Geoscience Reference
In-Depth Information
of young, aged, and maimed
individuals. There may also be a
sampling bias as early excavators
concentrated on collecting the larger,
more impressive, mammals. Given that
the preservation potential of a mammal
becoming stuck in the asphalt is very
high, it is a sobering fact that an
entrapment episode of a single
herbivore followed by, for instance, four
dire wolves, a sabre-toothed cat, and a
coyote need only occur once every
decade, over a period of 30,000 years, to
account for the number of mammals
represented in the collections (Stock
and Harris, 1992).
original form; see Guthrie, 1990.)
Carcasses are thus mummified (compare
with Dominican Republic amber, Chapter
13), and not only is the coarse outer hair
and soft downy inner hair perfectly
preserved, the meat is also so fresh that it
has been eaten by dogs, and apparently
also by humans. One of the first such
mammoths to be excavated and
examined scientifically was that from
Beresovka in Siberia in 1900. According
to Kurtén (1986) the excavators
attempted to eat the 40,000 year-old
meat, but were “unable to keep it down,
in spite of a generous use of spices”. This
mammoth is preserved with its final
mouthful of food still in its mouth, and is
on display at the Zoological Museum in
St Petersburg.
Several mammoths, woolly rhinos,
bison, horse, and musk ox have been
recovered from the permafrost since the
1970s, one of the most well known being
the complete baby woolly mammoth
(
Mammuthus primigenius
) found at
Magadan in Siberia in 1977. The young
male (christened 'Dima') was found
beneath 2 m (6.6 ft) of frozen silt and is
approximately 40,000 years old. Similar
remains have been found in the
permafrost of Alaska. In 1976 a partial
baby mammoth, with a rabbit, a lynx, and
a lemming (or vole), was discovered in the
Fairbanks district (Zimmerman and
Tedford, 1976) and dated by carbon-14 at
21,300 years BP. The skin, hair, and eyes of
the mammoth were well preserved and the
liver of the rabbit was recognizable after
rehydration, but most of the internal
organs were decayed and replaced by
bacteria. In 2006, geneticists from
McMaster University succeeded in
sequencing a portion of the genome of a
27,000 year old woolly mammoth from
Siberia (Poinar
et al
., 2006), leading to
speculation that mammoths might be
brought back to life by inserting their
DNA into the empty egg cell of an African
elephant. One can only speculate as to
how far back in time such a technique
could be used.
C
OMPARISON OF
R
ANCHO
L
A
B
REA
WITH OTHER
P
LEISTOCENE SITES
Permafrost of Siberia and Alaska
Many animals and plants survived the
glaciations by occupying slightly warmer
areas to the south of the ice sheets on
both the North American and Asian
continents. The Russian mammoth steppe
was a vast grassy tundra fringing the
northern ice sheet; its climate was too
dry to support a large build-up of ice, and
it was effectively a frozen version of
today's hot African grasslands. It was
home, 40,000 years ago, to woolly
mammoths, woolly rhinos, bison, giant
Irish deer, horses, and large predatory
cats and, although there was a summer
thaw allowing some vegetation, the
subsurface was permanently frozen. This
gave rise to what must be considered the
ultimate Fossil-Lagerstätte - the deep-
freeze of the Siberian permafrost.
Woolly mammoths and rhinos in
particular were sometimes engulfed in
bogs and deep-frozen in the permafrost,
where they have remained ever since.
Desiccation by freezing, where the
moisture is not released to the
atmosphere, but forms ice crystals
around the mummy, causes the carcass to
shrink and shrivel as it dries. (This should
not be confused with freeze-drying,
where moisture is removed by
sublimation and the carcass retains its
Search WWH ::
Custom Search