AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 89:183-195 (19921
Evaluation of Lead Concentrations in 18th-Century Omaha Indian Skeletons Using ICP-MS KARL J. REINHARD AND A. MOHAhUD GHMI Department of Anthropology, University of Nebraska, Lincoln, Nebraska 68588-0368 (K.J.R.J; Department of Geology, Uniriersity of Nebraska, Lincoln, Nebraska 68588-0340 (A.M.G.)
KEY WORDS
Lead poisoning, Trace element, Isotope ratio
The analysis oi skeletal remains of Omaha Indians buried between AD 1780 and 1820 indicated that lead was incorporated in cortical bone. The diagenetic or biogenetic origin of the lead was evaluated by examination of lead isotope ratios of the bones and artifacts, and comparison of lead concentrations in burial soils with those of the bones. The isotopic values of the lead artifacts demonstrate that the lead was mined in the Missouri region. Although the isotope ratios in the bones are not identical with that from the lead artifacts, there is a strong relationship between them. This finding indicates that the lead in the bone was at least partly derived from the artifacts. Because lead artifacts rarely accompanied the burials but lead was ubiquitous in the bones, we suggest a biogenetic origin for the lead. There is also the possibility that some of the lead may have been derived from pigments applied to the corpse during mortuary ritual. o 1992 Wiley-Liss, Inc.
ABS’T;lcAcT
The impact of lead poisoning on certain ancient cultures has been a topic of conjecture and debate for many years (Scarborough, 1985). Empirical assessment of ancient lead poisoning was achieved by analysis of lead content of ancient European bones (Waldron, 19731. The search for evidence of toxic clcmcnts is an important aspect of current trace element research (cf. Aufderheide, 1989). Lead analysis has proven particularly informative with respect to social interaction and status, assessment of lead technology, and predicting health effects (Aufderhiede et al., 1985, 1988). In addition, the comparative study of archaeological and contemporary human bone has verified the increase in lead contamination of modern populations (Rogers and Waldron, 1985). Essentially, lead content of archaeological bone is a mirror of long-term lead ingestion (Aufderheide et al., 1981). Because different subsets of human populations often experience different exposure levels t o lead, the use of concentrations in bone sometimes reflects social distance (Aufderheide et al., 1985) as exemplified by 0 1992 WILEY-LISS, INC
recent studies where lead concentrations in archaeological bone have indicated differences between slaves and plantation owners in colonial North America, between subgroups of slave populations (Aufderheide et al., 1988), and between high status and low status Romans (Fornaciari et al., 1984). Additional research has eniphasized the role of diagenesis in altering lead values and has called for maintaining healthy skepticism when interpreting lead data (Grupe, 1988; Klepinger et al., 1986; Lambert et al., 1985; Waldron, 1981). Trace element analysis of skeletal remains excavated from two Omaha cemeteries (25DK10 and 25DK2) dating between AD 1780 and 1820 was completed for evidence of toxic elements. Since trade between the Omaha and Euroamerican populations was well established at this time, finding over 1,300 artifacts along with 106 skeletons was not unexpected. The trade artifacts with the burials were mainly made of copper, brass. __ ~ _ _ _ _ Received September 6.1991, accepted March 9,1992
184
K.J. REINHARD AND A.M. GHAZI
iron, lead, and glass. Although ethnohis- by Stanley Bartos, Jr. and consisted of three torical documentation of Omaha manufac- low mounds, two of which contained burials. ture of metal tools is not present for this Detailed field drawings, a site map and field time period, artifactual evidence indicates notes from this excavation have been located that the Omaha were manufacturing imple- and have been studied as part of this analyments and ornaments from iron, copper, and sis. These excavations were part of a larger lead. The Omaha shaped implements from archaeological project funded by the W.P.A. iron and copper sheets, and lead was melted One excavation crew was composed of memand molded into objects such as musket bers of the Winnebago Tribe and the second balls and ornaments. Because lead was be- crew was composed of local farmers and ing melted and molded at the Omaha vil- townspeople residing in or near Homer. In 1990, a landowner disturbed Omaha lage, lead contamination of the village was a distinct possibility. Analysis of skeletal re- burials that were apparent!:7 part of25DK2, mains for lead content was undertaken to University of Nebraska-Lincoln physical andetermine if lead was an environmental con- thropology students, K.J. Reinhard, Debra K. Meier (University of Nebraska State Mutaminant at the village. The goals of this analysis are 1)to assess seum), Dennis Hastings (Omaha Tribal Histhe prevalence and concentration of lead in torian), and John R. Bozell (Nebraska State Omaha skeletal remains, 2) to determine Historical Society) excavated six exposed whether the origin of this lead was bioge- skeletons. This excavation provided the opnetic or diagenetic, 3 ) to determine the geo- portunity to collect soil samples from the logical origin of the lead artifacts traded to cemetery to assess lead concentrations in the Omaha, 4) to assess whether the lead in the local soils. the bones had an artifactual origin, and 5) to Preservation and curation determine whether certain segments of the population were differentially exposed to The preservation of bone and organic artilead. facts in the cemeteries was excellent. The soil matrix is composed of a fine grained, well drained, yellow loess and preservation ARCHAEOLOGICAL BACKGROUND of bone in this soil was ideal. Excavation Unfortunately, many burials were disSites 25DK10 and 25DK2 are cemeteries turbed by secondary intrusive burials by the associated with 25DK5, a large Omaha vil- Omaha, excavations by looters, and burrowlage site named Tonwantonga (25DK5). The ing animals before archaeological excavavillage was located in northeastern Ne- tions commenced. Often, the Omaha dilg braska along the Missouri River flood plain burial pits into already established Omaha near the modern town of Homer. Both ceme- graves resulting in disturbance of previous teries had been subjected to wind and water burials and discarding of bone. Single burierosion by the 1930s and exposed bones and als and multiple burials are present in the artifacts attracted looters who began to Omaha cemeteries. Single burials, with the plunder the cemeteries. In the late 1930s, body supine, are present, but multiple burithe sites were selected for scientific excava- als are more common. Up to five people of all tion along with the village site, 25DK5. ages shared the same burial pit. A few buri25DK10 is located approximately 1 mile als consist of a limited amount of bone, not northwest of the village site, on bluffs 300 anatomically arranged, placed in a burial feet above the flood plain. This site was ex- pit. Some of the bone from such burials excavated in 1940 under the direction of John hibits breakage and tooth marks from scavL. Champe. No site map was made of this enger activity. The finding of these incomcemetery and only partial field notes have plete skeletons may be explained, a t least in been found for this site. 25DK2 was estab- part, by the Plains practice of placing the lished on bluffs 1.25 miles southeast of the deceased on a scaffold above the ground for a village, approximately 350 feet above the time and then transferring the remains to a flood plain. The site was excavated in 1939 burial pit. During the period of scaffolding,
OMAHA LEAU CONTAMINATION
185
decomposition takes place and scavengers sence of 0s coxae, possible sex determination have access to the remains. This leaves a was based on cranial secondary sex characpartial skeleton for burial. These practices, teristics, and long bone robusticity. Six of plus animal disturbance and vandalism, re- the individuals that proved to have very sulted in the extensive disturbance of many high lead concentrations were selected for further lead isotope analysis as well as four skeletons which are now incomplete. Once excavated in 1940, the bones were artifacts. The four artifacts included a musbrought to the osteology laboratory at the ket ball, two lead coils, and a lead alloy University of Nebraska-Lincoln for preser- buckle. Lead musket balls and coils constivation. It does not appear that preservative tuted two of the most common forms of lead was applied to postcranial skeletons. How- artifacts found with the burials. Following Aufderheide’s (1989) suggesever, acetate sheets were occasionally used t o ho!d delicate or f r a p c n t a r y crania! tions for lead analysis, on!y cortica! b=nc bones together, especially of infants, neo- was used for this study. Grupe’s (1988) nates, and fetal individuals. Each bone was study of the variation in trace element conlabeled, and then bones from individual tent between different bones of the skeleton and between cortical and trabecular bone skeletons were placed in boxes for storage. The efficient preservation and storage led to the recommendation that the same techniques resulted in excellent bone pres- skeletal element should be chosen from all ervation. Considering that the burials were skeletons. For this study, rib fragments excavated in 1940, it is a testimony to the were removed from skeletons after age and archaeologists and curators of that time that sex determinations were completed. Only the bones are in such good condition at the fragments that exhibited no evidence of artitime of this writing. The Omaha Tribe has ficial pigmentation were used. In the analysis of the rib fragments, an chosen to rebury the remains and reburial Inductively Coupled Plasma-Mass Specoccurred on October 4,1991. trometer (VG Plasmaquad) was used t o MATERIALS AND METHODS measure the lead concentration and lead Three soil samples from the 1990 excava- isotope ratios. Samples were introduced via tions were analyzed. Sample 1 was taken a peristaltic pump (Minipuls 3, Gilson, Midfrom a cut in the site away from any burial dleton, WI). The ion lenses were optimized pits to provide a measure of the normal using 100 ng/ml indium solution, so that the amount of lead in undisturbed soil. Sample 2 count rates were relatively uniform across was taken from a double infant burial that the mass range. Standard reagents were used. Deionized contained a single lead coil. Sample 3 was collected from the burial pit of an adolescent water from a NANOpure system (Barnstead Corp.) at 18 MOhm was used in every step of without lead artifacts. To assess the potential impact of lead poi- the standard preparation and in cleaning soning on different age and sex subsets, ribs laboratory glassware. Nitric acid, Ultrex from infants, children, and adults of both grade (J.T. Baker Chemical Corp.) was used sexes were selected. In the light of past stud- for digestion and dilution of the samples and ies which showed a positive relation be- standards. Certified multielement standard tween age and lead concentration (Handler (SRM 3172) from the National Institutes of et al., 1986), we included a large proportion Standards and Technology and a single eleof subadults in the sample. Lead concentra- ment standard from Spex Industries were tion values were obtained from 39 individu- used to establish calibration curves. For the als. The age of subadult remains was as- isotope ratio measurements, an ACS certisessed on the basis of epiphyseal closure as fied Fisher brand lead nitrate was analyzed reviewed by Steele and Bramblett (1988) by a thermal ionization mass spectrometer and dental development as evidenced by ra- at the Geology Department, University of diographs. When at least one 0s coxa was Kansas. The NBS 981 common lead stanpresent, sex was positively determined on dard was not available at the time of analythe basis of 0s coxa morphology. In the ab- sis.
186
K J REINHARD AND A.M. GHAZI
The artifacts and ribs were processed in a closed teflon bomb by acid digestion procedure. Fragments of ribs measuring 0.5-1.0 ern were examined and cleaned. The ribs were split and the trabecular bone was removed from the dense cortical bone. The samples were washed in 1.0% HNO, to remove any surface material and dried in an oven at 75°C for 5 hours. For ashing, the bone were placed into porcelain crucible and heated 15-18 hours inside a muffle furnace at 550°C. The ashed samp!es were then c m ~ h e dand placed hark in the oven for 3 hours. The samples were then pulverized into a fine powder (
Evaluation of Lead Concentrations in 18th-Century Omaha Indian Skeletons Using ICP-MS KARL J. REINHARD AND A. MOHAhUD GHMI Department of Anthropology, University of Nebraska, Lincoln, Nebraska 68588-0368 (K.J.R.J; Department of Geology, Uniriersity of Nebraska, Lincoln, Nebraska 68588-0340 (A.M.G.)
KEY WORDS
Lead poisoning, Trace element, Isotope ratio
The analysis oi skeletal remains of Omaha Indians buried between AD 1780 and 1820 indicated that lead was incorporated in cortical bone. The diagenetic or biogenetic origin of the lead was evaluated by examination of lead isotope ratios of the bones and artifacts, and comparison of lead concentrations in burial soils with those of the bones. The isotopic values of the lead artifacts demonstrate that the lead was mined in the Missouri region. Although the isotope ratios in the bones are not identical with that from the lead artifacts, there is a strong relationship between them. This finding indicates that the lead in the bone was at least partly derived from the artifacts. Because lead artifacts rarely accompanied the burials but lead was ubiquitous in the bones, we suggest a biogenetic origin for the lead. There is also the possibility that some of the lead may have been derived from pigments applied to the corpse during mortuary ritual. o 1992 Wiley-Liss, Inc.
ABS’T;lcAcT
The impact of lead poisoning on certain ancient cultures has been a topic of conjecture and debate for many years (Scarborough, 1985). Empirical assessment of ancient lead poisoning was achieved by analysis of lead content of ancient European bones (Waldron, 19731. The search for evidence of toxic clcmcnts is an important aspect of current trace element research (cf. Aufderheide, 1989). Lead analysis has proven particularly informative with respect to social interaction and status, assessment of lead technology, and predicting health effects (Aufderhiede et al., 1985, 1988). In addition, the comparative study of archaeological and contemporary human bone has verified the increase in lead contamination of modern populations (Rogers and Waldron, 1985). Essentially, lead content of archaeological bone is a mirror of long-term lead ingestion (Aufderheide et al., 1981). Because different subsets of human populations often experience different exposure levels t o lead, the use of concentrations in bone sometimes reflects social distance (Aufderheide et al., 1985) as exemplified by 0 1992 WILEY-LISS, INC
recent studies where lead concentrations in archaeological bone have indicated differences between slaves and plantation owners in colonial North America, between subgroups of slave populations (Aufderheide et al., 1988), and between high status and low status Romans (Fornaciari et al., 1984). Additional research has eniphasized the role of diagenesis in altering lead values and has called for maintaining healthy skepticism when interpreting lead data (Grupe, 1988; Klepinger et al., 1986; Lambert et al., 1985; Waldron, 1981). Trace element analysis of skeletal remains excavated from two Omaha cemeteries (25DK10 and 25DK2) dating between AD 1780 and 1820 was completed for evidence of toxic elements. Since trade between the Omaha and Euroamerican populations was well established at this time, finding over 1,300 artifacts along with 106 skeletons was not unexpected. The trade artifacts with the burials were mainly made of copper, brass. __ ~ _ _ _ _ Received September 6.1991, accepted March 9,1992
184
K.J. REINHARD AND A.M. GHAZI
iron, lead, and glass. Although ethnohis- by Stanley Bartos, Jr. and consisted of three torical documentation of Omaha manufac- low mounds, two of which contained burials. ture of metal tools is not present for this Detailed field drawings, a site map and field time period, artifactual evidence indicates notes from this excavation have been located that the Omaha were manufacturing imple- and have been studied as part of this analyments and ornaments from iron, copper, and sis. These excavations were part of a larger lead. The Omaha shaped implements from archaeological project funded by the W.P.A. iron and copper sheets, and lead was melted One excavation crew was composed of memand molded into objects such as musket bers of the Winnebago Tribe and the second balls and ornaments. Because lead was be- crew was composed of local farmers and ing melted and molded at the Omaha vil- townspeople residing in or near Homer. In 1990, a landowner disturbed Omaha lage, lead contamination of the village was a distinct possibility. Analysis of skeletal re- burials that were apparent!:7 part of25DK2, mains for lead content was undertaken to University of Nebraska-Lincoln physical andetermine if lead was an environmental con- thropology students, K.J. Reinhard, Debra K. Meier (University of Nebraska State Mutaminant at the village. The goals of this analysis are 1)to assess seum), Dennis Hastings (Omaha Tribal Histhe prevalence and concentration of lead in torian), and John R. Bozell (Nebraska State Omaha skeletal remains, 2) to determine Historical Society) excavated six exposed whether the origin of this lead was bioge- skeletons. This excavation provided the opnetic or diagenetic, 3 ) to determine the geo- portunity to collect soil samples from the logical origin of the lead artifacts traded to cemetery to assess lead concentrations in the Omaha, 4) to assess whether the lead in the local soils. the bones had an artifactual origin, and 5) to Preservation and curation determine whether certain segments of the population were differentially exposed to The preservation of bone and organic artilead. facts in the cemeteries was excellent. The soil matrix is composed of a fine grained, well drained, yellow loess and preservation ARCHAEOLOGICAL BACKGROUND of bone in this soil was ideal. Excavation Unfortunately, many burials were disSites 25DK10 and 25DK2 are cemeteries turbed by secondary intrusive burials by the associated with 25DK5, a large Omaha vil- Omaha, excavations by looters, and burrowlage site named Tonwantonga (25DK5). The ing animals before archaeological excavavillage was located in northeastern Ne- tions commenced. Often, the Omaha dilg braska along the Missouri River flood plain burial pits into already established Omaha near the modern town of Homer. Both ceme- graves resulting in disturbance of previous teries had been subjected to wind and water burials and discarding of bone. Single burierosion by the 1930s and exposed bones and als and multiple burials are present in the artifacts attracted looters who began to Omaha cemeteries. Single burials, with the plunder the cemeteries. In the late 1930s, body supine, are present, but multiple burithe sites were selected for scientific excava- als are more common. Up to five people of all tion along with the village site, 25DK5. ages shared the same burial pit. A few buri25DK10 is located approximately 1 mile als consist of a limited amount of bone, not northwest of the village site, on bluffs 300 anatomically arranged, placed in a burial feet above the flood plain. This site was ex- pit. Some of the bone from such burials excavated in 1940 under the direction of John hibits breakage and tooth marks from scavL. Champe. No site map was made of this enger activity. The finding of these incomcemetery and only partial field notes have plete skeletons may be explained, a t least in been found for this site. 25DK2 was estab- part, by the Plains practice of placing the lished on bluffs 1.25 miles southeast of the deceased on a scaffold above the ground for a village, approximately 350 feet above the time and then transferring the remains to a flood plain. The site was excavated in 1939 burial pit. During the period of scaffolding,
OMAHA LEAU CONTAMINATION
185
decomposition takes place and scavengers sence of 0s coxae, possible sex determination have access to the remains. This leaves a was based on cranial secondary sex characpartial skeleton for burial. These practices, teristics, and long bone robusticity. Six of plus animal disturbance and vandalism, re- the individuals that proved to have very sulted in the extensive disturbance of many high lead concentrations were selected for further lead isotope analysis as well as four skeletons which are now incomplete. Once excavated in 1940, the bones were artifacts. The four artifacts included a musbrought to the osteology laboratory at the ket ball, two lead coils, and a lead alloy University of Nebraska-Lincoln for preser- buckle. Lead musket balls and coils constivation. It does not appear that preservative tuted two of the most common forms of lead was applied to postcranial skeletons. How- artifacts found with the burials. Following Aufderheide’s (1989) suggesever, acetate sheets were occasionally used t o ho!d delicate or f r a p c n t a r y crania! tions for lead analysis, on!y cortica! b=nc bones together, especially of infants, neo- was used for this study. Grupe’s (1988) nates, and fetal individuals. Each bone was study of the variation in trace element conlabeled, and then bones from individual tent between different bones of the skeleton and between cortical and trabecular bone skeletons were placed in boxes for storage. The efficient preservation and storage led to the recommendation that the same techniques resulted in excellent bone pres- skeletal element should be chosen from all ervation. Considering that the burials were skeletons. For this study, rib fragments excavated in 1940, it is a testimony to the were removed from skeletons after age and archaeologists and curators of that time that sex determinations were completed. Only the bones are in such good condition at the fragments that exhibited no evidence of artitime of this writing. The Omaha Tribe has ficial pigmentation were used. In the analysis of the rib fragments, an chosen to rebury the remains and reburial Inductively Coupled Plasma-Mass Specoccurred on October 4,1991. trometer (VG Plasmaquad) was used t o MATERIALS AND METHODS measure the lead concentration and lead Three soil samples from the 1990 excava- isotope ratios. Samples were introduced via tions were analyzed. Sample 1 was taken a peristaltic pump (Minipuls 3, Gilson, Midfrom a cut in the site away from any burial dleton, WI). The ion lenses were optimized pits to provide a measure of the normal using 100 ng/ml indium solution, so that the amount of lead in undisturbed soil. Sample 2 count rates were relatively uniform across was taken from a double infant burial that the mass range. Standard reagents were used. Deionized contained a single lead coil. Sample 3 was collected from the burial pit of an adolescent water from a NANOpure system (Barnstead Corp.) at 18 MOhm was used in every step of without lead artifacts. To assess the potential impact of lead poi- the standard preparation and in cleaning soning on different age and sex subsets, ribs laboratory glassware. Nitric acid, Ultrex from infants, children, and adults of both grade (J.T. Baker Chemical Corp.) was used sexes were selected. In the light of past stud- for digestion and dilution of the samples and ies which showed a positive relation be- standards. Certified multielement standard tween age and lead concentration (Handler (SRM 3172) from the National Institutes of et al., 1986), we included a large proportion Standards and Technology and a single eleof subadults in the sample. Lead concentra- ment standard from Spex Industries were tion values were obtained from 39 individu- used to establish calibration curves. For the als. The age of subadult remains was as- isotope ratio measurements, an ACS certisessed on the basis of epiphyseal closure as fied Fisher brand lead nitrate was analyzed reviewed by Steele and Bramblett (1988) by a thermal ionization mass spectrometer and dental development as evidenced by ra- at the Geology Department, University of diographs. When at least one 0s coxa was Kansas. The NBS 981 common lead stanpresent, sex was positively determined on dard was not available at the time of analythe basis of 0s coxa morphology. In the ab- sis.
186
K J REINHARD AND A.M. GHAZI
The artifacts and ribs were processed in a closed teflon bomb by acid digestion procedure. Fragments of ribs measuring 0.5-1.0 ern were examined and cleaned. The ribs were split and the trabecular bone was removed from the dense cortical bone. The samples were washed in 1.0% HNO, to remove any surface material and dried in an oven at 75°C for 5 hours. For ashing, the bone were placed into porcelain crucible and heated 15-18 hours inside a muffle furnace at 550°C. The ashed samp!es were then c m ~ h e dand placed hark in the oven for 3 hours. The samples were then pulverized into a fine powder (
