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Morphological and molecular approaches to characterise modifications relating to mammalian hairs in archaeological, paleontological and forensic contexts

Tridico, Silvana (2015) Morphological and molecular approaches to characterise modifications relating to mammalian hairs in archaeological, paleontological and forensic contexts. PhD thesis, Murdoch University.

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Mammalian hair is readily shed and transferred to persons or objects during contact; this property renders hair as one of the most ubiquitous and prevalent evidence type encountered in forensic investigations and at ancient burial sites. The durability and stability of hair ensures their survival for millennia; their status as a privileged repository of viable genetic material consolidates their value as a biological substrate. The aims of this thesis are to showcase the wealth, and breadth, of information that may be gleaned from these unique structures and address the current problem regarding the mis-identification of animal hairs.

Despite the similar appearance of human and animal hairs, the expertise required to accurately interpret their respective structures requires significantly different skill sets. Chapter Two in this thesis discusses the consequences of mis-identification of hair structures due to lack of competency or adequate training in regards to hair examiners and discusses some of the myths and misconceptions associated with microscopy of hairs.

Hairs are resilient structures capable of surviving for millennia as exemplified by extinct megafauna hairs; however, they are not totally immune to deleterious effects of environmental insults or biodegradation. There is a paucity of morphological data available illustrating the deleterious effects of biological agents on hairs. This void is filled through the comprehensive review of biodegradation of hair in Chapter 3 which showcases, for the first time, a collective visual catalogue of the destructive effects caused by an elite group of biological agents. These effects were evident in hairs from prehistoric, ancient and modern human and animal hairs.

During the course of this study hair morphologies were observed which challenged current paradigms in relation to their genesis. The results of the present study unequivocally demonstrate that hair structures, previously characterised as genetic in nature, are due to the effects of biodegradation. Furthermore, this body of work is the first to record that morphological characteristics previously ascribed to taphonomy (post-mortem insults), also occur in hairs from the living. The implications of the interpretation of hair structures in forensic investigations are discussed in greater detail in Chapter 3.

Chapter four represents the first demonstration of the advantages of adopting a multidisciplinary approach to hair examination. This chapter presents a detailed microscopical audit of extinct megafauna hair that was the remains of a larger hair sample previously consumed in more destructive analyses (molecular analyses and radio carbon dating). One of the most significant morphological finds of this work was the presence of unusual structural features, not previously recorded, that may have been central to the survival of extinct megafauna.

Lastly, Chapter Five introduces the concept of Next Generation Sequencing (NGS also referred to as massive parallel sequencing) to investigate the forensic potential of human hairs on the basis of transfer of their respective bacterial ‘profiles or signatures’.

Taken together, this body of work presents fresh approaches to the manner in which mammalian hairs could be processed in the future and demonstrates the benefits of multi-disciplinary approaches to their examination. Bacterial DNA profiles, derived from human hair using NGS technologies, may prove to be a valuable future addition to the forensic molecular toolkit. Furthermore, this present study challenges current paradigms regarding the interpretation of microscopic post-mortem artifacts that occur on ancient and modern mammalian hairs.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary and Life Sciences
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