SO you thought there weren't
any places left in this
ever-shrinking world to be
explored.
Richard Borowsky begs to
differ. A flag-carrying member of
the Explorers Club, he set off
earlier this month with two
colleagues to explore one of
Thailand's last frontiers: Its
caves.
Plunging into Phra That Cave in
Kanchanaburi's Erawan
National Park is like entering a
negative of the rich, forested
world above. There are few
colours here, and little life. Even
the air can forsake you, as
pockets of carbon dioxide
occasionally make it difficult to
breathe.
But still there are plenty of
marvels to be seen. Over
millions of years, the interaction
of water, air and limestone has
created bizarre rock formations
that lend the underworld an
austere beauty.
Huge flowstones of sensuously
rounded rock spill down to the
stream-bed. Tiny tendrils of
limestone, creamy white like
vanilla icing, drip down from the
ceiling, each tipped with a bead
of water, eventually to turn into
large stalactites. Elsewhere the
stone is shaped like curtains,
and in one instance we come
across large strips of striped
rock which cavers dub ''bacon''.
As you trudge, slip and slide
through this muddy, watery
world, it's easy to convince
yourself that you are crawling
through the Earth's innards.
What life that does exist here
seems out of its element, barely
clinging to the hard, rock walls --
much like the colony of bats
which, once disturbed, begin to
dive-bomb the intrepid
speleologists. In this realm,
geology rules.
That is fine with Dean Smart, a
cave consultant with the Royal
Forestry Department (RFD) who
is guiding the expedition. A
geologist by training, Smart has
been fascinated by caves ever
since he was a boy.
He seems at home in them,
even enervated by them. At one
point in Phra That Cave, he
scrambles off through a thin,
watery passage and is gone for
10 minutes. But nobody seems
alarmed. Elsewhere, fellow
spelunker Bill Fanning climbs up
through a narrow opening,
before retreating in the face of
foul air.
Over the last three years, Smart
has explored many impressive
caves in Thailand, including
Tham Sao Hin in Kanchanaburi,
home to the tallest natural
column in the world, around 61
metres high.
Now Smart intends to go a step
further by carrying out a
systematic study of hundreds of
caves in Thung Yai Naresuan
Wildlife Sanctuary, most of
which have probably never
been explored. The RFD project
has already been promised
financial support by the Thai
Research Fund.
''Caves preserve things,''
explains Smart, who hails from
the Peaks District in England,
where as a boy he used to
explore many old lead mines.
''We've found teak coffins
dating back 1,200 to 2,200
years that have carvings from
the beginning of Thailand's iron
age. Out in the field, they would
have been eaten by insects.
''So caves are important
historically. Thai kings used to
leave their signatures carved
into cave walls, and some cave
carvings in Ratchaburi prove
that Dvaravati-style Buddhism
was here before Theravada
Buddhism.''
Caves are also ecologically
important, largely thanks to their
constant environment.
According to Smart, for
instance, sediments preserved
in caves contain a great deal of
paleo-environmental information
-- telling us about climatic
conditions long ago -- probably
even more than ice cores or
deep-sea sediments which are
usually studied by scientists.
The steady nature of cave
environments also means that
the animals which become
adapted to them are often
unique and endemic. Smart
cites the example of a
one-millimetre long insect known
as a springtail (from the genus
troglopedetes ), which used to
live all over Thailand. Then the
climate changed, so that now,
he says, you can find 12
different species scattered in
different caves in northern and
central Thailand.
By the same token, however,
cave ecosystems are extremely
fragile. In Ratchaburi, for
instance, Tham Khao Bin -- a
tourist site supervised by the
Tourism Authority of Thailand
and a local consortium of
businessmen -- has been
destroyed by bad management,
according to Smart. Trails are
poorly marked, and tourists
wander where they like,
trampling the fragile soil.
''They are very proud of their
180,000-watt spotlights, but the
lights are far too big and hot for
the cave. As a result, the
temperature inside is at least
two degrees Celsius warmer
than it should be,'' he maintains.
''This not only kills the animals --
there are no more bats there,
and a species of millipede which
feed on their guano is gone, too
-- but also increases the
moisture in the air by sucking
water out of the speleotherms
[stalactites and stalagmites], so
they start drying out.''
One of the most interesting
things about caves, it turns out,
is observing how animals have
adapted to the harsh
environment. The most obvious
adaptations involve the
development of other senses
besides eyesight to navigate in
the pitch-black environment.
Bats, of course, use sonar.
They emit high-pitched sounds
and then ''read'' the echoes to
find their way around. So far,
109 species of bats have been
identified in Thailand -- including
Kitti's Hog-nosed Bat, the
world's smallest mammal -- and
five of them were actually
discovered here.
Other species have developed
their sense of touch. Some
cave crickets have feelers 20
times the length of their bodies,
while ''Hairy Mary's'' ( scutigera
centipedes) and cave-adapted
catfish also sport impressive
tendrils.
Most species of fish have a
lateral row of sensory to detect
movements in the water around
them, but those found in caves
tend to have more of them.
They are also usually blind and
colourless. At least five species
of cave fish are endemic to
Thailand, says Smart, and two
new species have been
tentatively identified at a cave
in Phitsanulok.
''Thailand has over 10 per cent
of the world's known species of
cave fish, and we hope to find
some more,'' he says.
In fact, that is the main reason
for Borowsky's visit to Thailand.
A biologist from New York
University who specialises in
genetics, Borowsky points out
that caves are an excellent
laboratory for studying both
ecosystems and evolution.
''Cave ecosystems have far
fewer variables than in the
outside world, so it's easier to
see how they interact,'' he
explains. ''In terms of evolution,
caves serve as a kind of
repeated experiment to see
what happens to animals who
end up in an environment where
there's no light and little food.''
Researchers like Borowsky find
that fish which have wandered
into caves and bred there tend
to undergo a process of
convergent evolution: They lose
their eyes and their skin colour,
their sensory pits increase, and
after a long time they lose their
diurnal rhythm -- the body's
natural sense of knowing when
it is day and night -- and even
their fear of predators, which
are few and far between in cave
streams.
At first glance, it seems like a
logical reaction. But think about
it a minute. Although eyes may
not be useful in caves, why
should fish with fully formed
eyes lose them over the
generations? Put another way,
what advantage do eyeless fish
have over normal ones in
caves?
According to Borowsky, some
theories suggest that, since it
requires energy for a body to
grow eyes, there is an
advantage if that energy is put
to some other use. Similarly,
there is a theory that
processing vision uses up
valuable space in the brain,
which again could be put to
better use processing other
senses.
But Borowsky tends to support
the hypothesis that complex
systems naturally degenerate
without the impetus of natural
selection. In other words, all
animals are randomly
susceptible to bad mutations,
and since cave fish don't need
their eyes to survive, those fish
born with poor or no eyesight
don't get weeded out. The bad
mutations accumulate through
the generations, so that
eventually cave fish can no
longer see.
''This process is known as
genetic drift, or random drift,
and it's occurring all the time,''
he says. ''Actually, genetic drift
is what makes the process of
DNA fingerprinting useful,
because our random mutations
mean that none of our genetic
codes are identical [except in
the case of identical twins].''
Borowsky supports this
''entropy'' argument because it
has been found that fish in
caves near one another lose
eyesight for completely different
reasons. For instance, in some
cases, the lens may have
receded completely into the
eyesocket, in others the nerves
connecting the eye to the brain
may no longer function.
''One species may lose the
function of genes A, B and C.
Another may lose D, E and F.
But when the two types are
hybridised, their offspring often
have sight, because they have
received all the necessary
genes: A,B,C,D,E, and F,'' he
explains.
Borowsky has also carried out
research in Mexico where he
found something even more
intriguing: cases where
evolution has seemingly
reversed itself. In one Mexican
cave, a wall had collapsed
letting sunlight in. Cave fish
swimming under this karst
window actually ''re-grew'' eyes.
''The case is interesting
because there is a law, known
as Dallo's Law, which states
that the course of evolution
cannot be reversed,'' notes
Borowsky. This is because
evolution is a random walk, so
even if the environment reverts
to its previous condition, it's
highly unlikely that life will go
back to ancient forms.
''But if Dallo's Law is violated in
the case of Mexican cave fish,
it would only be a
misdemeanour, because the
genetic vestiges of eyesight are
still there, so it's easy for the
fish to go back and regain their
eyes,'' Borowsky concludes.