Libby W. Cowgill

Associate Professor of Anthropology

Projects


Human Ecogeographic Variation

Biological anthropologists have long been interested in documenting ecogeographic variation in human body form, both in living and deceased people.  Specifically, individuals living in arctic climates have relatively higher body masses, wider trunks, and shorter limbs, while people in equatorial environments display relatively lighter body masses, narrower trunks, and longer limbs.  These patterns are predicated on both minimizing and maximizing the amount of surface area relative to volume so that body heat has relatively more or less area to escape through.  While ecogeographic variation has been well documented in adults, some of my past research as focused on evaluating variation in human body form in immature individuals (Temple et al., 2011; Cowgill et al. 2012; Child and Cowgill, 2017).

My recent work with Scott Maddux, Cara Ocobock, and Elizabeth Cho has focused on evaluating exactly how these documented patterns of variation in body form influence the thermoregulatory physiology of living humans.  The few attempts to experimentally verify the supposed functional advantages of surface area to volume ratios in response to climatic pressures have frequently produced inconclusive or contradictory results.  Consequently, we have almost no information about how specific morphological variables such as limb length or torso width influence measurable thermoregulatory outcomes such as water loss or core body temperature.  This has led to human climatic adaptation being referred to as an “unfinished agenda” and a call for renewed experimental testing of the fundamental assumptions of human climatic adaptation in biological anthropology (Steegmann, 2007).

Our research team is using state-of-the-art technologies to quantify the physiological responses of morphologically diverse living participants exposed to experimentally controlled environmental conditions in a climate chamber with simulates three global climate extremes: tropical rainforest (hot-humid), subtropical desert (hot-dry), and circumpolar tundra (cold-dry).  Specifically, to gain control over both soft and hard tissue anatomical variables in a way that was previously unattainable for many early studies of human thermoregulation and morphology, full-body computed tomography (CT) scans of 126 male and female participants will be obtained after quantifying their physiological responses to climatic conditions in a temperature and humidity-controlled chamber.  In sum, this study will explicitly link physiological outcomes (e.g. core body temperature, skin temperature, water loss, etc.) in three controlled environmental conditions to full-body hard and soft tissue morphology, establishing an association between anatomy and thermoregulatory function that will permit more confident assessment of climatic adaptation in both modern populations and the fossil record.

Bone Functional Adaptation in Living Human Populations

Human bone adapts to physical stresses by altering its quantity, quality, and shape, thus providing a partial record of a lifetime's habitual activities. Over the past fifty years, biological anthropology has significantly advanced our understanding of past human behaviors. While these insights have illuminated aspects of past subsistence and mobility patterns, skeletal data, when considered in isolation from soft tissue or documented activity patterns, offers an incomplete view. Critical questions arise: What types of activities stimulate bone growth in living humans? What level of activity is necessary for this growth? How are muscular strength and skeletal robustness interconnected? Furthermore, how does bone mineral density—a metric difficult to assess in skeletonized remains—integrate with other bone strength indicators, such as quantity and distribution? These questions underscore the necessity for a wide range of data from living humans to address issues that are completely inaccessible using undocumented skeletal collections. My recent work incorporates information from CT scans of living groups to better understand the factors that encourage bone growth, aiming to apply these insights to broader anthropological questions concerning behavior in the past.
In pursuit of these objectives, I have recently been awarded a National Science Foundation Mid-Career Advancement grant. This grant supports the development of my skills in using Avizo software for CT scan analysis and programming for statistical analysis, under the mentorship of Dr. Adam Sylvester, who has extensive experience with CT scans in anthropological research. My work from this grant is an integrative effort combining analyses of both hard and soft tissues, and incorporates data from accelerometers, activity pattern surveys, DEXA scans, and grip strength measurements. This comprehensive approach promotes a better understanding of the loading regimes that encourage bone deposition, enhancing our knowledge of human physiology in a way that directly applies to salient anthropological questions about physical activity in deceased human groups.

Functional Approaches to Human Growth and Development

Previous research on the link between function and form in the human skeleton has frequently dichotomized influences on the immature and the adult skeleton.  Studies of skeletal growth are often primarily concerned with the effect of nutrition or genetics; research on adult morphology is more likely to discuss the impact of activity patterns or repetitive behaviors on shaping the mature skeleton.  My research bridges this gap by positing that there is no developmental rubicon under which mechanical forces are not influential in shaping skeletal morphology, and that the activity patterns adopted in childhood are likely essential in the production of adult skeletal shape and strength.  By applying the techniques traditionally reserved for functional analyses of adults to juveniles, new insights can be gained into specific behaviors and activities that shape the immature form. 

Two examples of the utility of this combination of approaches is my continued research on both humeral asymmetry and the onset of walking (Cowgill, 2008; Cowgill et al., 2010; Cowgill & Johnson, 2018).  However, the specific perspective of combining development and functional morphology can be used to understand childhood and behavior in almost any past population, and I have successfully explored these issues in a wide variety of groups ranging from Upper Paleolithic early modern humans to the Jomon to Alaskan arctic foragers (Cowgill, 2007, 2010; Cowgill et al., 2007, 2011, 2012, 2016).  

Late Pleistocene Human Evolution

While my research spans multiple different time periods and geographic locations, much of it has focused on Late Pleistocene human evolution, specifically Neandertals and early modern humans.  My interests here are primarily functional anatomy and what we can reconstruct about lifestyles in the past from basic principles of bone functional adaptation.  I've had the opportunity of work with large samples of immature Late Pleistocene fossils (Cowgill, 2010; Cowgill and Johnston, 2018) and occasionally work with and describe original fossil specimens (Cowgill et al., 2008).  I am currently trying to finish up an edited volume titled Neandertal Functional Anatomy for Cambridge Press with Scott Maddux.

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