Scholarly article on topic 'Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna'

Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna Academic research paper on "Earth and related environmental sciences"

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Academic research paper on topic "Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna"

AUTHOR:

Nikolaas J. van der Merwe1

AFFILIATION:

1 Department of Archaeology, University of Cape Town, Cape Town, South Africa

CORRESPONDENCE TO:

Nikolaas van der Merwe

EMAIL:

nikolaas.vandermerwe@uct. ac.za

POSTAL ADDRESS:

Department of Archaeology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa

DATES:

Received: 12 Apr. 2013 Revised: 24 Jul. 2013 Accepted: 22 Aug. 2013

KEYWORDS:

carbon isotopes; oxygen isotopes; Olduvai fossils; moisture sources; vertebrate ecology

HOW TO CITE:

Van der Merwe NJ. Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna. SAfrJSci. 2013;109(11/12), Art. #2013-0105,14 pages. http://dx.doi.org/10.1590/ sajs.2013/20130105

© 2013. The Authors. Published under a Creative Commons Attribution Licence.

Isotopic ecology of fossil fauna from Olduvai Gorge at ca 1.8 Ma, compared with modern fauna

Light stable isotope ratios (513C and S180) of tooth enamel have been widely used to determine the diets and water sources of fossil fauna. The carbon isotope ratios indicate whether the plants at the base of the food web used C3 or C4 photosynthetic pathways, while the oxygen isotope ratios indicate the composition of the local rainfall and whether the animals drank water or obtained it from plants. The contrasting diets of two early hominin species - Homo habilis and Paranthropus boisei - of ca 1.8 Ma (million years ago) in Tanzania were determined by means of stable carbon isotope analysis of their tooth enamel in a previous study. The diets of two specimens of P. boisei, from Olduvai and Peninj, proved to be particularly unusual, because 80% of their carbon was derived from C4 plants. It was suggested that their diet consisted primarily of plants, with particular emphasis on papyrus, a C4 sedge. The dominance of C4 plants in the diet of P. boisei is a finding supported in another study of 22 specimens from Kenya. The isotopic ecology and diets of fossil fauna that were present at the same time as the two fossil hominin species are described here, in order to provide a fuller understanding of their contrasting diets and of the moisture sources of their water intake. This information was then compared with the isotopic composition of modern fauna from the same region of Tanzania. The carbon isotope ratios for both fossil and modern specimens show that the habitats in which these faunal populations lived were quite similar - grassland or wooded grassland. They had enough bushes and trees to support a few species of browsers, but most of the animals were grazers or mixed feeders. The oxygen isotope ratios of the fossil and modern fauna were, however, very different, suggesting strongly that the source of moisture for the rain in the Olduvai region has changed during the past 1.8 million years.

Introduction

The purpose of this article is to provide isotopic information on the ecology and diets of fossil fauna from Olduvai Gorge Beds I and II at ca 1.8 Ma, In order to provide an ecological context for the diets of two species of early hominins. Recent isotopic analyses of the tooth enamel of Homo habilis and Paranthropus boisei (formerly Zinjanthropus boisei, also Australopithecus boisei) showed that the two species had distinctly different diets.1"3

Three specimens of Homo habilis from Olduvai had, respectively, 23%, 27% and 49% of carbon derived from C4 plants, much like early hominins from South Africa4'6; their diets probably included grass-eating animals and/or insects. However, two specimens of P. boisei from Olduvai and Peninj had 77% and 81% of carbon derived from C4 plants. Because modern humans are limited to about 20-50% protein-rich foods for their energy requirements,7 it was suggested that the diet of P. boisei included a large component of C4 plants. As grasses, especially edible seeds, are highly seasonal at latitudes applicable to Olduvai, It was also suggested that the C4 sedge Cyperus papyrus, which was presumably available in the freshwater swamps at Lake Olduvai and Lake Natron (Peninj), may have been a major component in the diet of P. boisei. The very high contribution of C4 plants to the diet of this hominin has been confirmed by the isotopic analysis of 22 individuals from sites in Kenya that stretch over 700 km of the Rift Valley.3 The authors of the latter study suggested that P. boisei had a diet that comprised mostly C4 plants, without specifying whether these were grasses or sedges. An online comment on their article by Lee-Thorp8 supports the opinion that sedges were predominant in the diet. Recent publications provide further evidence to put these early hominin diets in context.910

An assessment of the isotopic ecology at Peninj and Olduvai during the presence of P. boisei cannot settle the argument about grasses and sedges in P. boisei's diet, but it can illuminate whether the environment was dominated by C4 plants and their consumers. This assessment is of particular importance at Olduvai around 1.8 Ma, for which the isotope values of the two hominins are available. In East Africa, C4 plants appeared in the Late Miocene and continued through the Pliocene,11'15 but did not become dominant until ca 1.8 Ma.16 At Olduvai, the carbon isotopes in palaeosol carbonates indicate that C4 plants made up about 40-60% of the biomass during the time of Beds I and II,17 but a preliminary study of the carbon isotopes in tooth enamel of fossil fauna indicate a much higher C4 component.16'18 An assessment of the isotopic ecology at Peninj was undertaken by measuring the carbon and oxygen isotopes In the tooth enamel of 40 specimens of fossil fauna from the Maritinane Type Section.2 These fossils were all grazers and the carbon isotopes were closely similar to those of modern fauna of related species from the modern Serengeti. The environment was essentially open grassland with very few trees. However, the fossil specimens were some 1.3 million years old, so the results do not provide information about the ecology of Olduvai at ca 1.8 Ma. It was noted that the S180 values of the Peninj fossils were distinctly negative, relative to the Vienna Pee Dee Belemnite (VPDB) standard, while those of the modern fauna were all positive. It was suggested that the moisture source of rain in this region had presumably changed during the past 1.3 million years; this suggestion Is addressed in detail here.

For this purpose, tooth enamel samples were obtained from 145 specimens of fossil fauna from Olduvai Gorge Middle Bed I (ca 1.785-1.83 Ma) and Lowermost Bed II (ca 1.75-1.83 Ma) and their 513C and 5180 values were measured. These values were then compared with those of 77 modern animals from six wildlife reserves, primarily Serengeti and Maswa, but also Lobo, Lukwati, Ugalla and Selous (Figure 1). Their carbon and oxygen isotope ratios were measured to illuminate their diets and water sources.

Figure 1: Map of Tanzania showing the six wildlife reserves from which modern fauna! specimens were collected, as well as Olduvai and Peninj.

Tooth enamel and stable light isotopes

The assessment of prehistoric diets and environments by means of isotopic analysis of bone has been developed over the past 30 years and Is widely used in archaeology19"21 (for review see Van der Merwe21). In the early development of this method, the major interest involved ,3C/12C ratios (613C values) in bone collagen, which provide a measure of the proportion of C3 and C„ plants at the base of the food web. However, collagen in bone has a limited lifetime, especially in hot and humid environments where organic materials deteriorate rapidly. The oldest hominin collagen specimens that have been analysed isotopically were those of Neanderthals from cold, dry caves.22'23 The fossilised faunal specimens from Olduvai contain no collagen, but carbon and oxygen isotopes can be measured in the mineral phase of their skeletons. The

earliest measurements on bone apatite were done on fossil bone,24'25 but tooth enamel has proved to be the most dependable material for isotopic analysis.26'27 Tooth enamel Is highly crystalline and resists alteration by carbonates in groundwater. Contaminating carbonates may precipitate in cracks in the tooth enamel, but this material is much more soluble than tooth enamel and is readily removed with dilute acetic acid.

Tooth enamel is a biological apatite with about 3% carbonate. With appropriate pretreatment, the carbon and oxygen isotope ratios of the carbonate can be measured with confidence to provide dietary information. The carbon isotope ratio is an average of the plants at the base of the food web, acquired by herbivores from eating the plants and passed along the food chain to omnivores and carnivores, with some

digestive differences between different species.28 The oxygen isotope ratio is a measure of the body water of an animal, acquired from plant water or from drinking water and is altered by the thermophysiology of the animal. The oxygen isotope ratio can contribute to dietary and environmental reconstructions9-29-30 and is particularly indicative of changes in humidity and aridity.31-33

To reach dietary conclusions based on carbon isotope ratios, it is necessary to determine the C3 and C4 end members for a given time and place. This determination is most readily achieved by measuring the tooth enamel 613C values of dedicated browsers and grazers. Giraffes, for example, rarely eat anything but C3 leaves of trees and shrubs, while alcelaphine antelope like the wildebeest concentrate on C4 grasses. At this point in time, dedicated browsing herbivores of the South African interior (whose tooth enamel the Cape Town laboratory has often analysed) have mean 513C values of -14.5%o, while dedicated grazers have mean values of -0.5%o. These values can be altered by changes in climate and in the atmosphere. The 'industrial effect' of the past 200 years, for example, substantially increased the C02 content of the atmosphere, as a result of fossil fuel burning, resulting in the S13C value of the atmosphere (and that of all plants) becoming more negative by 1.5%o. The 613C values of all modern specimens must consequently be corrected by adding 1,5%o to the measured number. Climatic changes that alter 513C values of plants include increased humidity, which may make the 513C values of C3 plants (but not C4) more negative by 2%o.34 Tropical forests provide an extreme example in this regard - their C3 plants (they have no C4 plants) have 513C values as much as 10%o more negative than those of plants growing in the open; this difference results from high humidity, low light and, especially, from recycled C02 produced by rotting leaf litter on the forest floor.35 In contrast, the 513C values may become more positive as a result of aridity and bright sunlight,36-37 while C4 plants may respond with slightly more negative values, as a result of the increased occurrence of enzymatic C4 subtypes that are adapted to such conditions.

The approximate ratio of C3 and C4 plants in the diet of herbivores can be arrived at by interpolating between the C3end member (100% C3 diet) and C4 end member (100% C4 diet) of the ecosystem under study, although there are some slight differences between different species that have the same diets.

Oxygen Isotope ratios in tooth enamel can help to understand certain elements of a local habitat. The primary source of oxygen In biological apatite is from water (drinking water or water in food) and from oxygen bound in food. The light 160 isotope evaporates more readily than the heavy 180 isotope, while the latter precipitates more readily. These characteristics have produced such localised effects as the water In modern East African lakes being enriched by 5-10%o compared to the waters flowing into them.17 Ultimately, the 180 content of water in an area depends on precipitation - or meteoric water (6180mw) - which decreases with distance from the source of moisture (an ocean or lake), increasing latitude, increasing altitude and decreasing temperature.3®-42 An example of the different moisture sources can be seen in East Africa, where 6180 values of waters in Kenya and Ethiopia differ by about 2-3%o.43 The 5180 value of leaf water derived from the same water source also varies with aridity, because of évapotranspiration.

The integrity of 513C and 5180 values in tooth enamel for a given time and place can best be judged by observing the pattern of results for all the animal species in the biome. A considerable database for the Plio-Pleistocene of Africa is available by now and can be used to judge the results of a given study. Browsing animals (C3 plant feeders) will have distinctly more negative 513C values than grazers (C4 plant feeders), with the most dedicated browsers and grazers differing by about 14%o. There is also a distinct pattern between different species of grazers, depending on the different amounts of C3 plants like forbs that are included in their diets. Wherever they have been compared, specimens of Damaliscus spp. (e.g. the tsessebe and topi) have more positive 613C values than Connochaetes spp. (wildebeest), which, in turn, have more positive values than Equus spp. (zebra). For oxygen isotopes, 5180 values of hippos are usually more negative than those of equids, because they

drink surface water that is closest to meteoric water and feed at night, when humidity Increases and plant 6180 decreases.44

Materials and methods

Samples of tooth enamel used for isotopic analysis In this study were removed from the tooth specimens at their location of storage. In the case of Olduvai Beds I and II, this sampling was done at the National Museum of Natural History in Arusha and at the Olduvai field station (Mary Leakey's old field camp, which has been expanded). Most of the teeth from Olduvai Beds I and II had been excavated by the Olduvai Landscape Paleoanthropology Project (OLAPP) - an international group of researchers who have been working at Olduvai during the midyear field season since 1989.45 Specimens from the OLAPP collections can be identified in Tables 1 and 2 on the basis of their catalogue numbers, which are in the format 95/43:156 (excavated 1995, trench 43, number 156). Some specimens from Mary Leakey's collection, which is stored at the Olduvai field station, were also sampled. These are from Bed II (Table 2), excavation sites FLK N and HWKE. In total, 145 faunal specimens were sampled from the collections of Olduvai Middle Bed I (ca 1.785-1.83 Ma) and Lowermost Bed II (ca 1.75-1.78 Ma).

The modern samples from the Serengeti National Park, Maswa Game Reserve (southern Serengeti), Lobo (northeast Serengeti) and Selous Game Reserve (southeast Tanzania) were obtained from collections at Seronera, the headquarters of Serengeti National Park, and from some of the other ranger stations in the park. A few specimens from Lukwati and Ugalla Game Reserves were sampled in Arusha at a taxidermy shop and at the Rock Art Centre. A collection of 77 modern bone specimens, primarily from Serengeti National Park which adjoins Olduvai, was also assembled (120 measurements).

Samples were removed from tooth specimens by using a variable speed drill with a dental diamond drill tip of 0.5-mm diameter. A sample of 3 mg enamel powder is sufficient for at least two isotopic analyses. This amount is the equivalent of about two sugar grains; if it is removed from a broken enamel edge, the sampling scar is usually invisible. By moving the drill tip along an enamel edge, broken along the length of a tooth, seasonal variations (particularly In 180) are averaged. The enamel powder was gathered on smooth weighing paper and poured into a small centrifuge vial with snap lid, in which all the subsequent chemical pretreatment was carried out at the Stable Light Isotope Facility of the University of Cape Town. The powder was pretreated with 1.5-2.0% sodium hypochlorite (to remove organic materials and humic acids), rinsed with water, and then reacted for 15 min with 0.1 M acetic acid (to remove readily dissolved carbonates).

After washing and drying, 1 mg of the enamel was weighed Into an individual reaction vessel of a Kiel II autocarbonate device (Thermo Electron Corporation, Bremen, Germany). The powder sample was reacted at 70°C with 100% phosphoric acid, which produces C02 from the carbonate in the enamel. This sample gas was cryogenically distilled and its isotope ratios were measured In a Finnegan MAT 252 ratio mass spectrometer (Thermo Electron Corporation, Bremen, Germany). The 613C and 5180 were calibrated against the international VPDB carbonate standard by using a calibration curve established from National Bureau of Standards standards 18 and 19, as well as by inserting internal laboratory standards of 'Lincoln limestone' and 'Carrara 2 marble' at regular intervals In the autocarbonate device. The precision of replicate analyses was better than 0.1 %o.

Results

The 613C and 5180 values for fossil fauna from Olduvai West Middle Bed I (Table 1) and Olduvai East Lowermost Bed II (Table 2) are combined in Figure 2 to illustrate the faunal community in the Olduvai region at ca 1.8 Ma. These values can be compared with the isotope ratios of modern fauna from the adjoining Serengeti National Park, plus some specimens from Maswa, Lobo, Ugalla, Lukwati and Selous wildlife reserves (Table 3, Figure 3). The 513C and 5180 values of the fossil and modern fauna are compared in Figures 4 and 5, respectively.

Table 1: Carbon and oxygen stable isotope ratios in tooth enamel of fossil fauna from Olduvai West Middle Bed I. [Stratigraphy: above Tuff 1B, 1.83 Ma; below 1.785 Ma].46

UCT no.______TZ £0.__0LAPP no. (year, trench, no.)_________Tooth 5"Q 5"0

ORDER: CARNIVORA

FAMILY: CANIDAE

Species: Canis mesomelas (black-backed jackal)

UCT7059 TZ150 96/57:862 LP, -7.3 -4.4

ARTIODACTYLA

SUIDAE

Phacochoerus modestus (cf. warthbg)

UCT7200 Ma 0.1 -1.4

UCT7186 M2 -0.3 0.1

Mean (s.d.),/1=2 -0.12(0.29) -0.65(0.01)

B0VIDAE

Sub-family: Reduncinae

Kobus sp.

UCT7056 TZ147 95/57:536 RMj -2.0 -1.4

UCT7057 TZ148 95/57:626 LM1'2 -5.0 -7.3

UCT7058 TZ149 95/57:621 RM"2 -3.8 -3.8

Mean (s.d.), n=3 -3.6(1.54) -4.17(2.95)

[These three specimens could be from one animal]

Hippotraginae

Hippotragus gigas

UCT7055 TZ146 96/65:443 RM3 -0.3 -3.0

Antelopinae

Gazellal Aepyceros (cf. large morph Grant's gazelle/ Im pala)

-1.54 TZ144 96/65:121 M3 0.1 -4.4

UCT7054 TZ145 96/57A:19 LM"2 -2.0 -1.2

Mean (s.d.), n=2 -1.76(0.30) -2.79(2.25)

Gazellal Antidorcas (cf. Thomson's gazelle/ springbok)

UCT7049 TZ140 96/65:287 LM1'2 -3.5 -3.1

UCT7050 TZ141 97/88:204 RM„ 0.7 -3.0

UCT7051 TZ142 96/65:481 RMa -4.1 -4.6

UCT7052 TZ143 95/57:863 RMla -1.9 -2.2

Mean (s.d.), n=4 -2.22(1.85) -3.21(0.97)

Alcelaphinae

Megalotragus sp.

UCT7037 TZ128 96/65:540 LM"2 -1.6 -3.7

Repeat -0.9 -3.5

UCT7038 TZ129 96/57A:18 M« -0.9 -4.8

UCT7039 TZ130 96/65:42 LM"2 1.7 -4.0

UCT7040 TZ131 96/65:480 M* 0.2 -5.4

Mean (s.d.), n=4 -0.29(1.31) -4.28(0.79)

Beatragusl Connochaetes (cf. wildebeest)

UCT7045 TZ136 96/65:148 RM"2 0.3 -5.7

UCT7046 TZ137 96/65:438 M"2 -1.1 -3.4

Repeat -1.1 -4.4

Repeat -1.1 -3.9

UCT7043 TZ132 96/88:67W M"2 0.2 -6.9

UCT7044 TZ133 96/88:73W RM"2 0.2 -4.0

Mean (s.d.), n=4 -0.11(0.66) -5.01(1.6)

Parmularius sp.

UCT7041 TZ132 96/65:286 LM"2 1.26 -2.50

UCT7042 TZ133 96/65:349 M* 1.09 -1.63

Mean (s.d.), /1=2 +1.17(0.12) -2.06(0.61)

Mean (s.d.), n=8 (all alcelaphines) +0.14(1.06) -4.21(1.44)

SQUAMATA

CROCODYLIDAE

Crocodylus niloticus

UCT7032 TZ123 96/57A:312 -2.7 -5.1

UCT7033 TZ124 96/57A:313 -3.1 -5.0

UCT7034 TZ125 96/57A187 -2.2 -5.0

UCT7036 TZ127 96/57A:75 -3.3 -6.3

Mean (s.d.),/1=4 -2.82(0.48) -5.36(0.64)

[These four specimens could be from one animal]

UCT7035 TZ126 96/57:491-2 -4.4 -7.6

Mean (s.d.), n=5 (all crocodiles) -3.14(0.82) -5.81(1.15)

Mean and standard deviation of 6"0 for 27 animals -4.95(1.83)

28 measurements from Olduvai West + 2 from Olduvai East are included in the table.

6'3C and 6 "0 values for individual specimens have been rounded off to 0.1 but mean and s. d. are based on original measurements.

In the column headings, the UCT numbers refer to the database of the Stable Light Isotope Facility in the Archaeology Department at the University of Cape Town; TZ numbers are from the author's field collection of specimens from Tanzania; and OLAPP numbers are from the excavations of the Olduvai Landscape Paleoanthropology Project.

Table 2: Carbon and oxygen stable isotope ratios in tooth enamel of fossil fauna from Olduvai East Lowermost Bed II (plus three hippos from Lower Bed II). [Stratigraphy: overlying Tuff 1F: 1.75-1.78 Ma].

UCT no. TZ no. 0LAPP no. (year, trench, no.) Tooth 5"C 6"0

ORDER: CARNIVORA

Family: CANIDAE

Hyaenid

UCT7016 TZ107 95/43:157 LP3 -1.3 -5.7

UCT7017 TZ108 89/3:106 RP, -2.5 -5.8

Mean (s.d.), n=2 -1.9(0.85) -5.73(0.03)

Acinonyx sp. (cf. cheetah)

UCT7018 TZ109 95/44:158 LI, -2.0 -4.8

Lycaon sp. (ct. wild hunting dog)

UCT7019 TZ110 LP2 -2.4 -7.88

UCT7020 TZ111 LM, -1.9 -6.66

Mean (s.d.),/7=5 -2.02(0.48) -6.168(1.15)

PR0B0SCIDEA

ELEPHANTIDAE

Elephas recki (grazing elephant)

UCT9936 TZ179 HWKE/104.4 L1 Juvenile? 2.3 -1.8

GRID3A

UCT9937 TZ180 HWKE/104.4L1 Deciduous 1.3 -2.0

UCT9937 TZ180F HWKE/104.4L1 Fragments of TZ180 0.4 -2.7

Mean (s.d.), /7=3 + 1.3(1.0) -2.2(0.5)

Deinotherium bozasi

UCT9938 TZ181 HWK E/104.4L1 Fist size tooth -11.1 -4.4

Grid 3A:35

UCT9938 TZ181 Repeat measurement -11.0 -4.3

-11.1 -4.3

UCT9939 TZ182 HWK E/104.4L1:36 Probably same animal as TZ181 -10.2 -5.8

UCT9939 TZ182 Repeat measurement -10.4 -5.7

Mean (s.d.),n=4 -10.68(0.42) -5.04(0.83)

Mean (s.d.), /7=2 animals -10.76(0.4) -4.9(0.78)

PERISSODACTYLA

EQUIDAE

Equus olduwayensis

UCT7561 TZ59 94/34:474 pym, 0.5 -2.0

UCT7563 TZ61 94/27:47 M* 0.2 -2.8

UCT7564 TZ62 94/27:47 M* -0.6 -2.3

TZ61 and TZ62 are the same tooth; mean: -0.4 -2.6

UCT7565 TZ63 94/34:222 M, -0.2 -2.5

UCT7566 TZ64 94/34:780 M, 1.4 -1.9

UCT7568 TZ65 94/53:85 1.0 -1.8

UCT7569 TZ66 95/44:1508 m1 -0.8 -3.7

UCT7573 TZ70 94/21:229 M* 0.7 -3.3

UCT7575 TZ72 94/34:230 -1.7 -3.0

Mean (s.d.),/7=8 +0.01(0.9) -2.59(0.6)

Equus olduwayensis?

UCT9940 TZ184 HWKE/104.2L8 Mx 2.7 -3.1

Equid (no species Identification)

UCT9941 TZ185 HWK E/104.4L1:7 3.0 1.1

Hipparion sp.

UCT7572 TZ69 94/39:4 M3 1.0 -5.3

UCT7001 TZ92 89/3:105 lp;m, -1.8 -4.5

Mean (s.d.),/7=2 -0.4(2.0) -4.9(0.6)

Ambiguous (small morph)

UCT7559 TZ57 95/43:496 m* -1.2 -2.8

UCT7560 TZ58 95/43:644 m* 0.9 -2.1

UCT7562 TZ60 94/21:302 i -0.4 -3.8

UCT7570 TZ67 95/43:655 M3 1.9 -1.7

UCT7571 TZ68 95/43:? 1.2 -4.0

UCT7574 TZ71 95/43:645 M* -0.2 -2.8

Mean (s.d.),/7=6 +0.37(1.16) -2.9(0.9)

All equids,/7=18 0.36(1.32) -2.75(1.30)

ARTIODACTYLA

HIPPOPOTAMIDAE

Hippopotamus gorgops

UCT7180 TZ01 94/21:321-26 ? 1.8 -6.2

UCT7199 TZ02 95/43:650 p3/4 1.4 -6.0

UCT7239 TZ03 94/34:5 ? 0.9 -4.3

UCT7185 TZ04 95/45:283 P/M -0.8 -5.4

UCT7225 TZ05 94/34:18 ? 1.7 -3.8

UCT7423 TZ06 94/21:220 ? 0.6 -2.4

UCT7181 TZ07 94/34:420 Tusk -0.8 -4.2

Continued on next page

UCTno. TZ no. OLAPP no. (year, trench, no.) Tooth 5"C 61,0

UCT6982 TZ73 97/98:36 ? 0.5 -5.1

Mean (s.d.), /?=8 +0.66(1.0) -4.7(1.2)

LOWER BED II

Hippopotamus gorgops

UCT9952 TZ196 HWK E/104.4 Canine 2.2 -7.2

GRID 1C, L1:25

UCT9953 TZ197 HWK E/104.4 0.6 -5.7

GRID 1 A, L1:37

UCT9954 TZ198 HWK E/104.4 M,? -0.9 -3.6

GRID 1B, L1:11

UCT9954 Repeat -0.8 -3.8

Average UCT9954 -0.85 -3.7

Mean (s.d.), n=3 1.64(1.5) -5.53(1.7)

SUIDAE

Phacochoerus modestus

UCT7196 TZ14 94/27:321 P,.............. -1.5 -3.7

UCT6987 TZ78 94/35:16 ? -2.0 -2.9

UCT6988 TZ79 95/44:331-2 ? -1.1 -4.7

UCT7548 TZ47 94/27:48 RC -1.1 -2.4

UCT7547 TZ46 94/27:48 LC -1.5 -3.1

UCT7549 TZ48 94/27:48 0.0 -1.8

[TZ46-48 are from the same animal; means -0.9, -2.4]

Mean (s.d.), n=4

Kolpochoerus limnetes

-1.4(0.5)

-3.4(1.0)

UCT7191

95/45:327

UCT7428

95/45:328

UCT6990

95/45:202

Mean (s.d.), /)=3

-1.0(0.4)

-2.7(0.4)

[These three teeth from trench 45 could be from the same animal]

Kolpochoerus afarensis

UCT7230 TZ10 95/44:1509 ? -0.5 -3.0

UCT7240 TZ11 95/43:824 M' -1.9 -3.2

UCT6992 TZ83 95/44:659 P" -2.5 -7.0

UCT6993 TZ84 95/44:1516 LM' -3.1 -6.5

UCT6994 TZ85 97/44:670 RP1 -3.1 -6.0

UCT6995 TZ86 97/44:1511 RM' -2.2 -7.0

UCT6996 TZ87 97/44:1510 ? -0.5 -5.4

UCT6997 TZ88 97/100:169 P4 -2.2 -5.3

Mean (s.d.), /7=8 -2.0(1.0) -5.4(1.6)

[Teeth from Trench 44 could be from the same animal]

B0VIDAE

Reduncinae

Kobus sp. (cf. Waterhuck)

UCT7015 ! TZ'06 95/43:662 LM"2 -0.6 -4.4

Tragelaphinae

Tragelaphus strepsiceros (greater kudu)

UCT6983 TZ74 89/11:45 RM3 -2.4 -0.3

UCT6984 TZ75 89/11:41-46 LM. -5.7 -0.1

Tragelaphus scriptus (bushbuck)

UCT6985 TZ76 94/43:196 LM, -5.7 0.6

Tragelaphus oryx (eland)

UCT7237 TZ21 94/24:12 Mx -4.2 -2.2

Tragelaphus sp. (no species Identification)

UCT7201 TZ20 94/21:104 ID? M? -2.9 -3.8

UCT76986 TZ77 94/23:73 H:...... -9.2 0.3

Mean (s.d.), /7=6 -5.0(2.5) -1.0(1.7)

Alcelaphinae

Connochaetes / Beatragus (cf. wildebeest)

UCT7193 TZ30 95/43:330 M"2 3.3 -2.1

UCT7223 TZ31 94/34:284 M* 2.3 -2.5

UCT7188 TZ35 95/50:2 M* 2.1 -1.2

UCT7426 TZ39 95/44:332 p4 1.2 -3.4

UCT7224 TZ41 95/43:940 P4 2.4 -1.4

UCT7234 TZ42 95/43:331 M3? 4.0 -3.8

UCT7422 TZ43 95/45:198 M3 3.5 -0.1

UCT7043 TZ134 96/88:67W M"2 0.2 -6.9

UCT7044 TZ135 96/88:73W RM«2 0.2 -4.0

Mean (s.d.), /7=9 +2.13(1.38) -2.82(2.0)

Parmularius sp.

UCT6981 TZ33 94/34:79 2.0 -2.3

UCT7198 TZ36 95/50:11 ....... M, 2.1 -1.3

UCT7228 TZ37 95/44:325 .... Mifl. 2.5 -4.2

UCT7238 TZ38 95/44:334 P» 3.8 -1.1

Continued on next page

UCT no. TZ no. OLAPP no. (year, trench, no.) Tooth 813C 5,s0

UCT7184 TZ40 95/21:101-102 M,» 0.9 -1.6

UCT7545 TZ44 95/50:10 M,„ 1.3 -1.3

UCT6999 TZ90 95/44:21 RM„ 1.1 -1.1

UCT7000 TZ91 95/43:142 ™V . 1.7 -4.5

Mean (s.d.),/7=8 + 1.9(1.0) -2.2(1.4)

Megaiotragus?

UCT9942 TZ186 Tri 04.2L8C -3.1

Hippolraginae

Hippotragus gigas (cf. roan, sable antelope)

UCT7002 TZ93 95/43:487 RM3 0.7 -3.9

UCT7003 TZ94 95/43:141 Mx -0.7 -2.5

UCT9943 TZ187 Tri 04.2L8 ......p._______________ 0.5 0.2

UCT9944 TZ188 Tr104.2L8 1.3 1.0

UCT9946 TZ190 Tri 04.2L8 p. 0.2 -0.1

UCT9946 Repeat 0.2 -0.1

UCT9946 Average 0.2 -0.1

UCT9947 TZ191 Tri 04.2L8 M, 0.5 -0.1

UCT9948 TZ192 Tri 04.2L8C p. 1.1 1.0

UCT9949 TZ193 Tri 04.2L8C p. 1.2 0.1

UCT9950 TZ194 Tri 04.2L8C Pv 0.8 0.8

Mean (s.d.),/7=9 +0.54(0.58) -0.33(1.51)

Antelopinae

Gazella sp. [large morph, cf. Grant's gazelle/ Aepyceros (impala)]

UCT7007 TZ98 95/44:1278 m 0.2 -6.2

UCT7008 TZ99 95/44:904 LM,, .. -7.7 -1.9

UCT7006 TZ97 95/44:1325 M„ -9.0 -7.5

Mean (s.d.), n=3 -5.5(5.0) -5.2(2.9)

[Compare modern Impala from Maswa, 6"C =1.8]

Gazella sp. [small morph, cf. Thomson's gazelle/ Antidorcas (springbok)]

UCT7009 TZ100 95/43:156 ..........M„............... 1.2 -1.6

UCT7012 TZ103 95/3:107 RM"2 0.3 -4.7

UCT7014 TZ105 95/43:35 RM1« 0.0 -2.9

UCT7010 12101 95/43:147 LM^ -5.2 -3.4

UCT7011 12102 95/43:163 LMS -5.6 1.1

UCT7013 ÏZ103 95/44:1314 -9.1 -5.6

Mean (s.d.), n=6 ....... -3.1(4.2) -2.85(2.4)

[Compare modern Thomson's gazelle from Maswa, 613C = -5.7, -6.7; springbok species have been grazers (A. bondi) and browsers (A. marsupialis)]

GIRAFFIDAE

Giraffa sp.

UCT7187 ÏZ24 95/57:797 Juvenile -8.1 -1.2

UCT7197 TZ25 94/34:940 jumae? -8.1 -3.7

UCT7227 TZ26 94/34:951 -11.2 -1.6

Mean (s.d.), /7=3 -9.1(1.8) -2.2(1.3)

Sivatherium sp. (giant grazing giraffe)

UCT7429 TZ23 96/57:797 M, -1.3 0.2

UCT7546 TZ45 94/34:940 Mx -3.7 2.2

UCT6998 TZ89 94/34:951 M2 0.5 -2.7

Mean (s.d.), n=3 -1.5(2.1) -0.1(2.5)

SQUAMATA

CROCODYLIDAE

Crocodylus niloticus

UCT7226 TZ15 94/21:103 N/A -0.7 -5.1

UCT7236 TZ16 95/44:1257 N/A -3.3 -4.2

UCT7424 TZ17 95/44:1258 N/A -2.3 -5.1

UCT7182 TZ18 94/23:72 N/A 0.2 -3.8

UCT7192 TZ19 94/21:109 N/A -2.5 -5.7

UCT9955 1Z201 FLK N Tr112B:2 N/A -0.5 -4.3

UCT9956 ÏZ202 FLK N Tr112B:1 N/A -2.2 -5.3

UCT9957 TZ203 HWKE Tr104.2L8B:9 -2.4 -6.3

UCT9957 Repeat -2.2 -5.5

UCT9957 Average -2.3 -5.8

UCT9958 ÏZ204 HWKETrt 04.4:25 2.5 -3.4

UCT9958 TZ204F Fragments of TZ204 1.7 -2.8

UCT9958 Average 2.1 -3.1

UCT9959 TZ205 VEKIII:26 N/A 1.04 -3.73

Mean (s.d.), /¡=10 -1.05(1.76) -4.62(0.92)

Mean(s,d.) 6,a0 for 112 animals = -3.19 (2.18)

120 measurements are included in the table.

5"C and 5"0 values for individual specimens have been rounded off to 0.1 but mean and s.d. are based on original measurements.

In the column headings, the UCT numbers refer to the database of the Stable Light Isotope Facility in the Archaeology Department at the University of Cape Town; TZ numbers are from the author's field collection of specimens from Tanzania; and OLAPP numbers are from the excavations of the Olduvai Landscape Paleoanthropology Project.

South African Journal of Science yfj Volume 109 | Number 11/12

http://www.sajs.co.za U November/December 2013

Table 3: Carbon and oxygen stable isotope ratios in tooth enamel of modern fauna from Serengeti National Park and Maswa Game Reserve (southwest Serengeti), Lobo (northeast Serengeti), Selous Game Reserve (southeast Tanzania), Ugalla and Lukwati (southwest Tanzania)

UCT no. TZ no. Collection locus ............ Tooth S13C 5"0

Order: CARNIVORA

Family: FELIDAE

Panthera partus (leopard)

UCT7076 TZ167 (1) Lukwati RM' -11.2 2.5

UCT7077 TZ167 (2) Lukwati LM' -10.7 1.7

Mean (s.d.), n=2 -10.95(0.40) +2.1(0.59)

[TZ167 (1 ) and (2) are from the same animal]

Panthera leo

UCT9974 TZ220 Serengeti -4.0 -0.2

UCT9993 TZ239 Serengeti -5.0 0.1

UCT10015 TZ261 Serengeti -3.1 -2.2

Mean (s.d.), n=3 -4.04(0.98) -0.73(1.24)

HYAENIDAE

Crocuta crocuta (spotted hyaena)

UCT9994 TZ240 Serengeti ? N/A only organic

UCT10002 TZ248 Serengeti ? -5.2 -0.7

UCT10018 TZ264 Serengeti ? -3.1 -2.8

Mean (s.d.), n=3 -4.18(1.5) -1.76(1.5)

Lycaon pictus (wild hunting dog)

UCT10019 TZ265 Serengeti -4.2 0.3

PROBOSCIDEA

ELEPHANTIDAE

Loxodonta alricana

UCT10014 TZ260 Serengeti ? -11.9 -1.6

PERISSODACTYLA

EQUIDAE

Equus burchelli

UCT9983 TZ229 Serengeti 7 0.6 2.8

UCT9984 TZ230 Serengeti ? 0.5 1.7

UCT9985 TZ231 Serengeti ? 0.6 3.4

UCT9986 TZ232 Serengeti ? 1.2 2.3

UCT9987 TZ233 Serengeti ? 1.1 3.3

UCT9988 TZ234 Serengeti ? 0.8 1.5

Mean (s.d.),/7=6 0.77(0.3) 2.49(0.81)

UCT7079 TZ169 (1) Lukwati RM3 -0.7 -1.2

REPEAT TZ169 (1) Lukwati RM3 -1.4 -2.6

UCT7079 TZ169 (2) Lukwati LM3 -3.1 -3.7

REPEAT TZ169 (2) Lukwati LM3 -2.7 -3.0

Mean (s.d.), /7=4 -1.97(1.13) -2.5(0.87)

RHINOCEROTIDAE

Diceros bicornis (black rhino)

UCT10025 TZ271 Serengeti ? -15.9 -0.1

UCT10026 TZ272 Serengeti ? -11.8 -2.9

Mean (s.d.),/7=2 -13.856(2.9) -1.5(1.5)

ARTIODACTYLA

HIPPOPOTAMIDAE

Hippopotamus amphibius

UCT9964 TZ210 Serengeti ? -6.1 -0.2

GIRAFFIDAE

G iraffa camelopardalis

UCT9973 TZ219 Serengeti -12.8 4.4

UCT9995 TZ241 Serengeti -12.8 3.2

Continued on next page

UCT no. TZ no. Collection locus Tooth 6«C 6"0

UCT10060 TZ306 Serengetl •12.6 3.3

Mean (s.d.), n=3 -12.71(0.14) 3.59(0.66)

B0VIDAE

Syncerus caffer (buffalo)

UCT7071 TZ162 Maswa RM3 0.7 -0.8

UCT9967 TZ213 Serengeti 2.0 3.3

UCT9968 TZ214 Serengeti 1.9 2.6

UCT9969 TZ215 Serengeti 2.3 3.6

UCT9970 TZ216 Serengeti -0.4 4.5

UCT9971 TZ217 Serengeti -0.2 3.2

UCT9975 TZ221 Serengeti 0.2 2.1

UCT10000 TZ246 Serengeti 1.4 3.3

UCT10001 TZ247 Serengeti 0.5 2.3

Mean (s.d.),/7=9 0.93(1.0) 2.69(1.48)

Tragelaphus strepsiceros (greater kudu)

UCT7062 TZ153 Maswa LM3 -14.1 2.0

UCT7063 TZ154 Maswa RM3 -16.6 -3.5

Mean (s.d.),/7=2 -15.35(1.7) -0.78(3.9)

Tragelaphus imberbes (lesser kudu)

UCT7061 TZ152 Maswa RM2 -12.6 0.5

Tragelaphus scriptus (bushbuck)

UCT7069 TZ160 Maswa RM3 -14.8 1.5

UCT7070 TZ161 Maswa RM3 -15.4 -1.8

Mean (s.d.),/7=2 -15.11(0.4) -0.13(2.3)

Redunca redunca (Bohor reedbuck)

UCT1067 T7158 Maswa RM3 -1.0 0.4

Kobus ellipsiprymnus (common Waterhuck)

UCT7068 TZ159 Maswa LM3 0.5 -0.7

Hippotragus niger (sable)

UCT 7060 TZ151 Maswa RM3 0.2 -0.1

Hippotragus eguinus (roan)

UCT7078 TZ168 (1) Ugalla 1.6 -0.2

UCT7078 TZ168 (2) llgalla 2.1 0.5

Mean (s.d.),/7=1 (same animal) 1.87(0.33) 0.67(0.45)

Connochaetes taurinus (blue wildebeest)

UCT7065 TZ156 Selous RM3 2.1 -1.2

Connochaetes gnu (black wildebeest)

UCT9965 TZ211 Serengeti 2.5 2.5

UCT9966 TZ212 Serengeti 1.2 3.9

UCT9976 TZ222 Serengeti 1.4 3.1

UCT9977 TZ223 Serengeti 0.6 3.0

UCT9978 TZ224 Serengeti 1.3 4.8

UCT9978 TZ225 Serengeti 2.66 -1.24

Repeat 2.69 -0.71

Average 2.68 -0.98

UCT9980 TZ226 Serengeti 1.5 2.8

UCT9981 TZ227 Serengeti 2.7 2.9

UCT9982 TZ228 Serengeti 1.6 4.9

UCT9996 TZ242 Serengeti 1.9 5.6

Mean (s.d.), /7=10 1.74(0.71) 2.54(2.3)

Alcelaphus buselaphus (Kongonl, Coke's hartebeest)

UCT7064 TZ155 Maswa LM3 0.5 -0.7

UCT10023 TZ269 Serengeti -1.0 1.7

UCT10024 TZ270 Serengeti 2.2 1.4

Mean (s.d.),/¡=3 0.55(1.63) 0.78(1.31)

Continued on next page

UCT no. TZ no. Collection locus Tooth 813C 51B0

Alcelaphus lichtensteini (Lichtenstein's hartebeest)

UCT7075 TZ166 Lobo LM3 2.1 0.4

Repeat 2.4 -0.6

Average 2.25 -0.27

UCT7076 TZ166 (1) 1.6 3.7

UCT7076 TZ166X 1.9 3.6

Repeat TZ166X 1.9 1.1

Mean (s.d.), n= 1 + 1.79(0.21) 2.80(1.51)

Mean (s.d.), n=2 2.08(0.22) 0.39(0.9)

Damaliscus lunatus (topi)

UCT10005 TZ251 Serengeti -1.2 1.0

UCT10005 TZ251 Repeat -0.9 2.1

Average TZ251 -1.05 1.55

UCT9990 TZ236 Serengeti 2.1 4.6

UCT7066 TZ157 Maswa RMZ -2.3 -4.1

Mean (s.d.), n=3 -0.38(2.28) 0.71(4.4)

Aepyceros melampus (impala)

UCT7074 TZ165 Maswa RM3 1.8 1.0

UCT9992 TZ238 Serengeti -2.6 0.5

UCT9999 TZ245 Serengeti -2.3 3.0

Mean (s.d.), n=3 -1.04(2.45) 1.50(1.3)

Gazella thomsonii (Thompson's gazelle)

UCT10016 TZ262 Serengeti -1.3 4.8

UCT10016 Repeat -1.2 5.1

UCT10016 Average /7 = 1 -1.2 4.9

UCT10006 TZ252 Serengeti -0.9 5.2

UCT10007 TZ253 Serengeti -2.4 5.0

UCT10008 TZ254 Serengeti -2.8 4.8

UCT10013 TZ259 Serengeti -3.0 4.9

UCT7072 TZ163 Maswa RM3 -6.7 -0.9

UCT7073 TZ164 Maswa RM3 -5.7 -0.8

Mean (s.d.), n=7 -3.26(2.19) 3.29(2.85)

Gazella granti

UCT10020 TZ266 Serengeti -7.7 5.0

UCT10020 Repeat -7.8 5.1

UCT10020 Average -7.7 5.8

UCT10021 TZ267 Serengeti -11.7 3.5

UCT10021 Repeat -11.6 3.7

UCT10021 Average -11.7 3.6

UCT10022 TZ268 Serengeti -8.4 2.9

UCT10022 Repeat -8.3 3.1

UCT10022 Average -8.4 3.0

Mean (s.d.), n=3 -9.25(2.11) +4.14(1.47)

Ostrich eggshell

UCT10003 TZ249 Serengeti -10.2 6.7

Repeat -10.0 6.7

Repeat -9.8 6.8

Mean (s.d.), /7=3 -9.99(0.19) 6.71(0.06)

6,B0 mean for Serengeti animals (tooth enamel) only, n=50: +1.78 (2.56)

78 tooth enamel samples (72 animals) and 1 ostrich eggshell are included In the table. Most of these specimens were sampled from the collections in Serengeti National Park; the specimens from Ugalla and Lukwati were sampled at a taxidermist in Arusha.

6 "C and 6 "0 values for individual specimens have been rounded off to 0.1 but mean and s. d. are based on original measurements. To compare modern 613C values with those of fossil specimens, 1.5% should be added to correct for the industrial effect of the past 200 years.

In the column headings, the UCT numbers refer to the database of the Stable Light Isotope Facility in the Archaeology Department at the University of Cape Town; 7Z numbers are from the author's field collection of specimens from Tanzania.

Bed I: a Bed II:

Giraffldae: Glraffa

Bovldae: Tragelaphus

Giraffldae: Slvatherlum

Bovldae: Gazella

Bovidae: Gazella

Suidae: Phacochoerus

Equidae:

Canldae: Canis

i Elephantidae: Loxodonta

Crocodylidae: Crocodylus

Equus & Hipparion

Elephantidae: Elephas

Crocodylidae: Crocodylus

Canidae: Hyaenld, Acinonyx, Lycaon

Suidae: Phacochoerus í Kolpochoerus

Hlppopotamldae: Hippopotamus

(1) (2) Bovidae: Kobus, Connochaetes, Parmularius, Megalotragus & Hlppotragus

-12 -11 -10

-7 -6 -5

Figure 2: 513C and 5,80 values obtained from tooth enamel of fossil fauna from Olduvai Beds I and II.

Serengetl: • Maswa: » Selous: x Ugalla: » Lukwati: ■ Lobo:-'

Bovldae: Gazella

Giraffldae: Glraffa

Bovldae: Syncerus, Connochaetes, Alcelaphus, Damaliscus, Aepyceros

Felldae: Panthera

Equidae: Equus

Hippopotamldae: Hippopotamus

Bovidae: Gazella

Elephantidae: Loxodonta

Hyaenldae: Crocuta & Lycaon

Bovldae: Redunca, Kobus, Hlppotragus, Alcelaphus, Damaliscus, Aepyceros & Syncerus

Felidae: Panthera

I Equidae: Equus

Bovldae: Hippotragus

Bovidae: Alcelaphus

x Bovldae: Connochaetes

-17 -16 -15 -14 -13 -12 -11 -10 -9

-7 -6 -5 -4-3-2-10 1 2 3

613CHh

Figure 3: 513C and 6180 values obtained from tooth enamel of modern fauna from Serengeti, Maswa, Lobo, Ugalla, Lukwati and Selous wildife reserves.

Diceros bicornls

Giraffe sp

Giraffa camelopardalis Loxodonta africana

Demotherhtm bozasi Suids

Phacochoerus modestus Panthera leo

Carnivores ¡Hyaenid. Acinonyx) Crocuta crocuta Canis mesomelas

Hipparion sp. Gazella sp.

Megalotragus sp.

Equus burchelli

Equus oldowayensis

Hippopotamus sp.

Hippotragus gigas Crocodylus nilotlcus

Sephas sp.

Connochaetes gnu

Aicelaphines

(Ccnnochaetes/Beatragus S Parmularius sp.)

Legend: Modern: black ■; Bed I: grey a; Bed II: grey a

■ ■ 2

I—-f—I 5

A I ,f „ 9

H-H 10

-14 -13 -12 -11 -10 -9

-7 -6 -s -4 -3 -2 -1 o 1 2 3 4 5

S'3c.„

+ 7.5%o has been added to the modern values to correct for the industrial effect.

Figure 4: 5I3C from tooth enamel of modern fauna from the Serengeti (in black) and from fossil fauna from Olduvai Beds I and II at ca 1.8 Ma (in grey).

Diceros bicomis

Giraffa sp

Giraffa camelopardalis Loxodonta africana

Deinothehum bozasi Suids

Phacochoerus modestus Panthera leo

Carnivores fh/aenid. Acinonyx) Crocuta crocuta Cams mesomelas

Kobus sp.

Hipparion sp. Gazella sp.

Megalotragus sp.

Equus burchelli

Equus oldowayensis

Hippopotamus sp.

Crocodylus niloticus

Elephas sp.

Connochaetes gnu

Alcelaphines

{Connochaetes/Beatragus & Parmularius sp.)

2 Legend: Modern: black ■; Bed I: grey a; Bed II: grey t

A 2 ■ 2

a 1 ▲

-7 -6 -5

•H 10

-3 -2 -1 0 1 2 3 4 5 6

5,8CLh

Figure 5: S180 from tooth enamel of modern fauna from the Serengeti (In black) and from fossil fauna from Olduvai Beds I and II at ca 1.8 Ma (In grey).

In general, the carbon isotope ratios of the same or related species have stayed remarkably similar over 1.8 million years. The available plant foods have obviously stayed much the same. The oxygen isotope ratios, in contrast, have become enriched by some 6%o. One obvious difference can be found in the case of hippos: the 11 specimens of Hippopotamus gorgops from Beds I and II were dedicated grazers, while the single modern specimen of Hippopotamus amphibious from the Serengeti was a mixed feeder. Hippos are generally regarded as dedicated grazers, but this assumption is not correct"1 - they will eat C3 plants if grasses are not available nearby.

Carbon isotopes

The collection from Olduvai West Bed I is somewhat limited: the 27 specimens comprise 1 black-backed jackal, 6 crocodiles and 20 grazing animals (suids and bovids). No browsers are Included, which makes it impossible to determine the C3 end member of this faunal community. At the C4 end of the collection, the most positive S13C value is that of +1.1%o for two specimens of Parmularius (an alcelaphine). The 513C values from the Bed I specimens are very similar to those from the larger collection of 118 specimens from Bed II, which includes canids, suids, hippotragines, antelopines, alcelophines and crocodylids. The values for Beds I and II have been added together in the figures to represent the fossil fauna.

Olduvai Bed II is represented by 118 specimens, which provide a comprehensive view of the community at ca 1.8 Ma. The browsing end of the spectrum is represented by two specimens of Deinotherium bozasi (-11.05; -10.32), a giant browsing elephant with tusks growing from its lower jaw and bent downwards towards the ground. A specimen of giraffe, Giraffa sp. (probably gracilis), has a less negative S13C value of -9.1 %o. It is of interest that Elephas recki, an elephant species that occurred widely from East to southern Africa at this time, was clearly a grazer (5,3C = +1.3), while Sivatherium sp. (also Libytherium sp.), a short-necked grazing giraffe (513C = -1.5), was also present during Bed II times. These species of elephant and giraffe were later replaced by the modern dedicated browsing elephant, Loxodonta africana, and giraffe, Girafla camelopardis. The grazing end of the spectrum at Olduvai in Bed II times was represented by alcelaphines of the genera Beatragus/ Connochaetes (513C = +2.1), Parmularius (+1.9) and Megalotragus (+2.7). Based on these values and that of Deinotherium bozasi, one can estimate the 5,3C values for the C3 and C4 end members for Bed II at about -11.5%o and +2.5%o, respectively.

It should be noted that the Bed II specimens are clustered toward the grazing end of the spectrum with few browser representatives. This pattern is especially evident when the Bed II assemblage is compared with that of the modern Serengeti, which has a similar scarcity of browsers. It Is noteworthy that the tragelaphines (kudu, bushbuck and eland) from Bed II have a mean 513C value of -5.0%o. They were evidently mixed feeders, in contrast to the modern kudu and bushbuck from Maswa, which are dedicated browsers with a mean 513C value of-14.7%o.

The 513C values for modern fauna (Table 3) have not been corrected for the Industrial effect. In order to compare them with the S13C values for Olduvai Beds I and II, it is necessary to add 1.5%o. Figure 4 shows the corrected values.

The 513C values of modern animals (Table 3) represent several different biomes in Tanzania. This multi-representation is immediately obvious when one compares the 613C values for Equus burchelli (plains zebra) from Serengeti National Park (+0.8) with those from Lukwatl (-2.0). Lukwatl is located near Lake Rukwa, between Lakes Tanganyika and Nyasa, and its grazers clearly have more C3 plants in their diet. Similarly, the browsers from the Serengeti include the modern giraffe (Giraffa camelopardis, S13C = -12.7), elephant (Loxodonta africana, 513C = -11.9) and black rhino (Diceros bicornis, S13C = -13.9). Maswa Game Reserve, which borders Serengeti on the southwest side but Is much more wooded, is represented among the browsers by three tragelaphines: the greater kudu (Tragelaphus strepsiceros, 513C = -15.4), lesser kudu (T. imberbes, 513C = -12.6) and bushbuck (T. scriptus, S,3C = -15.1). The grazing end of the Serengeti spectrum is represented by Hippotragus equinus (roan antelope, 513C = +1.9), Connochaetes gnu (black wildebeest, 513C = +1.7) and Alcelaphus lichtensteini (Lichtenstein's hartebeest, 513C = +2.0). In calculating the C3 and C4 end members, the Serengeti specimens have been emphasised, yielding approximately -12.5 and +1.5. When corrected for the industrial effect, the end members are about-11.0 and +3.0. This result is similar to that from Olduvai Bed II; however, similarity does not mean that the plant communities of the two biomes were the same, only that the availability of C3 and C4 plants for browsers and grazers were similar.

In Figure 1, a selection of tooth enamel 513C values from Olduvai Bed II and the modern Serengeti are compared; the modern values have been corrected for the industrial effect. The results are extraordinarily similar, suggesting two similar landscapes of wooded grassland. The exception is a single S13C value for a modern hippo from the Serengeti, which is evidently a mixed feeder.

Oxygen isotopes

From the 6180 values reported in Tables 1, 2 and 3, it is clear that oxygen isotope ratios vary substantially with time and place. Among 27 measurements for Olduvai West Bed I (27 animals, Table 1) there Is only a single positive value for 5180. Among 124 measurements for Olduvai East Bed II (111 animals, Table 2) there are only 10 positive 6180 values. Among 77 measurements for 5180 in the tooth enamel of modern animals (74 animals, Table 3), 56 values are positive. This contrast is well illustrated in Figure 5, which shows that modern animals have 5180 values that are more positive than those of the fossil specimens by about 6%o. To be precise, the 50 animals from the Serengeti are 6.24%o more positive than 27 animals from Bed I and 5.56 more positive than those from Bed II (112 animals). Of the 21 negative 5180 values for modern animals, 9 are for animals from the Serengeti (out of 53 animals, exact location unknown), 8 are for animals from Maswa (out of 13 animals) and 2 are for animals from Lukwati (out of 4 animals).

As the body water of animals is largely controlled by the rain in the area, it is suggested that the source(s) of rain in the Serengeti, Maswa and Lukwati are different. This hypothesis is under Investigation, with the aim of establishing when the change in the rain source in the Olduvai/ Serengeti area occurred.

Conclusions

The stable carbon and oxygen isotope ratios of faunal tooth enamel at Olduvai and in the adjoining Serengeti National Park in Tanzania provide valuable Information about the environment in that region at ca 1.8 Ma and In modern times. In general, the carbon isotope ratios Indicate that the environment of Olduvai Bed I and II was very similar to that of the modern Serengeti - that is, 'savannah grassland with scrub and bush' (Gentry and Gentry, quoted by Cerling and Hay17). In terms of the UNESCO definition,46 it was a wooded grassland with 10-40% woody plant cover or a grassland with less than 10% woody plants. When the carbon isotope ratios of modern fauna have been corrected for the industrial effect in the modern atmosphere, the values of the fossil fauna are essentially the same as those of their modern counterparts. There is, however, a contrast between the fossil and modern tragelaphines. The woody plants growing at Olduvai at ca 1.8 Ma were evidently insufficient for these animals to be dedicated browsers.

A major change in the environment at Olduvai obviously occurred when Lake Olduvai dried up when the Gorge was formed (later than Bed II). This change removed a number of water-related plant species and freshwater fauna from the environment, but did not result in major changes in the diets of browsing and grazing animals, or in their relative prevalence in the landscape. However, If the major component of the diet of P. boisei was papyrus, then their staple food disappeared.

In contrast to the lack of difference In carbon isotope signatures In the fauna at Olduvai between fossil and modern specimens, their oxygen isotope signatures are distinctly different. The S180 ratios of the modern faunal community are about 6%o more positive than those of the fossil fauna from Beds 1 and II. A change of this magnitude has been observed In palaeosol carbonates in Olduvai Gorge by Cerling and Hay17, with the major change taking place at about 0.5 Ma.

A ready explanation for such a change in S180 ratios is that there was a major change in temperature and humidity at some point during the past 1.8 Ma. This environmental change would have caused a major change in the rate of leaf water evaporation and would have increased the difference in enamel 5180 ratios between water-independent (evaporation-sensitive) Giraffidae and water-dependent (evaporation-insensitive) Hippopotimidae. Such an increase is not observable In this case. The 5180 ratios of Giraffa sp. (-2.2) and Hippopotamus gorgops (-5.5) from Lower Bed II differ by 3.3. Among the modern fauna, the 5180 ratios of Giraffa camelopardis (-3.6) and Hippopotamus amphibious (-0.2) differ by 3.4. Therefore the difference did not change, indicating that the humidity and temperature did not change. The relatively small difference between the 6180 ratios of water-dependent and water-Independent animals also indicates that the environment in each case was not very dry and that water was permanently available.

An alternative explanation for the change in enamel S180 ratios is that the primary source of meteoric water changed at some point during the past 1.8 Ma. It is suggested that this change took place with the introduction of the Indian Ocean monsoon to this part of East Africa. Currently, the major source of rain is the Indian Ocean monsoon which brings the 'long rains' at mid-year, while the Atlantic Ocean provides the 'short rains' at the end of the year. Given the long distance from the Atlantic Ocean, across Angola and Tanzania, the heavy Isotopes of hydrogen and oxygen are substantially rained out along the way. This phenomenon has been documented for the rainfall at the research station at Seronera in the Serengeti National Park. A research project, as yet unfinished, has been launched by the author in collaboration with Casslan Mumbi of TAWIRI (Tanzania Wildlife Research Institute) and staff members at Seronera, to measure the oxygen isotopes in samples from the rain gauge over nearly 2 years. The oxygen Isotope values of rain from the two oceanic moisture sources differ by as much as 10%o. It is also possible that nearby Lake Victoria, which was only formed around 50 ka, could be adding 180 to the local rainfall.

It is noteworthy that the same isotopic phenomenon (no change in 513C, but substantial enrichment in 5180) can be observed at Lake Natron between ca 1.5 Ma and modern times.2 As more isotopic analyses are done on fossil tooth enamel from northwest Tanzania, it is likely that the timing of this change will be established.

Acknowledgements

The fossil specimens from Olduvai were obtained from the collections of the Olduvai Landscape Archaeology and Paleoanthropology Project (OLAPP), curated at the National History Museum in Arusha and at the Olduvai Field Camp. Rutgers graduate student Amy Cushing identified the fossil specimens and helped with sampling. The modern specimens from Serengeti National Park were obtained from the Research Station at Seronera. Emily Kisamo, the acting chief warden of Serengeti National Park at the time, was instrumental in providing sampling access. The isotopic ratios of all the specimens were measured at the Stable Light Isotope Facility of the Archaeology Department at the University of Cape Town by Ian Newton and John Lanham. Cape Town graduate students helped with the production of the manuscript: Marlagrazia Gallmberti produced the figures, while Kerryn Warren typed the manuscript and checked the statistical calculations. I thank all of these individuals most heartily. Funds for the research were provided by the National Research Foundation of South Africa, the University of Cape Town, and the Landon T. Clay Fund of Harvard University.

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