Dawnie Wolfe Steadman

Pre-Columbian mycobacterial genomes reveal seals as a source of New World human tuberculosis

Modern strains of Mycobacterium tuberculosis from the Americas are closely related to those from Europe, supporting the assumption that human tuberculosis was introduced post-contact. This notion, however, is incompatible with archaeological evidence of pre-contact tuberculosis in the New World. Comparative genomics of modern isolates suggests that M. tuberculosis attained its worldwide distribution following human dispersals out of Africa during the Pleistocene epoch, although this has yet to be confirmed with ancient calibration points. Here we present three 1,000-year-old mycobacterial genomes from Peruvian human skeletons, revealing that a member of the M. tuberculosis complex caused human disease before contact. The ancient strains are distinct from known human-adapted forms and are most closely related to those adapted to seals and sea lions. Two independent dating approaches suggest a most recent common ancestor for the M. tuberculosis complex less than 6,000 years ago, which supports a Holocene dispersal of the disease. Our results implicate sea mammals as having played a role in transmitting the disease to humans across the ocean.

Estimation and evidence in forensic anthropology: Sex and race

Forensic anthropology typically uses osteological and/or dental data either to estimate characteristics of unidentified individuals or to serve as evidence in cases where there is a putative identification. In the estimation context, the problem is to describe aspects of an individual that may lead to their eventual identification, whereas in the evidentiary context, the problem is to provide the relative support for the identification. In either context, individual characteristics such as sex and race may be useful. Using a previously published forensic case (Steadman et al. (2006) Am J Phys Anthropol 131:15-26) and a large (N = 3,167) reference sample, we show that the sex of the individual can be reliably estimated using a small set of 11 craniometric variables. The likelihood ratio from sex (assuming a 1:1 sex ratio for the population at large) is, however, relatively uninformative in making the identification. Similarly, the known race of the individual is relatively uninformative in making the identification, because the individual was recovered from an area where the 2000 US census provides a very homogenous picture of (self-identified) race. Of interest in this analysis is the fact that the individual, who was recovered from Eastern Iowa, classifies very clearly with [Howells 1973. Cranial Variation in Man: A Study by Multivariate Analysis of Patterns of Difference Among Recent Human Populations. Cambridge, MA: Peabody Museum of Archaeology and Ethnology; 1989. Skull Shape and the Map: Craniometric Analyses in the Dispersion of Modern Homo. Cambridge, MA: Harvard University Press]. Easter Islander sample in an analysis with uninformative priors. When the Iowa 2000 Census data on self-reported race are used for informative priors, the individual is clearly identified as American White. This analysis shows the extreme importance of an informative prior in any forensic application.

Mississippians in motion? A population genetic analysis of interregional gene flow in west-central Illinois

Population genetic and biological distance studies of Late Woodland and Mississippian populations from west-central Illinois have provided insight into a number of prehistoric demographic processes at the regional level. However, a formal analysis of diachronic interregional gene flow has not been attempted within a population genetics framework. In this study, cranial measurements of 489 individuals from 13 skeletal samples across the central and lower Illinois valleys are analyzed to address two central issues. First, the potential impact of Cahokias decline and associated demographic events on the population structure of west-central Illinois Mississippians is examined. Second, the Mississippian and Late Woodland interregional migration patterns are compared to determine if geographic and/or cultural boundaries affected local population structure. Following Relethford and Blangero ([1990] Hum Biol 62:5–25), R matrix methods are utilized to calculate observed and expected phenotypic variances, minimum genetic distances, and FST values in order to detect patterns of differential external gene flow over time. The results indicate that Late Woodland peoples had a larger sphere of biological interaction than Mississippians. In the Mississippian period, culturally imposed barriers paralleled geographic boundaries between regions such that the geographic distribution of biological variation closely adheres to a classic isolation-by-distance model. Further, intraregional population movement was a more significant contributor to Mississippian population structure than interregional gene flow, even during periods of sociopolitical strife. Small-scale intraregional shuffling is consistent with other recent studies of prehistoric Mississippian biocultural and geographic landscapes in the southeast United States. Am J Phys Anthropol 114:61–73, 2001.

The Effects of Chemical and Heat Maceration Techniques on the Recovery of Nuclear and Mitochondrial DNA from Bone

ABSTRACT: Forensic anthropologists use a number of maceration techniques to facilitate skeletal analysis of personal identity and trauma, but they may unwittingly eliminate valuable DNA evidence in the process. This study evaluated the effect of 10 maceration methods on gross bone structure and the preservation of DNA in ribs of 12 pigs (Sus scrofa). A scoring system was applied to evaluate the ease of maceration and resulting bone quality while DNA purity was quantified by optical densitometry analysis, followed by polymerase chain reaction (PCR) amplification of three mitochondrial and three nuclear loci. The results demonstrated that while mitochondrial DNA could be amplified for all experiments, cleaning treatments using bleach, hydrogen peroxide, ethylenediaminetetraacetic acid/papain, room temperature water and detergent/sodium carbonate followed by degreasing had low DNA concentrations and failed to generate nuclear PCR products. In general, treatments performed at high temperatures (90°C or above) for short durations performed best. This study shows that traditionally “conservative” maceration techniques are not necessarily the best methods to yield DNA from skeletal tissue.

Warfare related trauma at Orendorf, a middle Mississippian site in west-central Illinois

Skeletal evidence of nonritual interpersonal trauma in the central Illinois valley is currently limited to the terminal prehistoric period in the region. Sixteen percent of the entire Norris Farms Oneota skeletal sample died violently, presumably because they intruded upon small groups of Mississippians who had not yet abandoned the region. Archaeological evidence of palisades, however, suggests that the region was embroiled in conflict before the Oneota arrived though the skeletal evidence supporting more than ritualized or geographically sporadic cases of scalping or embedded projectiles has been elusive. This study examines the frequency and nature of interpersonal trauma at Orendorf, a Middle Mississippian (AD 1150-1250) site at the northern periphery of the region. Nine percent (N = 25) of all 268 individuals documented at Orendorf suffered warfare-related trauma, including 13 cases of scalping, six instances of decapitation, five individuals with healed cranial blunt force trauma, three projectile point impacts, and eight cases of projectile injuries inferred by the burial context. All of the traumatized individuals were at or above the age of 15 years and males and females were victimized equally. The trauma rate among adults is 16%, which is less than that of the Norris Farms Oneota (34%) but higher than other Mississippian groups in the Southeast. The nature of the injuries is more consistent with attacks by outsiders than codified or ritualized intragroup violence.

A comparison of three established age estimation methods on an adult Spanish sample

Most current methods for adult skeletal age-at-death estimation are based on American samples comprising individuals of European and African ancestry. Our limited understanding of population variability hampers our efforts to apply these techniques to various skeletal populations around the world, especially in global forensic contexts. Further, documented skeletal samples are rare, limiting our ability to test our techniques. The objective of this paper is to test three pelvic macroscopic methods [(1) Suchey-Brooks; (2) Lovejoy; and (3) Buckberry and Chamberlain] on a documented modern Spanish sample. These methods were selected because they are popular among Spanish anthropologists and because they never have been tested in a Spanish sample. The study sample consists of 80 individuals (55 males and 25 females) of known sex and age from the Valladolid collection. Results indicate that in all three methods, levels of bias and inaccuracy increase with age. The Lovejoy method performs poorly (27%) compared with Suchey-Brooks (71%) and Buckberry and Chamberlain (86%). However, the levels of correlation between phases and chronological ages are low and comparable in the three methods (<0.395). The apparent accuracy of the Suchey-Brooks and Buckberry and Chamberlain methods is largely based on the broad width of the methods’ estimated intervals. This study suggests that before systematic application of these three methodologies in Spanish populations, further statistical modeling and research into the covariance of chronological age with morphological change are necessary. Future methods should be developed specific to various world populations and should allow for both precision and flexibility in age estimation.

The Scope of Anthropological Contributions to Human Rights Investigations

This paper examines the participation of anthropologists in international human rights investigations between 1990 and 1999 by surveying four of the most active organizations, including the Argentine Forensic Anthropology Team, the Guatemalan Forensic Anthropology Foundation, Physicians for Human Rights and the U.N.-sponsored International Criminal Tribunal for the former Yugoslavia. The education level, sex, nationality and primary role of the anthropological members of each team are quantified, as are the types of projects in which they contributed. The results show that 134 anthropologists from 22 nations investigated nearly 1300 sites in 33 countries during the study period. While involvement is not limited to those with advanced degrees and few obstacles are placed before anthropologists who wish to participate, full-time service within these organizations is rare and those interested in a career in forensic anthropology and human rights should understand the employment limitations.

The effects of different maceration techniques on nuclear DNA amplification using human bone.

Abstract:u2002 Forensic anthropologists routinely macerate human bone for the purposes of identity and trauma analysis, but the heat and chemical treatments used can destroy genetic evidence. As a follow‐up to a previous study on nuclear DNA recovery that used pig ribs, this study utilizes human skeletal remains treated with various bone maceration techniques for nuclear DNA amplification using the standard Combined DNA Index System (CODIS) markers. DNA was extracted from 18 samples of human lower leg bones subjected to nine chemical and heat maceration techniques. Genotyping was carried out using the AmpFℓSTR® COfiler® and AmpFℓSTR® Profiler Plus® ID kits. Results showed that heat treatments via microwave or Biz/Na2CO3 in sub‐boiling water efficiently macerate bone and produce amplifiable nuclear DNA for genetic analysis. Long‐term use of chemicals such as hydrogen peroxide is discouraged as it results in poor bone quality and has deleterious effects on DNA amplification.

The population shuffle in the central Illinois valley, a diachronic model of Mississippian biocultural interactions

Abstract A new population genetics method is applied to discriminate between processes of extraregional gene flow and intraregional biological continuity within and among three temporally sequential prehistoric Native American cultures in the central Illinois valley. Within a population genetics framework, the impact of regional and interregional cultural changes on local population structure can be quantified and the magnitude of biocultural interaction can be inferred. The results suggest that population structure within the region was relatively unaffected by the cultural transition from Late Woodland to Mississippian or by significant interregional sociopolitical changes in neighboring regions later in the Mississippian period. Finally, a Bold Counselor Phase Oneota population was morphologically distinct from Mississippians, supporting the archaeological model that this Oneota group was an intrusive, frontier population from the upper Mississippi valley. A population genetic approach is highly recomm...

Distinguished guests or agents of ingérence: foreign participation in Spanish Civil War grave excavations

For the past eight years Spanish scientists have collaborated with Spanish social and political organizations in an effort to incorporate empirical evidence from unmarked graves into the recovery of historical memory of the Spanish Civil War. Some teams have requested the assistance of experienced professionals from other countries for training and consultation. Other teams reject the influence of foreigners and prefer to view the issue of the Civil War missing as an internal matter. This paper recounts the role of forensic archaeology and anthropology in human rights investigations globally, critically examines the likelihood that the methods applied and the experiences gained elsewhere are relevant to Spain, and explores whether the implantation of foreign experts is required to achieve objectivity in Spanish human rights investigations.