Prehistoric Hunter-Gatherers of the Baikal Region, Siberia: Bioarchaeological Studies of Past Life Ways

9. Skeletal Morphology, Climatic Adaptation, and Habitual Behavior among Mid-Holocene Cis-Baikal Populations

Skeletal Morphology, Climatic Adaptation, and Habitual Behavior among Mid-Holocene Cis-Baikal Populations Jay T. Stock, Vladimir I. Bazaliiskii, Olga I. Goriunova, Nikolai A. Savel’ev, and Andrzej W. Weber The well-preserved and numerous Middle Holocene human remains from Cis-Baikal provide a rare opportunity to investigate patterns of human adaptation and skeletal mechanics in hunting and gathering populations across a period of significant cultural change. Many of the best-preserved human remains are derived from the earliest cemeteries that date to the Early Neolithic (Kitoi Culture) at the sites of Lokomotiv and Shamanka II. Interments in Kitoi cemeteries date to between 8,000–7,000 yrs BP,1 after which there was a hiatus in the use of formal cemeteries during the Middle Neolithic, followed by the Isakovo/Serovo and Glazkovo cultures, associated with the Late Neolithic and Bronze Age, respectively. Weber et al. (Chapter 2 this volume) provide more information on the relevant culture history of the region while White and Bush (Chapter 1 this volume) supply comprehensive environmental context for this study. Human Skeletal Morphology and Adaptation The anatomy of the human skeleton can inform us about long-term patterns of adaptation to environmental variation, body size, energetics and life history, and habitual behavior. We have come a long way toward understanding variation in the human postcranial skeleton based on a growing body of broadly based comparative research (Ruff et al. 1993; Ruff 1994, 1995; Ruff, Larsen, and Hayes 1997; Ruff 2002; Churchill 1994, 1996, 1998; Churchill, Weaver, and Niewoehner 1996; Holliday 1997, 1999, 2002; Trinkaus 1997; ‹ 9 › 194 J.T. Stock, V.I. Bazaliiskii, O.I. Goriunova, N.A. Savel’ev, and A.W. Weber Pearson 2000a; Stock 2002, 2006; Holt 2003). One of the most significant factors influencing patterns of human skeletal morphology is climate (Trinkaus 1981; Ruff 1994; Holliday and Falsetti 1995; Holliday 1999; Holliday and Ruff 2001), primarily due to thermoregulatory advantages associated with different physical characteristics. Clinal variation within broadly distributed mammalian species demonstrate that individuals in cold climates tend to have higher body mass and shorter limbs than populations in hot climates (Bergmann 1847; Allen 1877), a relationship which is also found in our species (Roberts 1978). Clinal variation in body size and limb proportions relates to thermoregulation through the relationship between body volume (mass) and surface area, where heat transfer with the environment occurs. Basal metabolism and heat production are proportionate to body mass. If body mass is distributed across a tall, thin physique, the ratio of surface area to volume of the body is maximized, allowing for more effective heat loss. As body breadth increases, surface area relative to body mass decreases, maximizing heat retention. These thermoregulatory factors appear to have been a fundamental selective force influencing hominin physique. Human populations from cold climates tend to have greater body mass and body breadth as reflected by bi-iliac breadths (Ruff 1994) and lower brachial and crural indices, representing the relationship between lengths of the forelimb segments (radius and tibia) relative to upper limb segment lengths (humerus and femur) (Trinkaus 1981). Body size is one of the most important biological characteristics of both species and populations, for reasons that extend beyond thermoregulation. Body size is an important correlate of many physiological characteristics (Schmidt-Nielsen 1984), development (Gillooly et al. 2002), patterns of mortality, and demographic parameters (Charnov 2002). It is most commonly expressed in terms of either stature or mass, both of which may be estimated from the skeleton. The most obvious method of size estimation is based upon the correlation between long bone lengths and stature (Trotter 1970; Feldesman, Kleckner, and Lundy 1990). Body mass may be estimated in a number of ways using either morphometric or mechanical methods, by estimating mass relative to overall body dimensions or mechanical loading of the lower limb (Auerbach and Ruff 2004). The most useful morphometric method involves combining an estimate of stature (using long bone length) and an estimate of body breadth (bi-iliac breadth) (Ruff 1994). This method of estimation is often difficult to achieve due to the requirement of a complete pelvis and Skeletal Morphology, Climatic Adaptation, and Habitual Behavior 195 an adequate comparative sample for stature estimation. A related mechanical approach using femoral head diameter to estimate body mass (Ruff, Larsen, and Hayes 1997) has been found to closely approximate estimates based on the morphometric approach (Auerbach and Ruff 2004). Many characteristics of skeletal morphology are...