Dr. Helen Kurki

Evolutionary models for skeletal morphology often apply “form follows function” explanations, focusing on the selective context of adult morphology. But, adult skeletal form is the product of the processes of growth and development, which are themselves subject to selection, and to environmental influences. Due to biological plasticity, human skeletal variation reflects, in part, differences in environmental (climate, terrain), ecological (resource availability, disease load), and lifestyle (diet, activity, technology) contexts. Challenging environments, with nutritional or dietary limitation, high activity budgets, or high parasitic or infectious disease loads lead to restricted skeletal growth, often leaving signatures in bone and dental tissues preserving evidence of these developmental stressors. Habitual activities load bones through body weight and muscle action and alter bone tissue distribution in the shafts of limb bones. As such, skeletal morphology can offer insights on evolutionary processes shaping our species, and factors affecting populations and individuals. But given the plasticity of skeletal tissue, these may not be the only ways in which these processes influence skeletal morphology during development. Joint regions of bones are thought to be tightly controlled during development by genetic factors and less responsive to the environment, suggesting their form should be more stable. Yet, ankle orientation varies in relation to substrate use, and the vertebral canal varies with stress. Plasticity exists in these regions. This research uses 3D geometric morphometric approaches to examine the size and shape characteristics of bones of the limbs and vertebrae in archaeologically derived human skeletal samples in relation to traditional skeletal indicators of developmental stress and habitual activity, to elucidate whether and how stress and activity during ontogeny can influence morphology. Anthropologists assume the morphology of extinct hominins largely reflects their evolutionary history as a product of normal growth, rather than plastic responses to environmental stressors. But in order to decipher the meaning of morphological variation in the fossil record we must understanding how plastic adaptive responses generate skeletal morphology. This is also important for bioarchaeologists, who employ outcomes of growth processes as indicators of population health through time in response to demographic and ecological changes. This research represents a novel approach to examining the influence of environment and activity in producing skeletal variation in humans. Understanding the interplay between plasticity and constraint (evolutionary, functional, developmental) in the generation of morphological variation in a species aids in identifying factors (environmental, ecological, lifestyle) that influence adaptation, which are of particular importance to evolutionary anthropologists, paleoanthropologists, and evolutionary anatomists.

This NSERC-funded project continues my collaboration with Dr. Lesley Harrington (University of Alberta).

Evolutionary explanations of the difficulty and risk to the mother and newborn associated with human childbirth have focused on the close fit between the size of the maternal pelvis and the size of the newborn as resulting from our distinctive method of walking on two legs and our large brains. This “obstetric dilemma” views female pelvic form as a compromise between the mechanical requirements of bipedalism for a narrow pelvis and the obstetric requirements for a roomy pelvic canal for our large-brained babies, resulting in strong selective pressures acting on the female pelvis among humans and over our evolutionary history. Physical variation within a population or species can be limited by such competing selective processes (as predicted by the obstetric dilemma hypothesis), yet morphology is also influenced by environmental stimuli acting during growth and development, through biological plasticity. For the pelvis these stimuli may include gait, activity levels and technological means of mitigating activity, diet, and health. Plastic responses generate variation among individuals and populations in anatomy and physiology. Hence, the cultural production of the human skeleton provides bioarchaeologists a window on the activities and adaptations of past populations. However, my research on adult skeletons has shown significant variation among and within human populations in pelvic canal shape and capacity. Further, historical preconceptions of an “obstetric dilemma” may actually be the result of differential plasticity between the maternal pelvis and newborn size in changing cultural environments. Under this model, human ecological and cultural changes may play a particular role in determining pelvic form.

I am collaborating on this NSERC-funded research project with Dr. Lesley Harrington (University of Alberta) examining the potential role of biological plasticity in shaping the bones of the human pelvis during growth. Human skeletal remains of juveniles from varied and well-documented archaeological contexts provide an opportunity to study factors influencing growth and development in specific ecological (e.g., subsistence, technologies, and geographical location) contexts. In order to understand the potential role of biological plasticity in shaping the maternal pelvis, we ask: when and why does variation in pelvic forms arise, and what role does biological plasticity play in generating variation in relation to environmental stimuli? This study utilizes three-dimensional (3D) approaches to studying the form of juvenile and adult human pelvic bones from diverse skeletal samples to investigate the relationships among ecological and cultural attributes of populations and pelvic growth and development.

• 2020 – C. Wall-Scheffler, H. Kurki & B. Auerbach. The Evolutionary Biology of the Human Pelvis: An Integrative Approach. Cambridge Studies in Biological and Evolutionary Biology. Cambridge University Press. Link

• 2022 - Young, M., Richard, D., Grabowski, M., Auerbach, B.M., de Bakker, B.S., Hagoort, J., Muthuirulan, P., Kharkar, V., Kurki, H.K., Betti, L., Birkenstock, L., Lewton, K., Capellini, T.D. The developmental impacts of natural selection on human pelvic morphology. Science Advances, 8(33), eabq4884. https://doi.org/10.1126/sciadv.abq4884
• 2022 - Kurki, H.K., Holland, S., MacKinnon, M., Cowgill, L., Osipov, B., Harrington, L. Appositional long bone growth: Implications for measuring cross‐sectional geometry.American Journal of Biological Anthropology. https://doi.org/10.1002/ajpa.24602 
• 2021 - Nowell, A., Mitchell, L.M., Kurki, H. Conceiving of reproduction in archaeology. In The Routledge Handbook of Anthropology and Reproduction (pp. 68–84). London: Routledge. https://doi.org/10.4324/9781003216452-6
• 2020 - Nowell, A.,  Kurki, H. . Moving Beyond the Obstetrical Dilemma Hypothesis: Birth, Weaning an Infant Care in the Plio-Pleistocene. In, R. Gowland & S. Halcrow (editors): The Mother-Infant Nexus in Anthropology: Small Beginnings, Significant Outcomes. Springer. Link
• 2018 - Calce, S.E., Kurki, H., Weston, D.A., Gould, L. The relationship of age, activity, and body size on osteoarthritis in weight-bearing skeletal regions. International Journal of Paleopathology. 22: 45-53. DOI: 10.1016/j.ijpp.2018.04.001 
• 2018 - Calce, S.E., Kurki, H., Weston, D.A., Gould, L. Effects of osteoarthritis on age-at-death estimates from the human pelvis. American Journal of Physical Anthropology. 167: 3-19. DOI: 10.1002/ajpa.23595
• 2017 - Kurki, H. Bilateral asymmetry in the human pelvis. Anatomical Record. 300:653-665. DOI 10.1002/ar.23546. https://doi.org/10.1002/ar.23546  
• 2016 - Calce, S.E., Kurki, H. Weston, D.A., Gould, L. 2016. Principal component analysis in the evaluation of osteoarthritis. American Journal of Physical Anthropology. 162:476-490 DOI 10.1002/ajpa.23130. https://doi.org/10.1002/ajpa.23130 
• 2016 - Tobolsky, V.A., Kurki, H., Stock, J.T. Patterns of directional asymmetry in the pelvis and pelvic canal. American Journal of Human Biology. 28:804-810. https://doi.org/10.1002/ajhb.22870 
• 2016 - Kurki, H., Decrausaz. S-L. Pelvic shape variation: What does it tell us about obstetric adaptation? American Journal of Physical Anthropology. 159:630-638. https://doi.org/10.1002/ajpa.22922 
• 2016 - Elliott, M., Kurki, H., Weston, D., Collard, M. Estimating body mass from post-cranial variables: an evaluation of current methods using three-dimensional computed tomography. Archaeological and Anthropological Sciences. 8:689-704.  https://link.springer.com/article/10.1007/s12520-015-0251-6 
• 2016 - Elliott, M., Kurki, H., Weston, D., Collard, M. Estimating body mass from skeletal material: New predictive equations and methodological insights from a known-mass sample of humans. Archaeological and Anthropological Sciences. 8:731-750. DOI 10.1007/s12520-015-0252-5 
• 2014 - Pfeiffer, S., Doyle, L.E., Kurki, H., Harrington, L., Ginter, J.K., Merritt, C.E. Discernment of mortality risk associated with childbirth in archaeologically derived forager skeletons. International Journal of Paleopathology 7:15-24. doi: 10.1016/j.ijpp.2014.05.005 
• 2014 - Elliott, M., Kurki, H., Weston, D., Collard, M. Estimating hominin body mass from cranial variables: An evaluation of current methods using three-dimensional computed tomography. American Journal of Physical Anthropology 154:201-214. doi: 10.1002/ajpa.22493.  
• 2013 - Kurki, H. Skeletal variability in the pelvis and limb skeleton of humans: Does stabilizing selection limit female pelvic variation? American Journal of Human Biology 25:795-802. doi:10.1002/ajhb.22455 
• 2013 - Kurki, H. Bony pelvic canal size and shape in relation to body proportionality in humans. American Journal of Physical Anthropology 151:88-101. doi:10.1002/ajpa.22243 
• 2012 - Kurki, H., Pfeiffer, S., Stynder, D. Allometry of head and body size in Holocene foragers of the South African Cape.  American Journal of Physical Anthropology 147:462-471. doi:10.1002/ajpa22024. 
• 2011 - Kurki, H. Pelvic dimorphism in relation to body size and body size dimorphism in humans.  Journal of Human Evolution 61:631-643. doi:10.1016/j.jhevol.2011.07.006 
• 2011 - Kurki, H. Compromised skeletal growth? Small body size and clinical contraction thresholds for the female pelvic canal. International Journal of Paleopathology 1:138-149. doi:10.1016/j.ijpp.2011.10.004. 
• 2010 - Kurki, H., Ginter, J., Stock, J., Pfeiffer, S. Body size reconstruction in a small-bodied sample: Applicability of current models.  American Journal of Physical Anthropology 141:169-180. doi:10.1002/ajpa.21127.           
• 2008 - Kurki, H., Ginter, J., Stock, J., Pfeiffer, S. Adult proportionality in small-bodied foragers: A test of ecogeographic expectations.  American Journal of Physical Anthropology136:28-38. doi:10.1002/ajpa.20774. 
• 2007 - Kurki, H.  Protection of obstetric dimensions in a small-bodied human sample.  American Journal of Physical Anthropology. 133:1152-1165. doi:10.1002/ajpa.20636.
• 2005 - Kurki, H. Use of the first rib for adult age estimation: A test of one method.  International Journal of Osteoarchaeology 15:342-350. doi:10.1002/oa.788.