Barberena_2013

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Chapter Title Isotopic Studies of Foragers Diet: Environmental Archaeological

Approaches

Copyright Year 2013

Copyright Holder Springer Science+Business Media New York

Corresponding Author Family Name Barberena

Particle

Given Name Ramiro

Suffix

Division/Department CONICET, Laboratorio de Geoarqueologa,

Facultad de Filosofa y Letras

Organization/University Universidad Nacional de Cuyo

Street Parque General San Martn

Postcode 5500

City Mendoza

Country Argentina

Email [email protected]

Comp. by: AJohn Marie Stage: Galleys Chapter No.: 811 Title Name: EGADate:10/4/13 Time:07:49:20 Page Number: 1

1 I

2 Isotopic Studies of Foragers Diet:3 Environmental Archaeological4 Approaches

5 Ramiro Barberena

6 CONICET, Laboratorio de Geoarqueologa,

7 Facultad de Filosofa y Letras, Universidad

8 Nacional de Cuyo, Mendoza, Argentina

9 Introduction

10 The introduction of stable isotopes into archaeo-

11 logical research began in the 1970s and

12 revolutionized the ways in which several key

13 issues are studied, including early hominin

14 diets, subsistence and spatial organization of for-

15 ager societies, and individual life histories (Price

16 & Burton 2011; Schwarcz & Schoeninger 2011).

17 Isotopic analysis of bones, teeth, and other

18 organic tissues is a tool for the quantitative recon-

19 struction of past human diets, providing an

20 archaeological measure of subsistence that

21 complements studies in zooarchaeology and

22 archaeobotany.

23 Isotopic research is based on the premise that

24 you are what you eat, in other words, that the

25 isotopic composition of an organisms tissues

26 is a function of the composition of its diet.

27 Nevertheless, isotopic values do not have direct

28 dietary meaning and need to be analyzed in an

29 environmental context. The isotopic values

30 for the vegetal and animal foods potentially

31available for forager populations in a given envi-

32ronment, known as the isotopic ecology, pro-

33vide the context for the interpretation of past

34foragers diets.

35Definition

36The different chemical elements that constitute

37all organic tissues (e.g., carbon, nitrogen,

38oxygen) are defined by the number of protons in

39their nucleus, which varies among elements and

40is unique to each of them. For example, carbon

41has six protons, nitrogen seven, and oxygen eight.

42An isotope is a variety of a chemical element

43defined by the number of neutrons in its nucleus.

44For instance, carbon has three isotopes used in

45archaeology: 12C, 13C, and 14C, possessing six,

46seven, and eight neutrons in the nucleus, respec-

47tively (Fig. 1). These carbon isotopes have

48different atomic masses that condition whether

49isotopes are stable, like 12C and 13C, or radioac-

50tive, like 14C. Stable isotopes do not change in

51abundance through time after an organism dies,

52whereas radioactive isotopes decay at a constant

53rate and are therefore useful as a radiometric-

54dating tool.

55Stable isotope values are a ratio between the

56heavier and the lighter isotope of each element

57(13C/12C, 15N/14N). Since absolute abundances of

58these isotopes are very small, this ratio is stan-

59dardized by comparison to international

60reference material (Vienna-Peedee Formation

C. Smith (ed.), Encyclopedia of Global Archaeology, DOI 10.1007/978-1-4419-0465-2,# Springer Science+Business Media New York 2013

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61 Belemnitella americana -V-PDB- for 13C and62 atmospheric N2 -AIR- for

15N), producing d63 values, and then multiplied 1,000 () as64 follows:

d Rsample=Rstandard 1 1; 000

65 R is the ratio of the heavier to the lighter

66 isotope.

67 Isotopic Fractionation

68 The process of incorporating and metabolizing

69 nutrients involves chemical reactions in which

70 nutrients are the dietary input or substrate of

71 the reactions, an organisms tissue (e.g., bone) is

72 the product, and the excreta (urine, feces) are

73 the output. Lighter isotopes of a given chemical

74 element undergo reactions at faster rates than

75 heavier isotopes, since bonds between the lighter

76 isotopes are broken more easily than those

77 between the heavy isotopes: for example,

7812C reacts faster than 13C. In the case of animals,

79 the differences in reaction rates produce

80 a concentration of molecules of the lighter iso-

81 topes in the excreta, resulting in impoverished

82 d13C values, while the tissues that constitute83 a living organism are enriched in the heavier

84 isotope (Wolf et al. 2009). This effect is called

85 isotopic fractionation and produces

86 a systematic isotopic enrichment in every step

87 along trophic chains. In the case of d13C,88 fractionation is on the order of +1.5 and +389 for d15N, although there is interspecific variabil-90 ity (Schwarcz & Schoeninger 2011). Isotopic

91 fractionation provides the basis for assessing

92 paleodiets. Without it, all the organisms

93 inhabiting a region would have the same isotopic

94 abundances and thus provide no paleodietary

95 information. This is actually the case with chem-

96 ical elements with large atomic weight and small

97 inter-isotope differences, characterized by negli-

98 gible fractionation (e.g., 87Sr/86Sr, see below).

99 d13C: A Marker of Photosynthetic Pathways

100 Photosynthesis allows plants to synthesize

101 nutrients, including carbon, from sunlight and

102 atmospheric carbon dioxide (CO2). There are

103 three alternative photosynthetic pathways

104(Ehleringer & Cerling 2001). The C3 or Calvin-

105Benson pathway synthesizes CO2 in the form of

106molecules with three-carbon atoms, with an

107average d13C value of 25, which ranges108between 34 and 20. Diverse factors109produce variation in these values, such as the

110existence of carbon reservoirs in closed forested

111environments, known as the canopy effect. C3112plants include most species from temperate and

113subarctic regions and high-altitude settings in

114general. The C4 or Hatch-Slack pathway synthe-

115sizes atmospheric CO2 as four-carbon molecules

116with an average d13C value of12 and a range117of 10 to 14. This pathway is character-118ized by a smaller isotopic fractionation and

119a more efficient use of nutrients, part of

120a physiological adaptation to arid and warm

121climates. C4 species include maize, sugarcane,

122and tropical grasses. Finally, the Crassulacean

123Acid Metabolism (CAM) pathway is character-

124ized by the facultative capacity to alternate

125between the C3 and C4 mechanisms according

126to prevailing circumstances, producing an isoto-

127pic range that overlaps with that of both C3 and

128C4 plants. It includes a small number of taxa, such

129as succulents from desert environments.

130Herbivores d13C values are positively corre-131lated with those of their diet, providing evidence

132of the plants consumed and, based upon this,

133paleoecological conditions. On the other hand,

134marine algae and plankton obtain their carbon

135from dissolved inorganic carbon, enriched by

1367 with respect to atmospheric CO2. Therefore,137tissues of marine animals are enriched in com-

138parison to those from terrestrial ecosystems.

139d13C values can be obtained from two main140components of bone: organic, or collagen, and

141inorganic, or apatite. Experimental work has

142demonstrated that the collagen isotopic signal

143reflects an average of the sources of protein

144consumed (e.g., meat), while the apatite signal

145reflects an average of the total diet (proteins,

146carbohydrates, and lipids). The integration of

147d13C values from collagen and apatite provides148additional dietary information (Ambrose &

149Norr 1993).

I 2 Isotopic Studies of Foragers Diet: Environmental Archaeological Approaches

ramirobarberenaSticky Note".


150 d15N: A Marker of Trophic Position151 In terrestrial ecosystems, nitrogen is ultimately

152 derived from soils. Soils from cool and moist

153 areas, such as forests, tend to have low d15N154 values, whereas soils from warm and dry ecosys-

155 tems, such as deserts, have high d15N values.156 These values are passed on to herbivores, plus

157 ca. 3 due to isotopic fractionation. The step-158 wise increase in d15N values marks every step159 within a food web and thus provides important

160 data on the trophic position of animals.

161 The d15N values of marine plants are about162 4 higher than those of terrestrial ones. Addi-163 tionally, marine food webs are usually longer

164 than those from terrestrial ecosystems, providing

165 more opportunities for isotopic fractionation and

166 trophic enrichment. Globally, marine animals

167 tend to have much higher values than terrestrial

168 animals.

169 Foragers and Isotopic Studies

170 The definition of foraging societies is not free

171 of ambiguity and discrepancy, given the

172 inherent complexity of human organization of

173 subsistence, and divergent theoretical views.

174 Nonetheless, it can be stated that foragers sub-

175 sistence relies to varying extents on gathering

176 plants and hunting and fishing animals (Fig. 2).

177 They do not control the reproductive cycle of the

178 resources they consume to any great extent when

179 compared to farming and herding societies.

180 Generally, this is equivalent to the hunter-gath-

181 erer category (Kelly 1995; Politis 2007).

182 The combined use of d15N and d13C values183 provides a means to quantify the main food clas-

184 ses consumed by foragers in various local

185 contexts around the world. Most importantly, it

186 provides subsistence data on the scale of the

187 individual, an analytical target that is usually

188 hard to reach, providing access to issues such as

189 subsistence variation by age and gender. In addi-

190 tion, subsistence can be studied at the population

191 level as well. Stable isotopes have contributed to

192 assessments of the dietary role of vegetal foods

193 (C3 or C4); terrestrial animals occupying diverse

194 trophic positions; marine animals including shell-

195 fish, fishes, and mammals; and freshwater

196 resources. On this basis, it is possible to evaluate

197variation across time and space in behaviors

198along the foraging spectrum (Kelly 1995).

199Historical Background

200Vogel and van der Merwe (1977) conducted the

201first stable isotopes study in archaeology,

202presenting an assessment of carbon isotopes in

203collagen from human bones from the Woodland

204period in Eastern North America. Around the

205same time, DeNiro and Epstein (1978) presented

206an isotopic study of organisms fed controlled

207diets, lending definitive support to the assertion

208that the diet determines the isotopic composition

209of animal tissues. Tauber (1981) developed the

210first isotopic test case for the consumption of

211marine foods by foragers, focusing on the Danish

212Mesolithic and Greenland Eskimos. Following

213these pioneering studies, isotopic research

214began to gain wide acceptance and, since the

215end of the 1980s, has grown in scholarly scope,

216as well as in geographical extent. The series of

217Advanced Seminars on Paleodiet beginning in2181986 witnessed and encouraged much of the

219methodological and theoretical growth visible in

220the archaeological field today (see references

221in Further Reading). Analysis of stable isotopes

222has become a routine worldwide.

223Key Issues/Current Debates

224Isotopic Ecology: Studying the Foragers

225Menu

226Isotope data from human remains must be

227interpreted in the context of the values of the

228potentially consumed foods or the isotopic

229ecology. This is an integral part of the

230paleodietary study of forager societies, because

231the values of human samples do not carry

232a precise dietary meaning per se. For example,

233a d13Ccollagen value of 15 from a human sam-234ple indicates an enriched signal, which may sug-

235gest the consumption of a certain amount of

236protein from marine mammals, fluvial fishes, or

237some terrestrial herbivores, among other likely

238explanations. Interpretations must be adjusted

Isotopic Studies of Foragers Diet: Environmental Archaeological Approaches 3 I


239 by placing human values in the context of isoto-

240 pic ecology. Usually, samples of archaeological

241 origin are analyzed as well as modern samples, in

242 order to widen the taxonomic range, in particular

243 for plants. When modern samples are included as

244 part of the context, it is fundamental to assess

245 whether the organisms may have ingested foods

246 that were not available in prehistoric times

247 (e.g., agricultural forage, domestic animals). It

248 is also necessary to correct the d13C values of249 modern samples for the so-called industrial or

250 Suess effect (ca. +1.5), which has altered251 global isotopic ratios by introducing carbon

252 derived from fossil fuels, depleted in 13C, to the

253 atmosphere.

254 A first step for building an isotopic ecology is

255 to define the foragers potential menu on the basis

256 of zooarchaeological and archaeobotanical evi-

257 dences from the study area. This involves consid-

258 ering foods that might be unrecorded

259 archaeologically, which is especially important

260 for items with poor preservation potential

261 (e.g., plant foods). Indeed, one of the merits of

262 stable isotope research is that it permits infer-

263 ences of past feeding behaviors that might other-

264 wise be invisible.

265 The isotopic ecology must be local in terms

266 of the archaeological problem at hand, since all

267 vegetal and animal isotopic values vary with

268 regional and local conditions climate, nutrient

269 availability, type of substrate, the existence of

270 marine or terrestrial isotopic reservoirs, and

271 physiological adaptations (Koch 2007). There is

272 no magic number of samples providing

273 a confident reconstruction of the isotopic ecology

274 of a given region. The goal is to accurately char-

275 acterize the isotopic variation of each of the main

276 food resources available for foragers, since the

277 use of inaccurate average and dispersion isotopic

278 values for the foods eaten by humans will lead to

279 wrong dietary interpretations. As a rule of thumb,

280 the more complex the ecosystems where foragers

281 make their living, the more extensive the isotopic

282 ecology sampling should be.

283 A large-scale project directed by Andrzej W.

284 Weber at the Lake Baikal region of Siberia,

285 Russian Federation, provides an exemplary case

286 of isotopic reconstruction of a complex

287ecological system intended to frame a regional

288study of forager populations inhabiting the area

289during the Middle Holocene (Weber et al. 2011).290Twomain food webs are present in the region: (a)

291a terrestrial food web composed of C3 plants

292consumed by herbivores (elk, red deer, hare), in

293turn consumed by carnivores (black bear, fox,

294dog), and (b) a freshwater food web of great

295complexity, as the Baikal is one of the largest

296freshwater ecosystems on Earth. The latter

297includes different groups of detrivorous and

298omnivorous fishes, fed on by seals (Fig. 3).

299Plots (a) and (b) from Fig. 3 represent the

300terrestrial food web, and plots (c) and (d) depict

301the aquatic food webs from fluvial and lacustrian

302contexts. The d15N data show that most of the303aquatic species are enriched with values above

30410. On the other hand, most of the terrestrial305species have d15N values below 10 with two306exceptions: the herring gull, which includes fish

307in its diet, and the dog. As the authors suggest,

308Since in most prehistoric societies, dogs are

309expected to feed mostly on human leftover food,

310dog stable isotope signatures are frequently

311accepted as a good measure of human diet at

312a group level. . . (Weber et al. 2011: 542). The

313Baikal freshwater isotope ecology is extremely

314complex, in particular regarding d13C values.315High variability in lake bathymetry, sunlight

316access, and availability of nutrients all produce

317a wide isotopic range (Fig. 3c) that stands in

318sharp contrast to the homogeneous C3 terrestrial

319environment (Fig. 3a).

320To summarize, the success of the Baikal

321isotope ecology project lies in having thoroughly

322characterized the isotopic ranges of the alterna-

323tive food classes available for foragers from

324terrestrial and freshwater ecosystems. On this

325basis, the authors are able to discriminate two

326main types of diet, Game-Fish and Game-

327Fish-Seal, each related to different ecosystems.

328This study accentuates the need for archaeolo-

329gists to determine the foraging menu via

330consideration of available food items; these

331provide the isotopic ecological context from

332which past forager diets can be reconstructed.



333 Isotopic Visibility of Feeding Behaviors: How

334 Much is Enough?

335 Isotopic results from human samples provide an

336 average of the values of the foods consumed337 during a given period of time. Therefore, isotopes

338 do not provide a record of rare feeding events.

339 Beyond this, it is fair to ask how much of a given

340 food must be eaten for it to be visible in the

341 isotopic record. Currently, some of the main vari-

342 ables that determine the isotopic visibility of

343 ancient feeding practices are known, while others

344 remain unknown. The target of isotopic analyses

345 is usually that of classes of foods grouped by

346 similarities in their d13C and d15N isotopic ranges347 (e.g., C3 or C4 vegetal species, ungulates from

348 open vs. forested environments, marine vs.

349 terrestrial protein). This is a kind of taxon-free

350 approach like that applied in Paleontology, where

351 the relevant variable is the niche that a species or

352 population occupies. Correspondingly, the scale

353 of analysis of isotopic research does not usually

354 reach the level of individual species, since differ-

355 ent species occupying similar niches may present

356 similar isotopic signals, as recorded for Baikal

357 fish (Fig. 3d).

358 Figure 4 illustrates a simple dietary recon-

359 struction with two stable isotope systems (d13C360 and d15N from collagen) where two classes of361 foods are present: proteins from marine and

362 terrestrial mammals. It shows that three individ-

363 uals consumed these two dietary sources in the

364 following proportions: (A) 100 % terrestrial pro-

365 tein, (B) 50% terrestrial and 50%marine protein,

366 and (C) 100 % marine protein. In a simple situa-

367 tion such as this, with only two classes of food

368 (usually termed isotopic end members) that are

369 isotopically distinct, a Linear Mixing Model can

370 be used. Basically, the closer one sample falls to

371 an end member, the larger the dietary importance

372 of that end of the continuum (Schwarcz et al.

373 2010).

374 The d13C and d15N values of sample375 A represent consumed terrestrial protein, plus

376 the isotopic fractionation affecting the relation

377 between substrate and product (diet and bone

378 collagen in this case). The same occurs with

379 sample C, which points to a 100 % marine-

380 based diet. Finally, sample B falls halfway

381along the theoretical mixing line, as might be

382expected for a diet combining both sources of

383protein in equal proportions. If isotopic variation

384of the terrestrial and marine isotopic end mem-

385bers were small and the spacing between them

386large, as in Fig. 4, a relatively small proportion of

387either type of protein in the total diet (e.g., 15 %)

388would be isotopically visible. As isotopic varia-

389tion of the end members increases, the spacing

390between them decreases, and larger inputs of the

391minor protein source are necessary in order to be

392visible. Therefore, the answer to How much is

393enough? depends on the local isotope ecology,

394which provides the average and dispersion values

395for the isotopic end members.

396In real cases, usually there are more than two

397dietary sources present, increasing the complex-

398ity of the isotopic ecology and therefore of the

399study of forager paleodiets (Weber et al. 2011).

400The use of several isotopic proxies from organic

401and inorganic bone phases increases resolution.

402Recently developed dietary models, such as

403IsoSource or SIAR, contribute to research on the

404diversity of dietary combinations that can pro-

405duce given isotopic values (Wolf et al. 2009).

406Early Hominin Foragers

407Enamel tissue may preserve an isotopic signal of

408diet over millions of years. This has made possi-

409ble the reconstruction of the subsistence of

410several species of early hominins including

411Mio-Pliocene fossils (Ardipithecus), Plio-

412Pleistocene gracile and robust australopiths

413(Australopithecus, Paranthropus), and early

414members of the genus Homo (Homo habilis,

415H. neanderthalensis). Carbon isotopes provide416information on the amount of C3 vis-a`-vis C4417vegetal foods eaten by early hominins,

418suggesting the type of environments inhabited,

419ranging from closed forest settings with a pure

420C3 isotopic signature to open savannas with

421a mixed C3/C4 signature. In conjunction with

422data on dental microwear, this information con-

423tributes to assessing the timing and geographic

424patterning of the evolution of arboreal and pedes-

425trian adaptations by early hominins. Current

426information indicates wide subsistence variabil-

427ity, challenging some long-held views in



428 paleoanthropology (Ungar & Sponheimer 2011).

429 Additionally, isotopic data from Middle and Late

430 Paleolithic foragers are beginning to provide

431 quantitative information on the consumption of

432 terrestrial, marine, and freshwater foods byHomo

433 neanderthalensis and early Homo sapiens,434 allowing assessment of changes in dietary

435 breadth and their relationship to demographic

436 processes (Richards 2009).

437 Forager Diet, Mobility, and Settlement

438 In forager societies, subsistence is tied to mobil-

439 ity and geographical organization (Kelly 1995;

440 Politis 2007). In this context, isotopically based

441 dietary studies may offer spatial insights, in par-

442 ticular in cases that involved the consumption of

443 foods with a spatially circumscribed availability

444 and a distinct isotopic signature. This is the case

445 with marine mammals and fishes, usually

446 enriched in both d13C and d15N (Schwarcz &447 Schoeninger 2011). In some regions, this is also

448 the case for fluvial or lake-dwelling mammals

449 and fishes, enriched in d15N and usually depleted450 in d13C, as shown in Baikal seals (Fig. 3d; see451 Weber et al. 2011).

452 In a classic article, Sealy and van der Merwe

453 (1986) tested a hypothesis that suggested

454 a seasonal round between the coast and the

455 hinterland for forager societies inhabiting the

456 Cape of South Africa during the Late Holocene.

457 This seasonal model of spatial organization

458 inspired by historic records would produce

459 a homogeneous isotopic signature mixing marine

460 and terrestrial foods. Isotopic analyses of human

461 samples from both ends of this alleged seasonal

462 round showed at least two different types of diet:

463 people from coastal sites with marine-based diets

464 and inland people who consumed negligible

465 amounts of marine resources. This not only

466 contradicted the expectations derived from the

467 seasonal model but also suggested the existence

468 of restricted ranges of mobility for foragers con-

469 suming marine foods. Similar patterns of isotopic

470 coastal-inland differentiation have been recorded

471 for regions of Australia, Peru, Argentinean

472 Patagonia, and the Northwest Coast of North

473 America. These cases highlight the attraction of

474 productive coastal settings to foraging societies,

475leading to spatially restricted home ranges and

476high demographic densities. On the other hand,

477wide territories integrating the coast and the

478hinterland have been suggested for Mesolithic

479Denmark, among other cases. This information

480is well suited for the analysis of catchment areas

481via the application of patch choice models

482derived from foraging theory.

483The Baikal Lake offers another important case

484where different aspects of forager mobility and

485settlement have been assessed. Evidence indi-

486cates that Middle Holocene forager ranges were

487smaller than those suggested by ethnographic

488data. In addition, there appears to be a marked

489temporal stability in foraging patterns, despite the

490changes documented in the culture history and

491paleoenvironment. To summarize, a web of

492diverse movements connecting the microenvi-

493ronments of the Baikal is recorded. This geo-

494graphic net is asymmetric, since some areas

495received large numbers of migrants, whereas

496others did not (Weber et al. 2011).

497The results of these case studies help place

498dietary information into a geographic context.

499Isotopic reconstructions of forager diets are cur-

500rently being developed to integrate diverse

501aspects of cultural geography such as territorial

502organization, foraging ranges, and logistical

503spheres of mobility. This is enhanced by the use

504of other isotope systems described below.

505Future Directions

506Overcoming Analytical Limitations:

507Compound-Specific Isotope Analyses

508Isotopic analysis at the level of specific com-

509pounds of bone, including amino acids, fatty

510acids, and cholesterol, is a new technique that

511allows a high-resolution alternative to bulk tissue

512analysis of d13C and d15N (Evershed et al. 2007).513Compound-specific studies provide a means to

514assess the dietary contribution of particular food

515classes, overcoming some limitations of forager

516paleodietary reconstruction, such as the d13C517overlap of C4 plants and marine resources and

518the 15N enrichment prevalent in arid environ-

519ments. Bone cholesterol in particular has been



520 shown to reflect the whole diet, playing an anal-

521 ogous role to apatite and contributing to assess its

522 preservation.

523 Dietary Changes and Life History

524 Stable isotope analyses can be performed on dif-

525 ferent organic tissues: bone, teeth, and soft tissues

526 such as hair and nails. Bones are remodeled

527 throughout life, whereas teeth, hair, and nails

528 have incremental growth patterns and do not

529 remodel once formed. The isotopic signal

530 retrieved from each tissue reflects an average of

531 the diet during the period of its formation. In the

532 case of bones, the remodeling process is on the

533 order of a decade and is active until the death of

534 the individual, offering an isotopic signal that

535 averages the diet during the last years of life.

536 Teeth, on the other hand, form only during the

537 first years of life, providing an evidence of diet

538 during different stages of childhood. Hair and

539 nails form rapidly and incrementally, providing

540 dietary information on very brief periods of life,

541 offering monthly dietary resolution. In fact, the

542 incremental formation of tooth dentine, hair, and

543 nails allows production of serial dietary recon-

544 structions (Schwarcz & Schoeninger 2011).

545 The combined analysis of different tissues

546 from a single individual provides the basis for

547 a life history approach to dietary studies

548 (Katzenberg 2008). On this basis, several key

549 issues of forager social organization and subsis-

550 tence have been addressed, particularly age of

551 weaning, life history traits by gender, and

552 changes in subsistence throughout the life of

553 foragers.

554 Isotopic Signatures of Forager Geography:

555 Oxygen Isotopes and Trace Elements

556 Following the lead of research on complex

557 societies such as the Maya and Tiwanaku, recent

558 studies of forager subsistence are progressively

559 including isotopic markers of geographic resi-

560 dence (Bentley 2006; Schwarcz et al. 2010;

561 Price & Burton 2011). Two isotope systems are

562 at the forefront of this methodological advance:

563 oxygen isotopes (18O/16O) and trace elements

564 like strontium (87Sr/86Sr).

565The use of 18O/16O ratios as markers of place

566of origin is based on two central facts: (a) Isotopic

567ratios in meteoric precipitations vary geographi-

568cally according to altitude, humidity, tempera-

569ture, and distance from the ocean and (b)

570isotopic ratios in human tissues depend on the

571water imbibed and, to a lesser extent, oxygen in

572air and food sources. Thus, oxygen values from

573human remains contain an averaged record of the

574places where a person lived during the period of

575time represented in the sampled tissue.

576Strontium isotopes (87Sr and 86Sr) have large

577atomic masses and differ little from each other.

578Therefore, rates of chemical reaction are very

579similar and isotopic fractionation between sub-

580strate and product is negligible. In this case, all of

581the organisms in a given region present the same

582isotopic abundances determined by the chemical

583signatures in the local geology, which are passed

584on to soils, circulating water, plants, animals, and

585humans (Bentley 2006).

586These two isotope systems must be used in the

587context of different frames of reference: isotope

588values in water sources in the case of d18O and589biologically available Strontium in the case of

590d87Sr. The natural variation in isotopic abun-591dances between different regions will determine

592the resolution that can be achieved in archaeolog-

593ical reconstructions (i.e., which regions have an

594isotopically distinct signature). Since these

595isotope systems are independent from each

596other and may offer complementary insights,

597their combined use is the best strategy.

598Since their introduction in Archaeology

59935 years ago, stable isotope analysis has provided

600a tool for the quantitative reconstruction of

601forager subsistence, thereby enlarging the range

602of topics addressed. Currently, the isotopic field

603has grown to include studies of isotopic ecology

604in complex ecosystems, forager diet, and geo-

605graphical issues including foraging ranges, terri-

606tories, and migrations, with a potential resolution

607reaching the scale of individual life histories. The

608theoretical and methodological limits of the iso-

609topic revolution in archaeology lie still far ahead.



610 Cross-References

611 Archaeology of Hunter-GatherersAu2612 Bone Chemistry and Ancient Diet613 Hunter-Gatherer Settlement and Mobility614 Hunter-Gatherer Subsistence Variability and615 Intensification

616 Radiocarbon Dating Methods in Archaeology617 Zooarchaeology

618 References

619 AMBROSE, S.H. & L. NORR. 1993. Relationship of carbon

620 isotope ratios of whole diet and dietary protein to those

621 of bone collagen and carbonate, in J. Lambert &

622 G. Grupe (ed.) Prehistoric human bone: archaeology623 at the molecular level: 1-38. Berlin: Springer-Verlag.624 BENTLEY, R.A. 2006. Strontium isotopes from the earth to

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636 EVERSHED, R.P., I.D. BULL, L.T. CORR, Z.M. CROSSMAN,

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638 A.J. MUKHERJEE & R.D. PANCOST. 2007. Compound-

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704New York: Kluwer Academics-Plenum Press.

705BARBERENA, R., A. GIL, G. NEME & R. TYKOT. (ed.) 2009.

706Special Issue: Stable isotopes and archaeology in

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708ism, and agriculture. International Journal of709Osteoarchaeology 19(2).


ramirobarberenaSticky NoteCross-References Updated:1. Isotope Geochemistry in Archaeology2. Hunter-Gatherers, Archaeology of3. Hunter-Gatherer Settlement and Mobility4. Bone Chemistry and Ancient Diet5. Bone, Chemical Analysis of6. Isotopic Studies of Husbandry Practices


710 HEDGES, R.E.M., R.E. STEVENS & P.L. KOCH. 2006.

711 Isotopes in bones and teeth, in M.J. Leng (ed.) Isotopes712 in paleoenvironmental research 10: 117-45. New713 York: Springer.

714 KOCH, P.L. & J. BURTON. (ed.) 2003. Special Issue: Bone

715 chemistry. International Journal of Osteoarchaeology716 13(1-2).

717WEBER, A.W., M.A. KATZENBERG & T. SCHURR. (ed.) 2010.

718Prehistoric hunter-gatherers of the Baikal region,719Siberia: bioarchaeological studies of past lifeways.720Philadelphia: University of Pennsylvania Press.



Isotopic Studies of Foragers Diet: Environmental Archaeological Approaches, Fig. 1 Atoms of the threecarbon isotopes used in archaeology

Isotopic Studies ofForagers Diet:EnvironmentalArchaeologicalApproaches,Fig. 2 South Americanforagers: (a) Hoti familyreturning from a fishing and

gathering trip (Venezuela);

(b) Nukak man fishing witha bow and harpoon

(Colombia) (Photographs

courtesy of Gustavo G.

Politis)



Isotopic Studies of Foragers Diet: EnvironmentalArchaeological Approaches, Fig. 3 IsotopicAu1 ecologyof the Baikal Region (Source: Weber et al. 2011: Fig. 2.

Journal of Anthropological Archaeology 30 (4). Reprintedwith permission from Elsevier. Courtesy of Andrzej W.

Weber)



Isotopic Studies of Foragers Diet: EnvironmentalArchaeological Approaches, Fig. 4 Dietary recon-struction based on a Linear Mixing Model with two

end members: terrestrial and marine protein



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414SjD0akJL4.1 Barberena 2013 (Springer)IIsotopic Studies of Foragers Diet: Environmental Archaeological ApproachesIntroductionDefinitionIsotopic Fractionationdelta13C: A Marker of Photosynthetic Pathwaysdelta15N: A Marker of Trophic PositionForagers and Isotopic Studies

Historical BackgroundKey Issues/Current DebatesIsotopic Ecology: Studying the Foragers MenuIsotopic Visibility of Feeding Behaviors: How Much is Enough?Early Hominin ForagersForager Diet, Mobility, and Settlement

Future DirectionsOvercoming Analytical Limitations: Compound-Specific Isotope AnalysesDietary Changes and Life HistoryIsotopic Signatures of Forager Geography: Oxygen Isotopes and Trace Elements

Cross-ReferencesReferencesFurther Reading

Barberena_2013

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