological models with isotope analyses for source inference. Examples of the forensic application of isotopes-including stable isotopes, radiogenic isotopes, and radioisotopes-span from cotton used in counterfeit bills to anthrax shipped through the U.S. Postal Service and from beer adulterated with cheap adjuncts to human remains discovered in shallow graves. Recent methodological developments and the generation of isotope landscapes, or isoscapes, for data interpretation promise that isotope analysis will be a useful tool in ecological and forensic studies for decades to come.

Aridification is often considered a major driver of long-term ecological change and hominin evolution in eastern Africa during the Plio-Pleistocene; however, this hypothesis remains inadequately tested owing to difficulties in reconstructing terrestrial paleoclimate. We present a revised aridity index for quantifying water deficit (WD) in terrestrial environments using tooth enamel δ 18 O values, and use this approach to address paleoaridity over the past 4.4 million years in eastern Africa. We find no long-term trend in WD, consistent with other terrestrial climate indicators in the Omo-Turkana Basin, and no relationship between paleoaridity and herbivore paleodiet structure among fossil collections meeting the criteria for WD estimation. Thus, we suggest that changes in the abundance of C 4 grass and grazing herbivores in eastern Africa during the Pliocene and Pleistocene may have been decoupled from aridity. As in modern African ecosystems, other factors, such as rainfall seasonality or ecological interactions among plants and mammals, may be important for understanding the evolution of C 4 grass- and grazer-dominated biomes., Competing Interests: The authors declare no conflict of interest.

Rationale: Oxygen isotope ratios (δ 18 O values) of hair largely reflect features of regional hydrology while strontium isotope ratios ( 87 Sr/ 86 Sr) are thought to reflect bedrock geology; combination of both isotope signatures may provide greater capacity for determining provenance and reconstructing travel history of an organism. To test this hypothesis, we compared the O-Sr isotope profiles of hair from domestic horses with known residency histories., Methods: Tail hairs were collected from a pair of horses pastured together for a period of 16 months, one of which lived in a different location for the 8 months prior. Hair samples were washed with solvents to remove external contaminants prior to sequential sampling for δ 18 O and 87 Sr/ 86 Sr analysis via TC/EA-IRMS and MC-ICP-MS, respectively. Hair digests were concentrated and analyzed employing low-flow natural aspiration to measure 87 Sr/ 86 Sr., Results: Tail hair from the control and transported horses had mean δ 18 O values of 11.25 ± 1.62 ‰ and 10.96 ± 1.53 ‰, and mean 87 Sr/ 86 Sr of 0.7101 ± 0.0006 and 0.7109 ± 0.0020, respectively. The δ 18 O and 87 Sr/ 86 Sr profiles for the control and transported horses were indistinguishable when they were pastured together. The 87 Sr/ 86 Sr profiles were significantly different during the period that the horses were living apart, while the δ 18 O values were indistinguishable during that period., Conclusions: By comparing the O-Sr isotope profiles of a control and transported horse, we investigated isotopic signal(s) potentially useful for reconstructing travel histories via high-resolution sequential sampling along single strands of tail hair. Improved analytical capabilities allowed for extremely low Sr abundance samples to be analyzed for 87 Sr/ 86 Sr and proved capable of resolving a horse's movement between distinct regions. Copyright © 2017 John Wiley & Sons, Ltd., (Copyright © 2017 John Wiley & Sons, Ltd.)

Carbon-14 measurements on 231 elephant ivory specimens from 14 large ivory seizures (≥0.5 ton) made between 2002 and 2014 show that most ivory (ca 90%) was derived from animals that had died less than 3 y before ivory was confiscated. This indicates that the assumption of recent elephant death for mortality estimates of African elephants is correct: Very little "old" ivory is included in large ivory shipments from Africa. We found only one specimen of the 231 analyzed to have a lag time longer than 6 y. Patterns of trade differ by regions: East African ivory, based on genetic assignments of geographic origin, has a much higher fraction of "rapid" transit than ivory originating in the Tridom region of Cameroon-Gabon-Congo. Carbon-14 is an important tool in understanding patterns of movement of illegal wildlife products., Competing Interests: I.D.-H. is chief executive officer of Save the Elephants, which provided partial funding for this research, and K.S.B. is employed by Vulcan, Inc., which provided partial funding for this research through the Paul G. Allen Family Foundation.

Stable isotope analysis is a promising tool for investigating primate ecology although nuanced ecological applications remain challenging, in part due to the complex nature of isotopic variability in plant-animal systems. The aim of this study is to investigate sources of carbon and nitrogen isotopic variation at the base of primate food webs that reflect aspects of primate ecology. The majority of primates inhabit tropical forest ecosystems, which are dominated by C3 vegetation. We used stable isotope ratios in plants from Kibale National Park, Uganda, a well-studied closed-canopy tropical forest, to investigate sources of isotopic variation among C3 plants related to canopy stratification, leaf age, and plant part. Unpredictably, our results demonstrate that vertical stratification within the canopy does not explain carbon or nitrogen isotopic variation in leaves. Leaf age can be a significant source of isotopic variation, although the direction and magnitude of this difference is not consistent across tree species. Some plant parts are clearly differentiated in carbon and nitrogen isotopic composition, particularly leaves compared to non-photosynthetic parts such as reproductive parts and woody stem parts. Overall, variation in the isotopic composition of floral communities, plant species, and plant parts demonstrates that stable isotope studies must include analysis of local plant species and parts consumed by the primates under study from within the study area. Am. J. Primatol. 78:1041-1054, 2016. © 2015 Wiley Periodicals, Inc., (© 2015 Wiley Periodicals, Inc.)

Megaherbivores (>1000 kg) are critical for ecosystem health and function, but face population collapse and extinction globally. The future of these megaherbivore-impoverished ecosystems is difficult to predict, though many studies have demonstrated increasing representation of C3 woody plants. These studies rely on direct observational data, however, and tools for assessing decadal-scale changes in African ecology without observation are lacking. We use isotopic records of historical common hippopotamus (Hippopotamus amphibius) canines to quantify herbaceous vegetation change in Queen Elizabeth National Park, Uganda following a period of civil unrest and poaching. This poaching event led to population collapse of two threatened African megaherbivore species: hippopotamus and African elephants (Loxodonta africana). Serial carbon isotope ratios (δ(13)C) in canine enamel from individuals that lived between 1960-2000 indicated substantial increases in C3 herbaceous plants in their diet (<20% C3 in the 1960s to 30-45% C3 in the 80s and 90s), supported by other observational and ecological data. These data indicate megaherbivore loss results in succession of both woody and herbaceous C3 vegetation and further reaching effects, such as decreased grazing capacity and herbivore biodiversity in the area. Given multiple lines of evidence, these individuals appear to accurately capture herbaceous vegetation change in Mweya.

The spread of C4 grasses in the late Neogene is one of the most important ecological transitions of the Cenozoic, but the primary driver of this global expansion is widely debated. We use the stable carbon isotopic composition (δ(13)C) of bison and mammoth tissues as a proxy for the relative abundance of C3 and C4 vegetation in their grazing habitat to determine climatic and atmospheric CO2 controls on C4 grass distributions from the Last Glacial Maximum (LGM) to the present. We predict the spatial variability of grass δ(13)C in North America using a mean of three different methods of classification and regression tree (CART) machine learning techniques and nine climatic variables. We show that growing season precipitation and temperature are the strongest predictors of all single climate variables. We apply this CART analysis to high-resolution gridded climate data and Coupled Model Intercomparison Project (CMIP5) mean paleoclimate model outputs to produce predictive isotope landscape models ("isoscapes") for the current, mid-Holocene, and LGM average δ(13)C of grass-dominated areas across North America. From the LGM to the present, C4 grass abundances substantially increased in the Great Plains despite concurrent increases in atmospheric CO2. These results suggest that changes in growing season precipitation rather than atmospheric CO2 were critically important in the Neogene expansion of C4 grasses.

Laser ablation of tooth enamel was used to analyze stable carbon isotope compositions of teeth of hominins, red deer, and bears from middle Pleistocene sites in the Sierra de Atapuerca in northern Spain, to investigate the possibility that this technique could be used as an additional tool to identify periods of physiological change that are not detectable as changes in tooth morphology. Most of the specimens were found to have minimal intra-tooth variation in carbon isotopes (< 2.3‰), suggesting isotopically uniform diets through time and revealing no obvious periods of physiological change. However, one of the two sampled hominin teeth displayed a temporal carbon isotope shift (3.2‰) that was significantly greater than observed for co-occurring specimens. The δ13C value of this individual averaged about -16‰ early in life, and -13‰ later in life. This isotopic change occurred on the canine crown about 4.2 mm from the root, which corresponds to an approximate age of two to four years old in modern humans. Our dataset is perforce small owing to the precious nature of hominid teeth, but it demonstrates the potential utility of the intra-tooth isotope profile method for extracting ontogenetic histories of human ancestors.

Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermophysiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endotherms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but ∼ 6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds.

Objective: Archaeological remains strongly suggest that the Holocene Japanese hunter-gatherers, the Jomon people, utilized terrestrial plants as their primary food source. However, carbon and nitrogen isotope analysis of bone collagen indicates that they primarily exploited marine resources. We hypothesize that this inconsistency stems from the route of protein synthesis and the different proportions of protein-derived carbon in tooth enamel versus bone collagen. Carbon isotope ratios from bone collagen reflect that of dietary protein and may provide a biased signal of diet, whereas isotope ratios from tooth enamel reflect the integrated diet from all macronutrients (carbohydrates, lipids, and proteins)., Methods: In order to evaluate the differences in inferred diet between the archaeological evidence and bone collagen isotope data, this study investigated carbon isotopes in Jomon tooth enamel from four coastal sites of the Middle to Late-Final Jomon period (5,000-2,300 years BP)., Results: Carbon isotope ratios of human teeth are as depleted as coeval terrestrial mammals, suggesting that C 3 plants and terrestrial mammals were major dietary resources for the Jomon people. Dietary dependence on marine resources calculated from enamel was significantly lower than that calculated from bone collagen. The discrepancy in isotopic ratios between enamel and collagen and the nitrogen isotope ratio in collagen shows a negative correlation on individual and population levels, suggesting diets with variable proportions of terrestrial and marine resources., Conclusion: This study highlights the usefulness of coupling tooth enamel and bone collagen in carbon isotopic studies to reconstruct prehistoric human diet. Am J Phys Anthropol 158:300-311, 2015. © 2015 Wiley Periodicals, Inc., (© 2015 Wiley Periodicals, Inc.)

A large stable isotope dataset from East and Central Africa from ca. 30 regional collection sites that range from forest to grassland shows that most extant East and Central African large herbivore taxa have diets dominated by C4 grazing or C3 browsing. Comparison with the fossil record shows that faunal assemblages from ca. 4.1-2.35 Ma in the Turkana Basin had a greater diversity of C3-C4 mixed feeding taxa than is presently found in modern East and Central African environments. In contrast, the period from 2.35 to 1.0 Ma had more C4-grazing taxa, especially nonruminant C4-grazing taxa, than are found in modern environments in East and Central Africa. Many nonbovid C4 grazers became extinct in Africa, notably the suid Notochoerus, the hipparion equid Eurygnathohippus, the giraffid Sivatherium, and the elephantid Elephas. Other important nonruminant C4-grazing taxa switched to browsing, including suids in the lineage Kolpochoerus-Hylochoerus and the elephant Loxodonta. Many modern herbivore taxa in Africa have diets that differ significantly from their fossil relatives. Elephants and tragelaphin bovids are two groups often used for paleoecological insight, yet their fossil diets were very different from their modern closest relatives; therefore, their taxonomic presence in a fossil assemblage does not indicate they had a similar ecological function in the past as they do at present. Overall, we find ecological assemblages of C3-browsing, C3-C4-mixed feeding, and C4-grazing taxa in the Turkana Basin fossil record that are different from any modern ecosystem in East or Central Africa.

Rationale: Hair keratin is a very important material in ecological and archaeological studies because it grows continuously, can be obtained non-invasively, does not require extensive processing prior to analysis and can be found in archaeological sites. Only a few studies have examined seasonal variations in hair isotope values, and there is no published dataset examining the isotope variability recorded in the keratinous tissues of stationary (i.e., non-migrating) domestic mammals., Methods: Thirty-six Irish sheep were sampled in eight farms every three months between September 2006 and June 2007. A shearing strategy was adopted to sample only the most recently grown wool in order to represent an average of the summer, autumn, winter and spring conditions. The stable isotope ratios of the ground samples were measured using two different stable isotope mass spectrometers operated in dual-inlet (C, N) and continuous-flow (O, H) mode., Results: Wool O isotope ratios are a good proxy for seasonal variability in climate and can be used to anchor a chronology independently of other isotope records (C, N) that are influenced by diet or physiology. By contrast, interpretation of seasonal variations in hair H isotope composition in terms of climate is more complex probably due to the influence of dietary H. The C and N isotope values of grass-fed animals varied seasonally, probably reflecting the annual cycle of seasonal variation in grass isotope values. The highest δ(13) C values were measured in summer-grown wool, while the highest δ(15) N values were measured in winter-grown wool. Supplementation of the sheep diet with concentrates was detected easily and was marked by an increase in δ(13) C values and a decrease in δ(15) N values in winter-grown wool., Conclusions: The present study demonstrates that time-resolved sampling and stable isotope ratio analysis of sheep wool can be used to identify short-term changes in diet and climate and therefore offer a tool to examine a wide variety of present and past husbandry practices., (Copyright © 2015 John Wiley & Sons, Ltd.)

Highly migratory organisms present major challenges to conservation efforts. This is especially true for exploited anadromous fish species, which exhibit long-range dispersals from natal sites, complex population structures, and extensive mixing of distinct populations during exploitation. By tracing the migratory histories of individual Chinook salmon caught in fisheries using strontium isotopes, we determined the relative production of natal habitats at fine spatial scales and different life histories. Although strontium isotopes have been widely used in provenance research, we present a new robust framework to simultaneously assess natal sources and migrations of individuals within fishery harvests through time. Our results pave the way for investigating how fine-scale habitat production and life histories of salmon respond to perturbations-providing crucial insights for conservation.

Specialized pastoralism developed ∼3 kya among Pastoral Neolithic Elmenteitan herders in eastern Africa. During this time, a mosaic of hunters and herders using diverse economic strategies flourished in southern Kenya. It has been argued that the risk for trypanosomiasis (sleeping sickness), carried by tsetse flies in bushy environments, had a significant influence on pastoral diversification and migration out of eastern Africa toward southern Africa ∼2 kya. Elmenteitan levels at Gogo Falls (ca. 1.9-1.6 kya) preserve a unique faunal record, including wild mammalian herbivores, domestic cattle and caprines, fish, and birds. It has been suggested that a bushy/woodland habitat that harbored tsetse fly constrained production of domestic herds and resulted in subsistence diversification. Stable isotope analysis of herbivore tooth enamel (n = 86) from this site reveals, instead, extensive C4 grazing by both domesticates and the majority of wild herbivores. Integrated with other ecological proxies (pollen and leaf wax biomarkers), these data imply an abundance of C4 grasses in the Lake Victoria basin at this time, and thus little risk for tsetse-related barriers to specialized pastoralism. These data provide empirical evidence for the existence of a grassy corridor through which small groups of herders could have passed to reach southern Africa.

Objectives: We conducted stable isotope and dietary analyses of women from higher and lower socioeconomic status (SES) groups in Cali, Colombia. The objectives were to test between-group differences in stable isotope, dietary, and anthropometric characteristics, and to evaluate relationships between diet and stable isotope values., Methods: Hair samples from 38 women (mean age 33.4) from higher and lower SES groups were analyzed for δ(13) C, δ(15) N, and δ(34) S values. Dietary intake was assessed via 24-h recalls. Anthropometric variables measured were body mass index, five body circumferences, and six skinfold thicknesses., Results: Mean δ(13) C and δ(15) N values of the higher SES group (-16.4 and 10.3‰) were significantly greater than those of the lower SES group (-17.2 and 9.6‰; P < 0.01), but mean δ(34) S values did not differ significantly between groups (higher SES: 4.6‰; lower SES: 5.1‰). The higher SES group consumed a greater percentage of protein than the lower SES group (14% vs. 12% of energy; P = 0.03), but the groups did not differ in other dietary characteristics or in anthropometric characteristics. δ(13) C, δ(15) N, and δ(34) S values were not correlated with intake of the dietary items predicted (sugars, animal-source protein, and marine foods, respectively). The lower SES group was more variable in all three stable isotope values (P < 0.05), mirroring a trend toward greater dietary variability in this group., Conclusions: Stable isotope values revealed a difference between SES groups that was not explained by the dietary data. The relationship between diet and stable isotope composition is complex., (© 2014 Wiley Periodicals, Inc.)

We investigated a novel application of stable isotope abundance analysis of nitrogen (15N), carbon (13C), hydrogen (2H), and oxygen (18O) to characterize pen ink. We focused on both ballpoint and gel pen inks. We found that the isotope ratios of ink from pens purchased together in a package were similar and within-package stable isotope ratio variability was not significantly larger than the variability of isotope reference materials used during analysis. In contrast, the isotope ratios of ink from pens of the same brand purchased in three states of the continental USA were significantly different from each other and there was isotope ratio variation among pens of the same brand but different, unknown production periods. The stable isotope ratios of inked paper were statistically distinguishable using measured δ15N values. Paper inked with different gel pens was statistically distinguishable using measured δ2H values. The capacity of stable isotope ratios to differentiate among ballpoint inks as well as gel inks shows that stable isotope analysis may be a useful and quantifiable investigative technique for questioned document examination, although current sample size requirements limit its utility. Application of the technique in casework will require the development of micro-scale sampling and analysis methods., (Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.)

Segmental analysis of hair has been used in diverse fields ranging from forensics to ecology to measure the concentration of substances such as drugs and isotopes. Multiple hairs are typically combined into a bundle for segmental analysis to obtain a high-resolution series of measurements. Individual hair strands cycle through multiple phases of growth and grow at different rates when in the growth phase. Variation in growth of hair strands in a bundle can cause misalignment of substance concentration between hairs, attenuating the primary body signal. We developed a mathematical model based on the known physiology of hair growth to describe the signal averaging caused by bundling multiple hairs for segmental analysis. The model was used to form an inverse method to estimate the primary body signal from measurements of a hair bundle. The inverse method was applied to a previously described stable oxygen isotope chronology from the hair of a murder victim and provides a refined interpretation of the data. Aspects of the reconstruction were confirmed when the victim was later identified.

Stable carbon isotope analysis in tooth enamel is a well-established approach to infer C3 and C4 dietary composition in fossil mammals. The bulk of past work has been conducted on large herbivorous mammals. One important finding is that their dietary habits of fossil large mammals track the late Miocene ecological shift from C3 forest and woodland to C4 savannah. However, few studies on carbon isotopes of fossil small mammals exist due to limitations imposed by the size of rodent teeth, and the isotopic ecological and dietary behaviors of small mammals to climate change remain unknown. Here we evaluate the impact of ecological change on small mammals by fine-scale comparisons of carbon isotope ratios (δ(13)C) with dental morphology of murine rodents, spanning 13.8 to ∼2.0 Ma, across the C3 to C4 vegetation shift in the Miocene Siwalik sequence of Pakistan. We applied in-situ laser ablation GC-IRMS to lower first molars and measured two grazing indices on upper first molars. Murine rodents yield a distinct, but related, record of past ecological conditions from large herbivorous mammals, reflecting available foods in their much smaller home ranges. In general, larger murine species show more positive δ(13)C values and have higher grazing indices than smaller species inhabiting the same area at any given age. Two clades of murine rodents experienced different rates of morphological change. In the faster-evolving clade, the timing and trend of morphological innovations are closely tied to consumption of C4 diet during the vegetation shift. This study provides quantitative evidence of linkages among diet, niche partitioning, and dental morphology at a more detailed level than previously possible.

Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon ((14)C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric (14)C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3-1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. (14)C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. (14)C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve (14)C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts.

Theropithecus was a common large-bodied primate that co-occurred with hominins in many Plio-Pleistocene deposits in East and South Africa. Stable isotope analyses of tooth enamel from T. brumpti (4.0-2.5 Ma) and T. oswaldi (2.0-1.0 Ma) in Kenya show that the earliest Theropithecus at 4 Ma had a diet dominated by C4 resources. Progressively, this genus increased the proportion of C4-derived resources in its diet and by 1.0 Ma, had a diet that was nearly 100% C4-derived. It is likely that this diet was comprised of grasses or sedges; stable isotopes cannot, by themselves, give an indication of the relative importance of leaves, seeds, or underground storage organs to the diet of this primate. Theropithecus throughout the 4- to 1-Ma time range has a diet that is more C4-based than contemporaneous hominins of the genera Australopithecus, Kenyanthropus, and Homo; however, Theropithecus and Paranthropus have similar proportions of C4-based resources in their respective diets.

Hominin fossil evidence in the Turkana Basin in Kenya from ca. 4.1 to 1.4 Ma samples two archaic early hominin genera and records some of the early evolutionary history of Paranthropus and Homo. Stable carbon isotopes in fossil tooth enamel are used to estimate the fraction of diet derived from C3 or C4 resources in these hominin taxa. The earliest hominin species in the Turkana Basin, Australopithecus anamensis, derived nearly all of its diet from C3 resources. Subsequently, by ca. 3.3 Ma, the later Kenyanthropus platyops had a very wide dietary range--from virtually a purely C3 resource-based diet to one dominated by C4 resources. By ca. 2 Ma, hominins in the Turkana Basin had split into two distinct groups: specimens attributable to the genus Homo provide evidence for a diet with a ca. 65/35 ratio of C3- to C4-based resources, whereas P. boisei had a higher fraction of C4-based diet (ca. 25/75 ratio). Homo sp. increased the fraction of C4-based resources in the diet through ca. 1.5 Ma, whereas P. boisei maintained its high dependency on C4-derived resources.

We use stable isotope ratios in feces of wild mountain gorillas (Gorilla beringei) to test the hypothesis that diet shifts within a single year, as measured by dry mass intake, can be recovered. Isotopic separation of staple foods indicates that intraannual changes in the isotopic composition of feces reflect shifts in diet. Fruits are isotopically distinct compared with other staple foods, and peaks in fecal δ(13)C values are interpreted as periods of increased fruit feeding. Bayesian mixing model results demonstrate that, although the timing of these diet shifts match observational data, the modeled increase in proportional fruit feeding does not capture the full shift. Variation in the isotopic and nutritional composition of gorilla foods is largely independent, highlighting the difficulty for estimating nutritional intake with stable isotopes. Our results demonstrate the potential value of fecal sampling for quantifying short-term, intraindividual dietary variability in primates and other animals with high temporal resolution even when the diet is composed of C(3) plants.

The stable isotopic composition of drinking water, diet, and atmospheric oxygen influence the isotopic composition of body water ((2)H/(1)H, (18)O/(16)O expressed as δ(2) H and δ(18)O). In turn, body water influences the isotopic composition of organic matter in tissues, such as hair and teeth, which are often used to reconstruct historical dietary and movement patterns of animals and humans. Here, we used a nonhuman primate system (Macaca fascicularis) to test the robustness of two different mechanistic stable isotope models: a model to predict the δ(2)H and δ(18)O values of body water and a second model to predict the δ(2)H and δ(18)O values of hair. In contrast to previous human-based studies, use of nonhuman primates fed controlled diets allowed us to further constrain model parameter values and evaluate model predictions. Both models reliably predicted the δ(2)H and δ(18)O values of body water and of hair. Moreover, the isotope data allowed us to better quantify values for two critical variables in the models: the δ(2)H and δ(18)O values of gut water and the (18)O isotope fractionation associated with a carbonyl oxygen-water interaction in the gut (α(ow)). Our modeling efforts indicated that better predictions for body water and hair isotope values were achieved by making the isotopic composition of gut water approached that of body water. Additionally, the value of α(ow) was 1.0164, in close agreement with the only other previously measured observation (microbial spore cell walls), suggesting robustness of this fractionation factor across different biological systems., (© 2012 Wiley Periodicals, Inc.)

An understanding of the factors influencing the isotopic composition of body water is important to determine the isotopic composition of tissues that are used to reconstruct movement patterns of humans. The δ(2)H and δ(18)O values of body water (δ(2)H(bw) and δ(18)O(bw)) are related to the δ(2)H and δ(18)O values of drinking water (δ(2)H(dw) and δ(18)O(dw)), but clearly distinct because of other factors including the composition of food. Here, we develop a mechanistic geographical information system (GIS) model to produce spatial projections of δ(2)H(bw) and δ(18)O(bw) values for the USA. We investigate the influence of gender, food, and drinking water on the predicted values by comparing them with the published values. The strongest influence on the predicted values was related to the source of δ(2)H(dw) and δ(18)O(dw) values. We combine the model with equations that describe the rate of turnover to produce estimates for the time required for a non-resident to reach an isotopic equilibrium with a resident population.

Although the globalization of food production is often assumed to result in a homogenization of consumption patterns with a convergence towards a Western style diet, the resources used to make global food products may still be locally produced (glocalization). Stable isotope ratios of human hair can quantify the extent to which residents of industrialized nations have converged on a standardized diet or whether there is persistent heterogeneity and glocalization among countries as a result of different dietary patterns and the use of local food products. Here we report isotopic differences among carbon, nitrogen and sulfur isotope ratios of human hair collected in thirteen Western European countries and in the USA. European hair samples had significantly lower δ(13)C values (-22.7 to -18.3‰), and significantly higher δ(15)N (7.8 to 10.3‰) and δ(34)S (4.8 to 8.3‰) values than samples from the USA (δ(13)C: -21.9 to -15.0‰, δ(15)N: 6.7 to 9.9‰, δ(34)S: -1.2 to 9.9‰). Within Europe, we detected differences in hair δ(13)C and δ(34)S values among countries and covariation of isotope ratios with latitude and longitude. This geographic structuring of isotopic data suggests heterogeneity in the food resources used by citizens of industrialized nations and supports the presence of different dietary patterns within Western Europe despite globalization trends. Here we showed the potential of stable isotope analysis as a population-wide tool for dietary screening, particularly as a complement of dietary surveys, that can provide additional information on assimilated macronutrients and independent verification of data obtained by those self-reporting instruments.

Published datasets of proteinaceous animal tissues suggest that co-variation between amino acid hydrogen (δ²H) and oxygen (δ¹⁸O) isotope ratios is a common feature in systems where isotopic variation is driven by geographic or temporal variation in the δ²H and δ¹⁸O values of environmental water. This has led to the development of models relating tissue δ²H and δ¹⁸O values to those of water, with potential application in a number of fields. However, the strength and ubiquity of the influence of environmental water on protein isotope ratios across taxonomic groups, and thus the relevance of predictive models, is an open question. Here we report strong co-variation of δ²H and δ¹⁸O values across a suite of terrestrial and aquatic animal meats purchased in American food markets, including beef, poultry (chicken and turkey), chicken eggs, pork, lamb, freshwater fish, and marine fish. Significant isotope co-variation was not found for small collections of marine bivalves and crustaceans. These results imply that isotopic signals from environmental water were propagated similarly through most of the diverse natural and human-managed foodwebs represented by our samples. Freshwater fish had the largest variation in δ²H and δ¹⁸O values, with ranges of 121‰ and 19.2‰, respectively, reflecting the large isotopic variation in environmental freshwaters. In contrast marine animals had the smallest variation for both δ²H (7‰ range, crustaceans) and δ¹⁸O (3.0‰ range, bivalves) values. Known-origin beef samples demonstrated direct relationships between the variance of environmental water isotope ratios and that of collected meats.

Stable isotopes provide an independent assessment of paleoenvironments in the Omo-Turkana Basin. Stable isotopes track the flow of oxygen and carbon through ecosystems and accordingly are not directly related to changes in mammalian faunal composition or sedimentology. Therefore, isotope studies give insight into the paleoenvironmental conditions in which human evolutionary trends have been recorded. The development of stable isotopes as indicators of continental environmental conditions has proceeded in parallel with questions about the conditions of human environment. What was the vegetation? How hot was it? How dry? What were the diets of animals living among early humans? And most persistently, how important were "savannas" to early hominids? In this review, we take the opportunity to provide extensive background on the use of isotopes in anthropological sites. The application of stable isotope ecology to anthropological sites in the Turkana Basin has a long history, but in many ways the Omo-Turkana Basin has been a proving ground for the development of new proxy methods for understanding tropical terrestrial environments in the Neogene and Quaternary. For that reason, we also describe some of the fundamental aspects of isotope ecology that developed outside the field of paleoanthropology., (Copyright © 2011 Wiley Periodicals, Inc.)

The role of African savannahs in the evolution of early hominins has been debated for nearly a century. Resolution of this issue has been hindered by difficulty in quantifying the fraction of woody cover in the fossil record. Here we show that the fraction of woody cover in tropical ecosystems can be quantified using stable carbon isotopes in soils. Furthermore, we use fossil soils from hominin sites in the Awash and Omo-Turkana basins in eastern Africa to reconstruct the fraction of woody cover since the Late Miocene epoch (about 7 million years ago). (13)C/(12)C ratio data from 1,300 palaeosols at or adjacent to hominin sites dating to at least 6 million years ago show that woody cover was predominantly less than ∼40% at most sites. These data point to the prevalence of open environments at the majority of hominin fossil sites in eastern Africa over the past 6 million years.