While the above case studies incorporate an anthropological perspective within a
This raises the question: If a biomechanical study can be done without an ontogenetic perspective, why consider ontogeny at all? In response to this, an ontogenetic perspective has much to contribute to studies of human biomechanics, as will be seen in this section.
During growth and development, bone stability is constantly being compromised with sudden increases in bone length, body mass and muscle growth (Cowgill, 2008). This means that the growth period is a crucial time for remodeling; bone must
continuously acclimate to these changes in growth in order to preserve structural integrity and avoid breakage. Therefore, in addition to activity level, the process of growth and development (i.e. ontogeny) contributes greatly to the biomechanical processes that take place in human bone. To ignore the ontogenetic pattern of biomechanical adaptations in humans would result in an incomplete understanding of said adaptations.
An analysis of biomechanical adaptive responses in bone during growth is also important because bone is most susceptible to mechanical loading forces during growth (Bertram and Swartz, 1991; Turner et al., 1995; Lieberman et al., 2004; Pearson and Lieberman, 2004). The adult form of bone is usually a reflection of the biomechanical adaptations that occurred during childhood as bone minimally responds to mechanical loading after maturity (Kriska et al., 1986; Karlsson et al., 1995, 2000; Teegarden et al., 1996; Bass et al., 1998; Khan et al., 1998; Micklesfield et el., 2003). Therefore, it
becomes necessary to understand the process by which that “final” adult form is reached and this can be done with the inclusion of an ontogenetic perspective. As an example, a study on the humeri of professional tennis players compared the cross-sectional
properties of individuals who began playing tennis before maturity to those who had only started playing after maturity (Jones, 1977). The result was that adults who had begun to play tennis prior to skeletal maturity had significantly more robust humeri than adults who took up tennis after maturity (Jones, 1977). This example shows the particular significance of the growth period to biomechanical adaptations in humans.
With an understanding that growth and development is useful when studying human biomechanics, this thesis will turn to the question: How do we interpret the biomechanical adaptations that occur during growth and development? This is
particularly important to consider because the timing of biomechanical adaptations is highly influenced by environmental context, which includes not only the physical environment but also the social environment. Factors that influence biomechanical outcomes pre-maturation usually can be connected to the process of enculturation experienced by an individual (Cowgill, 2008). Enculturation is a term for the process by which a child learns the norms and values of the society they were born into. Therefore, enculturation will vary depending on the society; as a reminder to the reader, populations from different climatic locations were chosen for comparison because it is assumed that cultural adaptations will differ based on the environmental context. This means that bone structure is influenced by the combined effect of the physical environment and the social environment in which an individual lives.
In order to fully understand the different biomechanical adaptations that occur in each sample population, knowledge of the process of enculturation within each group is necessary. However, such information is not always available due to the limited amount of literature concerning the activities of children. It can be assumed that the activity patterns of the adults provide a reflection of the activity patterns of the children since these are the behaviours that are likely to be taught during enculturation. In fact, some practices are quite common to the enculturation process in a variety of different cultures. A few examples are: sitting up without assistance, walking, gathering food, hunting small animals, carrying items, and travelling long distances (Cowgill, 2008). Depending on the societal norms, the extent to which these tasks are carried out will vary. Whether children are assisted in the learning process or expected to adopt the behaviour independently will also depend on cultural beliefs. This is why ethnographic data are useful for
biomechanical studies: not only does the environment shape the activity patterns of people but parental techniques also have a hand in the timing and magnitude of biomechanical adaptations in young children (Cowgill, 2008).
It should also be noted that some difficulties can arise when interpreting growth data from a biomechanical perspective. In this thesis, three diaphyseal points were used to calculate cross-sectional properties. These diaphyseal locations of interest were found using overall diaphyseal length. In adults, these locations can be compared because they
represent roughly the same location. However, in the humerus the proximal epiphysis contributes 80% of longitudinal growth which would cause the diaphyseal locations (i.e. mid-shaft, proximal third, distal third) measured on a juvenile humerus to be in slightly different locations than those measured on an adult humerus. This is a factor than cannot be controlled for in this thesis but may have some relevance to future studies.
To conclude, an ontogenetic perspective is important for the following reasons: Human bones are most susceptible to mechanical loading during the growth period. An analysis of the structural changes that take place during growth will result in a better understanding of the adult form of bone and also the process by which the adult form arises. Finally, a study of the bone structures of children, both within and between populations, can reveal a different aspect of societal life compared to an analysis of adult bone alone. The structure of bone during childhood can lend an understanding to the process of enculturation practiced within a given society.
Chapter 3
3
Materials
This chapter is an overview of each sample population studied. The environmental context of each population will be described as well as any archaeological or osteological evidence that may provide some information regarding the activity patterns of each group. Where possible, studies on the growth and development patterns of probable living descendants will be briefly outlined in the hopes that such information can shed light on the growth patterns of the groups studied.