PAST CRIMESAfter a few more days, a new fly emerges, leaving the empty pupa case
behind. Each stage takes a known amount of time, which varies according to
the species, weather and so on and this enables experts to estimate the period
in which the first flies laid their eggs, which will be close to the actual time of
death. The speed of their development gives clues about whether the body was
deposited at night or in the daytime, and whether the weather was warm or
cold. Marks from scavenging animals such as rats or foxes can also provide
further types of information.
Even in ancient burials, traces of pupa cases or the remains of beetles may
survive. It is important to record where each fragment is found. Flies will
normally lay their eggs in damp places such as the eyes or mouth, so
concentrations of remains on other parts of the body may indicate that there
was an open wound at that location.
As with all forms of forensic evidence, there are problems. A person killed
in the winter may not have insect evidence on their body–few insects are
very active in cold weather. If the body was sealed or wrapped after death,
insects may not have been able to reach it. Nevertheless, the humble fly is a
very useful witness.
Archaeological interest in the remains of insects and tiny snails reflects
what these can tell us about both activity and climate in the past, and in some
cases, about the kinds of plants that grew on that spot centuries ago.
Archaeological entomologists can identify these creatures, many of which
have very specific habitats and preferences. Some species like warm, wet
places; others prefer dry environments. Some species are closely associated
with certain types of food plants, suggesting the presence of those plant
species was likely at, or close to, the site, even if today’s environment is very
different. Other species point to specific types of activity such as domestic
housing. In Viking York, the remains of beetles, fly pupae, and even intestinal
worms demonstrated that public hygiene was very poor in and around the
houses of the inhabitants. Elsewhere, insects associated with cereal crops
show where grain had been stored or processed. All these help us to build a
picture of the life and activities of ancient communities.
A relatively new area of research uses isotope analysis from human and
animal remains. Chemical elements such as nitrogen, oxygen and hydrogen
have alternative forms which are basically the same but have a different
number of neutrons from their parent elements. These are called isotopes.
Some are stable and remain the same, and some are radioactive, decaying or
decreasing over a known amount of time. The radioactive isotope Carbon 14
is widely used in archaeology as a tool for dating. Carbon is present in all