Papers by Helen Kurki
The Mother-Infant Nexus in Anthropology
This chapter reviews current evidence of infant development and pelvic morphology from the homini... more This chapter reviews current evidence of infant development and pelvic morphology from the hominin fossil record over our evolutionary history and considers the implications for understanding obstetrical dilemmas from ecological and evolutionary perspectives, and for infant care and survivorship over time and across species. We begin by defining infants and addressing the challenges of doing so within a palaeospecies. We also consider the limitations to our study of hominin infants due to taphonomic factors. We present an overview of the fossil record of hominin pelves and evolutionary changes relating to bipedalism and obstetrics. We then trace the fossil record of hominin infants and the evidence for the evolution of infant developmental trajectories. Finally, we draw these lines of evidence together to consider the current state of our understanding about the evolution of childbirth, mother–infant survivorship and infant care over time and if the obstetrical dilemma hypothesis is no longer supported.
Objectives: The human pelvis is unique among modern taxa for supporting both parturition of large... more Objectives: The human pelvis is unique among modern taxa for supporting both parturition of large brained young and obligate bipedalism. Though much work has focused on pelvic development and variation, little work has explored the presence or absence of asymmetry in the pelvis despite well-known patterns of asymmetry in other skeletal regions. This study investigated whether patterns of directional asymmetry (DA) could be observed in the pelvis or pelvic canal. Methods: Seventeen bilaterally paired osteometric measurements of the os coxae (34 measures in total) were taken from 128 skeletons (female n 5 65, male n 5 63) from recent human populations in five geographic regions. Paired sample t-tests and Mann–Whitney U-tests were used to investigate DA. Results: Results from a pooled sample of all individuals showed that the pelvis exhibited a left-bias in DA. In contrast , the pelvic canal exhibited a pattern in which the anterior canal exhibited a right-bias and the posterior canal exhibited a left-bias. Neither sex nor populational differences in DA were observed in the pelvis or pelvic canal. Conclusions: The varying patterns of asymmetry uncovered here accord with prior work and may indicate that loading from the trunk and legs place differing stresses on the pelvis and canal, yielding these unequal asymmetries. However, this is speculative and the possible influence of genetics, biomechanics, and nutritional status on the development of pelvic and canal asymmetries presents a rich area for future study. Additionally, the potential influence of pel-vic canal asymmetry on obstetric measures of pelvic capacity merits future research. Am.
International Journal of Paleopathology, Dec 2014
International Journal of Paleopathology, 2014
American Journal of Physical Anthropology, Feb 26, 2014
Body mass estimates are integral to a wide range of inferences in paleoanthropology. Most techniq... more Body mass estimates are integral to a wide range of inferences in paleoanthropology. Most techniques employ postcranial elements, but predictive equations based on cranial variables have also been
developed. Three studies currently provide regression equations for estimating mass from cranial variables, but none of the equations has been tested on samples of known mass. Nor have the equations been compared to each other in terms of performance. Consequently, this study assessed the performance of existing cranial equations using computed tomography scans from a large, documented sample of modern humans of known body mass. Virtual models of the skull were reconstructed
and measured using computer software, and the resulting variables were entered into three sets of published regression equations. Estimated and known body masses were then compared. For most equations, prediction errors were high and few individuals were estimated within +/- 20% of their known mass. Only one equation satisfied the accuracy criteria. In addition, variables that had been previously argued to be good predictors of mass in hominins, including humans, did not estimate
mass reliably. These results have important implications for paleoanthropology. In particular, they emphasize the need to develop new equations for estimating fossil hominin body mass from cranial variables.
Archaeological and Anthropological Sciences, Jun 18, 2015
Estimating body mass from skeletal material is a key task for many biological anthropologists. As... more Estimating body mass from skeletal material is a key task for many biological anthropologists. As a result, several sets of regression equations have been derived for cranial and postcranial material. The equations have been applied to a wide range of specimens, but several factors suggest they may not be as reliable as generally assumed. Specifically, since many of the equations were derived from small reference samples using proxies for key variables and/or mean data, the nature of the relationship between the skeletal variables and body mass has often not been adequately demonstrated. In addition, few of the equations have been validated on known samples, making their accuracy and precision uncertain. Lastly, because no study has used cranial and postcranial material from the same individuals, the two approaches have never been systematically compared. The present study responded to these issues by deriving new regression equations from cranial and postcranial material using a large sample of modern humans of known-mass and associated skeletal variables measured from CT data. The equations were then
tested on an independent sample, also of known mass. The
results show that the newly derived equations estimate mass more accurately than existing equations for most variables. However, improvements were modest and accuracy rates remained relatively low. In addition, variables that had previously been argued to be ideal predictors were not the most accurate, and the current criteria used to assess equations did not ensure reliability. Overall, the results suggest that body mass estimates must be used cautiously and that further research is required.
Archaeological and Anthropological Sciences, May 29, 2015
Many inferences in palaeoanthropology and bioarchaeology rely on estimates of body mass from skel... more Many inferences in palaeoanthropology and bioarchaeology rely on estimates of body mass from skeletal material. Body mass estimation is also becoming an area of interest for forensic anthropologists. The most common approach to estimating body mass from the skeleton involves measurements of the postcranium, and a number of equations have been developed for femoral head size and stature plus biiliac breadth. These equations have become standard in biological anthropology, but they have rarely been tested on individuals of known mass. In addition, the effects of several assumptions involved in the application of the equations have not been rigorously investigated. Accordingly, this study employed CT scans from a sample of 253 adult modern humans of known body mass to test the accuracy of the most widely used postcranial body mass estimation equations. The results were then used to evaluate several claims concerning the performance of the equations relative to one another. Most of the equations that were tested met the criteria for acceptance as reliable estimators with the male and the combined-sex samples. However, females were not estimated as reliably. In addition, the equations did not always perform consistently or as expected. Overall, our results suggest that estimating body
mass with the postcranial equations that are currently available requires more caution than is usually exercised.
Tribology International
ABSTRACT Small body size has been used in bioarchaeological contexts as an indicator of poor heal... more ABSTRACT Small body size has been used in bioarchaeological contexts as an indicator of poor health and in clinical contexts as a risk factor for difficult childbirth, under the assumption that small size reflects compro- mised growth. Compromised growth in females may result in contracted pelvic dimensions and elevated risk of cephalopelvic disproportion. The basis for the use of clinical pelvic contracture thresholds for evaluating health and growth in skeletal populations is examined through comparisons of contracture frequencies and the relationships between pelvic canal size and body size in 11 skeletal samples (total n = 195). The small-bodied samples show higher frequencies of contracted inlet and midplane posterior space dimensions. Canal breadth is correlated with femoral head diameter and bi-iliac breadth, but not femoral length. These results suggest that modern clinical standards do not take into account the varia- tion in human body size and shape and the effect this variation may have on obstetric capacity without compromising obstetric function. It is problematic to use small pelvic dimensions, in the absence of evi- dence of death during childbirth, to infer compromised obstetric function resulting from biological stress, as is assuming that small size represents compromised skeletal growth.
American Journal of Human Biology
Objectives
This study tests the hypothesis, a correlate of the obstetric dilemma, that skeletal ... more Objectives
This study tests the hypothesis, a correlate of the obstetric dilemma, that skeletal variability in the human female pelvic canal is limited owing to the action of stabilizing selection. Levels of variation in three skeletal regions (pelvic canal, noncanal pelvis, and limbs) of females and males are compared to each other and between sexes.
Methods
Nine human skeletal samples (total female n = 101; male n = 117) representing diverse populations were included. Osteometric data were collected from the articulated pelvis, os coxa, sacrum, femur, tibia, humerus, radius, and clavicle. Coefficients of variation, adjusted for small sample size (V*), were calculated for variables in separate samples by sex, and mean V*s were taken for the skeletal regions. Size variances were measured as V* of the geometric mean (GM) of the skeletal region variables. Using nonparametric methods, coefficients were compared between sexes and skeletal regions and correlations among V*s were calculated.
Results
Females and males do not differ in levels of variation for any skeletal region. The pelvic canal is the most variable region in both sexes, while size variability (GM) is similar among the three skeletal regions. Across the samples, canal and noncanal pelvic regions share patterns of variability in females but not males, while variability of the limb skeleton is independent in both sexes.
Conclusions
The results suggest that stabilizing selection does not limit variability in the female pelvic canal. Biological plasticity may be greater in the canal than that in other skeletal regions. Am. J. Hum. Biol., 2013. © 2013 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Obstetric selection acts on the female pelvic canal to accommodate the human neonate and contribu... more Obstetric selection acts on the female pelvic canal to accommodate the human neonate and contributes to pelvic sexual dimorphism. There is a complex relationship between selection for obstetric sufficiency and for overall body size in humans. The relationship between selective pressures may differ among populations of different body sizes and proportions, as pelvic canal dimensions vary among populations. Size and shape of the pelvic canal in relation to body size and shape were examined using nine skeletal samples (total female n = 57; male n = 84) from diverse geographical regions. Pelvic, vertebral, and lower limb bone measurements were collected. Principal component analyses demonstrate pelvic canal size and shape differences among the samples. Male multivariate variance in pelvic shape is greater than female variance for North and South Africans. High-latitude samples have larger and broader bodies, and pelvic canals of larger size and, among females, relatively broader medio-lateral dimensions relative to low-latitude samples, which tend to display relatively expanded inlet antero-posterior (A-P) and posterior canal dimensions. Differences in canal shape exist among samples that are not associated with latitude or body size, suggesting independence of some canal shape characteristics from body size and shape. The South Africans are distinctive with very narrow bodies and small pelvic inlets relative to an elongated lower canal in A-P and posterior lengths. Variation in pelvic canal geometry among populations is consistent with a high degree of evolvability in the human pelvis. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
Opportunities to assess morphological allometry in small-bodied human populations are rare. The f... more Opportunities to assess morphological allometry in small-bodied human populations are rare. The foragers of the Later Stone Age of the South African Cape are characteristically small-bodied. Previous studies have shown that during the period of ca. 3500 to 2000 years BP (uncalibrated 14C dates), the regional population shows transient reduced stature, body mass, and cranial size, a pattern that has been tentatively tied to demographic pressure on resources. This study examines the relationships among cranial size (centroid size) and body size (femoral length, femoral head diameter, and bi-iliac breadth) during the second half of the Holocene (N = 62). Reduced major axis regression indicates negative allometry of cranial centroid size with body size. Residuals (from ordinary least squares regression of cranial centroid size on body size) are regressed on radiocarbon date to examine temporal changes in the relationship between cranial and body size. Cranial and pelvic sizes are most conserved through time, while more ancient skeletons possess shorter femora and smaller femoral heads. The relationship between cranial centroid size and femoral length shows larger and more variable residuals at more recent dates, indicating a greater or more variable disassociation between cranial size and stature relative to more ancient skeletons. A similar, but nonsignificant relationship exists between cranial size and bi-iliac breadth. These results provide insights into the use of aspects of body size and proportionality in the assessment of health in past populations.
Many mammalian species display sexual dimorphism in the pelvis, where females possess larger dime... more Many mammalian species display sexual dimorphism in the pelvis, where females possess larger dimensions of the obstetric (pelvic) canal than males. This is contrary to the general pattern of body size dimorphism, where males are larger than females. Pelvic dimorphism is often attributed to selection relating to parturition, or as a developmental consequence of secondary sexual differentiation (different allometric growth trajectories of each sex). Among anthropoid primates, species with higher body size dimorphism have higher pelvic dimorphism (in converse directions), which is consistent with an explanation of differential growth trajectories for pelvic dimorphism. This study investigates whether the pattern holds intraspecifically in humans by asking: Do human populations with high body size dimorphism also display high pelvic dimorphism? Previous research demonstrated that in some small-bodied populations, relative pelvic canal size can be larger than in large-bodied populations, while others have suggested that larger-bodied human populations display greater body size dimorphism. Eleven human skeletal samples (total N: male = 229, female = 208) were utilized, representing a range of body sizes and geographical regions. Skeletal measurements of the pelvis and femur were collected and indices of sexual dimorphism for the pelvis and femur were calculated for each sample [ln(M/F)]. Linear regression was used to examine the relationships between indices of pelvic and femoral size dimorphism, and between pelvic dimorphism and female femoral size. Contrary to expectations, the results suggest that pelvic dimorphism in humans is generally not correlated with body size dimorphism or female body size. These results indicate that divergent patterns of dimorphism exist for the pelvis and body size in humans. Implications for the evaluation of the evolution of pelvic dimorphism and rotational childbirth in Homo are considered.
American journal of physical anthropology, Jan 1, 2007
UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collectio... more UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissertations and theses. Learn more... ProQuest, Adaptive allometric modeling of the pelvis in small-bodied Later Stone Age (Holocene) foragers from southern Africa. ...
Conference Presentations by Helen Kurki
STEPHANIE E. CALCE(1), HELEN K. KURKI(1), DARLENE WESTON(2), AND LISA GOULD(1)
(1)Department of ... more STEPHANIE E. CALCE(1), HELEN K. KURKI(1), DARLENE WESTON(2), AND LISA GOULD(1)
(1)Department of Anthropology, University of Victoria, British Columbia, Canada.
(2)Department of Anthropology, University of British Columbia, British Columbia, Canada.
ABSTRACT
Predictable age-progressive morphological arthritic traits have been used to derive several methods of estimating adult age at death in various skeletal joints. This study examined the degree of error in age at death estimates when osteoarthritis (OA) is present in age estimation methods based on three separate pelvic joint areas: 1) pubic symphysis, 2) auricular surface, and 3) acetabulum on a modern known-age European cemetery sample (N=252).
Age at death ranged from 17–99 years (x̄ =50.9 years). OA in the pelvic joints was evaluated using standard ranked categorical scoring. Composite OA scores were derived through principal component analysis. Blind age assessments and all analyses were performed separately by region. Error between adult age groups (young, middle, old) and between OA severity groups (low, middle, high) was evaluated using one-way ANOVAs with post-hoc testing, ordinary least squares regression, and transition analysis with a cumulative probit model. Ages-at-transition were compared with Nphases2.
Three significant results emerge. First, OA severity has an effect on the accuracy of age estimates from os coxa joints in this sample. Second, this influence is most significant for different age cohorts in each joint region, demonstrating that varied rates of arthritic trait progression occur between the auricular surface, pubic symphyses, and acetabulum. Third, those with OA appear to be aging faster, a consistent trend among the os coxa regions. These results have significant consequences for understanding the rate of bone remodeling in relation to disease, aging, and the evaluation of skeletal age indicators.
Uploads
Papers by Helen Kurki
developed. Three studies currently provide regression equations for estimating mass from cranial variables, but none of the equations has been tested on samples of known mass. Nor have the equations been compared to each other in terms of performance. Consequently, this study assessed the performance of existing cranial equations using computed tomography scans from a large, documented sample of modern humans of known body mass. Virtual models of the skull were reconstructed
and measured using computer software, and the resulting variables were entered into three sets of published regression equations. Estimated and known body masses were then compared. For most equations, prediction errors were high and few individuals were estimated within +/- 20% of their known mass. Only one equation satisfied the accuracy criteria. In addition, variables that had been previously argued to be good predictors of mass in hominins, including humans, did not estimate
mass reliably. These results have important implications for paleoanthropology. In particular, they emphasize the need to develop new equations for estimating fossil hominin body mass from cranial variables.
tested on an independent sample, also of known mass. The
results show that the newly derived equations estimate mass more accurately than existing equations for most variables. However, improvements were modest and accuracy rates remained relatively low. In addition, variables that had previously been argued to be ideal predictors were not the most accurate, and the current criteria used to assess equations did not ensure reliability. Overall, the results suggest that body mass estimates must be used cautiously and that further research is required.
mass with the postcranial equations that are currently available requires more caution than is usually exercised.
This study tests the hypothesis, a correlate of the obstetric dilemma, that skeletal variability in the human female pelvic canal is limited owing to the action of stabilizing selection. Levels of variation in three skeletal regions (pelvic canal, noncanal pelvis, and limbs) of females and males are compared to each other and between sexes.
Methods
Nine human skeletal samples (total female n = 101; male n = 117) representing diverse populations were included. Osteometric data were collected from the articulated pelvis, os coxa, sacrum, femur, tibia, humerus, radius, and clavicle. Coefficients of variation, adjusted for small sample size (V*), were calculated for variables in separate samples by sex, and mean V*s were taken for the skeletal regions. Size variances were measured as V* of the geometric mean (GM) of the skeletal region variables. Using nonparametric methods, coefficients were compared between sexes and skeletal regions and correlations among V*s were calculated.
Results
Females and males do not differ in levels of variation for any skeletal region. The pelvic canal is the most variable region in both sexes, while size variability (GM) is similar among the three skeletal regions. Across the samples, canal and noncanal pelvic regions share patterns of variability in females but not males, while variability of the limb skeleton is independent in both sexes.
Conclusions
The results suggest that stabilizing selection does not limit variability in the female pelvic canal. Biological plasticity may be greater in the canal than that in other skeletal regions. Am. J. Hum. Biol., 2013. © 2013 Wiley Periodicals, Inc.
Conference Presentations by Helen Kurki
(1)Department of Anthropology, University of Victoria, British Columbia, Canada.
(2)Department of Anthropology, University of British Columbia, British Columbia, Canada.
ABSTRACT
Predictable age-progressive morphological arthritic traits have been used to derive several methods of estimating adult age at death in various skeletal joints. This study examined the degree of error in age at death estimates when osteoarthritis (OA) is present in age estimation methods based on three separate pelvic joint areas: 1) pubic symphysis, 2) auricular surface, and 3) acetabulum on a modern known-age European cemetery sample (N=252).
Age at death ranged from 17–99 years (x̄ =50.9 years). OA in the pelvic joints was evaluated using standard ranked categorical scoring. Composite OA scores were derived through principal component analysis. Blind age assessments and all analyses were performed separately by region. Error between adult age groups (young, middle, old) and between OA severity groups (low, middle, high) was evaluated using one-way ANOVAs with post-hoc testing, ordinary least squares regression, and transition analysis with a cumulative probit model. Ages-at-transition were compared with Nphases2.
Three significant results emerge. First, OA severity has an effect on the accuracy of age estimates from os coxa joints in this sample. Second, this influence is most significant for different age cohorts in each joint region, demonstrating that varied rates of arthritic trait progression occur between the auricular surface, pubic symphyses, and acetabulum. Third, those with OA appear to be aging faster, a consistent trend among the os coxa regions. These results have significant consequences for understanding the rate of bone remodeling in relation to disease, aging, and the evaluation of skeletal age indicators.
developed. Three studies currently provide regression equations for estimating mass from cranial variables, but none of the equations has been tested on samples of known mass. Nor have the equations been compared to each other in terms of performance. Consequently, this study assessed the performance of existing cranial equations using computed tomography scans from a large, documented sample of modern humans of known body mass. Virtual models of the skull were reconstructed
and measured using computer software, and the resulting variables were entered into three sets of published regression equations. Estimated and known body masses were then compared. For most equations, prediction errors were high and few individuals were estimated within +/- 20% of their known mass. Only one equation satisfied the accuracy criteria. In addition, variables that had been previously argued to be good predictors of mass in hominins, including humans, did not estimate
mass reliably. These results have important implications for paleoanthropology. In particular, they emphasize the need to develop new equations for estimating fossil hominin body mass from cranial variables.
tested on an independent sample, also of known mass. The
results show that the newly derived equations estimate mass more accurately than existing equations for most variables. However, improvements were modest and accuracy rates remained relatively low. In addition, variables that had previously been argued to be ideal predictors were not the most accurate, and the current criteria used to assess equations did not ensure reliability. Overall, the results suggest that body mass estimates must be used cautiously and that further research is required.
mass with the postcranial equations that are currently available requires more caution than is usually exercised.
This study tests the hypothesis, a correlate of the obstetric dilemma, that skeletal variability in the human female pelvic canal is limited owing to the action of stabilizing selection. Levels of variation in three skeletal regions (pelvic canal, noncanal pelvis, and limbs) of females and males are compared to each other and between sexes.
Methods
Nine human skeletal samples (total female n = 101; male n = 117) representing diverse populations were included. Osteometric data were collected from the articulated pelvis, os coxa, sacrum, femur, tibia, humerus, radius, and clavicle. Coefficients of variation, adjusted for small sample size (V*), were calculated for variables in separate samples by sex, and mean V*s were taken for the skeletal regions. Size variances were measured as V* of the geometric mean (GM) of the skeletal region variables. Using nonparametric methods, coefficients were compared between sexes and skeletal regions and correlations among V*s were calculated.
Results
Females and males do not differ in levels of variation for any skeletal region. The pelvic canal is the most variable region in both sexes, while size variability (GM) is similar among the three skeletal regions. Across the samples, canal and noncanal pelvic regions share patterns of variability in females but not males, while variability of the limb skeleton is independent in both sexes.
Conclusions
The results suggest that stabilizing selection does not limit variability in the female pelvic canal. Biological plasticity may be greater in the canal than that in other skeletal regions. Am. J. Hum. Biol., 2013. © 2013 Wiley Periodicals, Inc.
(1)Department of Anthropology, University of Victoria, British Columbia, Canada.
(2)Department of Anthropology, University of British Columbia, British Columbia, Canada.
ABSTRACT
Predictable age-progressive morphological arthritic traits have been used to derive several methods of estimating adult age at death in various skeletal joints. This study examined the degree of error in age at death estimates when osteoarthritis (OA) is present in age estimation methods based on three separate pelvic joint areas: 1) pubic symphysis, 2) auricular surface, and 3) acetabulum on a modern known-age European cemetery sample (N=252).
Age at death ranged from 17–99 years (x̄ =50.9 years). OA in the pelvic joints was evaluated using standard ranked categorical scoring. Composite OA scores were derived through principal component analysis. Blind age assessments and all analyses were performed separately by region. Error between adult age groups (young, middle, old) and between OA severity groups (low, middle, high) was evaluated using one-way ANOVAs with post-hoc testing, ordinary least squares regression, and transition analysis with a cumulative probit model. Ages-at-transition were compared with Nphases2.
Three significant results emerge. First, OA severity has an effect on the accuracy of age estimates from os coxa joints in this sample. Second, this influence is most significant for different age cohorts in each joint region, demonstrating that varied rates of arthritic trait progression occur between the auricular surface, pubic symphyses, and acetabulum. Third, those with OA appear to be aging faster, a consistent trend among the os coxa regions. These results have significant consequences for understanding the rate of bone remodeling in relation to disease, aging, and the evaluation of skeletal age indicators.