Comparison of the mortality profiles of Archaic Middle Woodland and Middle Mississippian skeletal populations.код для вставкиСкачать
Comparison of the Mortality Profiles of Archaic, Middle Woodland, and Middle Mississippian Skeletal Populations ROBERT I,. BLAKELY D e p a r t m e n t o j Antfzropology, Georgia State University, A t l a n t a , Georgia ABSTRACT Mortality profiles were constructed for four American Indian skeletal populations for the purpose of comparing the frequencies of deaths at given ages between and within the populations. An interpretation of the differential mortality frequencies is then possible. Selected for study were the Archaic population from Indian Knoll, Kentucky, an Illinois Archaic series and a Middle Woodland Hopewellian population, both from the Klunk Mounds in southwestern Illinois, and a Middle Mississippian population from Dickson Mounds, Illinois. It was found that in the Archaic populations there were significantly higher percentages of deaths throughout the first three decades than among either the Hopewell or Middle Mississippian populations. Although the mortality profiles of the latter two groups more closely approximated each other, the average age at death was greater for the Hopewellian population. Suggested are different behavioral adjustments to stress. However, with a few notable exceptions, the fluctuations in the frequencies of death follow similar profiles in the mortality curves, indicating that common to all four populations were certain ages at which time death was more likely to occur. Various interpretations are offered to explain these periods of greater mortality. I n this preliminary report, a n attempt is made to compare the mortality profiles of four prehistoric American Indian skeletal populations: two Archaic, a Middle Woodland Hopewellian, and a Middle Mississippian series. The mortality curves illustrate fluctuations in the relative frequencies of deaths occurring within all age groups. The modes, or apices, of the curve, which represent greater frequencies of death, may reflect differential stress factors, both physical and behavioral, operative at certain ages. To interpret the mortality profiles, then, the investigator must take into account such forces as subsistence patterns, disease vectors, conflict behavior, and funerary practices. By comparing the mortality curves of different populations, it is possible to distinguish both similar and dissimilar stresses. However, it should be realized that unrelated causal factors may produce parallel curves. AM J PHYS. ANTHROP, 34 43-54. MATEKlALS AND METHODS Selected for comparison as a representative Middle Mississippian skeletal population was the Dickson Mounds series of 479 individuals, the data for which were compiled by the author (Blakely and Walker, '68). The semilunar-shaped burial cemetery, one of over 1400 prehistoric American Indian sites i n Fulton County, Illinois, is located on a bluff overlooking the west floodplain of the Illinois River approximately 35 miles southwest of the present Peoria, Illinois. Radiocarbon dates for the Eveland Site, a Middle Mississippian occupation site adjacent to Dickson Mounds, range from 920 to 1120 AD (Crane and Griffin, '60). The Middle Woodland Hopewellian population of 294 individuals, originally analyzed by King B. Hunter ('65), was recovered at the Pete Klunk Mounds. The burial mounds are situated along the 43 44 ROBERT L. BI,AKELY Illinois River near its mouth at the Mississippi River in Calhoun County, Illinois. This mortuary complex contains separate Archaic, Middle Woodland, and Late Woodland skeletal series. A radiocarbon date of 187 AD (Perino, '68) has been assigned to the Middle Woodland Hopewellian burials. It was the writer's original intent to utilize the large Archaic Indian Knoll series of 844 individuals analyzed by the late Charles E. Snow (Snow, '48). The burials, excavated from large shell middens located along the Green River in Ohio County, western Kentucky, have been radiocarbon dated at 3352 BC (Deuel, '58). However, the shell date is probably too early and should be discounted. A much more likely dating for the site would be from circa 2500 to 2000 BC (Winters, '69). When the mortality profile was constructed for the Indian Knoll population, a n abnormally high mode was noted during the third decade, that is, between ages 20 and 29 years, representing 41% of the entire population (fig. 2). Jensen ('53) has suggested that extensive malnutrition and subsequent mortality may be the result of thiamin deficiencies from the destruction of thiamin by thiaminase of shellfish. However, the enzyme i n these foods is destroyed by cooking, which is known to have been practiced at that time because of the presence of hearths with fire-cracked rocks used in "stone-boiling" (Neumann, '66). Moreover, thiamin deficiency fails to account for the disproportionate number of deaths during the third decade. Because the Indian Knoll burials span a period of 500 years, i t is possible that the peak between ages 20 and 29 years represents deaths incurred during only a part of the total occupation. External or internal competition for basic resources, often coupled with population dispersion, occurred at various times i n sociocultural groups with a narrow spectrum economy such as that of the Indian Knoll Culture (communication from H. D. Winters). If this were the case, one would expect a disproportionately greater number of burials i n certain strata of the middens. However, a survey of the depths of the burials as reported by Webb ('46) does not reveal a clustering of skeletons which is confined to any particular temporal level. Finally, it should be noted that the sample from a single site of the Indian Knoll Culture does not necessarily represent the total population since some midwestern Archaic groups had seasonal subsistence patterns that involved occupation of several sitcs in a sequential, annual cycle. The writer recently had a n opportunity to examine the Indian Knoll skeletal material and found that Snow had utilized criteria for assessing age at death which were substantially different from, and less rigorous than, those employed by Hunter and myself (Snow, '48; Stewart, '62, Hunter, '65; Blakely and Walker, '68). I n fact, Snow had previously recognized the inadequacies of his original data, and in 1959 Johnston and Snow ('61) adjusted the ages and sexes of the Indian Knoll skeletons in light of the many refinements in the procedures for determining skeletal age and sex. By placing less reliance on suture closure, the authors substantially increased the validity of their methodology and, consequently, their results. The percentage of deaths throughout the third decade was thus reduced from 41 to 2 4 % . Nevertheless, Stewart ('62) points out that Johnston and Snow failed to take into account the frequency of distorted symphyseal surfaces among the adult Indian Knoll females (Stewart, '57). I n addition, continued reliance on dental attrition as ai accessory means of age estimalion is a questionable practice since it is of no more value than suture closure when it comes to distinguishing a 30 year old individual from a 40 year old individual (Stewart, '62). Obviously, a comprehensive reanalysis of the ages and sexes of the Indian Knoll burials is still badly needed. In the present study, multiple criteria for assessing skeletal age at death were applied discriminately to obtain maximum accuracy. Subadolescents, neonate to age 12 years, were assigned ages on the basis of the following criteria. (1) calcification and eruption of deciduous and permanent dentition (Dahlberg, '63), (2) linear length of long bone diaphyses up to age two years (unpublished regression formula for American Indian skeletal material by K. B. Hunter), and (3) ossification and fusion 45 MORTALITY CURVES OF PREHISTORIC INDIANS of bony elements such as the neural arches of vertebrae (Francis, '40; Noback, '54). It is generally assumed that the criteria substantiate each other and they usually do, but in some instances contradictory data make age assessment somewhat more difficult. I n these cases, dental development and eruption was conditionally regarded as the most reliable indicator of skeletal age, as suggested by Johnston ('69). The ages of adolescents (12 through 19 years) were determined from closure of the basilar suture (communication from G. K. Neumann) and epiphyseal union of long bones, taking into account sex differences i n the rate of maturation (Stewart, '54). According to Krogman ('62), the pubic symphysis is the most reliable criterion beyond age 19 years. I n this study, too, age changes in the symphyseal face (McKern and Stewart, '57) provided the most accurate and consistent measure of age and were relied upon when discrepancies arose. I n addition, epiphyseal union up to age 28 years (Stewart, '54), dental attrition among the Middle Mississippi (communication from A. D. Harn), and endocranid suture closure (Todd and Lyon, '25), when substantiated by other criteria or the only available evidence, were employed to determine the ages of individuals between 20 and 39 years. Because of the appearance of degenerative modifications and cumulative developmental changes, it is more difficult to assess the ages of individuals beyond the fourth decade. Changes in the pubic symphysis were again regarded as the most reliable criteria and were utilized in conjunction with suture closure. The presence of arachnoid granulations (communication from C . K. Neumann), the density of cortical bone (communication from A. J. Perzigian), and the incidence and degree of osteoarthritis (Chapman, '63) were used as broad markers of age a t death among mature and senile individuals. It will be recalled that ages of the Hopewellians were assigned by K. B. Hunter ('65) and the Middle Mississippi by the author (Blakely and Walker, '68). Both received their training under G. K. Neumann and therefore the criteria, if not the assessments, should be the same. Both Hunter and I have examined skeletons from the two sites and independent spot checks revealed few significant differences in the ages designated. I am confident that the results of these analyses are comparable, but I cannot say the same of comparisons with other mortality profiles. To avoid spurious conclusions based on unreliable information, less consideration has been given the Indian Knoll material and greater reliance placed on data from the Illinois Archaic series underlying the Hopewell burials at the Klunk Mounds. The Archaic skeletons have been radiocarbon dated at 908 BC (communication from K. B. Hunter). Unfortunately, the entire sample consists of only 101 individuals. It is important to realize that mortality profiles can be constructed in a number of ways, so that by modifying the age intervals, for example, one is able to change slightly the shape of the curve to meet the objectives of the investigator (Vallois, '60). The writer has chosen to plot the percentage of the total population dying within ten-year intervals (fig. 2) to illustrate gross fluctuations and in so doing has masked smaller but potentially significant modes within the intervals. Because it becomes increasingly difficult to assign specific ages at the time of death after the onset of degenerative skeletal changes and reduced rate of maturation, ten-year intervals are probably the most reliable indicators of the mortality frequencies of adults. Subadolescent deaths are grouped in one-year intervals (fig. 3 ) . Chi-square tests were employed to determine the significance of the following frequency distributions: (1) the difference between the number of male and female deaths (unsexed juveniles were excluded from the sample) in all age intervals within the Illinois Archaic, Hopewell, and Middle Mississippian series were compared; (2) inales and females in each series were then pooled and differences between the three populations compared at intervals of 0-19, 20-39, and 40 years. Chi-square value (x') and significance (p) are listed in table 3. Indian Knoll mortality frequencies were omitted from the statistical comparison because of the defective data. + 46 ROBERT L. BLAKELY RESULTS The sexual dimorphism of these prehistoric American Indian populations is great enough to insure consistent and accurate identification of the sex of adolescents and adults. Because there exist no good criteria for differentiating male and female subadolescents, no attempt has been made to separate the sexes o€ infants and children. The sex ratios for the three Illinois series deviate little from 50: 50, ranging from 53% males among the Middle Mississippi and 52% among the Hopewell to 50% among the Illinois Archaic. When the mortality profiles for the sexes are plotted independently, the differential percentages suggest differences i n stress (fig. 1). In all but the Illinois Archaic series, there was a greater percentage of female deaths during the third decade. For example, among the Hopewell in which the difference is most apparent, 27% of the adult female population died 50 30 Md.0 10 10 Percentage 30 between ages 20 and 29 years as compared with 11% of the adult males during the same age interval. Two possible alternatives may explain the discrepancy. One reasonable interpretation is that the higher percentage of females reflects deaths resulting from childbearing. If, on the other hand, male deaths a t this age resulted from activities conducted away from home and if these inales were not trxnsported back to the burial cemetery for interment, a similar ratio of male to female deaths during the third decade might be observed. This latter alternative seems unlikely, however, given the almost equal proportions of male and feniale adolescents and adults represented in the total samples. The average age at death for the entire Middle Woodland Hopewell population is 30 years as compared with 27 years among the Illinois Archaic and 24 years among the Middle Mississippi. The older mean 50 Fslnale Ill5nois EopnreU Fig. 1 Percentages of males and females (unsexed juveniles excluded) dying within tenyear intervals for four prehistoric American Indian populations. Proportions are based on 100% for each sex. MORTALITY CURVES OF PREHISTORIC INDIANS age at death for the Hopewellians is due in part to the relatively few subadolescent deaths (table 1). Only 28% of the Hopewell individuals died prior to age ten years as compared with 35 and 48% for the Middle Mississippian and Illinois Archaic populations, respectively. The depressed percentage of infant and childhood deaths among the Hopewell may well reflect funerary practices. Ethnographic and archaeological evidence have shown that upon death not all infants were interred or that, as among some early Mississippian groups, they were buried in cemeteries separate from those of adolescents and adults. Relating to these phenomena is the fact that Hopewellian societies were often socially stratified and burial grounds restricted to particular socioeconomic groups. If the Hopewell burials from the Klunk Mounds represent the elite of this hierarchy, it is probable that greater care was afforded these select subadolescents and consequently fewer fatalities incurred. In the three Illinois populations, the mean age at death is greater among males: one year for the Illinois Archaic (males, 27.5; females, 26.5), four years among the Middle Mississippi (males, 26; females, 22), and almost seven years for the Hopewell (males, 33.5; females, 26.5). In addition to childbearing, the interpopulational differences may denote sexual divisions of activities distinctive to each TABLE I Frequency and percefitage of deaths (sexes combined) within ten-year intervals for four prehistoric American Indian skeletal populations (N, total sample size; f,fiequency within interval; F , cumulativefiequency) F Age interval f 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 314 95 344 64 18 6 3 0 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 49 11 7 11 12 6 5 0 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 82 24 39 41 55 24 20 9 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 169 46 74 76 70 25 17 2 Per cent Cumulative per cent Indian Knoll Archaic (N = 844) 314 409 753 817 835 84 1 844 844 37 11 41 8 2 1 37 48 89 97 99 100 0 0 100 100 Illinois Archaic (N = 101) 49 60 67 78 90 96 101 101 48 11 7 11 12 6 5 0 48 59 66 77 89 95 100 100 Illinois Hopewell ( N = 294) 82 106 145 186 24 1 265 285 294 28 8 13 14 19 8 7 3 28 36 49 63 82 90 97 100 Illinois Middle Mississippi (N = 479) 169 215 289 365 435 460 477 479 47 35 9 15 16 14 6 4 1 35 44 59 75 89 95 99 100 48 ROBERT L. BLAKELY group, It is conceivable that the role of the male may have become less hazardous by the late Middle Woodland Period, perhaps with the shift in emphasis from a hunting and gathering subsistence economy to one of cultivation, as Caldwell (‘58) has suggested on the basis of settlement patterns in the Illinois Valley. However, there is little paleobotanical evidence for the cultivation of either corn or beans, although there may have been other cul- tigens at that time. It is possible that a pattern like that of the Iroquois may have pertained, with women doing the cultivating and males continuing their traditional activities of hunting and expanding the importance of warfare (communication from H. D. Winters). While there are obvious differences in the frequency distribution of male and female deaths, the results of the chisquare tests point up the fact that these TABLE 2 Frequency a n d percentage of deaths (sexes combinedjfrom birth to ten years in one-year intervals for four prehistoric American Indian skeletal populations (N, sample size; A frequency within interval; F, cumulativeP-equencyj Age interval 0-0.9 1-1.9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9-9.9 f F Indian Knoll Archaic (N = 314) 150 150 17 39 189 5 3 28 21 7 45 262 5 7 269 1 8 277 1 7 284 1 14 298 2 1 9 307 7 314 1 0-0.9 1-1.9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9-9.9 19 5 3 6 2 3 4 2 3 2 0-0.9 1-1.9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9-9.9 23 17 15 3 3 3 6 0-0.9 1-1.9 2-2.9 3-3.9 4-4.9 5-5.9 6-6.9 7-7.9 8-8.9 9-9.9 Per cent 6 3 3 Cumulative per cent 17 22 25 30 31 32 33 35 36 37 Illinois Archaic (N =: 49) 19 18 24 5 27 3 33 6 35 2 38 3 42 4 44 2 47 3 49 2 18 23 26 32 34 37 41 43 46 48 Illinois Hopewell (N = 82) 23 8 40 6 5 55 58 1 61 1 64 1 70 2 76 2 79 1 82 1 8 14 19 20 21 22 24 26 27 28 Illinois Middle Mississippi 71 71 30 101 19 120 16 136 8 144 3 147 7 154 -~ 7 161 6 167 2 169 ~ (N = 169) 1s ~. 6 4 4 2 1 1 1 1 0 1 5_ - 21 25 29 31 32 33 34 35 35 MORTALITY CURVES OF PREHISTORIC INDIANS discrepancies may be due to chance, rather than to sexual differences in behavior. There are no significant differences between the mortality frequencies of males and females in the Illinois Archaic, Hopewell, and Middle Mississippian populations. Chi-square tests were then employed to ascertain the significance of the differences among the mortality curves of the three Illinois series in which the sexes were combined. Tests were conducted for three age intervals, 0-19, 20-39, and 40-t years. In the Illinois Archaic sample, there are more deaths than expected in the 0-19 age-group and relatively fewer deaths than expected in the 20-39 and 4 0 + agegroups (table 3). In the Illinois Hopewell series, more deaths than expected were incurred in the 4 0 f age-group. These deviations may reflect sampling errors or, conceivably, differences in levels of subsistence and technological understanding of childbearing. If one considers deviations among the three populations for any one of the given age-groups, they are significantly different (table 3 ) . Following the expected high frequency of neonatal deaths in all but the Illinois Hopewell population (table 2 ) and subsequent decline in mortality is a relatively AP 49 small mode between ages three and four years (fig. 3 ) . It has been suggested that the higher mortality frequency at this age reflects unsuccessful weaning, that is, a failure on the part of the infant to successfully make the transition from a lactiferous to a hard diet (Blakely and Walker, '68). Substantiative evidence of avitaminosis, such as an increase in the incidence of dietary deficiency diseases like rickets, and possibly osteoporosis, is unavailable at this time. This mode has been observed i n several skeletal populations (Johnston and Snow, '61; Hunter, '65; Angel, '69) and is probably a manifestation of many related and unrelated factors. Angel ('69), €or example, reports that a high incidence of porotic hyperostosis in juveniles from several Bronze Age populations (Lerna IV, V, VI) may be indicative of anemia from abnormal hemoglobins. A less pronounced increase in the mortality frequency occurs between ages five and eight years among the Illinois Archaic and Hopewellian populations (fig. 3). The deaths represented by this mode may be attributable to fatalities resulting from aboriginal childhood diseases. How ever, because infectious diseases of this nature rarely produce bony lesions, ft is difficult 7 Mortality profiles of four prehistoric American Indian populations (sex combined) , I n d i a n Knoll Archaic (Snow, '48); Illinois Archaic; ' . . . . . . ' . . . . . . . ., Illinois Hopewell ; ___ , Illinois Middle Mississippi. Fig. 2 ------------i 50 ROBERT L. BLAKELY TABLE 3 Three-by-three contingency table comparing t h e distribution of mortality frequencies among uqe-qrvups 0-19,20-39, a n d 40 years in t h e three Illinois series (sexes c o m b i n e d ) + 40 20-39 0-19 + Age-group Observed Illinois Archaic d d2/e Hopewell d d21e Middle Mississippi d d21e Expected 1 Observed Observed Expected Total 60 (44.02) 18 (28.65) 23 (28.22) 101 106 ( 128.15) 80 (83.40) 108 (82.43) 294 215 (208.79) 150 (135.89) 114 (134.31) 479 Total 248 38 1 x2 = Zd2le = 27.37, p < 0.001 1 Expected 8 74 245 df3 = 4 Expected frequency values obtained o n the basis of marginal probabilities. to substantiate this hypothesis. The fact that prehistoric American Indian children suffered disabilitating diseases is evidenced by the presence of Harris' lines of arrested growth in subadolescents of all three Illinois populations (Morse, '69). Following the anticipated decline in the mortality frequency during adolescence is a substantial increase in the number of deaths during the third and fourth decades referred to above and attributed primarily to childbearing (fig. 2). Among the Middle Mississippian females, there are more deaths late in the childbearing years; 37 females died between the twenty-eighth and thirty-fifth year as 25% 1 0 A@ 2 3 h 5 6 7 8 9 lo in p a r s Fig. 3 Mortality profiles of four prehistoric American Indian populations expanded to s,how mortality from birth tv ten years (sexes combined). -.-.-.-.-.-.,Indian Knoll Archaic (Snow, 48); __________ _- Illinois Archaic; . . . . . . . . . . . . , Illinois Hopewell; , Illinois Middle Mississippi. MORTALITY CURVES OF PREHISTORIC INDIANS 51 contrasted to 24 fatalities between the ent because of the incomplete data upon twentieth and twenty-seventh year. On the which we are forced to rely. Perhaps, other hand, examination of female pelves then, attention should be directed to the reveals that multiparous individuals, ir- striking similarities between the mortality respective of age, were in no greater dan- profiles. It is because the curves approxger of dying than any other segment of imate one another that an attempt has the population (Blakely and Walker, ’68). been made to explain why there are cerIt is between ages 30 and 40 years that tain ages common to all three Illinois the combined male and female mortality populations at which time death was more profiles misrepresent the data, for among likely to occur; and it is important to identhe three Illinois populations the percent- tify and understand these similarities, for age actually denotes a bimodal curve with not only do they furnish the investigator higher frequencies both early and late with valuable demographic information in the decade separated by a relatively as such, but they also provide him with a low percentage at the median. Further- framework for recognizing and explaining more, the frequency at the beginning of the equally significant differences. the decade is probably the right hand tail For example, in figure 4 the frequency of the curve between ages 20 and 29 years. distribution of the Middle Mississippi is Thus the slope may represent the cessa- compared with mortality profiles of various tion of childbearing, perhaps due to the Old World populations antedating the onset of menopause. A concomitant re- Illinois occupation. The figures are from duction in the number and degree of Krogman (’58). As previously stated, cauhazardous activities at this age may have tion should be exercised when interpreting this data because of nonstandardized contributed to this decline in mortality. The large number of deaths late in the methodologies for assessing skeletal age same decade represents the initial slope as well as environmental and racial difof the so-called old age mode most evident ferences. In figure 4, top, the Middle Misin the profile of the Illinois Hopewell, sissippian curve approximates those for which subsequently declines in the ter- Neanderthal and Cro-Magnon series in minal decades (fig. 2). By age 50 years, terms of population distribution. HOW82% of the Hopewell population had died ever, the Mesolithic profile is dissimilar as compared with 89% among both the and, indeed, resembles the defective InIllinois Archaic and Middle Mississippi dian Knoll mortality profile (fig. 2). The (table 1). There is little evidence of Egyptian and Austrian Bronze Age curves trauma-induced diseases within this age (fig. 4, bottom), while close to each other, group; rather, these old age deaths are are unlike the distribution of the Middle the result of degenerative changes and Mississippi or Illinois Archaic and Hopeheightened susceptibility to infectious well series shown in figure 2. Johnston diseases which proved fatal. Degenerative and Snow (’61) attribute the reduced subdiseases, such as arteriosclerosis, aneur- adult mortality and greater mean age at ysms, brain tissue necrosis, and several death among the Bronze Age Austrians forms of cancer including carcinoma, and Egyptians to the fact that these cannot be detected osteologically and are groups belong to cultural levels more therefore lumped together under the technologically and economically adnebulous heading “old age diseases.” vanced over that of prehistoric American Indians in the Midwest. CONCLUSIONS This trend toward greater longevity, By comparing the mortality profilcs of which is continuing today, is reflected in the Archaic, Middle Woodland Hopewel- an increasing average life expectancy in lian, and Middle Mississippian skeletal most areas of the world. It will be remempopulations, certain discrepancies are bered that the mean ages at death for the noted, and one is inclined to attribute Illinois Archaic, Hopewell, and Middle these variations to differential ecological Mississippian populations were 27, 30, and behavioral stress factors operating and 24 years, respectively. Krogman (’58) upon each of the populations. However, reports the average in urban Rome of such interpretations are tenuous at pres- 2000 years ago to be about 20 years; i t 52 ROBERT L. BLAKELY D Fig. 4 Mortality profiles of the Middle Mississippi and some Old World populations antedating the Illinois occupation. (All but the American Indian profile after Krogman, '58.) was 35-39 years in 11-13th century England and just under 50 years in 1900 AD in the United States. With this information, it becomes increasingly possible to formulate generalized conclusions concerning the lives of the people discussed in this study. It has been my objective to provide data which, pending further archaeological and bioanthropological analyses from these and other sites, may contribute to a greater understanding o f prehistoric man in the Illinois Valley and elsewhere. ACKNOWLEDGMENTS I am indebted to Professor King B. Hunter for granting permission to utilize his unpublished data and to Dr. Georg K. Neumann and Dr. Howard D. Winters for their informative suggestions critical reading of this paper. and LITERATURE CITED Angel, J. L. 1969 Paleodemography and evolution. Am. J. Phys. Anthrop., 31 : 343-353. Blakely, R. L., and P. L. Walker 1968 Mortality profile of the Middle Mississippian population of Dickson Mounds, Fulton County, I1linois. Proc. Indiana Acad. Sci., 77: 102-108. Caldwell, J. R. 1958 Trend and tradition i n the prehistory of the Eastern United States. Scientific Papers, Vol. X. Illinois State Museum, Springfield, Ill. Chapman, F. 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