Mays, 2003

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Bone strontium: calcium ratios and duration of breastfeeding in a

Mediaeval skeletal population

Simon Mays *

Ancient Monuments Laboratory, English Heritage Centre for Archaeology, Fort Cumberland, Eastney, Portsmouth PO4 9LD, UK

Received 11 January 2002; received in revised form 23 May 2002; accepted 20 August 2002

Abstract

This work is an investigation of the value of bone strontium:calcium ratios in the study of duration of breastfeeding in earlier

human populations. The study material comprised human skeletal remains of Mediaeval date from England. Investigation of

diagenesis suggested that bone Sr:Ca ratios preserved a biogenic signal. Statistical analysis indicated significant age-related

patterning in bone Sr:Ca ratios in the juvenile cohort. Duration of breastfeeding estimated from infant bone Sr:Ca ratios was

concordant with that inferred from an earlier study of nitrogen stable isotope ratios from the same population. The value of bone

Sr:Ca data for studying weaning practices in earlier human populations is discussed.

2003 Elsevier Science Ltd. All rights reserved.

Keywords: Sr:Ca ratio; Bone; Weaning; Human; Wharram Percy

1. Introduction

In most cultures, babies are breastfed from birth, but

at some point other foods are introduced into the diet,

supplementing and eventually replacing breast milk, a

process known as weaning. Duration of breastfeeding

may have important implications for population dynam-

ics. Because lactation suppresses ovulation, duration of

breastfeeding is a major determinant of fecundity in

societies lacking effective artificial methods of contra-

ception. In addition, the immunity provided by breast

milk and the avoidance of early contact with potentially

contaminated food and drink has meant that histori-

cally, societies, which practiced regular breastfeeding

have shown lower infant mortality and morbidity than

those in which breastfeeding was rare or its duration

curtailed [68].

Recently, there has been considerable interest in

studying infant feeding practices in earlier populations

[29]. A number of studies have utilised bone chemistry to

investigate duration of breastfeeding in ancient times.

Most (e.g. Refs. [12,24,28,50,59,60]) have used bone-

stable isotopes, particularly those of nitrogen. Breast

milk is enriched in nitrogen-15 compared with mostpost-weaning foods and this is reflected in the infants

bones. However, another chemical technique, measure-

ment of infant bone strontium (Sr):calcium (Ca) ratios,

has also been used to shed light on weaning practices in

ancient times.

Strontium and calcium share similar chemical prop-

erties, and the behaviour of Sr and Ca in biological

systems has been extensively studied, principally in the

1950s and 1960s as a result of concern over the biologi-

cal effects of radioactive Sr-90 produced by atmospheric

nuclear tests. A number of aspects of the behaviour of Sr

and Ca render bone Sr:Ca ratios useful for investigatingancient weaning practices. Strontium is absorbed less

efficiently from food stuffs than is Ca, and a greater

proportion of Sr is excreted, so that Sr:Ca ratios in living

tissues are less than in the diet [8]. Most of the bodys

strontium is located in the skeleton [58], and there is a

firm relationship between the Sr:Ca ratio in diet and

in the bones of the consumer [9,14,48]. In human adults,

the relationship between dietary and bone Sr:Ca levels,

the bonediet Observed Ratio (ORbonediet), appears to

be about 0.18 [51]. In lactating women, the OR milkdietis

somewhat less than this at about 0.1 [38]. Sr:Ca ratios

in foetal tissues are lower than in maternal tissues, the* Tel.: +44-2392-856-779; fax: +44-2392-856-701.

Journal of Archaeological Science 30 (2003) 731741

SCIENCE

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ORfoetusmother is about 0.5 [8]. These latter two obser-

vations imply preferential transport of Ca with respect

to Sr across the mammary gland during lactation, and

during pregnancy across the placenta to the developing

foetus, and laboratory studies support this [23,32]. More

recent work [33,53] has elucidated this further, suggest-

ing that whilst there is active placental and mammarygland transfer of Ca, the transfer of Sr simply follows

concentration gradients. The studies of Krachler et al.

[33] and Rossipal et al. [53] appear consistent with

previous work in that they suggest somewhat higher

Sr:Ca ratios in maternal sera than in umbilical cord sera

or colostrum, although these authors did not statistically

analyse the patterning in Sr:Ca ratios. In any event, it is

clear that milk has a low Sr:Ca ratio compared to most

other foods [52].

The interpretation of infant bone Sr:Ca values is

complicated somewhat by the fact that the ability of

the gastro-intestinal system to discriminate against

strontium develops with age, only reaching adult levels

at about 810 years old [51]. Age-related changes in

bone Sr:Ca ratios may therefore be expected in infants

and children due both to the increasing discrimination

against strontium absorption and to the dietary changes

of weaning. The precise form of the plot of Sr:Ca ratio

against age is affected by a number of variables, particu-

larly timing and duration of weaning, however, in

general, one might expect fairly low Sr:Ca ratios in

neonatal infants and the breastfed, then a rise reflecting

the introduction of solid foods of higher Sr:Ca ratio,

followed by a steady reduction as the guts ability to

discriminate against strontium develops so that eventu-ally the bone Sr:Ca ratio resembles to that seen in adults

[63]. The ORbonedietis known for immature humans at

different ages [51] so that dietary Sr:Ca ratios can be

estimated from bone values.

Although the potential of bone Sr:Ca ratios for the

investigation of weaning in palaeopopulations was rec-

ognised nearly 20 years ago, long before the nitrogen

isotope technique was applied, to date, few Sr:Ca studies

of weaning have been published [19,26,63]. In part, this

reflects the general move away from bone trace-element

studies for investigating ancient diets, which has oc-

curred since about the mid-1980s in the face of thegrowing realisation both of the pervasiveness of dia-

genetic chemical change in bone mineral, and of the

complexity of the physiological determinants of trace-

element concentrations in biological tissues [56,64].

The present study is an investigation of the value of

the Sr:Ca method for estimating the duration of breast-

feeding in an archaeological population.

2. Materials and methods

The human skeletal material for this study came from

the deserted Mediaeval village of Wharram Percy,

England [3,4]. The burials date mainly from AD 10th

to 16th century, and represent interments of ordinary

peasants who lived at the village of Wharram Percy or

elsewhere in this rural parish. This material was selected

for a number of reasons. The assemblage contains large

numbers of juvenile skeletons, permitting study of a

larger sample of immature individuals than has beenpossible in previous bone Sr:Ca investigations of wean-

ing, facilitating statistical validation of results. A nitro-

gen isotope study of duration of breastfeeding in this

population [44,50] has previously been conducted, al-

lowing comparison of results using the two different

techniques. The soil conditions at the site make the

skeletal material a promising substrate for bone trace-

element studies. The burials were inserted into calcare-

ous soil overlying cretaceous chalk. Unfortunately, no

soil samples are available from the graves themselves,

but analyses of samples from various parts of the site

indicate that local soils are alkaline, pH ranging from

7.3 to 8.3 [1,30]. Acidic conditions favour dissolution of

hydroxy-apatite [37], so skeletal material buried in an

alkaline soil environment is likely to be preferable for

trace-element work.

The strategy for the present work is as follows.

Firstly, attempts will be made to demonstrate that the

level of diagenesis in the study material is likely to be

sufficiently slight so that a biogenic bone Sr:Ca signal

can be discerned. Secondly, any age-related patterns in

Sr:Ca ratios will be described and attempts will be made

to validate them using statistical techniques. Thirdly,

ORbonedietdata, derived from Sr-90 studies on modern

subjects [51], will be used to estimate dietary Sr:Ca ratiosand, hence, to make inferences about weaning practices.

Bone samples were taken for analysis from 50 imma-

ture skeletons, ranging in age at death from neonatal to

17 years. Samples from 50 adult (18+ years) skeletons

were also taken; these provide a base line with which to

compare the juvenile cohort. Compact bone rather than

trabecular bone was chosen for analysis; the latter

was avoided as its large surface area renders it more

vulnerable to diagenesis [18,34].

Samples consisted of diaphysial bone from the femur

or humerus. Approximately 12 g of bone was removed

using a hack-saw. In each sample, periosteal and endo-steal surfaces were removed by scraping to a depth of

12 mm to remove soil contaminants, which may accu-

mulate on the surfaces of buried bone [35]. Samples were

then cleaned in an ultrasonic cleaner and dried to

constant weight at 110 (C. They were then pulverised in

an agate ball-mortar.

All elemental determinations were carried out in

the Mineralogy Department at the Natural History

Museum, London. Samples were analysed for a spec-

trum of trace and bulk elements using inductively

coupled plasma atomic emission spectroscopy (ICP

AES). In this article, only Sr, Ca and phosphorus (P)

S. Mays / Journal of Archaeological Science 30 (2003) 731741732

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results are reported. Approximately 500 mg aliquots of

powdered bone (accurately weighed) were digested in a

mixture of concentrated nitric and perchloric acids and

the resulting solutions made up to 50 ml for analysis.

Analytical grade reagents, or better, and de-ionised

water were used throughout. The ICP instrument (an

ARL 3410 Minitorch system) was calibrated using solu-

tions prepared from commercial single element stand-

ards. Under the instrumental operating parameters used,

the detection limits for Sr, Ca and P in the bones were

0.5, 150 and 100 ppm (parts per million), respectively.

Replicate analyses of test solutions showed the precision

of the analytical procedure to be better than 1.5%. The

accuracy of the method was tested by analysing a

standard reference material, H-5. The results obtained

were in good agreement with the published data and are

presented in Table 1.

In whole bone from archaeological contexts, concen-

tration of trace and bulk elements mainly or entirely

residing in the mineral fraction will vary according to

the amount of organic material surviving in the speci-

mens. This dilution of element concentrations by the

variable amount of organics preserved is generally anunwanted source of variability in the data. Destruction

of the organic component by ashing at elevated tempera-

ture has frequently been used to circumvent this problem

in studies of archaeological bone. However, exposure of

bone to high temperatures may lead to losses in some

elements [13,20]. The preliminary step of ashing the

samples was therefore avoided in the current study.

Instead, the weight of the organic component was

estimated from the bone nitrogen content and sub-

tracted from the whole to give an estimated weight for

the mineral part. Elemental concentrations were then

expressed relative to this value. The purpose here was toenable comparison of levels of individual elements in the

buried bone from Wharram Percy with values in modern

bone reported with respect to the mineral component.

This procedure will, of course, leave Sr:Ca ratios un-

affected. Whole-bone nitrogen was determined using a

CHN elemental analyser. A separate sub-sample of bone

(815 mg, accurately weighed) was used. The detection

limit for nitrogen was 3000 ppm. Nitrogen content of

whole bone reflects accurately the organic content, pro-

vided, the nitrogen level is greater than about 0.4% by

weight [46], as was invariably the case in the current

material. Collagen makes up approximately 8590% of

the organic component of bone [27], and for the pur-

poses of providing an approximate estimate of the

weight of organics, it was assumed that the composition

of the entire organic component resembled that of

collagen. The proportion of nitrogen by weight in bone

collagen was taken as 0.1591 [15].

For the juveniles, age at death was determined usingdental development [57]. Adult age at death was esti-

mated using dental wear, calibrated using the juvenile

part of the assemblage [45]. Sex in adults was determined

using dimorphic aspects of the pelvis and skull [5].

No attempt was made, for the present purposes, to

determine sex in juveniles.

3. Results

Summary statistics for the results in juveniles and

adults are given in Table 2. Lilliefors tests [11] provided

no evidence for deviations from normality for any of theparameters listed in Table 2.

3.1. Diagenesis

There are a number of techniques for evaluating

diagenesis in elemental composition of ancient bones

[40, p. 192]. Rather than relying on a single technique,

most researchers use a combination to build up a picture

of diagenetic change in the material under study (e.g.

articles in Ref. [55]). This is the approach used in this

study.

The Ca:P ratio has frequently been used as a generalindicator of the preservational integrity of the mineral

fraction of buried bone, following Ref. [62]. Discrepan-

cies from values characteristic of living bone are taken as

indicative of diagenesis (although it should be born in

mind that Ca:P ratios are, at best, only proxy measures

of the integrity of bone Sr:Ca ratios [7]). Mean Ca:P

ratios in modern bone lie approximately in the range

2.212.27 (calculated from Ref. [22]: Table 1). The

Wharram Percy mean Ca:P ratios (Table 2) resemble

modern values.

If element levels in buried bones are outside physio-

logical levels seen in modern bone, then this suggests

Table 1

Measurements on standard reference material animal bone H-5

Sr

(ppm)

Ca

(%)

P

(%)

Reference

100 21.4 10.3 This work (mean of four replicate analyses)

96 21.2 10.2 IAEA, Vienna, Austriaproposed values

Table 2

Summary statistics for elemental analyses

Adults (N50) Juveniles (N50)

Mean SD Mean SD

Sr (ppm) 249.6 54.7 306.8 42.6

Ca (%) 36.2 1.3 35.9 1.1Ca:P 2.27 0.10 2.28 0.11

Sr:Ca (104) 6.92 1.57 8.55 1.20

Bone Sr and Ca concentrations expressed with respect to the

mineral component (see text)

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diagenesis in the ancient specimens [49]. Mean bone Sr

levels reported in studies of modern adults generally lie

in the range 100300 ppm [22,25,58,65,66], mean Ca

levels in the range 3640% [22,47,51]. Table 2 indicates

that the Wharram Percy data are consistent with these

values. Concentrations of essential elements (those

which fulfil vital physiological functions) would be ex-pected to be normally distributed, reflecting the fact that

their concentrations are homeostatically regulated [36].

There is evidence that some non-essential trace elements

show a lognormal distribution in human populations

[36]. However, although it is a non-essential trace ele-

ment, this does not appear to be the case for Sr in bone,

for which a normal distribution has been reported [65].

The distributions of Sr and Ca in the Wharram Percy

group resemble those in modern samples in that they do

not deviate from normality.

For bone buried in calcareous soils, such as at

Wharram Percy, contamination with calcite is a concern

[2]. However, evidence suggests that in the present

material, this problem may not be great. There is no

sign of increased calcium concentrations. Work on the

Wharram Percy bone using X-ray diffraction [42] and

carbonate:phosphate ratios (Ref. [46]: Table 4) provides

no evidence for elevated calcite levels.

Evaluation of histological sections of Wharram Percy

bone by scanning electron microscopy [43,46,67] indi-

cates that preservation of histological detail is poor.

Grupe and Piepenbrink [21] suggest, from laboratory

experiments, that this type of alteration in the histologi-

cal structure of buried bone, which is generally accepted

to be caused by the activities of soil-dwelling micro-organisms, may potentially cause changes in elemental

composition. However, the degree to which the existence

of such changes in archaeological material can be used

as an indicator of diagenetic changes in particular

elements is unclear. Schutkowski et al. [61] found that

there was no correlation between the state of histological

preservation of early Mediaeval bones and their mineral

integrity (as measured by the Ca:P ratio), and they felt

that the histological preservation of specimens was not a

good guide to the validity of element data derived from

them. The fact that bone Sr and Ca levels at Wharram

Percy remain within modern ranges, despite the poorhistological state of the material, is consistent with

this. In addition, preliminary results on Wharram Percy

bone [67] suggest that although biodeterioration due to

invasion by micro-organisms may result in localised

dissolution and re-precipitation of bone mineral, for

calcium at least there is little net loss or gain. The poor

preservation of Wharram Percy bone at the histological

level does not necessarily mean poor preservation of

biogenic trace or bulk element signals.

Although the evidence is not fully conclusive, it seems

reasonable from the above discussion to suggest that

diagenetic changes in Sr and Ca levels may be suf-

ficiently slight to permit a biogenic signal to be dis-

cerned. On this basis, we proceed to the next phase of

the analysis, the investigation of age-related trends in the

Sr:Ca data.

3.2. Age-related variation in Sr:Ca ratios

Analysis of variance and t-tests revealed no evidence

for any significant variation in Sr:Ca ratios with age or

sex in the adult cohort. Variation in Sr:Ca ratios with

respect to age in juveniles is depicted in Fig. 1.

Fig. 1 suggests that infants and young children show

higher Sr:Ca ratios than older individuals, and that there

is a steady decline in Sr:Ca ratios from about 2 years so

that by the age of about 8 years, values resemble those of

adults. Statistical analyses confirm the validity of these

patterns (Tables 3 and 4).

A high Sr:Ca ratio in young children, with a subse-

quent decline to adult values, is expected on physiologi-

cal grounds, given the increasing discrimination against

Sr absorption with respect to calcium with age in the

immature gut [51]. The presence of such a trend rein-

forces the idea that biogenic signals are preserved in the

present Sr:Ca data. However, there is no evidence of a

particularly low Sr:Ca ratio in very young infants, a

pattern which might have been expected in those exclu-

sively breastfed, given the low Sr:Ca ratio of human

breast milk.

3.3. Inferring age at weaning

The ORbonediet values from Ref. [51] were used toestimate dietary Sr:Ca ratios. The results are plotted

against age in Fig. 2. A dietary Sr:Ca ratio of about

1103 is indicated for those under about 1 year. This

appears to rise steeply between about 1 and 2 years so

that by the latter age it reaches a value of about

4103, which resembles the adult mean value of

3.8103.

The question arises as to how realistic these inferred

dietary Sr:Ca ratios are likely to be, given what is known

of Mediaeval diet. Wharram Percy was a poor agrarian

community primarily based on arable farming, but with

some livestock. Peasant diet in Mediaeval times waschiefly made up of foods derived from cereals; animal fat

and protein were at a premium [17]. At Wharram Percy,

it is known that the sea-food component of diets was

minor [39]. Runia [54] measured Sr and Ca in experi-

mentally grown cereal crops, and found ratios ranging

between 3103 and 6103. There is variation in

Sr:Ca ratios in crops according to the soils upon which

they are grown, but if Runias figures can at least be

taken as a very general guide (and the obser-

vation that they resemble figures given for Sr:Ca ratios

in cereal-based diets in different parts of the world [8,52]

suggests that they can), the dietary Sr:Ca ratios inferred


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Fig. 1. Strontium:calcium ratios (104) in immature individuals from Wharram Percy. Mean values according to age groups are superim

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for adults and older juveniles at Wharram Percy appear

reasonable. Given an ORmilkdiet of approximately 0.1

[38], our estimated dietary Sr:Ca ratio of 3.8103 in

adults gives an approximate Sr:Ca ratio of 3.8104

in breast milk. This is in approximate agreement with

values found for human milk in modern studies (ap-

proximately 1.43.4104 [33,52]). However, the in-

ferred dietary Sr:Ca ratios of young infants are greater

than this value, by a factor of at least three for those

under 1 year (Fig. 2).

Fig. 2 indicates a fairly rapid rise in dietary Sr:Ca ratiobetween 1 and 2 years, suggesting that weaning likely

occurred at around that time, so that by the latter age

breast milk had ceased to make a significant contribution

to diet. It is difficult to be more precise about timings

because of uncertainties over the rapidity with which

dietary change in infants is reflected in bone Sr:Ca ratios.

A further caveat is that because these results were gener-

ated on those who died in childhood, they may not be

fully representative of those who survived to older ages.

At this juncture, it is useful to make comparison

between the inferences made from the present results

and those made from previous work on nitrogen stable

isotope ratios at Wharram Percy [44,50]. The nitrogen

isotope results plotted against age are reproduced in Fig.

3. The stable isotope ratios are elevated in young infants,

with a peak at about 1 year. There is a rapid decline

between about 1 and 2 years, indicating weaning, so that

by the latter age, values resemble those in older children

and adults, showing that breast milk was no longer

making a significant contribution. The concordance of

the isotopic and Sr:Ca data indicating weaning between

1 and 2 years of age is striking.

It is worth returning to the observation, made earlier,

of the rather high Sr:Ca ratios in infants under about

1 year of age. The nitrogen data (Fig. 3) indicate thatindividuals in this age range were not yet weaned, but

nevertheless the Sr:Ca ratios are higher than might be

expected with a wholly breast-milk diet. A possible

explanation may be that at Wharram Percy, maternal

milk was being supplemented with small amounts of

foods of higher Sr:Ca ratio even in very young infants.

Mediaeval documentary evidence suggests the use of

cereal-based foods or animal milk to supplement and

eventually replace breast milk in the weaning process

[16]. The inclusion of animal milk would be difficult to

detect using the nitrogen isotope technique, as wouldsupplementation with modest amounts of cereal-based

foods because of their low-protein content. Herbivore

milk appears to have a somewhat higher Sr:Ca ratio

(about 2.41041.5103 [8,52]) than human milk,

and the Sr:Ca ratio of cereal-based foods is up to an

order of magnitude greater [54]. Bone Sr:Ca ratios are

disproportionately influenced by foods with a high cal-

cium content, so that high calcium foods will tend to

mask, in bone Sr:Ca signals, the contribution to diets of

foods lower in calcium [6]. Calcium levels in human milk

are about 200300 ppm [33,38], in cows milk about

10001200 ppm [52] and in cereal grains about 300600 ppm [54]. Given that the calcium levels in the latter

two foods are somewhat greater than that in human

milk, their signals ought not to be masked by the

breast-milk signal. Supplementation of infant diets with

animal milk or cereal foods should therefore be poten-

tially detectable in the bone Sr:Ca technique by elevation

in Sr:Ca ratios in infants.

Studies on other Mediaeval European skeletal

material [19,26] resemble the present one in that they

have also found somewhat greater Sr:Ca ratios in young

infants than might have been expected given breastfeed-

ing alone. These authors ascribed this phenomenon to

early supplementation of breast milk with other foods,

specifically animal milk. It may be that a similar expla-

nation applies at Wharram Percy. A close clustering of

data-points for infants under 1 year is observed (Fig. 2),

so if this explanation is correct, supplementation must

have been undertaken almost from birth and it must

have been a general practice, at least as far as the infants

sampled were concerned, rather than representing an

unusual feeding regime. If it occurred, such an early

supplementation would have had potentially damaging

consequences in that it would expose the infant to poten-

tial sources of infection associated with foods other than

breast milk at an unnecessarily early age. This practicedoes not accord with most Mediaeval documentary

sources on infant feeding, which do not recommend

supplementation of breast milk with other foods imme-

diately from birth, but at some later time, generally when

Table 3

Infant or young child (age:birth3 years) Sr:Ca ratios (104)

N Mean SD tadult vs infant/young child p

32 8.85 1.07 6.58

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Fig. 2. Dietary strontium:calcium ratios (104) in immature individuals from Wharram Percy estimated from bone Sr:Ca ratios using the OR bonediet daSr:Ca value for adults is superimposed.

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Fig. 3. Rib 15N for immature individuals from Wharram Percy aged from birth to 17 years (N65). Mean values for foetal material (aged 2839 weeksuperimposed. Data from Ref. [44].

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providing background data on technical aspects of ICP

AES. Two anonymous reviewers are thanked for perti-

nent comments, which have improved this article.

References

[1] P. Abrahams, Soil Report From Wharram Percy, North

Yorkshire, Ancient Monuments Laboratory Report, 2360,

English Heritage, Portsmouth, 1977.

[2] J.P. Baraybar, C. de la Rua, Reconstruction of diet with trace

elements of bone at the Chalcolithic site of Pico Ramos, Basque

Country, Spain, Journal of Archaeological Science 24 (1997)

355364.

[3] M. Beresford, The Wharram research project: results to 1983,

Mediaeval Archaeology 28 (1983) 77111.

[4] M. Beresford, J. Hurst, Wharram Percy, Batsford/English

Heritage, London, 1990.

[5] D.R. Brothwell, Digging Up Bones, third ed., Oxford University

Press/British Museum (Natural History), Oxford, 1981.

[6] J.H. Burton, L.E. Wright, Nonlinearity in the relationship be-

tween bone Sr/Ca and diet: paleodietary implications, American

Journal of Physical Anthropology 96 (1995) 273282.

[7] J.H. Burton, T.D. Price, W.D. Middleton, Correlation of bone

Ba/Ca and Sr/Ca due to biological purification of calcium,

Journal of Archaeological Science 26 (1999) 609616.

[8] C.L. Comar, Some over-all aspects of strontiumcalcium

discrimination, in: R.H. Wasserman (Ed.), The Transfer of Cal-

cium and Strontium Across Biological Membranes, Academic

Press, New York, 1963, pp. 405417.

[9] C.L. Comar, R.S. Russell, R.H. Wasserman, Strontiumcalcium

movement from soil to man, Science 126 (1957) 485492.

[10] C.L. Comar, R.H. Wasserman, S. Ullberg, G.A. Andrews, Stron-

tium metabolism and strontiumcalcium discrimination in man,

Proceedings of the Society for Experimental Biology andMedicine 95 (1957) 386391.

[11] W.J. Conover, Practical Non-Parametric Statistics, Wiley, New

York, 1971.

[12] T.L. Dupras, H.P. Schwarcz, S.I. Fairgrieve, Infant feeding and

weaning practices in Roman Egypt, American Journal of Physical

Anthropology 115 (2001) 204212.

[13] J.B. Edward, R.A. Benfer, J.S. Morris, The effects of dry ashing

on the composition of human and animal bone, Biological and

Trace Element Research 25 (1990) 219231.

[14] R.W. Elias, Y. Hirao, C.C. Patterson, The circumvention of

natural biopurification of calcium along nutrient pathways by

atmospheric inputs of industrial lead, Geochimica et Cosmo-

chimica Acta 46 (1982) 25612580.

[15] L.F. Fieser, M. Fieser, Advanced Organic Chemistry, Chapman

and Hall, London, 1961.[16] V.A. Fildes, Breasts, Bottles and Babies: A History of Infant

Feeding, Edinburgh University Press, Edinburgh, 1986.

[17] F. Gies, J. Gies, Life in a Mediaeval Village, Harper & Row,

London, 1990.

[18] G. Grupe, Impact of the choice of bone samples on trace element

data in excavated human skeletons, Journal of Archaeological

Science 15 (1988) 123129.

[19] G. Grupe, H. Bach, Life style, subsistence and mortality in the

Slavonic village at Espenfeld (Kr. Arnstadt, FRG). A trace

element study, Anthropologischer Anzeiger 51 (1993) 317332.

[20] G. Grupe, S. Hummel, Trace element studies on experimentally

cremated bone. I. Alterations of the chemical composition at high

temperatures, Journal of Archaeological Science 18 (1991)

177186.

[21] G. Grupe, H. Piepenbrink, Impact of microbial activity on

trace element concentrations in excavated bones, Applied

Geochemistry 4 (1989) 293298.

[22] R.G.V. Hancock, M.D. Grynpas, K. Akesson, K.B. Obrant, J.

Turnquist, M.J. Kessler, Baselines and variabilities of major and

trace elements in bone, in: J.B. Lambert, G. Grupe (Eds.),

Prehistoric Human Bone Archaeology at the Molecular Level,

Springer, Berlin, 1993, pp. 188201.[23] E.W. Hartsook, T.V. Hershberger, Strontiumcalcium discrimi-

nation during placental transfer and foetal uptake in rats, Pro-

ceedings of the Society for Experimental Biology and Medicine

143 (1973) 343349.

[24] D.A. Herring, S.R. Saunders, M.A. Katzenberg, Investigating

the weaning process in past populations, American Journal of

Physical Anthropology 105 (1998) 425439.

[25] R.M. Hodges, N.S. MacDonald, R. Nusbaum, R. Stearns, F.

Ezmirlian, P. Spain, C. McArthur, The strontium content of

human bones, Journal of Biological Chemistry 185 (1950)

519524.

[26] G. Huhne-Osterloh, G. Grupe, Causes of infant mortality in the

middle ages revealed by chemical and palaeopathological analyses

of skeletal remains, Zeitschrift fur Morphologie und

Anthropologie 77 (1989) 247258.[27] M.A. Katzenberg, Stable isotope analysis: a tool for studying past

diet, demography and life history, in: M.A. Katzenberg, S.R.

Saunders (Eds.), Biological Anthropology of the Human

Skeleton, Wiley-Liss, New York, 2000, pp. 305327.

[28] M.A. Katzenberg, S. Pfeiffer, Nitrogen isotope evidence for

weaning age in a nineteenth century skeletal sample, in: A. Grauer

(Ed.), Bodies of Evidence, Wiley, New York, 1995, pp. 221235.

[29] M.A. Katzenberg, D.A. Herring, S.R. Saunders, Weaning and

infant mortality: evaluating the skeletal evidence, Yearbook of

Physical Anthropology 39 (1996) 177199.

[30] H. Keeley, Wharram Percy, Yorkshire, Soil Report, manuscript

on file at English Heritage, Portsmouth, unpublished.

[31] S.E. King, S.J. Ulijaszek, Invisible insults during growth and

development: contemporary theories and past populations, in:

R.D. Hoppa, C.M. Fitzgerald (Eds.), Human Growth in the Past:

Studies From Bones and Teeth, Cambridge University Press,

Cambridge, 1999, pp. 161182.

[32] K. Kostial, N. Grunden, A. Durakovic, Intestinal Absorbtion of

Calcium-47 and Strontium-85 in Lactating Rats, Calcified Tissue

Research 4 (1969) 1319.

[33] M. Krachler, E. Rossipal, D. Micetic-Turk, Trace element trans-

fer from the mother to the newborn investigations of triplets of

colostrum, maternal and umbilical cord sera, European Journal

of Clinical Nutrition 53 (1999) 486494.

[34] J.B. Lambert, S.M. Vlasak, A.C. Thometz, J.E. Buikstra, A

comparative study of the chemical analysis of ribs and femurs

in Woodland populations, American Journal of Physical

Anthropology 59 (1982) 289294.

[35] J.B. Lambert, S. Vlasak-Simpson, J.E. Buikstra, D. Hanson,Electron microprobe analysis of elemental distribution in

excavated human femurs, American Journal of Physical


[36] K. Liebscher, H. Smith, Essential and non-essential trace

elements, Archives of Environmental Health 17 (1968) 881890.

[37] W.L. Lindsay, Chemical Equilibria in Soils, Wiley, New York,

1979.

[38] S.A. Lough, G.H. Hamada, C.L. Comar, Secretion of dietary

strontium 90 and calcium in human milk, Proceedings of the

Society for Experimental Biology and Medicine 104 (1960)

194198.

[39] S. Mays, Carbon stable isotope ratios in Mediaeval and Later

human skeletons from northern England, Journal of Archaeologi-

cal Science 24 (1997) 561567.


8/11/2019 Mays, 2003

11/11

[40] S. Mays, The Archaeology of Human Bones, Routledge/English

Heritage, London, 1998.

[41] S. Mays, New directions in the analysis of stable isotopes in bones

and teeth, in: M. Cox, S. Mays (Eds.), Human Osteology in

Archaeology and Forensic Science, Greenwich Medical Media,

London, 2000, pp. 425438.

[42] S. Mays, The human bones, in: A. Clark (Ed.), Wharram Percy:

The Churchyard, in press.[43] S. Mays, G.M. Taylor, A.J. Legge, D.B. Young, G.

Turner-Walker, Palaeopathological and biomolecular study of

tuberculosis in a Mediaeval skeletal collection, American Journal

of Physical Anthropology 114 (2001) 298311.

[44] S.A. Mays, M.P. Richards, B.T. Fuller, Bone stable isotope

evidence for infant feeding in Mediaeval England, Antiquity 76

(2002) 654656.

[45] A.E.W. Miles, The dentition in the assessment of individual age in

skeletal material, in: D.R. Brothwell (Ed.), Dental Anthropology,

Pergamon, Oxford, 1963, pp. 191209.

[46] C.M. Nielsen-Marsh, R.E.M. Hedges, Patterns of diagenesis in

bone. I: The effects of site environments, Journal of Archaeologi-

cal Science 27 (2000) 11391150.

[47] D. Pate, K.A. Brown, The stability of bone strontium in the

geochemical environment, Journal of Human Evolution 14 (1985)483491.

[48] T.D. Price, R.W. Swick, E.P. Chase, Bone chemistry and pre-

historic diet: strontium studies of laboratory rats, American


[49] S.C. Radosevich, The six deadly sins of trace element analysis: a

case of wishful thinking in science, in: M.K. Sandford (Ed.),

Investigations of Ancient Human Tissue, Gordon and Breach,

Reading, 1993, pp. 269332.

[50] M.P. Richards, S. Mays, B. Fuller, Stable carbon and nitrogen

isotope values of bone and teeth reflect weaning age at the

Mediaeval Wharram Percy site, Yorkshire, UK, American


[51] J. Rivera, J.H. Harley, The HASL bone program: 19611964,

United States Atomic Energy Commission Health and Safety

Laboratory Report No. 163, 1965.[52] H.L. Rosenthal, Content of stable strontium in man and animal

biota, in: C. Skoryna (Ed.), Handbook of Common Strontium,

Plenum, New York, 1981, pp. 503514.

[53] E. Rossipal, M. Krachler, F. Li, D. Micetic-Turk, Investigation of

the transport of trace elements across barriers in humans: studies

of placental and mammary transfer, Acta Paediatrica 89 (2000)

11901195.

[54] L.T. Runia, Strontium and calcium distribution in plants: effect

on palaeodietary studies, Journal of Archaeological Science 14

(1987) 599608.

[55] M.K. Sandford (Ed.), Investigations of Ancient Human Tissue,

Gordon & Breach, Reading, 1993.

[56] M.K. Sandford, D.S. Weaver, Trace element research in anthro-

pology: new perspectives and challenges, in: M.A. Katzenberg,

S.R. Saunders (Eds.), Biological Anthropology of the HumanSkeleton, Wiley-Liss, New York, 2000, pp. 329350.

[57] I. Schour, M. Massler, The development of the human dentition,

Journal of the American Dental Association 28 (1941) 11531160.

[58] H.A. Schroeder, I.H. Tipton, A.P. Nason, Trace metals in man:

strontium and barium, Journal of Chronic Diseases 25 (1972)

491517.

[59] M.R. Schurr, Stable nitrogen isotopes as evidence for the age of

weaning at the Angel site: a comparison of isotopic and demo-

graphic measures of weaning age, Journal of Archaeological

Science 24 (1997) 919927.

[60] M.R. Schurr, Using stable nitrogen isotopes to study weaning

behaviour in past populations, World Archaeology 30 (1998)

327342.

[61] H. Schutkowski, B. Herrmann, F. Wiedemann, H. Bocherens, G.

Grupe, Diet, status and decomposition at Weingarten: traceelement and isotope analyses on early Mediaeval skeletal

material, Journal of Archaeological Science 26 (1999) 675685.

[62] A. Sillen, Diagenesis of the inorganic phase of cortical bone, in:

T.D. Price (Ed.), The Chemistry of Prehistoric Bone, Cambridge

University Press, Cambridge, 1989, pp. 211229.

[63] A. Sillen, P. Smith, Weaning patterns are reflected in strontium

calcium ratios of juvenile skeletons, Journal of Archaeological

Science 11 (1984) 237245.

[64] A. Sillen, J.C. Sealey, J. van der Merwe, Chemistry and palaeo-

dietary research: no more easy answers, American Antiquity 54

(1989) 504512.

[65] D.L. Thurber, J.L. Kulp, E. Hodges, P.W. Gast, J.M. Wampler,

Common strontium content of the human skeleton, Science 128

(1958) 256257.

[66] K.K. Turekian, J.L. Kulp, Strontium content of human bones,Science 124 (1956) 405407.

[67] G. Turner-Walker, S. Mays, U. Syversen, An SEMBSE study

of bone mineral diagenesis. Where does all the calcium go?,

Taphonomy and Diagenesis Newsletter 7 (2000) 33.

[68] V.J. Vitzthum, Comparative study of breastfeeding structure and

its relation to human reproductive ecology, Yearbook of Physical


S. Mays / Journal of Archaeological Science 30 (2003) 731741 741

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