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THE PALEODEMOGRAPHY OF WESTERN SIBERIA IN THE MIDDLE AND LATE BRONZE AGE
ARCHAEOLOGY, ETHNOLOGY & ANTHROPOLOGY OF EURASIA Archaeology Ethnology & Anthropology of Eurasia 34/2 (2008) 143–153 E-mail: [email protected]
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ANTHROPOLOGY A.V. Zubova Institute of Archaeology and Ethnography, Siberian Branch, Russian Academy of Sciences, Akademika Lavrentieva 17, Novosibirsk, 630090, Russia E-mail: [email protected]
THE PALEODEMOGRAPHY OF WESTERN SIBERIA IN THE MIDDLE AND LATE BRONZE AGE* Based on the paleodemographic evaluation of human skeletal remains from Yelovsky-2, Chernoozerye-1, Zhuravlevo-4, Tanay-7, and Zarechnoye-1, those populations fall into two groups differing in their cumulative stress level, which was high during the Andronovo period, and decreased by the Late Bronze Age. This is evidenced by a lower age of death and earlier onset of mortality peaks in samples from Chernoozerye and Yelovsky. Two models of demographic adaptation to changing conditions are proposed: emigration for Tanay, and the inclusion of new members into the aging population for Yelovsky. Introduction Human adaptation is a complex process involving a variety of morphological, functional, and socio-cultural features. Demographic parameters, too, are involved, and they are intrinsically related to cultural features studied by archaeologists. The demographic structure of an ancient population can shed light on the factors underlying cultural changes. Demographic decline or success may cause migrations, extending the marital distance and eventually leading to the distribution of cultural features or to the replacement of old traditions by new ones. In archaeological studies, cultural changes and migrations are commonly believed to result from outward factors such as environmental changes and political conicts. Intrinsic demographic features receive much less attention, and biological laws underlying population structure are generally disregarded. Attempts to reconstruct the demographic characteristics of prehistoric populations of Western Siberia on the
basis of archaeological and skeletal data have been made more than once (Bobrov, Chikisheva, Mikhailov, 1993; Chikisheva, 2000; Matveyeva, 2002; Tikhonov, 1993). Cross-population analysis of mortality curves has rarely been attempted, and the relationship between demographic and socio-cultural features has not been assessed, nor has the relevance of demographic data for adaptation been evaluated. In the present article, demographic parameters are analyzed with regard to the stability of the group and its biological potential. We will refrain from using evaluative terms such as “negative” or “positive” with regard to the demographic situation, because any mortality and fertility fluctuations may be adaptive responses to environmental changes. The objective of the study is to use demographic data as a source for assessing the adaptation of Middle and Late Bronze Age Western Siberian populations. Materials and methods
*This study is part of the Russian Academy of Sciences Project “Adaptation of Peoples and Cultures to Environmental, Social, and Technogenic Transformations.”
The skeletal samples used in this study are the best preserved Middle and Late Bronze Age materials from
Copyright © 2008, Siberian Branch of Russian Academy of Sciences, Institute of Archaeology and Ethnography of the Siberian Branch of the Russian Academy of Sciences. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aeae.2008.07.014
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Table 1. Sex composition of the populations Groups
Males
Females
Children
Indeterminate
Total
Yelovsky-2, Andronovo period
74 (33.2)
59 (26.5)
89 (39.9)
0
223 (100)
Same, Yelovka culture
26 (23.4)
38 (34.2)
35 (31.5)
12 (10.8)
111 (100)
22 (?)
28 (?)
–
0
–
Zhuravlevo-4
47 (33.8)
50 (35.97)
42 (30.2)
0
139 (100)
Tanay-7
15 (23.4)
15 (23.4)
25 (39)
9 (14.06)
64 (100)
Zarechnoye-1
17 (27.9)
16 (26.23)
17 (27.9)
11 (18.03)
61 (100)
Stary Sad
20 (41.7)
15 (31.25)
13 (27.08)
0
48 (100)
Chernoozerye-1
Note. Here and in Table 2, percentages are indicated in parentheses.
Table 2. Age structure of the populations Yelovsky-2 Age, years
Andronovo period
Yelovka culture
Chernoozerye-1
Zhuravlevo-4
Tanay-7
Stary Sad
Zarechnoye-1
1 (5.89)
Males 16–20
3 (4.23)
2(10)
0
0
2 (13.33)
2 (10)
21–25
9 (12.68)
1 (5)
1 (4.55)
3 (6.38)
1 (6.67)
1 (5)
26–30
10 (14.08)
3 (15)
3 (13.63)
7 (14.89)
6 (40)
3 (15)
31–35
17 (23.94)
1 (5)
5 (22.73)
5 (10.64)
4 (26.67)
1 (5)
36–40
15 (21.13)
6 (30)
8 (36.36)
15 (31.91)
0
8 (40)
41–45
5 (7.04)
4 (20)
2 (9.09)
8 (17.02)
1 (6.67)
1 (5)
46–50
2 (2.82)
3 (15)
1 (4.55)
5 (10.64)
0
1 (5)
10 (14.08)
0
2 (9.09)
4 (8.51)
1 (6.67)
3 (15)
2 (11.76)
2 (12. 5)
50 +
3 (17.64)
6 (35.29)
5 (29.41)
Females 16–20
6 (11.54)
5 (16.13)
3 (10.7)
10 (20)
2 (13.33)
1 (6.67)
21–25
10 (19.23)
2 (6.45)
6 (21.43)
6 (12)
3 (20)
1 (6.67)
26–30
9 (17.3)
6 (19.35)
5 (17.85)
11 (22)
3 (20)
0
31–35
16 (30.77)
1 (3.23)
2 (7.14)
1 (2)
5 (33.33)
1 (6.67)
36–40
4 (7.69)
3 (9.68)
4 (14.28)
5 (10)
1 (6.67)
4 (26.67)
41–45
1 (1.92)
3 (9.68)
1 (3.57)
8 (16)
0
6 (40)
46–50
3 (5.77)
5 (16.13)
3 (10.7)
7 (14)
1 (6.67)
2 (13.33)
50 +
3 (5.77)
6 (19.35)
2 (7.14)
2 (4)
0
0
3 (18.75)
4 (25)
4 (25)
3 (18.75)
Children 0–5
59 (65.6)
22 (62.9)
–
30 (71.4)
18 (75)
8 (61.5)
8 (50)
6–10
28 (31.11)
3 (8.57)
–
7 (16.67)
3 (12.5)
2 (15.38)
5 (31.25)
11–15
3 (3.33)
10 (28.57)
–
5 (11.9)
3 (12.5)
3 (23.07)
0
0
0
–
0
0
0
3 (18.75)
Indeterminate
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Western Siberia. Because only series from completely or nearly completely excavated cemeteries are suitable for demographic analysis (Alekseyev, 1989; Buzhilova, 1997), only seven groups were used. Andronovo-type cemeteries include Yelovsky-2 in Tomsk Province, and Chernoozerye-1 in Omsk Province (the Irtysh Basin); those of the Yelovka culture are represented by Yelovsky-2; those of the Inya variant of the Irmen culture, by Zarechnoye-1, Zhuravlevo-4, and Tanay-7, and those of the Late Bronze Age, by Stary Sad. Sex and age determinations for Yelovsky-2, Chernoozerye-1, and Zarechnoye-1 were made by V.A. Dremov and have been partly published (Zakh, 1997; Matyuschenko, 2004); those for Zhuravlevo-4 and Stary Sad, by T.A. Chikisheva (Bobrov, Chikisheva, Mikhailov, 1993; Chikisheva, 2000); the sex and age of certain individuals were redened by the present author (Tables 1, 2). The analysis was conducted in two stages. First, the local characteristics of each population were evaluated; second, separate Bronze Age populations were compared with one another and with other groups to assess general demographic tendencies. The demographic structure was evaluated using standard life tables to assess survivorship (Ubelaker, 1978) and to generate mortality curves. Also, the average age at death, the sex ratio as an indicator of effective reproduction, the mean number of dead children per female dying in the reproductive age, and the
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numerical relationship between reproductive (16 – 40) and postreproductive (above 40) parts of the population was calculated (Tables 3 – 6). Results Chernoozerye-1 (Andronovo period). While the total number of burials excavated at that cemetery approaches 170, sex and age determinations are available for fifty adults only. The average age of death is rather low according to Bronze Age standards (Table 3). Mortality peaks coincide with 21 – 25 and 36 – 40 age intervals in females, and with the last age interval in males (Fig. 1). During the early reproductive period (16 – 20), the number of females surpasses the number of males, but age 30 was reached by fourteen females (50.2 %) and eighteen males (81.8 %) (Table 2). Due to a higher mortality in males in the 30 – 40 age interval, the sex ratio becomes nearly 1:1 by age forty. Because child mortality cannot be assessed from materials of that site, no denite conclusions as to the age structure of the population or its reproductive potential can be made. It can only be suggested that this potential was limited by a high female mortality in the reproductive period. Mortality curves for Chernoozerye-1 (Fig. 1), point to a regular stress experienced by the reproducing part of the population.
Table 3. Average age at death Groups
Males
Females
Adults
Total
35.7
31.2
33.8
21.4
36
37.09
36.7
24.17
Chernoozerye-1
37.27
32.58
34.93
–
Zhuravlevo-4
37.5
31.8
34.6
25.3
Tanay-7
31
29.3
30.3
19.01
Zarechnoye-1
38
34.5
36.25
20.27
Stary Sad*
38
36.1
36.9
28.2
Karasuk-3 (Afanasyev culture, Minusinsk Basin)**
36.2
39.4
37.8
24.1
Tasty-Butak (Andronovo culture, Kazakhstan)**
34.4
37.5
35.95
18.7
Balanovo-2 (Fatyanovo culture)**
31.4
32
31.7
20.3
27
32.7
29.85
25.1
Mokrin (Mound culture, Yugoslavia)**
37.4
38.6
38
–
Sapallitepa (Painted ware culture, Uzbekistan)**
33.8
36.7
35.25
22.9
Yelovsky-2, Andronovo period Same, Yelovka culture
Khryaschevka and Yagodnoye (Timber-grave culture)**
*After T.A. Chikisheva (2000). **After V.P. Alekseyev (1989).
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Table 4. Number of individuals in the reproductive and postreproductive age, percent Groups
Males
Females
Adults
Percent of total group size
Reproductive Yelovsky-2, Andronovo period
61.97
86.54
80.49
46.48
65
54.84
58.82
34.89
Chernoozerye-1
77.27
71.43
74
–
Zhuravlevo-4
63.83
66
64.95
45.32
Tanay-7
86.67
93.33
90.32
50.91
Zarechnoye-1
58.82
60
60.61
36.36
75
46.67
62.86
45.84
Same, Yelovka culture
Stary Sad
Postreproductive Yelovsky-2, Andronovo period
38.03
13.46
19.51
11.27
35
45.16
41.18
24.42
Chernoozerye-1
22.73
28.57
26
–
Zhuravlevo-4
36.17
34
35.05
24.46
Tanay-7
13.33
6.67
9.68
5.45
Zarechnoye-1
41.18
40
39.39
23.64
25
53.33
37.14
27.08
Same, Yelovka culture
Stary Sad
Table 5. Percentage of individuals having reached the reproductive age Groups
Table 6. Percentage of individuals having reached age 30 Males
Females
Reproduction rate
69.01
52
2
70
58.07
2.06
Chernoozerye-1
81.82
50.02
–
69.78
Zhuravlevo-4
78.73
46
1.27
23.4
60.87
Tanay-7
40
42.67
1.76
54.85
45.45
71.74
Zarechnoye-1
70
60
1.78
41.7
31.25
72.95
Stary Sad
76.47
86.66
1.89
Males
Females
Adults
Yelovsky-2, Andronovo period
33.2
26.5
59.7
Yelovsky-2, Andronovo period
Same, Yelovka culture
23.4
34.2
57.6
Same, Yelovka culture
–
–
–
Zhuravlevo-4
33.8
35.98
Tanay-7
23.4
Zarechnoye-1 Stary Sad
Chernoozerye-1
Yelovsky-2 (Andronovo period). The average age of death in this group is higher than that of Chernoozerye-1. There is an appreciable sex difference in this respect (Table 3). The sex ratio in the early reproductive period was markedly shifted toward males (71 males versus 52 females), and the 1:1 ratio was not approached even by age forty. The fertility level largely depends on the number of females in the reproductive age. The most prolic period is between 20 – 29, followed by a slow
Groups
decline (Chamberlain, 2001). The number of males is much less important for population growth. As J. Birdsell remarked, one sexually active male can impregnate ten females in no time, so the number of births would be the same as with ten males. If, however, there are ten males per one female, the birth rate would be ten times less (quoted after (Harris, 2003)). Some 48 % of females in Yelovsky died by age thirty, before the end of the reproductive period. There were two children per each
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female in the reproductive period, which is rather high for the Bronze Age. The high birth rate, however, was not enough to counter demographic stress, as the population was overloaded by nonreproductive males, whose number in the 26 – 30 age group was 22, and by postreproductive males and females older than forty. The data suggest that the group experienced a demographic crisis. Possibly, the need to overcome it was the main factor causing the transformation of Andronovo traditions and cultural and economic changes eventually leading to the emergence of the Yelovka culture, represented by a group of burials at Yelovsky-2. Yelovsky-2 (Yelovka culture). Compared to the Andronovo period, the Yelovka people show a certain
147
improvement in the demographic situation. The mean age at death is rather high in this populations (Table 3). Mortality curves attest to demographic stability, with a slight increase even at the major peaks, and a large number of females above fty (Fig. 1). The mortality prole of males is similar to that of Zhuravlevo-4 (the Irmen culture) and Stary Sad, and the female curve is close to that of Zhuravlevo-4. Differences concern mainly the number of aged individuals. Among the Yelovka, 19.4 % of women are older than fty, as opposed to only 4 % among the the Irmen. The sex ratio is 26 males per 38 females. A larger number of males is seen already in the early age cohorts (Table 2). This appears to be a rather typical feature of
Ⱥ 1
4
2
5
3
6
B
Fig. 1. Mortality curves for males (A) and females (B). 1 – Yelovsky-2, Yelovka culture; 2 – Yelovsky-2, Andronovo period; 3 – Zhuravlevo-4; 4 – Tanay-7; 5 – Stary Sad; 6 – Chernoozerye-1, Andronovo period.
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Western Siberian prehistoric demography. The same regularity was registered by N.P. Matveyeva (2002) in Kirillovka-3, Yelunino-1, and Bystrovka-1 (the early stage of the Kamen culture), and by T.A. Chikisheva (2003) in Yustyd (Pazyryk culture). Because the mean age at death was lower in females than in males by nearly ten years in those groups, it is probable that the numerical predominance of females was a biological adaptation to high female mortality in the early reproductive period. In the Yelovka people, the mean age at death was quite high, especially in females (Table 3). Therefore the greater number of females compared to males must have been caused by other factors. The most likely explanation is the need to surmount the consequences of a demographic crisis that struck the population during the Andronovo period, and to rapidly restore population size. Because, based on archaeological data, certain burials at Yelovsky-2 appear to be transitional from the Andronovo to the Yelovka cultures and inuenced by traditions of pitand-comb ceramics, the demographic decline during the Andronovo period probably caused the incorporation of native women into the Andronovo society. This led to cultural transformation and demographic changes. Due to the gradual nature of this transformation and to the fact that it occurred over a long period, the demographic changes were less radical than those expected under the migration hypothesis; indeed, no radical predominance of young individuals is observed. The principal demographic change was a fertility boom. Due to a sharp increase in the number of women and their greater longevity, the number of children per woman in the reproductive age reached a very high level – 2.06. The proportion of women older than 40 is larger in this group compared to other groups (eleven, or 25.5 % of the total number of women). This may have caused a relatively low mortality of children aged 6 – 10 (lower than in other groups) due to the grandmother effect. Concerning the age-specic mortality in children, it is noteworthy that an unusual amount of children’s deaths in the Yelovka population occurred in the 11 – 15 age interval (Table 2). This might have been the time when children passed on to the category of adults. Apart from demographic stabilization, the transition from the Andronovo period to the Yelovka period was marked by cultural and economic changes. As a result, in terms of female mortality, Yelovka-2 is much closer to the Irmen (Zhuravlevo-4) than the Andronovo population, represented by the series from the same burial ground. The improvement of the demographic situation and the increase in the number of women was paralleled by the lowering of the social status of women in the Yelovka society compared to the Andronovo society, evidenced by a smaller number of bronze artifacts in female burials, by a higher level of nutrition
stress markers, and by symptoms of domestic violence (Tikhonov, 1993; Zubova, 2007). Stary Sad (Late Bronze Age Culture). The average age at death was rather high in this group (Table 3). The male mortality curve is nearly identical to those for Yelovsky-2 (Yelovka group) and Zhuravlevo-4; in all three cases the major peak coincides with the 36 – 40 age interval (Fig. 1, A). The female mortality curve is very peculiar: peaks at 16 – 20 and 26 – 30 intervals, typical of most female groups of the Bronze Age, are absent, whereas the highest level is observed during the 41 – 45 interval (Fig. 1, B). T.A. Chikisheva (2000) suggested two explanations that might account for a small number of young females in that population. First, this might be due to a migration from another region. The alternative reason of the lack of high mortality at 16 – 20 is that the peak of female fertility coincided with a higher age. There are no females aged 26 – 30 among those buried at Stary Sad. Certain writers believe that a complete absence of a certain age cohort points to a lack of demographic continuity. However, given the small size of the Late Bronze Age sample from that cemetery, the population may have been small as well, resulting in a high role played by random factors. While the absence of girls born over a period of ve years or the death of all such girls before 16 is unlikely in a group of 10 – 15 families, the probability is much higher if the group consists of just two or three families. Judging by ethnographic parallels with the Siberian Selkups, whose family size could reach twenty (16.3 in the northern Selkups and 11.1 in the Narym Selkups (Gemuyev, 1984)), the Stary Sad population might have consisted of 3 – 4 families at best. The analysis of the age structure of Selkup families suggests, rstly, that the number of individuals aged 16 – 30 was small and comparable with that of the Stary Sad population; and secondly, that when the number of families is 3 – 4 (whether picked at random or representing the entire village), certain age cohorts may well be missing. This prompts us to reject the migration hypothesis with regard to Stary Sad, the more so because the male mortality curve, as noted above, is quite similar to that of other Late Bronze Age populations of Western Siberia. Since the sex ratio in the Stary Sad population is unfavorable for reproduction (15 females per 20 males, and 7 females per 15 males in the reproductive age), population growth must have been slow. The mean number of children per woman dying in the reproductive age is 1.89, which is close to respective values in other groups. Like in the Yelovka population, the mortality of children aged 11 – 15 is relatively high. Generally, in terms of mortality, the Stary Sad population differs from other Bronze Age groups of
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Fig. 2. Mortality curve for the Stary Sad population.
Western Siberia. Markers of occasional and speci c stress in the female sample are exceptionally rare, while being frequent in other groups (Zubova, 2007). Apparently, special socio-cultural mechanisms reducing biological stress and the mortality of young individuals functioned in this group. Those mechanisms may account for the fact that the general mortality type is closer to the classic U-distribution than it is in other groups (Fig. 2). Zhuravlevo-4 (Irmen culture). While the skeletal remains from Zhuravlevo-4 were demographically analyzed by T.A. Chikisheva, her results required correction, because her survivorship tables include data on three populations – Zhuravlevo-4, 1, and 3; also, the age of certain individuals had to be specied. The revision resulted in a change in certain characteristics and in the general demographic status of the population compared to that reconstructed in (Bobrov, Chikisheva, Mikhailova, 1993) and used by the present author previously (Zubova, 2006). In absolute terms, the average age at death in this population falls within the Bronze Age range (Table 3). However, the difference between age at death in males and females (nearly six years) is larger than in other Late Bronze Age groups of Western Siberia. Male and female mortality curves resemble those for the Yelovka people. In terms of male mortality, the group is close to Stary Sad (Fig. 1). The sex ratio is rather unfavorable. In the male series, no individuals aged 16 – 20 are present, whereas ten females (20 % of the entire reconstructed cohort), are of that age. In the next age group, an opposite disproportion is seen: 40 females versus 47 males. Later in life, the sex ratio becomes even more biased: 23 females (46 %) versus 37 males (78 %) attained the age of 30. By the
time that the cemetery ceased to function, the birth rate must have been low. An additional demographically adverse factor was the fact that due to the rise in female mortality, women of the next generation married at an earlier age, resulting in a further increase of mortality in females aged 16 – 20. The earlier marital age in this group is possibly evidenced by markers of dietary stress (enamel hypoplasia on third molars) in several girls aged 13 – 15, possibly due to the deterioration of diet in newly-married women. The mean number of children per female in the reproductive age in Zhuravlevo-4 is 1.27, which is lower than in most Late Bronze Age groups and may signal low fertility. The percentage of children who died before the age of ve is somewhat higher than in other groups (Table 2), possibly due to poor hygienic conditions. Interestingly, no males aged 16 – 20 are found in the sample, although females of that age are present. Could this be accidental, as in Stary Sad? Because far more people were buried at Zhuravlevo-4 than at Stary Sad, it appears biologically unlikely that not a single boy was born in that population for ve years. Two social reasons may account for the observed fact. The rst is that males aged 16 – 20 may have left the group to search for marital partners in other groups. This is possible given that no males of the age most suitable for marital migrations are present, whereas in later cohorts the sex ratio is biased toward males. The second possibility is purely speculative: the population might have been initially formed in a non-natural way – by capturing a certain number of girls and women by a group of males. Because this idea is unsupported by the available evidence, there is no need to dwell upon it. Regardless of other factors accounting for the absence of the remains of 16 – 20 year old males
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in a large skeletal sample, the fact may indicate that the cemetery at Zhuravlevo-4 functioned for a short time – a little more than one generation. Otherwise, even if all the young males had simultaneously left the population, other males of a similar age, born in the preceding or the next generation, would be present among the buried. Tanay-7. Most demographic parameters of that population attest to extreme conditions. The average age at death is quite low compared to other groups (Table 3). Mortality curves differ from those for other Late Bronze Age cemeteries (Fig. 1). Among the males, peaks and lows of mortality, beginning from the main peak, regularly occurred ten years earlier than in Yelovsky-2, Stary Sad, and Zhuravlevo-4; the main peak is not preceded by a low, and the intermediate peak at 26 – 30, seen in other groups, is absent as well. In general shape (gradual increase, followed by decrease and another rise), this mortality
curve resembles that of Andronovo populations from Chernoozerye-1 and Yelovsky-2. The female mortality curve, too, differs from others. A marked rise at 16 – 19 followed by a decline is absent; instead, there is a gradual rise from 16 – 19 to 31 – 35, followed by a sharp drop due to the extinction of most females. This curve shows a perfect match with that of Andronovo females of the Tomsk Ob area, differing only in the absence of individuals older than fty (Fig. 1). The reproductive potential of the population was apparently rather high. The sex ratio is nearly 1:1. The extinction rates of females and males in early age groups are virtually identical, and only three individuals were in the postreproductive period. Yet, the population could hardly have grown rapidly, as most females died at a very young age, before having given birth to all potential children. The reproduction rate equals 1.76 – Ⱥ
B
Fig. 3. Mortality curves for males (A) and females (B) in Zarechnoye-1.
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a medium value according to Bronze Age standards. Also, child mortality was elevated in the rst ve years of life (Table 2). Such a demographic situation was likely caused by a high stress related to the need to adapt to a new environment. Several arguments can be brought forward to support this idea. Firstly, Tanay-7 is one of the earliest Irmen sites in the Kuznetsk Basin, so its demographic situation may well be typical of the initial stage in the development of a new subsistence strategy. Despite the low values of principal demographic indicators, the relative difference between the female and the male parts of the population is broadly the same as in other Bronze Age groups. That the group consisted of immigrants, is indirectly evidenced by a low average age of buried people; indeed, the age structure of immigrant groups generally reveals the predominance of adults in the “age of the rst marriage” (around twenty), since this is the age when the probability of migrating is maximal (Chamberlain, 2001). An elevated mortality of males aged 26–30 speaks in favor of this suggestion. According to Buzhilova (1997), migration stress affects the demographic curve and results in a peak of mortality in young adults. Zarechnoye-1. Only ten mounds have been excavated, limiting the possibilities for reconstruction. However, because the series is rather large, some conclusions can be made. Survivorship tables are based on a ten-year interval, due to V.A. Dremov’s method of age determination. Age at death is higher than in two other Irmen cemeteries (Table 3). The male mortality curve reveals a peak in the 31 – 40 interval (Fig. 3, A), whereas the female mortality curve is characterized by a peak at 21 – 30 followed by a decrease, and then a stable level until the complete extinction of females by age of 60 (Fig. 3, B). Judging by the sex ratio (15:16), the balance was not disturbed. Seven males and six females (4.6 % of all adults) were in the nonreproductive age. This must have affected the reproductive potential of the population. Infantile mortality in the rst ve years of life is minimal, but, because only part of the cemetery has been excavated, the conclusions are tentative. Certain features of the demographic situation in Bronze Age Western Siberia Based on the results of the analysis of demographic processes in Late Bronze Age Western Siberian populations, the following conclusions can be made. The average age at death of adults buried in two cemeteries representing the Andronovo culture is 32.3 (males, 36.5; females, 31.9). In the Late Bronze Age,
151
this parameter increases (34.1), and the difference between males and females decreases (36.1 and 34.2, respectively); if children are taken into account, then the mean age at death is 23.7. In Irmen and Andronovo populations, males died at a later age than females. No such conclusion can be made with regard to other Late Bronze age groups, since both Yelovka and “Late Bronze Age Culture” are represented by only one suitable sample each. Child mortality ranges from 27.05 – 39.9 %. The number of dead children per female of reproductive age is 1.27 – 2.06; it is mostly less than 2 – the number required for maintaining a stable population size. The reason is that only some of the children died, and sex and age structure must be evaluated on the basis of their remains. Judging from the results, the mean number of dead children per female was close to two in the Bronze Age. During the rst ve years of life, 50 – 75 % of children died. The highest gures were registered in Zhuravlevo-4 and Tanay-7, with the lowest in Zarechnoye-1. The number of children who died at ages 6 – 10 is maximal in Zarechnoye-1 and in Andronovo burials of Yelovsky-2 – about 30 %. The corresponding proportion is 12.5 – 16.7 % in Zhuravlevo-4, Stary Sad, and Tanay-7, and 9.0 % in Yelovka. In all groups, male and female mortality curves differ. Females tended to die at a young age, whereas males mostly died at older ages. In the postreproductive period, the extinction of females proceeded at the same or slower rate than that of males. As for general regularities, factors of male and female mortality were evidently not the same. Male mortality at that stage is mainly caused by the exhaustion of the organism’s intrinsic resources due to stable and high stress during subsistence activities; the role of social factors is less. Female mortality, on the other hand, was primarily related to childbirth and therefore depended on the level of medicine and hygiene, as well as on general living standards. The sex-and-age structure of prehistoric populations is shaped by three categories of factors. The rst category included local factors such as migrations, warfare, epidemics, etc. Their effect is apparently present in two groups: Tanay-7, which retained the features of an immigrant group, and Zhuravlevo-4, probably affected by emigration. Factors of the second category are broadly related to the “cultural model of adaptation” and include type of economy, social system, and religious beliefs. Some of those factors determine the cumulative stress level and thereby affect basic demographic parameters involved in the reproduction of the group under the given environmental conditions (fertility and mortality levels, life expectancy, etc.). The cultural model of adaptation, then, defines the limits of the population’s demographic “norm of
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reaction” to external changes. If these limits are violated, the law of population stability takes effect to bring population size back within the limits optimal under the given conditions. This is the third factor shaping the demographic proles of ancient and modern traditional groups both biologically (by affecting mortality and fertility levels) and socially. One example of a direct effect of the stability law on the social life of a traditional community is the decline of nuptiality and the rise of endogamy of the Selkups and the Sosva Mansi after a period of population growth under highly favorable environmental conditions in the late 1700s and early 1800s (Lebedev, Oborotova, 1991). In the analyzed prehistoric populations, the stability law may have affected mortality and fertility changes in females following a period of rapid growth, after the optimal difference in male and female age of death (about ten years) was reached. This law may also have operated after the arrival of immigrants, because this factor disrupted the traditions and violated the limits of the “demographic norm of reaction.” The comparison of mortality curves suggests that spatially separated, but culturally and economically similar populations have similar demographic proles, whereas those occupying the same ecological niche at various chronological stages (and thus economically divergent) display marked demographic differences. In terms of mortality, two populations fall into two groups. In females, one group includes the Yelovka people (Yelovsky-2) and the Irmen people (Zhuravlevo-4), while another group includes the Irmen people from Tanay-7 and the Andronovo people from Yelovsky-2. The second group may also include females from Chernoozerye-1, despite the absence of the mortality peak at 31 – 35. Stary Sad females are intermediate. A marked mortality peak links them to the Andronovo people from Yelovsky-2, whereas the position of that peak (in the second half of the reproductive period) is close to that of Irmen females from Zhuravlevo-4 (see Fig. 1, B). Among males, one group includes the Zhuravlevo-4, Stary Sad, and Yelovka people, while another group includes the Andronovo people from Yelovsky-2 and Chernoozerye-1, and the Irmen people from Tanay-7 (Fig. 1, A). Based on the analysis of mortality curves, several conclusions can be drawn. Firstly, living standards in the Late Bronze Age were higher than in the preceding Andronovo period. Andronovo populations exhibit a high level of cumulative stress, evidenced by high mortality among young people. The stress level shows a marked decrease in the Late Bronze Age, and mortality peaks shift toward later age intervals. The second conclusion concerns sex differences in the diachronic and local variation of mortality curves. Male curves reveal minor differences within the same
cultural stage, while showing considerable changes from the Andronovo period to the Late Bronze Age, perhaps due to economic progress. Other factors, such as climatic, were largely similar across vast areas, resulting in similar levels of stress affecting the same age categories. Female mortality curves, in contrast, demonstrate greater intrinsic variability both within archaeological cultures and within chronological stages. This may be due to differences in the social status of women and to concomitant traditions regarding female hygiene level and lifestyle. Generally, cumulative stress in females drops from the Andronovo period to the Late Bronze Age, and age intervals that are potentially dangerous in terms of mortality become more pronounced. The analysis of the sex-and-age structure of prehistoric populations of Western Siberia suggests that in the Late Bronze Age, two models of demographic adaptation to environmental change existed. The rst model was based on emigration, as demonstrated by Tanay-7. The second one was based on immigration and the incorporation of immigrants into the aging population, as seen in Andronovo-Yelovka materials from the Tomsk part of the Ob Basin.
References Alekseyev V.P. 1989 Paleodemograya: Soderzhanie i rezultaty. In Istoricheskaya demografiya: Problemy i suzhdeniya. Moscow: Nauka, pp. 63 – 90. Bobrov V.V., Chikisheva T.A., Mikhailov Yu.I. 1993 Mogilnik epokhi pozdnei bronzy Zhuravlevo-4. Novosibirsk: Nauka. Buzhilova A.P. 1997 Izuchenie vozrastnyh piramid i pokazatelja srednego vozrasta smerti v arkheologicheskom kontekste (po antropologicheskim i istoricheskim materialam drevnerusskogo naseleniya). In Novye metody – novye podkhody v sovremennoi antropologii. Moscow: Izd. Mosk. Gos. Univ., pp. 33 – 44. Chamberlain A.T. 2001 Palaeodemography. In Handbook of Archaeological Sciences, D.R. Brothwell, A.M. Pollard (eds.). New York, London: John Wiley and Sons, pp. 259 – 267. Chikisheva T.A. 2000 On the formation of the anthropological composition of the West-Siberian population in the Late Bronze Age (Interpretation of the paleoanthropological materials from the burial ground of Stary Saad in central Baraba). Archaeology, Ethnology and Anthropology of Eurasia, No. 2 (2): 131 – 147. Chikisheva T.A. 2003 Paleodemograficheskaya kharakteristika naseleniya pazyrykskoi kultury, In Naselenie Gornogo Altaya v epokhu rannego zheleznogo veka kak etnokulturnyi fenomen: Proiskhozhdenie, genezis, istoricheskie sudby, V.I. Molodin (ed.). Novosibirsk: Izd. SO RAN, pp. 69 – 73.
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Gemueyv I.N. 1984 Semya u selkupov (XIX – nachalo XX v.). Novosibirsk: Nauka. Harris M. 2003 Proiskhozhdenie voiny. In Voina i geopolitika. Novosibirsk: Izd. Novosibirsk. Gos. Univ., pp. 121 – 134. (Vremya mira; vol. 3). Lebedev V.V., Oborotova E.A. 1991 K voprosu ob ekologicheskom gomeostaze v traditsionnykh obschestvakh Arktiki i Subarktiki. In Etnicheskaya ekologiya: Teoriya i praktika. Moscow: Nauka, pp. 270 – 286. Matveyeva N.P. 2002 Nekotorye paleodemogracheskie kharakteristiki kamenskoi kultury lesostepnogo Priobya . Vestnik arkheologii, antropologii i etnogra¿i (Tyumen), vol. 4: 149 – 161. Matyuschenko V.I. 2004 Elovskii arkheologicheskii kompleks. Pt. 2: Elovsky-2 mogilnik. Doirmenskie kompleksy. Omsk: Izd. Omsk. Gos. Univ. Tikhonov S.S. 1993 Analiz struktury naseleniya Verkhnego Priobiya v epokhu pozdnei bronzy. Cand. Sc. (History) Dissertation. Novosibirsk.
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Ubelaker D.H. 1978 Human Skeletal Remains: Excavation, Analysis, Interpretation. Chicago: Aldine Publishing Company. Zakh V.A. 1997 Epokha bronzy Prisalairya. Novosibirsk: Nauka. Zubova A.V. 2006 Paleodemograya irmenskoi kultury Kuznetskoi kotloviny. In Sovremennye problemy arkheologii Rossii: Materialy Vseros. arkheologicheskogo siezda, vol. 1. Novosibirsk: Izd. IAE SO RAN, pp. 375 – 377. Zubova A.V. 2007 Nekotorye paleopatologicheskie kharakteristiki naseleniya Zapadnoi Sibiri epokh razvitoi i pozdnei bronzy. In Problemy arkheologii, etnografii, antropologii Sibiri i sopredelnykh territorii: Materialy Godovoi sessii Instituta arkheologii i etnogra¿i SO RAN 2007goda, vol. 13. Novosibirsk: Izd. IAE SO RAN, pp. 244 – 248.
Received January 15, 2008.
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ANTHROPOLOGY A.V. Zubova Institute of Archaeology and Ethnography, Siberian Branch, Russian Academy of Sciences, Akademika Lavrentieva 17, Novosibirsk, 630090, Russia E-mail: [email protected]
THE PALEODEMOGRAPHY OF WESTERN SIBERIA IN THE MIDDLE AND LATE BRONZE AGE* Based on the paleodemographic evaluation of human skeletal remains from Yelovsky-2, Chernoozerye-1, Zhuravlevo-4, Tanay-7, and Zarechnoye-1, those populations fall into two groups differing in their cumulative stress level, which was high during the Andronovo period, and decreased by the Late Bronze Age. This is evidenced by a lower age of death and earlier onset of mortality peaks in samples from Chernoozerye and Yelovsky. Two models of demographic adaptation to changing conditions are proposed: emigration for Tanay, and the inclusion of new members into the aging population for Yelovsky. Introduction Human adaptation is a complex process involving a variety of morphological, functional, and socio-cultural features. Demographic parameters, too, are involved, and they are intrinsically related to cultural features studied by archaeologists. The demographic structure of an ancient population can shed light on the factors underlying cultural changes. Demographic decline or success may cause migrations, extending the marital distance and eventually leading to the distribution of cultural features or to the replacement of old traditions by new ones. In archaeological studies, cultural changes and migrations are commonly believed to result from outward factors such as environmental changes and political conicts. Intrinsic demographic features receive much less attention, and biological laws underlying population structure are generally disregarded. Attempts to reconstruct the demographic characteristics of prehistoric populations of Western Siberia on the
basis of archaeological and skeletal data have been made more than once (Bobrov, Chikisheva, Mikhailov, 1993; Chikisheva, 2000; Matveyeva, 2002; Tikhonov, 1993). Cross-population analysis of mortality curves has rarely been attempted, and the relationship between demographic and socio-cultural features has not been assessed, nor has the relevance of demographic data for adaptation been evaluated. In the present article, demographic parameters are analyzed with regard to the stability of the group and its biological potential. We will refrain from using evaluative terms such as “negative” or “positive” with regard to the demographic situation, because any mortality and fertility fluctuations may be adaptive responses to environmental changes. The objective of the study is to use demographic data as a source for assessing the adaptation of Middle and Late Bronze Age Western Siberian populations. Materials and methods
*This study is part of the Russian Academy of Sciences Project “Adaptation of Peoples and Cultures to Environmental, Social, and Technogenic Transformations.”
The skeletal samples used in this study are the best preserved Middle and Late Bronze Age materials from
Copyright © 2008, Siberian Branch of Russian Academy of Sciences, Institute of Archaeology and Ethnography of the Siberian Branch of the Russian Academy of Sciences. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aeae.2008.07.014
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Table 1. Sex composition of the populations Groups
Males
Females
Children
Indeterminate
Total
Yelovsky-2, Andronovo period
74 (33.2)
59 (26.5)
89 (39.9)
0
223 (100)
Same, Yelovka culture
26 (23.4)
38 (34.2)
35 (31.5)
12 (10.8)
111 (100)
22 (?)
28 (?)
–
0
–
Zhuravlevo-4
47 (33.8)
50 (35.97)
42 (30.2)
0
139 (100)
Tanay-7
15 (23.4)
15 (23.4)
25 (39)
9 (14.06)
64 (100)
Zarechnoye-1
17 (27.9)
16 (26.23)
17 (27.9)
11 (18.03)
61 (100)
Stary Sad
20 (41.7)
15 (31.25)
13 (27.08)
0
48 (100)
Chernoozerye-1
Note. Here and in Table 2, percentages are indicated in parentheses.
Table 2. Age structure of the populations Yelovsky-2 Age, years
Andronovo period
Yelovka culture
Chernoozerye-1
Zhuravlevo-4
Tanay-7
Stary Sad
Zarechnoye-1
1 (5.89)
Males 16–20
3 (4.23)
2(10)
0
0
2 (13.33)
2 (10)
21–25
9 (12.68)
1 (5)
1 (4.55)
3 (6.38)
1 (6.67)
1 (5)
26–30
10 (14.08)
3 (15)
3 (13.63)
7 (14.89)
6 (40)
3 (15)
31–35
17 (23.94)
1 (5)
5 (22.73)
5 (10.64)
4 (26.67)
1 (5)
36–40
15 (21.13)
6 (30)
8 (36.36)
15 (31.91)
0
8 (40)
41–45
5 (7.04)
4 (20)
2 (9.09)
8 (17.02)
1 (6.67)
1 (5)
46–50
2 (2.82)
3 (15)
1 (4.55)
5 (10.64)
0
1 (5)
10 (14.08)
0
2 (9.09)
4 (8.51)
1 (6.67)
3 (15)
2 (11.76)
2 (12. 5)
50 +
3 (17.64)
6 (35.29)
5 (29.41)
Females 16–20
6 (11.54)
5 (16.13)
3 (10.7)
10 (20)
2 (13.33)
1 (6.67)
21–25
10 (19.23)
2 (6.45)
6 (21.43)
6 (12)
3 (20)
1 (6.67)
26–30
9 (17.3)
6 (19.35)
5 (17.85)
11 (22)
3 (20)
0
31–35
16 (30.77)
1 (3.23)
2 (7.14)
1 (2)
5 (33.33)
1 (6.67)
36–40
4 (7.69)
3 (9.68)
4 (14.28)
5 (10)
1 (6.67)
4 (26.67)
41–45
1 (1.92)
3 (9.68)
1 (3.57)
8 (16)
0
6 (40)
46–50
3 (5.77)
5 (16.13)
3 (10.7)
7 (14)
1 (6.67)
2 (13.33)
50 +
3 (5.77)
6 (19.35)
2 (7.14)
2 (4)
0
0
3 (18.75)
4 (25)
4 (25)
3 (18.75)
Children 0–5
59 (65.6)
22 (62.9)
–
30 (71.4)
18 (75)
8 (61.5)
8 (50)
6–10
28 (31.11)
3 (8.57)
–
7 (16.67)
3 (12.5)
2 (15.38)
5 (31.25)
11–15
3 (3.33)
10 (28.57)
–
5 (11.9)
3 (12.5)
3 (23.07)
0
0
0
–
0
0
0
3 (18.75)
Indeterminate
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Western Siberia. Because only series from completely or nearly completely excavated cemeteries are suitable for demographic analysis (Alekseyev, 1989; Buzhilova, 1997), only seven groups were used. Andronovo-type cemeteries include Yelovsky-2 in Tomsk Province, and Chernoozerye-1 in Omsk Province (the Irtysh Basin); those of the Yelovka culture are represented by Yelovsky-2; those of the Inya variant of the Irmen culture, by Zarechnoye-1, Zhuravlevo-4, and Tanay-7, and those of the Late Bronze Age, by Stary Sad. Sex and age determinations for Yelovsky-2, Chernoozerye-1, and Zarechnoye-1 were made by V.A. Dremov and have been partly published (Zakh, 1997; Matyuschenko, 2004); those for Zhuravlevo-4 and Stary Sad, by T.A. Chikisheva (Bobrov, Chikisheva, Mikhailov, 1993; Chikisheva, 2000); the sex and age of certain individuals were redened by the present author (Tables 1, 2). The analysis was conducted in two stages. First, the local characteristics of each population were evaluated; second, separate Bronze Age populations were compared with one another and with other groups to assess general demographic tendencies. The demographic structure was evaluated using standard life tables to assess survivorship (Ubelaker, 1978) and to generate mortality curves. Also, the average age at death, the sex ratio as an indicator of effective reproduction, the mean number of dead children per female dying in the reproductive age, and the
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numerical relationship between reproductive (16 – 40) and postreproductive (above 40) parts of the population was calculated (Tables 3 – 6). Results Chernoozerye-1 (Andronovo period). While the total number of burials excavated at that cemetery approaches 170, sex and age determinations are available for fifty adults only. The average age of death is rather low according to Bronze Age standards (Table 3). Mortality peaks coincide with 21 – 25 and 36 – 40 age intervals in females, and with the last age interval in males (Fig. 1). During the early reproductive period (16 – 20), the number of females surpasses the number of males, but age 30 was reached by fourteen females (50.2 %) and eighteen males (81.8 %) (Table 2). Due to a higher mortality in males in the 30 – 40 age interval, the sex ratio becomes nearly 1:1 by age forty. Because child mortality cannot be assessed from materials of that site, no denite conclusions as to the age structure of the population or its reproductive potential can be made. It can only be suggested that this potential was limited by a high female mortality in the reproductive period. Mortality curves for Chernoozerye-1 (Fig. 1), point to a regular stress experienced by the reproducing part of the population.
Table 3. Average age at death Groups
Males
Females
Adults
Total
35.7
31.2
33.8
21.4
36
37.09
36.7
24.17
Chernoozerye-1
37.27
32.58
34.93
–
Zhuravlevo-4
37.5
31.8
34.6
25.3
Tanay-7
31
29.3
30.3
19.01
Zarechnoye-1
38
34.5
36.25
20.27
Stary Sad*
38
36.1
36.9
28.2
Karasuk-3 (Afanasyev culture, Minusinsk Basin)**
36.2
39.4
37.8
24.1
Tasty-Butak (Andronovo culture, Kazakhstan)**
34.4
37.5
35.95
18.7
Balanovo-2 (Fatyanovo culture)**
31.4
32
31.7
20.3
27
32.7
29.85
25.1
Mokrin (Mound culture, Yugoslavia)**
37.4
38.6
38
–
Sapallitepa (Painted ware culture, Uzbekistan)**
33.8
36.7
35.25
22.9
Yelovsky-2, Andronovo period Same, Yelovka culture
Khryaschevka and Yagodnoye (Timber-grave culture)**
*After T.A. Chikisheva (2000). **After V.P. Alekseyev (1989).
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Table 4. Number of individuals in the reproductive and postreproductive age, percent Groups
Males
Females
Adults
Percent of total group size
Reproductive Yelovsky-2, Andronovo period
61.97
86.54
80.49
46.48
65
54.84
58.82
34.89
Chernoozerye-1
77.27
71.43
74
–
Zhuravlevo-4
63.83
66
64.95
45.32
Tanay-7
86.67
93.33
90.32
50.91
Zarechnoye-1
58.82
60
60.61
36.36
75
46.67
62.86
45.84
Same, Yelovka culture
Stary Sad
Postreproductive Yelovsky-2, Andronovo period
38.03
13.46
19.51
11.27
35
45.16
41.18
24.42
Chernoozerye-1
22.73
28.57
26
–
Zhuravlevo-4
36.17
34
35.05
24.46
Tanay-7
13.33
6.67
9.68
5.45
Zarechnoye-1
41.18
40
39.39
23.64
25
53.33
37.14
27.08
Same, Yelovka culture
Stary Sad
Table 5. Percentage of individuals having reached the reproductive age Groups
Table 6. Percentage of individuals having reached age 30 Males
Females
Reproduction rate
69.01
52
2
70
58.07
2.06
Chernoozerye-1
81.82
50.02
–
69.78
Zhuravlevo-4
78.73
46
1.27
23.4
60.87
Tanay-7
40
42.67
1.76
54.85
45.45
71.74
Zarechnoye-1
70
60
1.78
41.7
31.25
72.95
Stary Sad
76.47
86.66
1.89
Males
Females
Adults
Yelovsky-2, Andronovo period
33.2
26.5
59.7
Yelovsky-2, Andronovo period
Same, Yelovka culture
23.4
34.2
57.6
Same, Yelovka culture
–
–
–
Zhuravlevo-4
33.8
35.98
Tanay-7
23.4
Zarechnoye-1 Stary Sad
Chernoozerye-1
Yelovsky-2 (Andronovo period). The average age of death in this group is higher than that of Chernoozerye-1. There is an appreciable sex difference in this respect (Table 3). The sex ratio in the early reproductive period was markedly shifted toward males (71 males versus 52 females), and the 1:1 ratio was not approached even by age forty. The fertility level largely depends on the number of females in the reproductive age. The most prolic period is between 20 – 29, followed by a slow
Groups
decline (Chamberlain, 2001). The number of males is much less important for population growth. As J. Birdsell remarked, one sexually active male can impregnate ten females in no time, so the number of births would be the same as with ten males. If, however, there are ten males per one female, the birth rate would be ten times less (quoted after (Harris, 2003)). Some 48 % of females in Yelovsky died by age thirty, before the end of the reproductive period. There were two children per each
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female in the reproductive period, which is rather high for the Bronze Age. The high birth rate, however, was not enough to counter demographic stress, as the population was overloaded by nonreproductive males, whose number in the 26 – 30 age group was 22, and by postreproductive males and females older than forty. The data suggest that the group experienced a demographic crisis. Possibly, the need to overcome it was the main factor causing the transformation of Andronovo traditions and cultural and economic changes eventually leading to the emergence of the Yelovka culture, represented by a group of burials at Yelovsky-2. Yelovsky-2 (Yelovka culture). Compared to the Andronovo period, the Yelovka people show a certain
147
improvement in the demographic situation. The mean age at death is rather high in this populations (Table 3). Mortality curves attest to demographic stability, with a slight increase even at the major peaks, and a large number of females above fty (Fig. 1). The mortality prole of males is similar to that of Zhuravlevo-4 (the Irmen culture) and Stary Sad, and the female curve is close to that of Zhuravlevo-4. Differences concern mainly the number of aged individuals. Among the Yelovka, 19.4 % of women are older than fty, as opposed to only 4 % among the the Irmen. The sex ratio is 26 males per 38 females. A larger number of males is seen already in the early age cohorts (Table 2). This appears to be a rather typical feature of
Ⱥ 1
4
2
5
3
6
B
Fig. 1. Mortality curves for males (A) and females (B). 1 – Yelovsky-2, Yelovka culture; 2 – Yelovsky-2, Andronovo period; 3 – Zhuravlevo-4; 4 – Tanay-7; 5 – Stary Sad; 6 – Chernoozerye-1, Andronovo period.
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Western Siberian prehistoric demography. The same regularity was registered by N.P. Matveyeva (2002) in Kirillovka-3, Yelunino-1, and Bystrovka-1 (the early stage of the Kamen culture), and by T.A. Chikisheva (2003) in Yustyd (Pazyryk culture). Because the mean age at death was lower in females than in males by nearly ten years in those groups, it is probable that the numerical predominance of females was a biological adaptation to high female mortality in the early reproductive period. In the Yelovka people, the mean age at death was quite high, especially in females (Table 3). Therefore the greater number of females compared to males must have been caused by other factors. The most likely explanation is the need to surmount the consequences of a demographic crisis that struck the population during the Andronovo period, and to rapidly restore population size. Because, based on archaeological data, certain burials at Yelovsky-2 appear to be transitional from the Andronovo to the Yelovka cultures and inuenced by traditions of pitand-comb ceramics, the demographic decline during the Andronovo period probably caused the incorporation of native women into the Andronovo society. This led to cultural transformation and demographic changes. Due to the gradual nature of this transformation and to the fact that it occurred over a long period, the demographic changes were less radical than those expected under the migration hypothesis; indeed, no radical predominance of young individuals is observed. The principal demographic change was a fertility boom. Due to a sharp increase in the number of women and their greater longevity, the number of children per woman in the reproductive age reached a very high level – 2.06. The proportion of women older than 40 is larger in this group compared to other groups (eleven, or 25.5 % of the total number of women). This may have caused a relatively low mortality of children aged 6 – 10 (lower than in other groups) due to the grandmother effect. Concerning the age-specic mortality in children, it is noteworthy that an unusual amount of children’s deaths in the Yelovka population occurred in the 11 – 15 age interval (Table 2). This might have been the time when children passed on to the category of adults. Apart from demographic stabilization, the transition from the Andronovo period to the Yelovka period was marked by cultural and economic changes. As a result, in terms of female mortality, Yelovka-2 is much closer to the Irmen (Zhuravlevo-4) than the Andronovo population, represented by the series from the same burial ground. The improvement of the demographic situation and the increase in the number of women was paralleled by the lowering of the social status of women in the Yelovka society compared to the Andronovo society, evidenced by a smaller number of bronze artifacts in female burials, by a higher level of nutrition
stress markers, and by symptoms of domestic violence (Tikhonov, 1993; Zubova, 2007). Stary Sad (Late Bronze Age Culture). The average age at death was rather high in this group (Table 3). The male mortality curve is nearly identical to those for Yelovsky-2 (Yelovka group) and Zhuravlevo-4; in all three cases the major peak coincides with the 36 – 40 age interval (Fig. 1, A). The female mortality curve is very peculiar: peaks at 16 – 20 and 26 – 30 intervals, typical of most female groups of the Bronze Age, are absent, whereas the highest level is observed during the 41 – 45 interval (Fig. 1, B). T.A. Chikisheva (2000) suggested two explanations that might account for a small number of young females in that population. First, this might be due to a migration from another region. The alternative reason of the lack of high mortality at 16 – 20 is that the peak of female fertility coincided with a higher age. There are no females aged 26 – 30 among those buried at Stary Sad. Certain writers believe that a complete absence of a certain age cohort points to a lack of demographic continuity. However, given the small size of the Late Bronze Age sample from that cemetery, the population may have been small as well, resulting in a high role played by random factors. While the absence of girls born over a period of ve years or the death of all such girls before 16 is unlikely in a group of 10 – 15 families, the probability is much higher if the group consists of just two or three families. Judging by ethnographic parallels with the Siberian Selkups, whose family size could reach twenty (16.3 in the northern Selkups and 11.1 in the Narym Selkups (Gemuyev, 1984)), the Stary Sad population might have consisted of 3 – 4 families at best. The analysis of the age structure of Selkup families suggests, rstly, that the number of individuals aged 16 – 30 was small and comparable with that of the Stary Sad population; and secondly, that when the number of families is 3 – 4 (whether picked at random or representing the entire village), certain age cohorts may well be missing. This prompts us to reject the migration hypothesis with regard to Stary Sad, the more so because the male mortality curve, as noted above, is quite similar to that of other Late Bronze Age populations of Western Siberia. Since the sex ratio in the Stary Sad population is unfavorable for reproduction (15 females per 20 males, and 7 females per 15 males in the reproductive age), population growth must have been slow. The mean number of children per woman dying in the reproductive age is 1.89, which is close to respective values in other groups. Like in the Yelovka population, the mortality of children aged 11 – 15 is relatively high. Generally, in terms of mortality, the Stary Sad population differs from other Bronze Age groups of
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Fig. 2. Mortality curve for the Stary Sad population.
Western Siberia. Markers of occasional and speci c stress in the female sample are exceptionally rare, while being frequent in other groups (Zubova, 2007). Apparently, special socio-cultural mechanisms reducing biological stress and the mortality of young individuals functioned in this group. Those mechanisms may account for the fact that the general mortality type is closer to the classic U-distribution than it is in other groups (Fig. 2). Zhuravlevo-4 (Irmen culture). While the skeletal remains from Zhuravlevo-4 were demographically analyzed by T.A. Chikisheva, her results required correction, because her survivorship tables include data on three populations – Zhuravlevo-4, 1, and 3; also, the age of certain individuals had to be specied. The revision resulted in a change in certain characteristics and in the general demographic status of the population compared to that reconstructed in (Bobrov, Chikisheva, Mikhailova, 1993) and used by the present author previously (Zubova, 2006). In absolute terms, the average age at death in this population falls within the Bronze Age range (Table 3). However, the difference between age at death in males and females (nearly six years) is larger than in other Late Bronze Age groups of Western Siberia. Male and female mortality curves resemble those for the Yelovka people. In terms of male mortality, the group is close to Stary Sad (Fig. 1). The sex ratio is rather unfavorable. In the male series, no individuals aged 16 – 20 are present, whereas ten females (20 % of the entire reconstructed cohort), are of that age. In the next age group, an opposite disproportion is seen: 40 females versus 47 males. Later in life, the sex ratio becomes even more biased: 23 females (46 %) versus 37 males (78 %) attained the age of 30. By the
time that the cemetery ceased to function, the birth rate must have been low. An additional demographically adverse factor was the fact that due to the rise in female mortality, women of the next generation married at an earlier age, resulting in a further increase of mortality in females aged 16 – 20. The earlier marital age in this group is possibly evidenced by markers of dietary stress (enamel hypoplasia on third molars) in several girls aged 13 – 15, possibly due to the deterioration of diet in newly-married women. The mean number of children per female in the reproductive age in Zhuravlevo-4 is 1.27, which is lower than in most Late Bronze Age groups and may signal low fertility. The percentage of children who died before the age of ve is somewhat higher than in other groups (Table 2), possibly due to poor hygienic conditions. Interestingly, no males aged 16 – 20 are found in the sample, although females of that age are present. Could this be accidental, as in Stary Sad? Because far more people were buried at Zhuravlevo-4 than at Stary Sad, it appears biologically unlikely that not a single boy was born in that population for ve years. Two social reasons may account for the observed fact. The rst is that males aged 16 – 20 may have left the group to search for marital partners in other groups. This is possible given that no males of the age most suitable for marital migrations are present, whereas in later cohorts the sex ratio is biased toward males. The second possibility is purely speculative: the population might have been initially formed in a non-natural way – by capturing a certain number of girls and women by a group of males. Because this idea is unsupported by the available evidence, there is no need to dwell upon it. Regardless of other factors accounting for the absence of the remains of 16 – 20 year old males
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in a large skeletal sample, the fact may indicate that the cemetery at Zhuravlevo-4 functioned for a short time – a little more than one generation. Otherwise, even if all the young males had simultaneously left the population, other males of a similar age, born in the preceding or the next generation, would be present among the buried. Tanay-7. Most demographic parameters of that population attest to extreme conditions. The average age at death is quite low compared to other groups (Table 3). Mortality curves differ from those for other Late Bronze Age cemeteries (Fig. 1). Among the males, peaks and lows of mortality, beginning from the main peak, regularly occurred ten years earlier than in Yelovsky-2, Stary Sad, and Zhuravlevo-4; the main peak is not preceded by a low, and the intermediate peak at 26 – 30, seen in other groups, is absent as well. In general shape (gradual increase, followed by decrease and another rise), this mortality
curve resembles that of Andronovo populations from Chernoozerye-1 and Yelovsky-2. The female mortality curve, too, differs from others. A marked rise at 16 – 19 followed by a decline is absent; instead, there is a gradual rise from 16 – 19 to 31 – 35, followed by a sharp drop due to the extinction of most females. This curve shows a perfect match with that of Andronovo females of the Tomsk Ob area, differing only in the absence of individuals older than fty (Fig. 1). The reproductive potential of the population was apparently rather high. The sex ratio is nearly 1:1. The extinction rates of females and males in early age groups are virtually identical, and only three individuals were in the postreproductive period. Yet, the population could hardly have grown rapidly, as most females died at a very young age, before having given birth to all potential children. The reproduction rate equals 1.76 – Ⱥ
B
Fig. 3. Mortality curves for males (A) and females (B) in Zarechnoye-1.
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a medium value according to Bronze Age standards. Also, child mortality was elevated in the rst ve years of life (Table 2). Such a demographic situation was likely caused by a high stress related to the need to adapt to a new environment. Several arguments can be brought forward to support this idea. Firstly, Tanay-7 is one of the earliest Irmen sites in the Kuznetsk Basin, so its demographic situation may well be typical of the initial stage in the development of a new subsistence strategy. Despite the low values of principal demographic indicators, the relative difference between the female and the male parts of the population is broadly the same as in other Bronze Age groups. That the group consisted of immigrants, is indirectly evidenced by a low average age of buried people; indeed, the age structure of immigrant groups generally reveals the predominance of adults in the “age of the rst marriage” (around twenty), since this is the age when the probability of migrating is maximal (Chamberlain, 2001). An elevated mortality of males aged 26–30 speaks in favor of this suggestion. According to Buzhilova (1997), migration stress affects the demographic curve and results in a peak of mortality in young adults. Zarechnoye-1. Only ten mounds have been excavated, limiting the possibilities for reconstruction. However, because the series is rather large, some conclusions can be made. Survivorship tables are based on a ten-year interval, due to V.A. Dremov’s method of age determination. Age at death is higher than in two other Irmen cemeteries (Table 3). The male mortality curve reveals a peak in the 31 – 40 interval (Fig. 3, A), whereas the female mortality curve is characterized by a peak at 21 – 30 followed by a decrease, and then a stable level until the complete extinction of females by age of 60 (Fig. 3, B). Judging by the sex ratio (15:16), the balance was not disturbed. Seven males and six females (4.6 % of all adults) were in the nonreproductive age. This must have affected the reproductive potential of the population. Infantile mortality in the rst ve years of life is minimal, but, because only part of the cemetery has been excavated, the conclusions are tentative. Certain features of the demographic situation in Bronze Age Western Siberia Based on the results of the analysis of demographic processes in Late Bronze Age Western Siberian populations, the following conclusions can be made. The average age at death of adults buried in two cemeteries representing the Andronovo culture is 32.3 (males, 36.5; females, 31.9). In the Late Bronze Age,
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this parameter increases (34.1), and the difference between males and females decreases (36.1 and 34.2, respectively); if children are taken into account, then the mean age at death is 23.7. In Irmen and Andronovo populations, males died at a later age than females. No such conclusion can be made with regard to other Late Bronze age groups, since both Yelovka and “Late Bronze Age Culture” are represented by only one suitable sample each. Child mortality ranges from 27.05 – 39.9 %. The number of dead children per female of reproductive age is 1.27 – 2.06; it is mostly less than 2 – the number required for maintaining a stable population size. The reason is that only some of the children died, and sex and age structure must be evaluated on the basis of their remains. Judging from the results, the mean number of dead children per female was close to two in the Bronze Age. During the rst ve years of life, 50 – 75 % of children died. The highest gures were registered in Zhuravlevo-4 and Tanay-7, with the lowest in Zarechnoye-1. The number of children who died at ages 6 – 10 is maximal in Zarechnoye-1 and in Andronovo burials of Yelovsky-2 – about 30 %. The corresponding proportion is 12.5 – 16.7 % in Zhuravlevo-4, Stary Sad, and Tanay-7, and 9.0 % in Yelovka. In all groups, male and female mortality curves differ. Females tended to die at a young age, whereas males mostly died at older ages. In the postreproductive period, the extinction of females proceeded at the same or slower rate than that of males. As for general regularities, factors of male and female mortality were evidently not the same. Male mortality at that stage is mainly caused by the exhaustion of the organism’s intrinsic resources due to stable and high stress during subsistence activities; the role of social factors is less. Female mortality, on the other hand, was primarily related to childbirth and therefore depended on the level of medicine and hygiene, as well as on general living standards. The sex-and-age structure of prehistoric populations is shaped by three categories of factors. The rst category included local factors such as migrations, warfare, epidemics, etc. Their effect is apparently present in two groups: Tanay-7, which retained the features of an immigrant group, and Zhuravlevo-4, probably affected by emigration. Factors of the second category are broadly related to the “cultural model of adaptation” and include type of economy, social system, and religious beliefs. Some of those factors determine the cumulative stress level and thereby affect basic demographic parameters involved in the reproduction of the group under the given environmental conditions (fertility and mortality levels, life expectancy, etc.). The cultural model of adaptation, then, defines the limits of the population’s demographic “norm of
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reaction” to external changes. If these limits are violated, the law of population stability takes effect to bring population size back within the limits optimal under the given conditions. This is the third factor shaping the demographic proles of ancient and modern traditional groups both biologically (by affecting mortality and fertility levels) and socially. One example of a direct effect of the stability law on the social life of a traditional community is the decline of nuptiality and the rise of endogamy of the Selkups and the Sosva Mansi after a period of population growth under highly favorable environmental conditions in the late 1700s and early 1800s (Lebedev, Oborotova, 1991). In the analyzed prehistoric populations, the stability law may have affected mortality and fertility changes in females following a period of rapid growth, after the optimal difference in male and female age of death (about ten years) was reached. This law may also have operated after the arrival of immigrants, because this factor disrupted the traditions and violated the limits of the “demographic norm of reaction.” The comparison of mortality curves suggests that spatially separated, but culturally and economically similar populations have similar demographic proles, whereas those occupying the same ecological niche at various chronological stages (and thus economically divergent) display marked demographic differences. In terms of mortality, two populations fall into two groups. In females, one group includes the Yelovka people (Yelovsky-2) and the Irmen people (Zhuravlevo-4), while another group includes the Irmen people from Tanay-7 and the Andronovo people from Yelovsky-2. The second group may also include females from Chernoozerye-1, despite the absence of the mortality peak at 31 – 35. Stary Sad females are intermediate. A marked mortality peak links them to the Andronovo people from Yelovsky-2, whereas the position of that peak (in the second half of the reproductive period) is close to that of Irmen females from Zhuravlevo-4 (see Fig. 1, B). Among males, one group includes the Zhuravlevo-4, Stary Sad, and Yelovka people, while another group includes the Andronovo people from Yelovsky-2 and Chernoozerye-1, and the Irmen people from Tanay-7 (Fig. 1, A). Based on the analysis of mortality curves, several conclusions can be drawn. Firstly, living standards in the Late Bronze Age were higher than in the preceding Andronovo period. Andronovo populations exhibit a high level of cumulative stress, evidenced by high mortality among young people. The stress level shows a marked decrease in the Late Bronze Age, and mortality peaks shift toward later age intervals. The second conclusion concerns sex differences in the diachronic and local variation of mortality curves. Male curves reveal minor differences within the same
cultural stage, while showing considerable changes from the Andronovo period to the Late Bronze Age, perhaps due to economic progress. Other factors, such as climatic, were largely similar across vast areas, resulting in similar levels of stress affecting the same age categories. Female mortality curves, in contrast, demonstrate greater intrinsic variability both within archaeological cultures and within chronological stages. This may be due to differences in the social status of women and to concomitant traditions regarding female hygiene level and lifestyle. Generally, cumulative stress in females drops from the Andronovo period to the Late Bronze Age, and age intervals that are potentially dangerous in terms of mortality become more pronounced. The analysis of the sex-and-age structure of prehistoric populations of Western Siberia suggests that in the Late Bronze Age, two models of demographic adaptation to environmental change existed. The rst model was based on emigration, as demonstrated by Tanay-7. The second one was based on immigration and the incorporation of immigrants into the aging population, as seen in Andronovo-Yelovka materials from the Tomsk part of the Ob Basin.
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Received January 15, 2008.