Chemistry Reference
In-Depth Information
mountains of northern Argentina and Chile and southern Peru (Reinhard
1996), the Ice Maiden from the Altai mountains in Siberia (Polosmak 1994),
and the Iceman found in the Tyrolean Alps, at the border between Italy and
Austria (Kutschera and Rom 2000; Barfield 1994).
The chemical reactivity of most biological matter is also greatly dimin-
ished in the absence of water. Under temperate environmental conditions,
therefore, an important factor for the preservation of biological matter and
hence, for the mummification of dead animals or plants, is the absence of
water from their dead remains. The hot and dry conditions prevalent in
desert regions, such as the Egyptian sands, for example, provide a suitable
environment for the desiccation of corpses that became mummified soon
after burial. Thus were mummified the bodies of dead Egyptians since the
fourth millennium B.C.E., wrapped just in clothing or matting; their dehy-
drated muscles and other soft tissues of the body shrank almost to nothing,
encased within the tightly stretched dry skin (Fleming 1980).
Anaerobic
conditions (that include little or no oxygen) as exist, for
example, in
bogs
, provide an environment appropriate for the preservation
of biological matter.
Bogs
are spongy wetlands in which the soil consists
mostly of
peat
(a dark, fibrous accumulation of partly decomposed vegetable
matter with little associated mineral sediment), and in the stagnant water
humic acid and tannins derived from the dead vegetable matter are dis-
solved (see Textbox 62). The scarcity or total absence of oxygen in bogs
inhibits the decay and disintegration of animal remains; the tannins in the
acid water tan the skin and other animal tissues, converting the skin into
leather, and the acid water dissolves most of the inorganic components of
the bones, which become spongy and soft. Corpses buried in bog environ-
ments are generally naturally preserved. Since the bones are partly dissolved
away, the corpse is usually flaccid; its skin, however, is generally well
preserved, as is also the hair and the contents of the digestive system
(Brothwell 1987).
Not all corpses recovered from bogs are naturally preserved in exactly
the same way. In some cases, all muscle and skin have decayed, leaving only
the skeleton. Sometimes the opposite occurs, and all the bones in a bog's
corpse are dissolved away, leaving only soft tissue and tanned skin. Some of
these discrepancies are difficult to explain. Peat bog conditions seem to be
detrimental to the preservation of DNA. Still, several thousands of more or
less well preserved bog corpses, dating from about 100 B.C.E. to 500 C.E., have
been found during the last two centuries in northern Europe, mainly in
Scandinavia. Some, such as the Tollund and Grabaulle men from Denmark
and the Lindow man from England, have been thoroughly studied and
described (Glob 1972; Turner and Scaife 1995).
