Biology Reference
In-Depth Information
Diagenesis
Diagenesis refers to physical and chemical degradation of organic materials, thus fitting
under the auspices of taphonomy (see Marden et al., [Chapter 9], this volume). This can occur
in bone and these taphonomic processes can be visible histologically. Histotaphonomy exam-
ines diagenesis at the microstructural scale (
Bell, 2012; Crowder and Stout, 2012
). Such
changes can give indications about post-depositional environments. For example, tapho-
nomic changes to human remains that have decomposed in marine environments (
Bell
et al., 1996
, 2008) will differ in timing and manifestation than those found in a burial or
arid setting. The time frame of different types of postmortem change to bone microstructure
is not only useful to the forensic anthropologist but also of interest to the paleoanthropologist,
skeletal biologist, and bioarchaeologist.
One of the earliest types of taphonomic change to affect bone microstructure is microbial,
or bacterial, attack (
Jans et al., 2004
). For example, Bell and colleagues (1996) looked at how
bones were taphonomically altered in terrestrial, intertidal, and lacustrine contexts. They
found evidence of microbial attack in bone as soon as 3 months postmortem and as late as
83 years postmortem. The bone with a postmortem interval of 83 years was interred in
a dry coffin and exhibited no macroscopic or histological evidence of alteration while the
tibial fragment recovered after 3 months postmortem from carnivore scat in a wet environ-
ment had evidence of focal destruction (
Bell et al., 1996
). They also found microscopic
destruction in a rib found 15 months postmortem on the surface of a waterlogged musket
bog. Bell and colleagues demonstrated the vital importance of postmortem environment as
it relates to destruction of bone.
Hackett (1981)
has classified and described four categories of postmortem microstructural
focal destructive changes that can be observed histologically. These are called Wedl, linear
longitudinal, budded, and lamellate (
Hackett, 1981; Bell, 2012
). Wedl microbial attack causes
tunneling while the additional three categories are assumed to be bacterial in nature and
can be distinguished by size and shape histologically (
Wedl, 1864; Hackett, 1981; Jans
et al., 2004
).
BASIC CONCEPTS IN DENTAL HISTOLOGY
Due to their unique physiology and anatomy, teeth bear the special distinction of being
both the most durable part of the hard tissues and the only part directly exposed to the envi-
ronment during the life of the individual. These two facts make dentition a gold mine for
anthropologists to collect information regarding the biology, phylogeny, and health of human
populations
d
both past and present (
Scott and Turner, 1988
). Teeth also have the unique
distinction in the human body of recording their own growth during their creation. They
provide tiny snapshots into the life and health of an individual during the period that the
teeth were being formed.
In the field of human evolution and paleoanthropology, there are numerous areas of
research analyzing dentition from both a morphological and a histological perspective
(for complete reviews see
Dean, 2006
). Dental histology also contributes heavily to the field
of forensic anthropology. Numerous studies have been conducted looking at a variety of
