The Alvastra diet from bone chemistry Sælebakke, Inger
Fornvännen 1988, 1-5
http://kulturarvsdata.se/raa/fornvannen/html/1988_001 Ingår i: samla.raa.se
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The Alvastra diet from bone chemistry
By Inger Saelebakke and Stig Welinder
Saelebakke, I. & Welinder, S., 1988. The Alvastra diet from bone chemistry. Forn- vännen 83. Stockholm.
Three individuals from the Alvastra pile-dwelling, c. 4500 B.P., have been studied as regards food intake. The methods used are measurements of "C-content and the strontium/calcium (Sr/Ca) ratio in bone tissue. The diet is demonstrated to have been remarkably similar. It was dominated by plant food; there are no ap- preciable traces of marine food.
Inger Salehakke and Stig Welinder, Universitetets Oldsaksamling, Frederiksgt. 2. N-0164 Oslo 1, Norway.
M a n is an omnivorous creature. His ability to adapt diets from a wide range of ecological niches is one of the reasons why he inhabits almost the entire surface of the earth.
M a n differs from animals in his complex way ol food-sharing. Food is shared not only be- tween close kin, but also within a social network which may differ from one society to another.
However, food is not shared indiscriminatdy, because it is a scarce resource and linked to sur- vival (van den Berghe 1984),
In all societies rituals are connected with food-sharing, and express how we transform nature into culture. Anthropological studies show us how culture influences our relationship to what we eat. O f a l l nutrients available only some will be recognized as food. Food is dassified in a n u m b e r of ways according to medical and religious bdiefs, and variables such as status, sex and age (Foster et al. 1978).
T h e traditional methods which archaeolo- gists use to study prehistoric diet are based on ccofacts and skeletal data. It is possible to assess with some certainly, which of the nutrients available to a society were actually exploited.
Seasonal change in diet may also be studied. A main problem in the study of prehistoric diet and economy is the quantification of the pro- portions of meat and vegetarian food, and also how food was distributed to subgroups within a society.
T h e study of prehistoric diet was criticised by
Dennell in 1979. In his opinion archaeological data pertain to the production of food rather than its consumption. He characterizes the devdopments in the study of prehistoric economy in the 70's as " a p p a r e n t rather than r e a l " and states that (op.cit., p. 131) " . . . it seems unlikely that the size of prehistoric com- munities can be calculated from settlement data with sufficient precision to be used in evaluations of prehistoric food consumption".
Although we realize that Dennell pointed out crucial problems concerning the study of prehistoric diet, we see reason to revise his pessimism.
A main topic of the doctoral thesis by H a n s Browall in 1986 is an investigation of the eco- nomy of a Middle Neolithie settlement site at Alvastra, Sweden (Fig. 1). T h e source material comprises the remnants of a pile-dwelling, which was occupied fora short time c. 4500 B.P.
For the suggested resource area of the settlement site, Browall presents three hypothetical models for consumption of meat versus vegetarian food:
(A) 75 % m e a t - 2 5 % vegetarian food, (B) 50 % - 5 0 % and (C) 25 % - 7 5 %.
Model A could immediatdy be rejected because the resource area would not provide sufficient grazing land for the animals re- quired. Models B and C seem more likely.
Via new methods for the study of prehistoric diet we may be able to decide which of the two remaining m o d d s is the more likely. These
2 /. Scelebakke & S . Welinder
methods are based on chemical components in skeletal tissue and how they reflect the composi- tion of meat and plant-food, marine and ter- restrial food in diet.
We may also test whether archaeological data are reliable as indicators of prehistoric econo- my.
Methods
Cortical bone samples of three adult humans, undetermined as regards sex, and bones from red deer, wild boar and wolf found at the Alvastra pile-dwelling, were subjected to analysis via the Sr/Ca-method and the " C - method to determine whether their diet con- sisted of meat or plants, and marine or ter- restrial food. T h e former method is based on the relation between strontium (Sr) and calcium (Ca) in the inorganic part of the bone.
T h e latter method is based on the proportion of
" C in bone collagen.
T h e study of diet from chemical elements in bone, involves three major problems. These are listed below with reference to relevant litera- ture:
1) T h e overall distribution of the element to be studied, and the metabolic considera- tions in the uptake and deposition in skeletal tissue. (Sr/Ca: C o m a r et al. 1957; Kulp et al.
1957; Toots et al. 1965; Schoeninger 1979.
,:,C: DeNiro et al. 1983; Olsson 1985.)
2) Diagenetic processes in interred bones (DeNiro et al. 1985; Lambert et al. 1985; Wing et al. 1979; Sillen 1981).
3) Measuring techniques, preparalion tech- niques (Schoeninger 1979; S z p u n a r e t al. 1978;
Brown et al. 1978; Chisholm et al. 1983).
The Sr/Ca-method
T h e Sr/Ca-ratio is decreasing through a food- chain, from plants to herbivores, to carnivores.
A person living mainly on plants is thus likely to have a higher Sr/Ca-ratio in the skeletal tissue than one who eats a great deal of meat.
Brown 1974 was the first to apply this method to h u m a n subfossil bones. Research on the in- corporation of strontium into skeletal tissue was prompted by the fallout of '"'Sr from nuclear tests. A review of the method as used in paleodietary research is given by Sillen et al.
1982.
Fig. 1. The Middle Neolithie Alvastra pile-dwelling at Lake Vättern 110 km from the sea. — Alvastra pål- byggnad vid Vättern, 110 km från havet.
In our particular study bone samples of h u m a n s and animals were prepared according to lhe principles described by Brown et al. 1978 and Szpunar et al. 1978. T h e content of stron- tium and calcium was measured by I C P emis- sion spectroscopy.
The "C-method
This method derives from the 14C-dating method. As used in studies of prehistoric diet, it was originally applied to early maize-cultiva- ting societies. Maize incorporates the carbon isotope " C differently from most other plants (e.g. Vogel et al. 1977). Tauber first applied this method to distinguish between marine and ter- restrial food in 1981, and it was låter used in similar ways by other scientists (Hobson et al.
1984; Chisholm 1983).
Both marine food and terrestrial plants con- tain strontium in similar proportions. An in- dividual with a high Sr/Ca-ratio, and an un- known proportion of marine food in his diet, is difficult to evaluate, because the high ratio may
Fornvännen 3.1 (1933)
Table 1. Skeletal chemistry data from the Middle Neolithie pile-dwelling Alvastra, Sweden. — Kemiska analyser av ben från Alvastra pålbyggnad.
(1) (2) (3) (4) (5) (6) (7) (8)
Red deer Wild boar Wolf H u m a n s
3 3 1 3
.021 .013 .020 .013
29.7 27.0 31.7 31.6
.70 .47 .63 .42
. 5 7 - . S 7 . 3 7 - . 5 5
. 4 1 - . 4 2 .13
.08
.01 - 2 1 . 1 3 .20
(l) = n u m b c r of samples, (2) = mean content of Sr (%), (3) = mean content of C a ( % ) , (4) = m e a n ratio S r / C a ( x 10'), (5) = range of ratio S r / C a (xlO3), (6) = stand. dev. of (4), (7) = mcan 5, : !C P D B ("/oo), (8) = stand. dev. of (7). — ( 1 ) - a n t a l prover, (2) = strontiuininnehåll, medelvärde (%), (3) = cak iuminnehåll, medelvärde (%), (4) = kvoten Sr/Ca, medelvärde (xlO3), (5) = minsta och största värde lör (4), (6)»standardavvikelse för (4), ( 7 ) - ä1 3C PDB, medelvärde ("/oo), (8)-standardavvikelse för (7).
be due to either plant or marine food. To ex- d u d e marine food as a source of error in our analyses, the "C-content in the h u m a n bones was analysed.
T h e h u m a n bone samples (all of them from fibulae) were treated according to Method 2 as described by Chisholm et al. 1983. This method implies that the bone samples are steeped in caustic soda for 18—20 hours in one step of the preparalion procedure. As compared with other methods this may cause a variation of 0.6—0.8 "Am, which should be borne in mind when the results are evaluated. T h e content of
" C in prepared solid bone collagen was measured by mäss spectronomy.
Results and discussion
T h e Sr/Ca and " C values are displayed in Table 1. T h e results obtained from the " C analyses show values indicating a terrestrial diet for all three of the humans. Even with a va- riation of 0.6—0.8 "/oo due to preparalion pro- cedure, and one of 1 "/oo caused by metabolic differences in individuals having the same diet (DeNiro et al. 1983) the results still fall within the range of terrestrial food-choice.
However, sources of error were indicated by a study of the diet of occupants of (coastal) sett- lements on the Baltic (Welinder 1985). T h e freshwater content of the Baltic is higher than that of the North Atlantic, and this may cause differences in "C-content. T h e r e are, however, no obvious errors in the "C-content of existing measurements of individuals from coastal and inland settlements in the Baltic area, as dif-
ferences actually exist between these two sets of data (cf Olsson 1985). It is thus likely that we have interpreted the Alvastra values correctly, and can state that marine food was of insignifi- cant importance for the inhabitants of Alvastra.
T h e values of the Sr/Ca analyses should now be reliable since marine food is exduded as a main source. T h e values obtained for the Sr/Ca ratio in the bone samples from the species analysed fall approximately within the range of 20 % to the mean ratio for each species (Schoeninger 1979). Red deer have a diet comp- letely based on plants, and have the highest Sr/Ca-ratio. T h e only carnivore present, a wolf, has a Sr/Ca-ratio of 0.63, which qualifies it as a herbivore. Overlap between carnivores and herbivores has previously been reported (Sillen 1981), and the unfortunate fact that we have had only one carnivore available for our analyses may have caused this result.
T h e Sr/Ca-ratio for the wolf must also be considered from another point of view. Wolves are reported to migrate (Bjärvall et al. 1986, Pulliainen 1979). Male wolves of about 2—3 years of age may leave the group to roam often for long distances. T h u s , it is possible that the woll came from far away. Individuals raised on diets from different areas with different stron- tium levels in the soil should not be directly compared (Sillen et al. 1982).
T h e h u m a n s in our study have values within the range of those of the wild boars. An analysis of the stomach-contents of several hundred wild boars in D D R shows that they eat mainly plant-food and prefer acorns when available (Briedermann 1976). T h e Sr/Ca-ratio of the
4 /. Scelebakke & S . Welinder
A l v a s t r a wild b o a r s c o m p a r e d w i t h t h a t of t h e r e d d e e r s h o w s t h a t t h e y w e r e n o t e n t i r e l y d e p e n d e n t o n p l a n t f o o d . T h i s m a y c o n f o r m t o L e p i k s a a r ' s (1974) t h e o r y c o n c e r n i n g t h e wild b o a r s at t h e M i d d l e N e o l i t h i e site A s , i.e.
g r o u p s of wild b o a r lived close t o t h e s e t t l e m e n t in t h e w i n t e r - s e a s o n w h e r e t h e y h a d e a s y access t o s c r a p s a n d refuse f r o m h u m a n food- p r e p a r a t i o n a n d c o n s u m p t i o n . T h u s , t h e wild b o a r s w o u l d have e a t e n m o r e m e a t t h a n t h e i r p r e s e n t r d a t i v e s in D D R , w h i c h r a r d y e a t m o r e t h a n 5 % m e a t a n n u a l l y . It h a s also b e e n s u g g e s t e d t h a t t h e A l v a s t r a s p e c i m e n s in fact r e p r e s e n t d o m e s t i e p i g s ( J o n s s o n 1986).
A c c o r d i n g to t h e S r / C a a n a l y s e s of t h e h u m a n b o n e s a m p l e s f r o m A l v a s t r a a n d t h e c o m p a r i s o n w i t h t h o s e a n i m a l s w i t h a k n o w n d i e t from t h e s a m e site, we have c o m e to t h e c o n d u s i o n t h a t M o d e l C is t h e m o s t p r o b a b l e for t h e c o n s u m p t i o n of m e a t a n d p l a n t - f o o d , viz. t h e c o n s u m p t i o n of m e a t was a p p r o x i m a t e - ly 25 % a n d t h e r e m a i n i n g 75 % p l a n t s .
O u r r e s u l t s a g r e e closely w i t h B r o w a l F s h y p o t h e s i s , w h i c h m a y p r o v e , o r at least i n - d i c a t e , t h a t ecofact a n d site c a t c h m e n t d a t a c o u l d b e u s e d for r e c o n s t r u c t i o n of p r e h i s t o r i c food c o n s u m p t i o n a n d p a l e o e c o n o m y .
By u s i n g b o n e s t r o n t i u m ä s a n i n d i c a t o r of access t o m e a t , skeletal s a m p l e s from H u i t z o , M e x i c o , w e r e a n a l y s e d by B r o w n 1974. H i s r e s u l t s s h o w t h a t in u n s t r a t i f i e d societies m a l e s a t e m o r e m e a t t h a n females. T h e s a m e a n a l y s i s s h o w e d t h a t a s t h e society b e c a m e stratified, t h e h i g h - r a n k i n g i n d i v i d u a l s a t e m o r e m e a t t h a n t h o s e of low s t a t u s . S k e l e t o n s f r o m C h a l c a t z - ingo, M e x i c o , i n d i c a t e t h e s a m e t e n d e n c y ( S c h o e n i n g e r 1979). T h e difference b e t w e e n t h o s e b u r i e d w i t h j a d e a r t e f a c t s a n d t h o s e w i t h o u t g r a v e - g o o d s w a s significant w i t h r e s p e c t t o access t o m e a t . F u r t h e r , Sillen 1981 h a s found a slight d i f f e r e n c e b e t w e e n m a l e s a n d f e m a l e s from t h e N a t u f i a n levels in t h e H a y o n i m C a v e , I s r a e l . T h e m a l e s h a d t h e lowest S r / C a - r a t i o , w h i c h m e a n s t h a t t h e y a t e m o r e m e a t t h a n t h e females.
T h e t h r e e h u m a n s from A l v a s t r a a r e u n d e t e r m i n e d a s r e g a r d s sex a n d n o i n f o r m a - t i o n o n s t a t u s is a v a i l a b l e . Still we a r e a b l e to suggest t h a t t h e r e w a s n o significant d i f f e r e n c e in diet b e t w e e n t h e m , w i t h r e s p e c t e i t h e r t o t h e
c o n s u m p t i o n of p l a n t s a n d m e a t , o r t o m a r i n e a n d t e r r e s t r i a l food.
W i t h t h e s e c o m p a r a t i v d y n e w m e t h o d s in t h e s t u d y of p r e h i s t o r i c d i e t , it is p o s s i b l e t o ex- c e e d t h e f r a m e w o r k w i t h i n w h i c h a r - c h a e o l o g i s t s h a v e w o r k e d t o s e p a r a t e p r o d u c - t i o n from c o n s u m p t i o n a n d p e n e t r a t e t h e c o m - plex s y s t e m s of s u b d i v i s i o n of food in p r e h i s t o r i c societies. T h e m e t h o d s d e v e l o p e d a r e in fact a c o n s e q u e n c e of r e s e a r c h o n n u c l e a r w e a p o n s a n d fallout of s t r o n t i u m f r o m n u c l e a r tests. P a l e o d i e t a r y r e s e a r c h m a y p e r h a p s , for s a d r e a s o n s , be i n t e n s i f i e d in y e a r s t o c o m e , a s s c i e n t i s t s s t u d y t h e fallout of ' " C s f r o m C h e r - n o b y l , a n d its d e p o s i t i o n in l i v i n g o r g a n i s m s .
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Alvastra-diet och benkemi
K e m i s k a u n d e r s ö k n i n g a r av b e n k a n i n d i k e r a d e l e v a n d e i n d i v i d e r n a s k o s t h å l l . " C - i n n e h å l - let i b e n e n ä r ett m å t t på a n d e l e n m a r i n föda i d e t t o t a l a k o s t h å l l e t , k v o t e n s t r o n t i u m / c a l c i u m ett m å t t på r e l a t i o n e n m e l l a n a n i m a l i s k föda o c h v ä x t f ö d a .
F ö r t r e i n d i v i d e r från A l v a s t r a p å l b y g g n a d g ä l l e r att d e r a s kosthåll h a r varit lika m e d avse- e n d e p å d e o v a n r e f e r e r a d e p a r a m e t r a r n a . D e l - ta kosthåll h a r i n t e i n n e h å l l i t m a r i n föda eller e n d a s t försumbart lite m a r i n föda u t a n h a r d o - m i n e r a t s av v ä x t f ö d a . E n k a l i b r e r i n g m o t d e på
b o p l a t s e n förekommande d j u r a r t e r n a v i s a r att d e ätit a n i m a l i s k föda i u n g e f ä r lika s t o r m ä n g d s o m v i l d s v i n e n . M o d e r n a ö s t t y s k a v i l d s v i n ä t e r h ö g s t 5 — 1 0 % a n i m a l i e r . M e l l a n n e o l i t i s k a v i l d s v i n , s o m h a r haft t i l l g å n g till a v f a l l s h ö g a r - n a r u n t e n b o p l a t s , k a n förväntas h a ätit m e r a a n i m a l i s k föda.
V å r b e d ö m n i n g är, att av d e av Browall 1986 för A l v a s t r a f ö r e s l a g n a e k o n o m i s k a m o d e l l e r n a ä r m o d e l l C d e n s a n n o l i k a s t e . D e n n a i n n e b ä r ett kosthåll m e d 25 % a n i m a l i s k föda och 75 %
växtföda.
