Chemistry Reference
In-Depth Information
have therefore used their own feces and those of domesticated animals as
manure
, or
fertilizers
, to improve the quality of agricultural soils and the pro-
ductivity of cultivated plants (see Chapter 6). Furthermore, much of the
organic matter in feces is combustible, and in many parts of the world dry
feces - such as those of cows in India and of camels in many desert regions
- have been burned as fuel in fires used for domestic, crafts, and manufac-
turing purposes.
Coprolites
The feces of domesticated animals are often used as fertilizers and fuel, but
the bulk of feces are recycled soon after excretion (Putnam 1983). Under
adventitious environmental conditions, however, feces may endure natural
recycling processes, be preserved, and become what is known as
coprolites
,
hard, brittle concretions often found in archaeological excavations, particu-
larly in desert climate areas or in caves. Their name, coprolites, means “dung
stone” (
kopros
is dung and
lithikos
is stone in Greek); they are dry feces whose
original composition has often been preserved practically unaltered, having
undergone only slight changes (Bryant and Williams-Dean 1975). The preser-
vation of feces and their eventual conversion to coprolites is related to the
nature of the organic matter they originally contained: the higher the rela-
tive amount of organic matter they incorporate, the faster they decay. But
their water content and particularly the environmental conditions at the site
where the feces were excreted and became preserved are the main deter-
mining factors for their preservation. The coprolites of carnivorous animals,
for example, are more likely to be preserved than are those of herbivores,
since carnivores derive a relatively high amount of minerals from the bone
of the prey they consume as food. When these minerals are excreted they
provide better initial preservation conditions for the feces. Appropriate envi-
ronments for the preservation of coprolites exist in sites where dehydration
(loss of water) is rapid and anaerobic (lacking in oxygen) conditions prevail.
Dehydration is rapid in desert areas, dry caves, and floodplains associated
with rivers (in the latter, feces deposited on dry parts of a plain are some-
what dehydrated before being rapidly buried by river floods). Anaerobic
conditions prevail at the bottom of some ponds and swamps, particularly in
bogs.
The study of coprolites, particularly of their composition, throws light
on the
paleodiets
(the feeding behavior) of ancient animals as well as humans
and on the diseases that affected them. Coprolites composed only of plant
material, for example, are indicative of a herbivorous diet; bone remains in
the feces denote carnivorous behavior, while remains of both plant and
