Proceedings of the National Academy of Sciences of the United States of America

Proc Natl Acad Sci U S A. 115(52): 13330-13335

Dietary versatility of Early Pleistocene hominins

http://orcid.org/0000-0002-9165-2586Tina Lüdeckea¹, Ottmar Kullmerbc, Ulrike Wackerd², Oliver Sandrocke, Jens Fiebigad, Friedemann Schrenkbc, Andreas Mulchad

aSenckenberg Biodiversity and Climate Research Centre, 60325 Frankfurt, Germany;

bDepartment of Paleoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, 60325 Frankfurt, Germany;

cInstitute for Ecology, Evolution and Diversity, Department of Paleobiology and Environment, Goethe University, 60439 Frankfurt, Germany;

dInstitute of Geosciences, Goethe University, 60438 Frankfurt, Germany;

eEarth- and Life History, Hessisches Landesmuseum, 64283 Darmstadt, Germany

¹To whom correspondence should be addressed. Email: tina.luedecke@senckenberg.de.

Edited by Thure E. Cerling, University of Utah, Salt Lake City, UT, and approved November 5, 2018 (received for review June 1, 2018)

Author contributions: T.L., O.K., F.S., and A.M. designed research; T.L. performed research; T.L., U.W., and J.F. contributed new reagents/analytic tools; T.L. analyzed data; and T.L., O.K., O.S., F.S., and A.M. wrote the paper.

²Present address: Thermo Scientific GmbH, 28199 Bremen, Germany.

Copyright © 2018 the Author(s). Published by PNAS.

DOI: 10.1073/pnas.1809439115

Published in print: 26 December 2018

Published online: 10 December 2018

Significance

Clumped and stable isotope data of paleosol carbonate and fossil tooth enamel inform about paleoenvironments of Early Pleistocene hominins. Data on woodland- vs. grassland-dominated ecosystems, soil temperatures, aridity, and the diet of Homo rudolfensis and Paranthropus boisei ca. 2.4 Ma show that they were adapted to C₃ resources in wooded savanna environments in relatively cool and wet climates in the Malawi Rift. In contrast, time-equivalent Paranthropus living in open and drier settings in the northern East African Rift relied on C₄ plants, a trend that became enhanced after 2 Ma, while southern African Paranthropus persistently relied mainly on C₃ resources. In its early evolutionary history, Homo already showed a high versatility, suggesting that Pleistocene Homo and Paranthropus were already dietary generalists.

Abstract

New geochemical data from the Malawi Rift (Chiwondo Beds, Karonga Basin) fill a major spatial gap in our knowledge of hominin adaptations on a continental scale. Oxygen (δ¹⁸O), carbon (δ¹³C), and clumped (Δ₄₇) isotope data on paleosols, hominins, and selected fauna elucidate an unexpected diversity in the Pleistocene hominin diet in the various habitats of the East African Rift System (EARS). Food sources of early Homo and Paranthropus thriving in relatively cool and wet wooded savanna ecosystems along the western shore of paleolake Malawi contained a large fraction of C₃ plant material. Complementary water consumption reconstructions suggest that ca. 2.4 Ma, early Homo (Homo rudolfensis) and Paranthropus (Paranthropus boisei) remained rather stationary near freshwater sources along the lake margins. Time-equivalent Paranthropus aethiopicus from the Eastern Rift further north in the EARS consumed a higher fraction of C₄ resources, an adaptation that grew more pronounced with increasing openness of the savanna setting after 2 Ma, while Homo maintained a high versatility. However, southern African Paranthropus robustus had, similar to the Malawi Rift individuals, C₃-dominated feeding strategies throughout the Early Pleistocene. Collectively, the stable isotope and faunal data presented here document that early Homo and Paranthropus were dietary opportunists and able to cope with a wide range of paleohabitats, which clearly demonstrates their high behavioral flexibility in the African Early Pleistocene.

Dietary adaptations are responsible for significant behavioral and ecological differences among humans and other primates (1, 2). Early hominin diets in Africa before 4 Ma were dominated by C₃ resources and diversified over time (3). Increasing contributions of C₄ plants were triggered by biomes gradually shifting to more open C₄ grasslands since the Late Miocene (4–8). In eastern Africa, dietary versatility was very likely an integral part of early hominin adaptations to open landscapes (7, 9–12), yet it is unclear whether this assumption holds for African Early Pleistocene hominin evolution in general.

Here, we present multiproxy carbon (δ¹³C), oxygen (δ¹⁸O), and clumped (Δ₄₇) isotope data focusing on paleoenvironmental patterns and diets of Paranthropus boisei and Homo rudolfensis. Both hominin taxa coexisted around 2.4 Ma in the Western (Malawi) Branch, the southern part of the East African Rift System (EARS), a region representing a large geographical gap in our knowledge of Early Pleistocene hominin adaptations on a continental scale (13–16). Paleosol development characterizes the lacustrine and deltaic deposits of the Chiwondo Beds (Karonga Basin, northern Malawi) (16). These deposits yielded remains of H. rudolfensis at Uraha (17) and Mwenirondo (15), as well as Paranthropus remains at Malema, which were assigned to P. boisei due to, for example, tooth morphology and palatal height (18). Collectively, these hominin localities of the Chiwondo Beds are less than 50 km apart and are situated today in the Zambesi Ecozone of the African Savannas just south of the boundary to the Somali-Masai Ecozone, and hence outlining the southernmost extent of the Intertropical Convergence Zone. Given this unique location, the Chiwondo Beds data are crucial for understanding hominin–environment interactions and are broadening our view on habitat flexibility and dietary adaptation in early hominins.

The Karonga Basin lies in the southeastern African hominin corridor region, connecting eastern and southern African endemic faunal zones (19). Hominins thriving in these faunal zones indicate different behaviors: Eastern African Paranthropus robustus had a mixed to C₄-dominated diet around 2.4 Ma, while P. boisei, younger than 2 Ma, provides robust evidence for C₄-dominated consumption in this region. This clearly distinguishes them from age-equivalent southern African P. robustus, which shows mixed or C₃-dominated diets (20–23). Early Homo had a highly variable diet, including C₃ and C₄ resources (3, 6).

In contrast to the mostly open C₄ grasslands of the northern EARS, the Malawi Rift was dominantly covered by persistent wooded savannas throughout the Plio-Pleistocene (24). Despite exhibiting a woody cover exceeding 60% and only regional patches of open C₄ grasslands (24, 25), this part of the EARS was populated by early P. boisei and H. rudolfensis, pointing to a much broader dietary versatility of early East African P. boisei than previously assumed.

We utilize a multiproxy approach for reconstructing habitats and diets during the earliest phases of coexisting Homo and Paranthropus in the Malawi Rift. Our study of δ¹³C and δ¹⁸O values in tooth enamel of H. rudolfensis and P. boisei provides insight into dietary preferences, flexibility, and adaptation in variably open and closed savanna environments. In contrast, intratooth δ¹³C and δ¹⁸O time series from contemporaneous equids (Eurygnathohippus sp.) and bovids [Alcelaphinae (Alc.) Megalotragus sp.], in addition to δ¹³C and δ¹⁸O data from pedogenic carbonate of the hominin fossil sites, allow the reconstruction of vegetation patterns (25, 26). The Δ₄₇ data from paleosols of the hominin fossil sites are from the southern part of the EARS and provide insight into regional temperature differences during the time of early hominin evolution. Our results show that early hominins must have been able to adapt to different environmental settings and diets as early as 2.4 Ma, indicating high behavioral flexibility already in the early stages of hominin evolution, as first indicated by, for example, Turkana Basin Kenyanthropus platyops individuals at 3.4–3.0 Ma (3).

Results

We report δ¹³C and δ¹⁸O data from tooth enamel of all three Chiwondo Bed hominin individuals, as well as age-equivalent bovid (n = 2) and equid (n = 3) specimens [sample IDs stated according to the Hominin Corridor Research Project (HCRP), with location ID followed by the individual sample number]. We complement these by δ¹³C and δ¹⁸O (n = 199 samples) as well as Δ₄₇ thermometry (n = 12 samples) data of pedogenic carbonate. All samples originate from unit 3-A2 (ca. 2.5–2.3 Ma) of the Chiwondo Beds (27) in the Karonga Basin at the northwest margin of Lake Malawi. In addition, we present modern soil temperatures that were monitored at three locations (full shade, partial shade, and full sun) throughout a complete year (n = 26,280 measurements) in the depth of typical pedogenic carbonate precipitation within the region (∼40 cm below the surface). Results are shown in Figs. 1–3 and listed in SI Appendix, Tables S2–S8.

Fig. 1.View larger versionFig. 1. Intratooth δ¹³C and δ¹⁸O variations in equid and bovid teeth vs. distance from the crown; hence, time of tooth growth. The hominin tooth enamel sample quantity was too small to determine intratooth patterns; each sample averages almost the entire interval of enamel development. Bovids and equids were coexistent with the early hominins, and fossils were collected at the same localities. Different patterns indicate different migratory behavior of the individuals and/or seasonal changes. Eur., Eurygnathohippus; gen. indet., genus indeterminate.

Fig. 2.View larger versionFig. 2. δ¹³C, δ¹⁸O, and ∆₄₇ values for Karonga Basin paleosol carbonate from the 2.5- to 2.3-Ma-old hominin fossil sites of Malema (A) and Uraha (B). Definitions of biome abbreviations are provided in Fig. 4. The black line shows modern MAAT.

Fig. 3.View larger versionFig. 3. Mean monthly soil temperatures (circles) measured for this study (2016/2017) with day and night air temperatures (diamonds), mean precipitation (blue), and average sunshine hours (orange) (32). Soil temperatures (columns on the left represent the complete temperature span of the full year in the respective color) generally follow air temperature patterns and correlate with sunshine hours, especially in soil directly exposed to the sun; here, the soil is usually warmer than the air due to the effect of direct solar radiation. Bars at the left of the figure show the maximum range of measured soil temperatures at the different locations. Temp., temperature.

Hominin and Herbivore Tooth Enamel δ¹³C and δ¹⁸O Data.

H. rudolfensis.

Each tooth shows only a small range in δ¹³C and δ¹⁸O values, but the two individuals show a clear geochemical distinction in their tooth enamel, with a mean difference of 3.8‰ in δ¹³C and 2.5‰ in δ¹⁸O (Fig. 1).

The δ¹³C and δ¹⁸O values from the Uraha individual HCRP-U18-501 (n = 3) are −6.3‰, −6.0‰, and −5.3‰ (mean = −5.9‰, σ = 0.5‰, C₃/C₄ ratio = ∼65:35) and 25.9‰, 26.5‰, and 26.9‰ (mean = 26.4‰, σ = 0.5‰), respectively.

The δ¹³C and δ¹⁸O values from the Mwenirondo specimen HCRP-MR10-1106 (n = 3) are more negative, with δ¹³C values of −9.9‰, −9.8‰, and −9.5‰ (mean = −9.7‰, σ = 0.2‰, C₃/C₄ ratio = ∼95:5) and δ¹⁸O values of 23.6‰, 23.9‰, and 24.1‰ (mean = 23.9‰, σ = 0.2‰).

P. boisei.

The molar from the Malema individual HCRP-RC11-911 (n = 3) shows δ¹³C values of −7.0‰, −6.9‰, and −6.8‰ (mean = −6.9‰, σ = 0.1‰, C₃/C₄ ratio = ∼70:30). The δ¹⁸O values are 26.3‰, 26.8‰, and 27.2‰ (mean = 26.8‰, σ = 0.5‰).

Bovids (Alcelaphinae).

The Alcelaphini Megalotragus sp. molar HCRP-U18-401 (n = 9) from the H. rudolfensis fossil site has much more positive δ¹³C values compared with the hominins, with a range between −2.6‰ and 0.8‰ (mean = −1.7‰, σ = 1.3‰, C₃/C₄ ratio = ∼30:70). The δ¹⁸O values range between 26.3‰ and 28.4‰ (mean = 27.3‰, σ = 0.7‰).

The δ¹³C and δ¹⁸O values of Alc. genus and sp. indeterminate HCRP-RC11-595 (n = 19) from the P. boisei locality at Malema are generally even more positive than the Megalotragus sp. data; δ¹³C values range from 0.7 to 2.0‰ (mean = 1.5‰, σ = 0.4‰, C₃/C₄ ratio = ∼2:98). Only a slight positive shift of 1.3‰ is present in this very narrow range. The δ¹⁸O values show a curved pattern between 27.5‰ and 29.5‰ (mean = 28.5‰, σ = 0.5‰).

Equids (Eurygnathohippus sp.).

Similar to Alcelaphinae, a very narrow range in δ¹³C values and a larger variability in δ¹⁸O values characterize the stable isotope data of the three sampled Eurygnathohippus sp. teeth from different individuals, which show a clear geochemical distinction, especially in δ¹³C (Fig. 1).

The premolar of HCRP-U17-390 (n = 11) (location U17 is the same age and spatially correlated with H. rudolfensis from U18) has δ¹³C values between −1.2‰ and 0.2‰ (mean = −0.2‰, σ = 0.5‰, C₃/C₄ ratio = ∼15:85). The δ¹⁸O values are between 27.5‰ and 28.7‰ (mean = 28.1‰, σ = 0.3). HCRP-RC11-528 (n = 12) from the P. boisei site has δ¹³C values between −2.4‰ and −1.3‰ (mean = −1.9‰, σ = 0.4‰, C₃/C₄ ratio = ∼30:70) and δ¹⁸O values from 27.2 to 28.6‰ (mean = 28.1‰, σ = 0.5‰). HCRP-RC11-545 (n = 14) also shows more negative δ¹³C values than the other Eurygnathohippus sp., with a very narrow range from −5.7 to −5.0‰ (mean = −5.3‰, σ = 0.2‰, C₃/C₄ ratio = ∼50:50), while the δ¹⁸O values are generally more positive, between 29.0‰ and 30.3‰ (mean = 29.8‰, σ = 0.4‰).

Pedogenic Carbonate Δ₄₇ Temperatures.

Pedogenic carbonate Δ₄₇ temperatures from the H. rudolfensis site U18 (Uraha) range from 19 to 38 °C (mean = 28 °C, σ = 8.3 °C; n = 6). The dataset seems to be bimodal, with values grouping at relatively high temperatures (mean = 35 °C, σ = 2.2 °C; n = 3) and another cluster of low temperatures (mean = 21 °C, σ = 1.8 °C; n = 3). A trend over time (i.e., across the sampled fossil horizon) is not present.

Paleosol temperatures from the P. boisei site RC11 (Malema) show a smaller variation, with values between 22 °C and 29 °C (mean = 26 °C, σ = 2.9 °C; n = 6).

Karonga Basin soil water δ¹⁸O values (δ¹⁸OSW) were calculated using the δ¹⁸O values of the carbonate and their Δ₄₇ temperatures according to the methods of Kim et al. (28) and Kim and O’Neil (29), resulting in δ¹⁸OSW values between −5.4‰ and −1.5‰ (mean = 3.6‰, σ = 1.2‰ °C; n = 12).

Pedogenic Carbonate δ¹³C and δ¹⁸O Values.

Uraha.

The δ¹³C values of pedogenic carbonate from a soil profile at the H. rudolfensis site U18 (n = 52) range between −11.0‰ and −7.0‰ (mean = −9.1‰, σ = 0.8‰). The estimated fraction of woody cover (fwc) (5) ranges between 0.5 and 0.8. The corresponding δ¹⁸O values lie between 23.6‰ and 24.9‰ (mean = 24.3‰, σ = 0.3‰).

Malema.

The δ¹³C values of pedogenic carbonate from the P. boisei site RC11 (n = 147) cover a similar range as at the Uraha site, with δ¹³C values between −10.7‰ and −6.3‰ (mean = 8.5‰, σ = 1.1‰). The estimated fwc values range from 0.4 to 0.8. The δ¹⁸O values show a slightly larger variation than at the Uraha site, with values between 23.3‰ and 24.7‰, excluding one outlier with a value of 25.2‰ (mean = 24.1‰, σ = 0.4‰).

Correlation Between Stable and Clumped Isotope Data.

(Negative) correlation between datasets was determined by using the Pearson correlation coefficient. Statistically (negative) correlation is significant at the 95% level.

We observe a statistically relevant positive correlation between δ¹⁸O and δ¹³C values in the Uraha (P = 0.5) and Malema (P = 0.8) datasets, suggesting a higher fraction of woody cover during periods of wetter climates.

Reconstructed Δ₄₇ soil temperatures and δ¹⁸O and δ¹³C values show a strong negative correlation at the Malema site RC11 (P = −0.9 for δ¹⁸O and P = −0.8 for δ¹³C); hence, high (soil) temperatures coincide with a moister climate, which produces an even denser canopy cover serving as a buffer and resulting in less thermal loss at night. This is complemented by the small range in soil temperatures at this site (Fig. 5).

Modern Soil Temperatures.

Soil temperatures were measured hourly 40 cm below the surface under conditions of full shade, partial shade, and full sun (Fig. 3).

Full shade.

Over the course of 1 y (August 1, 2016 to July 31, 2017), soil temperatures in sandy soil under dense tree cover range from ca. 23 to 27 °C (mean = 26 °C, σ = 0.9 °C; n = 8,760). Temperature differences between day and night, as well as between dry and wet seasons, are relatively small (generally ca. 0.5 °C and 2 °C, respectively).

Partial shade.

Recorded soil temperatures (August 1, 2016 to July 31, 2017) show a range of 21 to 32 °C (mean = 27 °C, σ = 2.1 °C; n = 8,760) ∼50 m away from the full-shade location. Here, temperatures below 24 °C are limited to a few outliers (n = 98; i.e., 1%) during the wet season, probably due to extreme rainfall and resulting soil water saturation. Day/night differences at around 0.5 °C are comparable to the full-shade site, but the difference between dry and wet seasons is more pronounced, with almost 6 °C warmer soil temperatures during the end of the dry season.

Full sun.

Soil temperature loggers were put directly in the Chiwondo Bed sandy deltaic deposits at the open habitat of the Malema P. boisei site (RC11). The recorded temperatures (August 15, 2016 to August 14, 2017) are higher than at the locations of full shade and partial shade and range from 25 to 37 °C (mean = 31 °C, σ = 3.2 C; n = 8,760). Day/night temperature differences are >2 °C and increase during the rainy season, with maximum day temperatures of generally 36 °C contrasting with night temperatures, which regularly drop below 32 °C.

Discussion

Paleoenvironmental Reconstruction of H. rudolfensis and P. boisei Sites in the Karonga Basin.

The results of paleosol stable isotope geochemistry from the Karonga Basin hominin sites indicate woodland, bushland, and scrubland to grassy woodland environments characterized by 40–80% woody cover (Figs. 3 and 4 and SI Appendix, Tables S4 and S5) during the time of early hominin occupation at ca. 2.5–2.3 Ma. Reconstructed mean paleosol Δ₄₇ temperatures attain 26 °C for the Malema P. boisei (Malema) site and 28 °C at the Uraha H. rudolfensis (Uraha) site, which are similar to today’s partial shade soil temperatures in the region (Figs. 3 and 5). Especially the Malema Δ₄₇ temperatures (usually reflecting soil temperatures below 30 cm), which are considered to have a strong seasonal bias toward dry and warm periods when carbonate precipitation predominantly occurs, are relatively cool compared with the Eastern Rift paleosol temperature data of 2.8–1.8 Ma, which are typically in excess of 35 °C (30) (e.g., Turkana; Fig. 5), indicating that hominins thrived under different temperature conditions in different parts of the EARS during the Early Pleistocene.

Fig. 4.View larger versionFig. 4. Comparison of environmental proxies between the Malawi Rift and Eastern Rift. Biome cover, relative proportions of biomes based on paleosol δ¹³C values (5), and boundaries between biomes are described in SI Appendix. The Malawi Rift was dominated by a more wooded environment (in a generally moister and cooler climate; Fig. 5) during the time of early hominin evolution compared with the Eastern Rift.

Fig. 5.View larger versionFig. 5. Clumped isotope paleosol temperatures (○, with black lines representing the mean) from paleosol carbonates of the Karonga Basin (n = 12) vs. the Turkana Basin (n = 8) (30) between 2.8 Ma and 1.8 Ma. For direct comparison, the Turkana Basin ∆₄₇ data were recalculated to the absolute reference frame using the technique of Uno et al. (49) and the calibration of Cerling et al. (50) (SI Appendix, Table S1). Gray bars represent today’s minimum to maximum soil temperatures in 40 cm (Karonga Basin) or 50 cm (Turkana Basin), with the thick line as the overall mean. Turkana Basin soil temperatures are measured under sparse deciduous bush vegetation, while the thin lines in the Karonga Basin data represent mean temperatures of soils exposed to full sun (top), partial shade (middle), and full shade (bottom). Black stars show MAATs. Similar to modern data, reconstructed soil temperatures are generally lower in the Karonga Basin, which created a landscape with different (food) resources than in the hotter Turkana Basin. Temp., temperature.

The present-day Karonga Basin is characterized by a tropical savanna climate (31) with mean annual air temperatures (MAATs) of ∼25 °C and mean annual precipitation (MAP) of ∼1,170 mm·y⁻¹ (32), which results in the wooded savanna ecosystem of the Zambezian woodland savanna. The Turkana Basin, in contrast, is characterized by a hot desert/semiarid climate (31), with MAATs exceeding 29 °C and MAP < 200 mm (32), creating open savanna settings with dominantly C₄ grasses, similar to reconstructed landscapes in the Early Pleistocene (Fig. 4). Soils exposed to direct sunlight at both localities exhibit soil temperatures (>35 °C) that are typically warmer than measured air temperatures (5, 30) (Figs. 3 and 5), reflecting the effect of radiative heating under sparse canopy cover. This indicates that the generally lower Karonga soil temperatures during the Early Pleistocene were triggered, among other factors, by a higher fraction of woody cover in the southern part of the EARS. Complementary calculated Karonga Basin δ¹⁸Osoilwater data (depending on δ¹⁸O values of the carbonate and their Δ₄₇ temperature) show ca. 5‰ more negative average values than the Turkana data (30), pointing to a smaller effect of evaporation of the soil water in the southern part of the EARS. The δ¹⁸O values from Karonga Basin pedogenic carbonates are generally lower than data observed at most other African hominin sites (ref. 33 and references therein), which suggests more humid conditions and less influence of evaporation in the cooler and more wooded habitats of the Malawi Rift in contrast to those of eastern Africa.

Consequently, larger fractions of woody cover imply more shade, shelter, and dietary resources for early hominins in the Zambesi Ecozone in the Malawi Rift, accompanied by lower air temperatures during the dry season. Ecosystem diversity of the Pleistocene Karonga Basin is reflected by the high (<30 °C) reconstructed soil temperatures of individual pedogenic carbonates from the Uraha site, pointing to temporary direct sun exposure of the soil in a possibly patchy landscape (also ref. 25).

Intratooth δ¹³C variability (−5.7 to 2.0‰) of herbivorous mammals coexisting with H. rudolfensis and P. boisei indicate that both C₃ and C₄ vegetation was available for consumption, which permitted highly variable foraging strategies for migrating mammals (25). Alcelaphini and equids were able to either feed almost selectively on C₄ resources or exhibit mixed grazing and browsing foraging strategies (25) (Fig. 1). These migrating and often specialized feeders, however, do not necessarily reflect the dominant paleoenvironment, but typically select their dietary niche. On the contrary, (Pleistocene) suids are considered generalists, and suid enamel δ¹³C values hence average local resource δ¹³C variability. The δ¹³C tooth enamel data for Karonga Basin Plio-Pleistocene suids indicate a predominantly C₃ browsing diet during the time of early Homo sp. evolution (24) (Fig. 6). This suggests that early Karonga Basin hominins had access to a wide range of vegetation types, such as gallery forest near the freshwater sources and open C₄ grasslands in the more elevated or arid regions at the rift shoulders, providing a diverse spectrum in food supply and shelter (cf. refs. 24, 25).

Fig. 6.View larger versionFig. 6. δ¹³C values of hominin tooth enamel with respect to the age of the fossils. Karonga Basin Malawi H. rudolfensis and P. boisei of this study are compared with Homo sp., P. boisei, and P. aethiopicus of the Turkana Basin (3) and P. robustus from South Africa (20–23). The percentage of C₄ consumption is calculated using the method of Cerling et al. (5) and is explained in SI Appendix. Especially P. boisei of the Karonga Basin therefore had a diet much more influenced by C₃ intake than their younger Eastern Rift relatives, indicating an adaptation to more open environments in the Eastern Rift. Gray areas indicate δ¹³C values of coexiting suids for the Karonga Basin (16) (Left) and the Eastern Rift (49–56) (Right), reflecting a dominantly C₃ diet of Karonga Basin omnivores and a highly C₄-influenced diet of Eastern Rift ones, which, in turn, reflects the main vegetation type of the hominin sites.

Diets of Early H. rudolfensis and P. boisei in the Malawi Rift.

The δ¹³C values of the Karonga Basin hominins at ca. 2.4 Ma suggest variable, mixed diets with only small portions of C₄ intake (<40%; Fig. 6). Stable isotope geochemical data suggest that the two H. rudolfensis individuals showed different foraging strategies. HCRP-U18-501 was a mixed feeder with 60–70% C₃ resources, while HCRP-MR10-1106 fed almost exclusively on C₃ resources and had less than 6% C₄ intake (Fig. 6). This suggests an adaptation to versatile ecosystem parameters with varying types of food supply and/or selective foraging strategies. The coexisting P. boisei individual reflects a similar diet, where C₃ resources amounted to ca. 70%. Early Paranthropus in the Karonga Basin therefore relied heavily on the presence of woodland habitats.

The two analyzed hominin taxa are geochemically indistinguishable due to the relatively large spread in δ¹³C and δ¹⁸O values measured for the two individuals of H. rudolfensis and the fact that P. boisei isotope data lie within the same range (Figs. 1 and 6).

The δ¹³C values of Homo and Paranthropus point to food intake that consisted dominantly of C₃ resources, such as forest foods, while xeric plant foods [e.g., C₄ underground storage organs (USOs), such as tubers, corms, roots, and bulbs, but also sedges, termites (20, 34, 35), or C₄ grass leaves (36)] were not dominant. However, δ¹³C data alone may not decipher C₃ and C₄ resources of dietary patterns because plant-based, meat-based, and omnivore diets cannot be distinguished with this method (e.g., ref. 37).

The narrow range of soil water and paleosol carbonate δ¹⁸O values from the Karonga Basin hominin sites (Fig. 2) suggests relatively constant climatic conditions in the vicinity of paleolake Malawi. H. rudolfensis individual HCRP-MR-1106 shows the lowest δ¹⁸O values, while the δ¹⁸O values of H. rudolfensis HCRP-UR-501 and P. boisei HCRP-RC-911 overlap. The relatively low δ¹⁸O values in concert with the δ¹³C data render it likely that both hominin taxa had access to drinking water only little affected by evaporation (and associated ¹⁸O-enrichment). The δ¹⁸O values of the hominin teeth are generally lower than the δ¹⁸O values from coexisting bovids and equids (Fig. 1). The spread in δ¹⁸O values of tooth enamel of both Megalotragus sp. and Eurygnathohippus sp. is larger than the scatter measured for the hominin individuals. Migrating herbivores had access to different drinking water sources of distinct oxygen isotope compositions, whereas hominins probably remained rather stationary near freshwater sources, such as tributaries of paleolake Malawi.

Comparison with Other African Hominins.

Stable carbon isotope analysis of African hominins suggests an increasing intake of C₄ biomass between ca. 4.1 Ma and 1.4 Ma throughout eastern, southern, and central Africa (Fig. 6). While hominins prior to 4 Ma (e.g., Ardipithecus ramidus and Australopithecus anamensis) depended almost fully on C₃ resources, an expansion toward mixed diets that included C₄ resources is observed starting at 3.75 Ma [e.g., Australopithecus bahrelghazali, Australopithecus afarensis, K. platyops, Hominini indet (3, 4, 7, 20, 38–42)]. By ca. 2 Ma, the genus Homo had a highly variable mixed C₃/C₄ diet in the Turkana Basin, while P. boisei was characterized by a strongly C₄-dominated diet with only <25% C₃ intake (Fig. 6), pointing to a diet characterized by USOs and other C₄ resources. The evolution of (open) wooded C₄ grassland savannas in the Eastern Rift presents a very different ecological setting from the persistent wooded savanna environments of the Karonga Basin (24, 25) (Fig. 4). This indicates different feeding strategies of Homo sp. and Paranthropus sp. in the increasingly open grassland savannas of the Eastern Rift (3, 6), and is a potential key for understanding the dietary evolution of early hominins. H. rudolfensis HCRP-U18-501 had a similar diet as younger (ca. 2.3–1.4 Ma) Homo species from the Turkana Basin (3). The almost exclusive C₃ diet of individual HCRP-MR10-1106, however, is rarely observed in Pleistocene Turkana hominins; the widely variable diet of eastern African Homo sp. rarely includes such selected feeders (3) (Fig. 6), indicating an adjustment to the denser wooded landscape of the Malawi Rift and/or to the more open savanna landscapes in the Eastern Rift.

Based on the existing spatial and temporal coverage of P. boisei remains, P. boisei adopted a significantly different diet in the diverging biomes of the Eastern Rift and Malawi Rift, supporting an unexpected versatile adaptive behavior. This predicts significantly different feeding strategies of P. boisei in the Karonga Basin at ca. 2.4 Ma compared with Turkana Basin individuals dated <2 Ma, which consumed predominantly C₄ biomass (>40%) (6). The latter most likely relied heavily on the intake of sedges (37, 43). In contrast, the Karonga Basin P. boisei foraging strategies even involved a higher fraction of C₃ food resources than coexisting Turkana Basin Paranthropus aethiopicus, which, in turn, consumed less C₄ plants than the younger P. boisei in the same region (3, 6). South African P. robustus (Sterkfontein Valley and Gauteng; ca. 1.8–1.0 Ma) probably also lived in a woodland environment and had a similarly mixed diet like P. boisei in the Karonga Basin (3, 20–23).

Collectively, this points to an adaptive behavior toward increasing C₄ biomass consumption [e.g., sedges, termites (20, 37) if these were easily accessible] but an enduring C₃-dominated diet in wooded settings throughout the time of early hominin evolution. However, due to the lack of Karonga Basin hominins younger than 2 Ma and/or sufficient data of Eastern Rift hominins older than 2 Ma that thrived in a woodland-dominated ecosystem, it is difficult to determine if the adaptation could be a supraregional effect or the result of local ecosystem pressure.

Conclusions

Stable carbon and oxygen isotope data of hominin fossil tooth enamel from the Malawi Rift show that early (ca. 2.4 Ma) H. rudolfensis and P. boisei included a large fraction of C₃ food resources in their diets. Abundant C₃ resources were provided by relatively cool and well-watered wooded savanna ecosystems in the vicinity of paleolake Malawi in the southern part of the EARS. Younger (<2 Ma) Paranthropus individuals from the Eastern Rift incorporated an increasing amount of C₄ resources in hotter, more arid, and open savanna settings, while P. robustus maintained a C₃-dominated diet in the wetter and more mesic environments of southern Africa. Throughout the Early Pleistocene, Homo shows a high versatility in the diverse habitats of the EARS. H. rudolfensis and P. boisei were therefore dietary generalists, able to adapt to different paleohabitats, successfully utilizing a broad range of ecosystems, including freshwater environments near the tributaries to paleolake Malawi.

Methods

Teeth of three hominins, three equids, and two bovids temporarily housed in the Senckenberg Research Institute and from the Cultural and Museum Centre Karonga were sampled using a high-speed, rotary, diamond-tip drill to obtain 2.5–5 mg of enamel powder from each of the up to 19 samples per tooth. To remove organic and potential diagenetic carbonate, enamel was pretreated with 2% sodium hypochlorite solution for 24 h, followed by treatment with 1 M Ca-acetate acetic buffer solution for another 24 h (44). Additionally, 199 pedogenic carbonate nodules were analyzed. Then, 600–1,200 μg of pretreated enamel and 100–160 μg of untreated pedogenic carbonate material were reacted with 99% H₃PO₄ for 90 min at 70 °C in continuous flow mode using a Thermo Finnigan 253 mass spectrometer interfaced to a Thermo GasBench II. All analyses were performed at the Goethe University Frankfurt–Senckenberg Biodiversity and Climate Research Centre Stable Isotope Facility. Analytical procedures followed the technique of Spötl and Vennemann (44). Final isotopic ratios are reported versus VPDB (Vienna Pee Dee Belemnite; δ¹³C) and VSMOW (Vienna Standard Mean Ocean Water; δ¹⁸O); overall analytical uncertainties are better than 0.3‰.

Homogenized powder of 12 selected soil nodules measured for stable isotopes was additionally used for clumped isotope analyses, which were performed in the same laboratory. Untreated carbonate powder (5–15 mg) was digested in ≥106% H₃PO₄ at 90 °C for 15–30 min, using a semiautomated acid bath (45, 46). The produced CO₂ was cleaned by flowing through cryogenic traps at −80 °C before and after passage through a Porapak Q-packed gas chromatography column to remove traces of water and hydrocarbons (cf. refs. 45, 46). The purified CO₂ was analyzed using a Thermo Scientific MAT 253 gas source isotope ratio mass spectrometer dedicated to the determination of masses 44–49 in 10 acquisitions consisting of 10 cycles each, with an ion integration time of 20 s per cycle. Five to six replicates were run per carbonate sample. The best precision that can be achieved under these conditions is represented by the shot noise limit, which is 0.004‰ for n = 5 and 0.003‰ for n = 6. The Δ₄₇ values are reported in the absolute reference frame (47) and were processed according to the protocol of Fiebig et al. (48). Apparent carbonate crystallization temperatures were computed from measured Δ₄₇ values using the empirical calibration technique of Wacker et al. (46).

Soil temperatures (quoted accuracy of ±0.1 °C) were measured hourly using Voltcraft DL-101T USB-Temperature loggers, which were buried within polyethylene-plastic bottles ca. 40 cm below the surface in narrow trenches (∼15 cm wide), which were subsequently backfilled with the soil removed during excavation.

SI Appendix, Materials and Methods includes additional information on analytical procedures, data processing, dating, time interval recorded in enamel and pedogenic carbonate, isotope enrichment factors in mammals, stratigraphic information, and biome classifications used in this work.

Acknowledgments

We thank the Cultural Museum Centre Karonga, our local Malawian field crew, and the Malawian Government for the long-term cooperation with the HCRP. We particularly thank H. Simfukwe (Cultural Museum Centre Karonga) for assistance and hospitality. T.L. thanks U. Treffert, N. Löffler, K. Methner (Senckenberg Biodiversity and Climate Research Centre), and S. Hofmann (Goethe University Frankfurt) for laboratory support and H. Thiemeyer (Goethe University Frankfurt) for support in the field. The paper was greatly improved by the thoughtful comments of two anonymous reviewers. T.L. acknowledges funding by Deutsche Forschungsgemeinschaft Grant LU 2199/1-1.

Footnotes

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1809439115/-/DCSupplemental.

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

PMC Copyright Notice

The articles available from the PMC site are protected by copyright, even though access is free. Copyright is held by the respective authors or publishers who provide these articles to PMC. Users of PMC are responsible for complying with the terms and conditions defined by the copyright holder.

Users should assume that standard copyright protection applies to articles in PMC, unless an article contains an explicit license statement that gives a user additional reuse or redistribution rights. PMC does not allow automated/bulk downloading of articles that have standard copyright protection.

See the copyright notice on the PMC site, https://www.ncbi.nlm.nih.gov/pmc/about/copyright/, for further details and specific exceptions.

References

1. Ungar P, author. 1998;Dental allometry, morphology, and wear as evidence for diet in fossil primates. Evol Anthropol. 6:205–217

2. Fleagle J, author. 2013. Primate Adaption and Evolution. Academic; San Diego: 3rd Ed.

3. Cerling TE, et al., authors. 2013;Stable isotope-based diet reconstructions of Turkana Basin hominins. Proc Natl Acad Sci USA. 110:10501–10506. [PubMed]

4. Sponheimer M, et al., authors. 2013;Isotopic evidence of early hominin diets. Proc Natl Acad Sci USA. 110:10513–10518

5. Cerling TE, et al., authors. 2011;Woody cover and hominin environments in the past 6 million years. Nature. 476:51–56. [PubMed]

6. Cerling TE, et al., authors. 2011;Diet of Paranthropus boisei in the early Pleistocene of East Africa. Proc Natl Acad Sci USA. 108:9337–9341. [PubMed]

7. Levin NE, Haile-Selassie Y, Frost SR, Saylor BZ, authors. 2015;Dietary change among hominins and cercopithecids in Ethiopia during the early Pliocene. Proc Natl Acad Sci USA. 112:12304–12309. [PubMed]

8. Uno KT, et al., authors. 2018;Large mammal diets and paleoecology across the Oldowan-Acheulean transition at Olduvai Gorge, Tanzania from stable isotope and tooth wear analyses. J Hum Evol. 120:76–91. [PubMed]

9. Ungar PS, Grine FE, Teaford MF, authors. 2006;Diet in early Homo: A review of the evidence and a new model of adaptive versatility. Annu Rev Anthropol. 35:209–228

10. Teaford MF, Ungar PS, authors. 2000;Diet and the evolution of the earliest human ancestors. Proc Natl Acad Sci USA. 97:13506–13511. [PubMed]

11. Ungar PS, Grine FE, Teaford MF, authors. 2008;Dental microwear and diet of the Plio-Pleistocene hominin Paranthropus boisei. PLoS One. 3:e2044 [PubMed]

12. Scott RS, et al., authors. 2005;Dental microwear texture analysis shows within-species diet variability in fossil hominins. Nature. 436:693–695. [PubMed]

13. Bromage TG, Schrenk F, Zonneveld FW, authors. 1995;Paleoanthropology of the Malawi rift: An early hominid mandible from the Chiwondo Beds, northern Malawi. J Hum Evol. 28:71–108

14. Schrenk F, Kullmer O, Sandrock O, Bromage TG, authors. 2002;Early hominid diversity, age and biogeography of the Malawi-rift. J Hum Evol. 17:113–122

15. Kullmer O, et al., authors. 2011;New primate remains from Mwenirondo, Chiwondo Beds in northern Malawi. J Hum Evol. 61:617–623. [PubMed]

16. Lüdecke T, Thiemeyer H, authors. 2013;Paleoenvironmental characteristics of the Plio-Pleistocene Chiwondo and Chitimwe Beds (N-Malawi). J Palaeoecol Afr. 32:143–161

17. Schrenk F, Bromage TG, Betzler CG, Ring U, Juwayeyi YM, authors. 1993;Oldest Homo and Pliocene biogeography of the Malawi rift. Nature. 365:833–836. [PubMed]

18. Kullmer O, et al., authors. 1999;The first Paranthropus from the Malawi rift. J Hum Evol. 37:121–127. [PubMed]

19. Bromage TG, Schrenk F, authors. 1995;Biogeographic and climatic basis for a narrative of early hominid evolution. J Hum Evol. 28:109–114

20. Sponheimer M, et al., authors. 2005;Hominins, sedges, and termites: New carbon isotope data from the Sterkfontein valley and Kruger National Park. J Hum Evol. 48:301–312. [PubMed]

21. Sponheimer M, et al., authors. 2006;Isotopic evidence for dietary variability in the early hominin Paranthropus robustus. Science. 314:980–982. [PubMed]

22. Lee-Thorp J, Thackeray JF, van der Merwe N, authors. 2000;The hunters and the hunted revisited. J Hum Evol. 39:565–576. [PubMed]

23. Lee-Thorp JA, van der Merwe NJ, Brain CK, authors. 1994;Diet of Australopithecus robustus at Swartkrans from stable carbon isotopic analysis. J Hum Evol. 27:361–372

24. Lüdecke T, et al., authors. 2016;Persistent C₃ vegetation accompanied Plio-Pleistocene hominin evolution in the Malawi rift (Chiwondo Beds, Malawi). J Hum Evol. 90:163–175. [PubMed]

25. Lüdecke T, et al., authors. 2016;Stable isotope dietary reconstructions of herbivore enamel reveal heterogeneous wooded savanna ecosystems in the Plio-Pleistocene Malawi rift. Palaeogeogr Palaeoclimatol Palaeoecol. 459:170–181

26. Kohn MJ, Cerling TE, authors. 2002. . Stable isotope compositions of biological apatite. Phosphates. Geochemical, Geobiological, and Materials Importance, Reviews in Mineralogy and Geochemistry, eds Kohn MJ, Rakovan J, Hughes JM (Mineral Soc Am, Washington, DC), Vol 48, pp 455–488.

27. Kullmer O, author. 2008;The fossil suidae from the Plio-Pleistocene Chiwondo Beds of northern Malawi, Africa. J Vertebr Paleontol. 28:208–216

28. Kim S-T, O’Neil JR, Hillaire-Marcel C, Mucci A, authors. 2007;Oxygen isotope fractionation between synthetic aragonite and water: Influence of temperature and Mg²⁺ concentration. Geochim Cosmochim Acta. 71:4704–4715

29. Kim S-T, O’Neil JR, authors. 1997;Equilibrium and nonequilibrium oxygen isotope effects in synthetic carbonates. Geochim Cosmochim Acta. 61:3461–3475

30. Passey BH, Levin NE, Cerling TE, Brown FH, Eiler JM, authors. 2010;High-temperature environments of human evolution in East Africa based on bond ordering in paleosol carbonates. Proc Natl Acad Sci USA. 107:11245–11249. [PubMed]

31. Peel MC, Finlayson BL, McMahon TA, authors. 2007;Updated world map of the Köppen-Geiger climate classification. Hydrol Earth Syst Sci. 11:1633–1644

32. Climate-Charts.com, author. 2010. . Climate charts. Available at https://www.climate-charts.com/Locations/m/MW67423.html. Accessed October 2, 2017.

33. Levin NE, author. 2013. . Compilation of East Africa Soil Carbonate Stable Isotope Data. Available at get.iedadata.org/doi/100231. Accessed Feburary 16, 2018.

34. Sponheimer M, de Ruiter D, Lee-Thorp J, Späth A, authors. 2005;Sr/Ca and early hominin diets revisited: New data from modern and fossil tooth enamel. J Hum Evol. 48:147–156. [PubMed]

35. Sponheimer M, Lee-Thorp JA, authors. 2003;Differential resource utilization by extant great apes and australopithecines: Towards solving the C₄ conundrum. Comp Biochem Physiol A Mol Integr Physiol. 136:27–34. [PubMed]

36. Paine OCC, et al., authors. 2018;Grass leaves as potential hominin dietary resources. J Hum Evol. 117:44–52. [PubMed]

37. Dominy NJ, author. 2012;Hominins living on the sedge. Proc Natl Acad Sci USA. 109:20171–20172. [PubMed]

38. Wynn JG, et al., authors. 2013;Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia. Proc Natl Acad Sci USA. 110:10495–10500. [PubMed]

39. White TD, et al., authors. 2009;Macrovertebrate paleontology and the Pliocene habitat of Ardipithecus ramidus. Science. 326:87–93. [PubMed]

40. Sponheimer M, Lee-Thorp JA, authors. 1999;Isotopic evidence for the diet of an early hominid, Australopithecus africanus. Science. 283:368–370. [PubMed]

41. van der Merwe NJ, Thackeray JF, Lee-Thorp JA, Luyt J, authors. 2003;The carbon isotope ecology and diet of Australopithecus africanus at Sterkfontein, South Africa. J Hum Evol. 44:581–597. [PubMed]

42. Lee-Thorp J, et al., authors. 2012;Isotopic evidence for an early shift to C₄ resources by Pliocene hominins in Chad. Proc Natl Acad Sci USA. 109:20369–20372. [PubMed]

43. WoldeGabriel G, et al., authors. 2009;The geological, isotopic, botanical, invertebrate, and lower vertebrate surroundings of Ardipithecus ramidus. Science. 326:65e1–5

44. Spötl C, Vennemann TW, authors. 2003;Continuous-flow isotope ratio mass spectrometric analysis of carbonate minerals. Rapid Commun Mass Spectrom. 17:1004–1006. [PubMed]

45. Wacker U, Fiebig J, Schoene BR, authors. 2013;Clumped isotope analysis of carbonates: Comparison of two different acid digestion techniques. Rapid Commun Mass Spectrom. 27:1631–1642. [PubMed]

46. Wacker U, et al., authors. 2014;Empirical calibration of the clumped isotope paleothermometer using calcites of various origins. Geochim Cosmochim Acta. 141:127–144

47. Dennis KJ, Affek HP, Passey BH, Schrag DP, Eiler JM, authors. 2011;Defining an absolute reference frame for ‘clumped’ isotope studies of CO₂. Geochim Cosmochim Acta. 75:7117–7131

48. Fiebig J, et al., authors. 2016;Slight pressure imbalances can affect accuracy and precision of dual inlet-based clumped isotope analysis. Isotopes Environ Health Stud. 52:12–28. [PubMed]

49. Uno KT, et al., authors. 2011;Late Miocene to Pliocene carbon isotope record of differential diet change among East African herbivores. Proc Natl Acad Sci USA. 108:6509–6514. [PubMed]

50. Cerling TE, Harris JM, Leakey MG, authors. 2003. Isotope paleoecology of the Nawata and Nachukui formations at Lothagam, Turkana Basin, Kenya. Lothagam: The Dawn of Humanity in Eastern Africa. Leakey MG, Harris JM, editors. Columbia Univ Press; New York: p. 583–604

51. Semaw S, et al., authors. 2005;Early Pliocene hominids from Gona, Ethiopia. Nature. 433:301–305. [PubMed]

52. Harris JM, Cerling TE, authors. 2002;Dietary adaptations of extant and Neogene African suids. J Zool. 256:45–54

53. Bibi F, Souron A, Bocherens H, Uno K, Boisserie J-R, authors. 2012;Ecological change in the lower Omo valley around 2.8 Ma. Biol Lett. 9:20120890 [PubMed]

54. Drapeau MSM, et al., authors. 2014;The Omo Mursi formation: A window into the East African Pliocene. J Hum Evol. 75:64–79. [PubMed]

55. Morgan ME, Kingston JD, Marino BD, authors. 1994;Carbon isotopic evidence for the emergence of C₄ plants in the Neogene from Pakistan and Kenya. Nature. 367:162–165

56. Kingston JD, author. 2011. . Stable isotopic analyses of Laetoli fossil herbivores. Paleontology and Geology of Laetoli: Human Evolution in Context, Geology, Geochronology, Vertebrate Paleobiology and Paleoanthropology Series, ed Harrison T (Springer, Berlin), Vol 1, pp 293–328.

[Back]

Fig. 1.

Intratooth δ¹³C and δ¹⁸O variations in equid and bovid teeth vs. distance from the crown; hence, time of tooth growth. The hominin tooth enamel sample quantity was too small to determine intratooth patterns; each sample averages almost the entire interval of enamel development. Bovids and equids were coexistent with the early hominins, and fossils were collected at the same localities. Different patterns indicate different migratory behavior of the individuals and/or seasonal changes. Eur., Eurygnathohippus; gen. indet., genus indeterminate.

[Back]

[Back]

Fig. 2.

δ¹³C, δ¹⁸O, and ∆₄₇ values for Karonga Basin paleosol carbonate from the 2.5- to 2.3-Ma-old hominin fossil sites of Malema (A) and Uraha (B). Definitions of biome abbreviations are provided in Fig. 4. The black line shows modern MAAT.

[Back]

[Back]

Fig. 3.

Mean monthly soil temperatures (circles) measured for this study (2016/2017) with day and night air temperatures (diamonds), mean precipitation (blue), and average sunshine hours (orange) (32). Soil temperatures (columns on the left represent the complete temperature span of the full year in the respective color) generally follow air temperature patterns and correlate with sunshine hours, especially in soil directly exposed to the sun; here, the soil is usually warmer than the air due to the effect of direct solar radiation. Bars at the left of the figure show the maximum range of measured soil temperatures at the different locations. Temp., temperature.

[Back]

[Back]

Fig. 4.

Comparison of environmental proxies between the Malawi Rift and Eastern Rift. Biome cover, relative proportions of biomes based on paleosol δ¹³C values (5), and boundaries between biomes are described in SI Appendix. The Malawi Rift was dominated by a more wooded environment (in a generally moister and cooler climate; Fig. 5) during the time of early hominin evolution compared with the Eastern Rift.

[Back]

[Back]

Fig. 5.

Clumped isotope paleosol temperatures (○, with black lines representing the mean) from paleosol carbonates of the Karonga Basin (n = 12) vs. the Turkana Basin (n = 8) (30) between 2.8 Ma and 1.8 Ma. For direct comparison, the Turkana Basin ∆₄₇ data were recalculated to the absolute reference frame using the technique of Uno et al. (49) and the calibration of Cerling et al. (50) (SI Appendix, Table S1). Gray bars represent today’s minimum to maximum soil temperatures in 40 cm (Karonga Basin) or 50 cm (Turkana Basin), with the thick line as the overall mean. Turkana Basin soil temperatures are measured under sparse deciduous bush vegetation, while the thin lines in the Karonga Basin data represent mean temperatures of soils exposed to full sun (top), partial shade (middle), and full shade (bottom). Black stars show MAATs. Similar to modern data, reconstructed soil temperatures are generally lower in the Karonga Basin, which created a landscape with different (food) resources than in the hotter Turkana Basin. Temp., temperature.

[Back]

[Back]

Fig. 6.

δ¹³C values of hominin tooth enamel with respect to the age of the fossils. Karonga Basin Malawi H. rudolfensis and P. boisei of this study are compared with Homo sp., P. boisei, and P. aethiopicus of the Turkana Basin (3) and P. robustus from South Africa (20–23). The percentage of C₄ consumption is calculated using the method of Cerling et al. (5) and is explained in SI Appendix. Especially P. boisei of the Karonga Basin therefore had a diet much more influenced by C₃ intake than their younger Eastern Rift relatives, indicating an adaptation to more open environments in the Eastern Rift. Gray areas indicate δ¹³C values of coexiting suids for the Karonga Basin (16) (Left) and the Eastern Rift (49–56) (Right), reflecting a dominantly C₃ diet of Karonga Basin omnivores and a highly C₄-influenced diet of Eastern Rift ones, which, in turn, reflects the main vegetation type of the hominin sites.

[Back]