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hidden away in the vastness of the Pacific an undiscovered by men until
only a few centuries ago either group of strange volcanic islands each is a
crucible where evolution proceeds have extraordin the speed
abacus
each island contains its own unique community
the discovery of these creatures inspired an idea that change our
understanding of life on Earth evolution
and today scientists on purpose are continuing to make discoveries that shed
light on that crucial process and have revealed that human beings can be just
as powerful a driving force of change as any other factor
something here was the catalyst that produced the most spectacular explosion
of biological diversity in the world it's not just the number of species that
appeared but the rate at which they did so and the result is so extraordinary it
inspired the most important of all biological theories Charles Darwin's
evolution by natural selection and now 200 years later we are beginning to
understand the deep lying forces that produce this biological Wonderland
one of those factors is isolation
a part of Isabella Island the largest of the sixteen in the archipelago is so
difficult to get to it's hardly ever visit
wolf volcano
it's John crater lives exactly on the equator and is encircled internally by
steep cliffs
and on its Franks evidence was discovered of a catastrophe that might
under Doc's Utley eventually lead to the creation of a new species
this flow of recently solidified lava has created an impossible barrier a
hundred metres wide right through the vegetation
the fresh lava is razor sharp enormous impossible to cross on it lie bones
bleached white by the baking Sun there those of John tortoises
some animals that got stuck here are still clinging to life
tortoises are tough they can survive for months without any food or water
and that worsened their fate it will take the months to die
why so many tortoises tried to cross the lava barrier nobody knows what drove
them to keep attempting this impossible journey perhaps they were desperately
trying to rejoin other members of their group their deaths however are
significant they illustrate a principle that applies to the whole of nature it's
not unique to the Galapagos but it's because of the Calipari's that we first
came to understand in this tragic scene film for the first time may provide a
clue as to how a new species may start to evolve
the lava flow created an impossible physical barrier across the tortoises
territory dividing it into two
so - tortoise populations that were once one must now live apart if there is any
significant difference now or in the future between their two territories the
tortoises may eventually become two different species
animals and plants are evolving throughout the natural world but it was
the strange creatures of Galapagus that first revealed how that happens nearly
200 years ago the islands were visited by a young naturalist on September the
16th 1835 HMS Beagle arrived in the Galapagos Islands and the 26 year-old
Charles Darwin stepped ashore to explore at the time very little was known about
the natural history of the islands
Darwyn initially was fascinated by its geology
but it was the animals that gave him his historic insight
Darwin was only on these islands for five weeks but in that short time there
were things he saw and conversations he had which stuck in his mind for example
the British vice-governor of floreana island said that he could tell which
island the giant tortoise came from simply by the shape of its shell
he pondered on the vice governor's castle remarked why were populations of
tortoises on separate islands all slightly different from one another
he set about making a collection of animals and plants from all the islands
he visited although it was the tortoises at first alerted Darwin that the
differences between animals on different islands
it was his collection of these undramatic little birds the finches
which provided him with the most substantial evidence for his great
theory we now know that the ancestral Galapagos finches arrived in these
islands about two million years ago since then they have diversified into a
number of different species today there are 13 of them distributed throughout
the archipelago each has its own special talents the woodpecker Finch has
discovered how to use a tool to Winkle grubs out of their burrows and the
branches of trees the vampire finches learned how to extract blood from
sitting birds Darwin when he returned to England brought back with him a wide
variety of specimens of all time and he spent years studying his
collections
he had a range of finches from several of the islands and he noticed one
particular way in which they different they had beaks of different sizes why
an idea grew in his mind
it could also apply to tortoises maybe to all animals and plants wherever they
occurred painstakingly meticulously he started to accumulate evidence from all
over the world to support his idea and he called the process that produced new
species evolution by natural selection
and nowhere is its workings more vividly evident than here when it first occurred
to him in the Galapagos he realized why it was that the worst several species of
giant tortoises that original species probably had a high down shell like this
one and that's very useful and well watered islands like this where you have
to barge your way through the vegetation but on other islands there are other
problems
in the southeast corner of the archipelago lies espaƱola island
here there is virtually no edible vegetation at all except that is for
this prickly pear cactus opuntia but this species of opuntia is very tall and
it has a tough *** trunk
the only parts worth eating are the fleshy leaves and flowers that pop any
chant taught us that could reach them could get a meal tortoises with low
round fronts to their shells couldn't do that
but those were the peak at the front of the shell and longnecks could just
manage it so they were the ones that survived and produced young
over many thousands of generations and millions of years the shell shape of the
Espanola tortoise became more and more exaggerated
now the peek at the front of the shell is shaped like a saddle
such a change didn't happen just on Espanola different islands had their own
versions
eventually there were 15 different species in the islands all descended
from a single founder
but why should the environments of the islands be so different well a hint of
that reason may come from looking at films I shot right here back in 1978 in
these programs we're going to survey the unmeasurable variety of animals that
have been produced by natural selection and look at them not as isolated
oddities that image of me shot 30 years ago indicates something extraordinary in
that time the rock on which I was sitting has moved its position by about
a meter from where I was then to where I am now in fact the whole of this island
is drifting across the surface of the globe at a rate of about three
centimeters a year roughly the rate at which my fingernails grow that may not
sound much but in the three million odd years since this island emerged above
the surface of the ocean it has drifted in a southeasterly direction by about
sixty miles
movements in the Earth's crust are the key to understanding the archipelago's
extraordinary evolutionary history a giant hot spot rising from the Earth's
molten core began to build the Galapagos 4 million years ago
but as the island different away from it other volcanoes replaced it one after
the other
each was built from an accumulation of ash and lava
but then as each moved away eruptions ceased
so a group of items appeared one after the other
the islands are separated from one another by water so their populations
can't for the most part mix but they're just close enough for an occasional
animal to float across and so seed a newly emerging Island because the
islands are of different ages they contain between them a great variety of
environments
and each has mode in its inhabitants in its own way
that is why their animals are so diverse
each is a separate evolutionary community
Darwin had noticed some of the clearest differences but there are many others
with a less obvious an isolated population of animals can change not
only in their Anatomy but in their behavior
little lizards like this are found throughout the archipelago each island
has its own distinct species and they differ not so much in the way they'd
look that's the way they behave this is a lava lizard there are lots of them on
the rocks around here and in the breeding season which is now the males
are competing with one another both for territory and for females and the way
they do say it's with press-ups watch actually this is a model there's
things for scientists to investigate the way in which these lizards communicate
with one another let's see how it gets on
and there's a response these press ups vary both in the number and the
intensity the speed there from species to species in other words each species
language there are slight physical differences between the species of lava
lizard on different islands but now because they have developed different
gestures they can't interbreed even if they meet they're separated by a
language barrier new technology now enables scientists to investigate the
workings of evolution in ways that Darwin could hardly have ever imagined
x-rays are being used to work out what's happening to one of the least impressive
animals on the island a tiny land snail
it's been known for a long time that there are many different snail species
all closely related
but a recent study of their shells using x-rays has demonstrated just how diverse
they have become
the length of the shell compared to the diameter of the tube inside is
marginally different in different populations
it's certainly different enough to define them as different species and
there is an extraordinary large number of them throughout the islands without
seem to be very complex into relationships in fact there are more
species of them than any other kind of animal on the islands even one small
island may contain several different species but why
it's all to do with the different microclimates that occur even within a
single small island
black novel rock has one species and sandy beach is close by a very different
one
a dark cave has one sort and a leafy forest growing around its mouth yet
another kind and it seems to be connected with
humidity at the one extreme there are these with a wide mouth they come from
relatively well watered islands and the wide mouth like that has a body which
produces a roughly globular shell but on dry islands the mouth has to be very
small to prevent evaporation and that produces
a long conical shape so Galapagos is new species range from the subtly different
like snails to the obvious like the marine iguanas in other parts of the
world evolution usually proceeds in a slow gradual way it can take millions of
years for new species to appear but in Galapagos it's been happening in an
evolutionary blink Bernard
Galapagos for its size has more unique species than anywhere else on earth
and all have appeared in the islands comparatively short history
that raises another intriguing question why did such a great number appear so
quickly
the answer is to do with the absence of some animals predators the few that are
here are all very small this is one of the most lethal scholar pendra a
centipede it roams the undergrowth searching for prey which it kills by
injecting venom from the sharp claws on its front legs but it's only 30
centimeters long so its victims are mr. tiny bigger animals like mockingbirds
can easily subdue one they even feed centipedes to their chicks the greatest
concentration of predators in the whole archipelago is found on the rocky island
of Fernandina but they - of their kind are rather small and comparatively
ineffectual snakes
the Galapagos racer they search for prey in the colonies of marine iguanas
but all they can manage to do is to pick off the young the weak of the dying and
even that they find quite difficult they hunt in the rocks around the fringes of
the colony they have to use a combination of both venom and
constriction to make a kill and even then because there are small snakes it
may take more than one to overcome a victim and then there's a tug-of-war
between the winners to settle who has surprised
there are other predators that prey on the iguanas from the air the galapagos
hawk
but even this hunter is seldom powerful enough to subdue a big man
it usually waits until it finds one that is weak or encumbered
a pregnant female tried to find a place to lay her eggs
and there are not many Hawks here only a hundred and fifty mated pairs because
there's only a limited number of nesting sites there are so few birds that they
make very little impact on the iguana population so why are there no larger
predators on collab occurs most of the Galapagos animals came from the
rainforests of South America 600 miles away there are plenty of big predators
in these forests
reptiles got to Galapagos by floating across the ocean on rafts of vegetation
only Hardy animals like the koalas and tortoises could make that 600 mile
voyage
the great predators of the junglers however are mammals big fast and
warm-blooded like Jaguars
if any of them had ever been carried away on a raft of vegetation they would
have perished out on the open ocean within a few days so now while there are
many kinds of herbivorous reptiles in the carapace there are no large
predatory mammals of any kind and this has had a profound effect on
the animals that did get here it's something noticed by every visitor who
comes to the island all the animals here are amazingly tame even the little
finches are happy to bathe within inches of a stranger the lack of predators may
have a surprisingly widespread effect it's not just that animals are not
frightened of strangers the so-called island tameness
but that time that would be spent hiding from attackers can now be used to find
food by mates and raise young and so produced more young which hastens the
progress of evolution
there is no more impressive example of that than Fernand Dina's iguana colony
with no significant predators around these herbivores produce lots of young
so many that their problem is not how to defend themselves but how to find enough
food to support their great numbers so they ventured into the sea itself to
graze seaweed on the seafloor and although swimming in the cold sea cools
them uncomfortably with no predators around they can soon put that right by
stretching out in the Sun
the lack of big predators has had an effect on all the animals of the
Galapagos they reproduce freely so populations increase rapidly and so
consequently does evolutionary change
but island tameness has dangerous if a major predator does appear then
wildlife will be ill-equipped to defend itself
and one did in the year of 1535 the most successful predatory animal of all
arrived
by the beginning of the 17th century the islands had become a haven for pirates
by the 19th century whalers and Burton men were calling here regularly and all
these ships had a disastrous effect
there is little or no freshwater on these islands but they have a much rarer
resource Jan tortoises can survive without food or water for very long
periods so ships could come here collect the tortoises stow them in the hold and
then after weeks at sea bring one out butcher it and have a meal of fresh meat
slow lumbering and with no way of defending themselves the tortoises were
easy victims the population was decimated between the
16th and 20th centuries more than a hundred thousand were taken away and
slaughtered and the ships brought other dangerous rats
they feasted on the tortoises eggs on the island of pins on rats consumed
nearly every single egg leaving the tortoise population on the brink of
extinction but another island lost its tortoise population altogether
pinter located on the shipping route around the north and fringe of the
archipelago was a favorite stopover for ships and they're hungry crews and the
unique winter tortoise was presumed extinct by the early 20th century
but in 1972 an amazing discovery was made and filmed a living male Pinta
tortoise was discovered in the undergrowth he was taken off to a
protected enclosure on the main island to live out his days in comfort and
safety here he became an international celebrity and he was given a name to
reflect his state known some George
he's about 18 years old and he's getting at mr. creaky in his joints I was indeed
am i he is arguably the rarest animal in the world certainly there can be none
rarer for he is the last of his kind his female died a long long time ago
when he dies the Pinta species of Galapagos tortoise will be extinct
but he is a very important animal probably more than any other single
creature he's focused the attention of the world on the fragility of our
environment and he stimulated science to look into whole new areas of research
here in the Galapagos
just 14 days after we filmed lonesome he died in his sleep but is not forgotten
and some George's story like Darwin's fleeting but famous visit 200 years ago
has attracted many visitors to the islands
today the archipelago is the basis of a multi-million dollar tourist industry
30,000 people live here in three small towns and fleets of small boats take
visitors on carefully planned trips to see the islands main sights
it took animals and plants millions of years to find and colonize the Galapagos
now new species of animals and plants from the world's continents can get here
in a matter of hours and having got here they're often inadvertently spread
almost immediately through the islands
seeds of foreign plants hitch a ride on the air currents generated by passing
traffic and the Galapagos is network of roads is now lined by foreign invaders
among them the common European blackberry a plant that can grow a
centimeter a day and create impenetrable thickets four metres thick they not only
choke and kill native plants they even blocked the paths of large animals such
as the tortoises scientists are now trying to analyze the impact of human
beings on the course of evolution in the islands
and surprisingly perhaps the finches that Darwin made famous are still
providing new insights
biologist Andrew Hendry is looking at how the finches evolution may have been
affected by human settlements when humans come into a new location
essentially what they do is they change the environment and and that's that's
changing selection is acting on the populations Hendrie is studying one
particular species the medium ground ok yeah remarkably he's found that this
Finch in its natural setting is on the verge of dividing into two separate
species the two are defined by the size of their beaks one is small the other
large the difference between them has been caused by the types of food they
eat so if you feed on some small seed then you tend to have a small beak and
if you feed on a large seed then you tend to have a really big beak and you
tend to have a hard bite remarkably Henry has found that among medium ground
finches that live near human beings the distinct big and small beak forms are
getting fewer
it's as if the two variants are here merging back is the one
the presence of human beings has stopped this Finch from evolving we found that
they feed a lot on human foods ranging from rice to fruit to grains to potato
chips and feeding on those types of different foods doesn't really seem to
matter what your beak size is anymore so there isn't that pressure to have a
small beak version and a large beak version and there's no selection against
those intermediate Birds anymore there's plenty of foods for them to eat so it
seems like humans have caused the speciation reversal there they're fusing
back together again as a result of human influences
so human beings can be just as much a part of nature as the forces that first
shaped these islands and the organisms that live on them but human beings
cannot only destroy they can conserve in the 1970s the tortoise population
reached an all-time low there were only a few thousand of them left but now
there's a major breeding program for
them
the tortoise population today is increasing once threatened species have
been brought back from the brink
and scientists are discovering just how important and influential this
reintroduction program might be on our seder volcano home for the largest
population of free roaming jar tortoises a study has shown that they're crucial
to the health of all the surrounding wildlife today there are some 15,000
tortoises on the collab occurs and they're an essential element in the
islands ecosystem one study in particular has shown just how important
they are biologist Steve Blake uses satellite tags to track their movements
they reveal to most people's great surprise that the tortoises migrate over
huge distances from the depths of the crater right up to the rim it's just
phenomenal why would a 600-pound reptile migrate from sea level to to up to a
thousand meters on some Islands
from the air the roots the tortoises take are clearly visible
and they use the same highways year after year
one of the fundamental drivers of the migration seems to be food tortoises
tend to come to the highlands at the coolest time of year up in the highlands
they can feed on a year-round low quality food source but then when the
rains kick in the lowlands tend to green up and the tortoises go down there
probably to fatten up but Blake's studies reveal much more about the
tortoises than just where they go they demonstrate the extraordinary effect
that tortoises have on their surrounding environment
they create special conditions that suit all kinds of other animals they shape
and prune the landscape they disperse seeds travel down the undergrowth and
trim the lowest branches of the bushes and all that allows seeds to germinate
it disturbs insects so that they can be gathered by hungry predators
their dung is also crucial to the survival of many other creatures beetles
lay their eggs in it and their larvae grow fat on the nutriment that it still
contains
tortoises are definitely the megafauna of the islands they're like the
elephants of Galapagos they're out there in large numbers
they've got big bodies they're creating myriad micro habitats for other species
they truly are gardeners of Galapagos that's probably the best way to sum up
their ecological role
the implications are very important they suggest that the reintroduction of
tortoises to islands where their numbers have been seriously reduced could
restore the richness of the whole environment we have the chance to bring
back the full glory of these fragile ecosystems
today unlike many other tropical islands elsewhere 95% of Galapagus biodiversity
still survives just
and amazingly new species are still being discovered
one was found just a 35 miles north of our Seder on the giant little visited
volcano wolf
to get the wolf you really need a helicopter it's one of the most hostile
and least explored parts of the whole archipelago
there had been rumors of something strange living up on these remote high
slopes
something that lived in burrows and only emerged every now and then to feed
a scientific team went out to investigate
what they discovered astonished everybody a completely new and unknown
species of reptile
a pink iguana
until now it was thought that the Galapagus possessed only three species
of equal honor the black marine iguana that lives on the seashore and two
species of yellow iguana that live inland feeding on cacti and other
vegetation
this land iguana is setting it the most closely related to the newly discovered
genetic studies of the hundred or so individuals that make up this tiny
population have shown that it diverged from its land iguana cousins more than
five million years ago so amazingly it has been here just as long as the other
two but has remained unknown to science until now the discovery also means that
it is even older than wolf volcano where it now lives
and of course there is another great mystery that no one has yet explained
nobody knows why it's pink could it be that to be pink up here brings something
good we don't know maybe this was once spread widely over the island and this
is just the relic population that's left again we don't know for by but there's
one thing that is quite certain and that is that there's a lot we have yet to
learn about the enchanted Islands and about the animals that have evolved here
and one thing I have no doubt Charles Darwin would be delighted
in just a few million years this empty expanse of ocean was transformed a
series of volcanoes broke the surface and built the islands
against heavy odds a few species managed to reach them
they adapted to what they found
and so evolved into a multitude of new species
each new discovery we make gives Darwin's theory a greater relevance
but beyond the strange grants and reserve anna-news there is a greater
significance
what we've learned here has given us a greater understanding of our planet
this small group of islands has revealed in microcosm the processes that have
shaped all life