A selection of clips taken from BBC programmes about Darwin and evolutionary biology.
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Darwin was loath to admit his evolutionary view.
He began breeding pigeons and joined fanciers clubs.
He wanted to know how they created their extraordinary strangely feathered birds.
Darwin bought and kept every known breed in England and many of the types he kept survive today.
These were the sorts of fancy breeds that existed in Darwin's day.
Here we have the English pouter, the biggest and tallest of the pouters. This big yellow one.
He knew if these birds were wild they would have been classed as distinct species.
Miniature, where it gets its name from. The pygmy.
And the Jacobin, which is the exotic feathering...
But all the fancy breeds were of one species.
He crossed his tumblers and fantails to prove it.
Different from the common garden fantails you see.
And the runt...
All had been bred over generations from one ancestral type.
The breeders' craft was a mysterious business. More art than science.
But Darwin knew that within it lay their secrets of selection.
We're just waiting for... the markings are all right.
We can already see at this stage how much better it is in length of leg.
These minute differences are what we're looking for all the time.
-So that's the champion?
-Hopefully, if everything carries on developing, yes.
-At what age can you first spot the difference?
-As early as day one.
We have two babies here one day old and you can see the difference.
-From the same nest?
From day one you can see the difference in the beak.
He found what he'd expected. The individual birds were composed
of a myriad tiny variations, invisible to all but experienced fanciers.
The selecting hand was artificial, but all nature must be like this.
Nature was a supreme selector picking out those with an edge, discarding and killing the rest.
Pigeon breeding gave Darwin the most graphic example of how new species originate.
In Victorian times, the collecting of butterflies that showed any slight variation
from the normal pattern was fashionable.
It was popularly thought that such varieties were unimportant, they just died off.
Darwin didn't think that at all.
"These individual differences are of the highest importance for they're often inherited."
And as the variation is inherited, Darwin thought wild animals,
just like our domestic animals, had the potential to change, too.
"According to my view, varieties are species in the process of formation."
This was a startling idea.
Although it was accepted that new species could appear and old ones disappear,
these changes were commonly believed to be due to divine acts of creation or destruction.
But Darwin believed he'd discovered a natural process by which
a variety could evolve into a brand new species.
He was supplanting God's work by a natural process.
It was a dangerous idea.
How exactly did Darwin think new species came into being?
Before answering that, he had to propose a view of nature that went against a romanticised,
Victorian ideal of how the natural world worked.
"We behold the face of nature bright with gladness,
"we forget that the birds idly singing around us mostly
"live on insects or seeds and are thus constantly destroying life.
"Or we forget how their eggs or nestlings are destroyed by birds or beasts of prey."
He was suggesting that the tranquil beauty around us is largely an illusion.
In the natural world, life is often a struggle just to survive, let alone breed.
Of all the arguments raised against his ideas,
nothing troubled Darwin more than that about the origin of the eye.
"The belief that an organ so perfect as the eye could have been
"formed by natural selection is enough to stagger anyone."
It certainly staggered his critics.
"It's only here or there that a second rate naturalist would
"sympathise at all with such dreamy views."
They simply couldn't believe that such an intricate mechanism could arise by any natural process.
Darwin thought it could.
"If numerous gradations from a simple eye to one complex and perfect can be shown to exist,
"each grade useful to its possessor, then the difficulty of believing a complex eye could be formed
"by natural selection shouldn't be considered as subversive of the theory."
The earthworm has a layer of light, sensitive cells in its skin that can detect light from dark.
It's the simplest eye possible and all that an earthworm needs.
If a random variation should cause these cells to be set back in a pit,
then the animal can detect the direction of light just as the limpet can.
The snail has an additional refinement.
A blob of mucus in the pit acts as a simple lens.
The snail can seek a roughly focused image.
If the lens then hardens, the vision becomes better.
The conch has this kind of eye.
Darwin argued that there were no limits to what such a process might ultimately produce.
"A structure even as perfect as an eagle's eye might thus be formed."
The eagle's vision is said to be
eight times more acute than our own.
It can spot prey at distances over which we would spot nothing.
Darwin believed his theory could explain the entire variety of life on Earth.
Through the adding up of tiny variations, fish would have evolved into amphibians.
At every stage, the new form would be better adapted to an amphibious life than the last.
In the struggle for life, the new kind would out compete the old and drive it to extinction.
In the end result is a world today with fish and amphibians, but nothing in between.
But don't the missing links turn up as fossils?
"It's been asserted over and over again that geology yields no linking forms."
Darwin's critics maintained he couldn't point to a single
fossil intermediate between two different groups of living animals.
He replied that few animals have ever become preserved as fossils.
The fossil record was like an incomplete book.
"Only here and there a short chapter has been preserved
"and of each page only here and there a few lines."
Yet he was sure that in time
intermediate forms would come to light.
One year after The Origin Of Species was published,
an extraordinary fossil was found in Germany.
It had a mouthful of teeth like a reptile and feathers like a bird.
This is Archaeopteryx.
It's an animal intermediate between two living animal groups.
Darwin felt this natural process would hinge on which animals
survived the struggle for life to breed and which do not.
"Individuals having any advantage, however slight, over others would
have the best chance of surviving and procreating their kind."
This gazelle may be just that bit fast or stronger than the rest.
"The preservation of favourable individual differences and the destruction
"of those which are injurious I've called natural selection or survival of the fittest."
So here is the crux of Darwin's great theory.
A natural law, survival of the fittest,
determines which animals will live long enough to have offspring.
If this natural selection were to go on constantly
perhaps those tiny individual differences could add up, then wild species might change.
"Natural selection is daily and hourly scrutinising
"the slightest variations, rejecting those that are bad,
"preserving and adding up all those that are good."
This scrutiny may be constant, but the resulting change would be slow.
The variation between individuals of a species
are usually very slight
yet the differences between one species and another
may be very great, a lot of adding up of tiny differences
would be needed to produce a new and different species.
If he's looking a little smug, it may be with good reason.
Joshua is the very first of a new kind of cat.
You can stroke him all day long without risk of red eyes, sneezing or skin rash.
In the UK alone, 8 million cats are kept as household pets,
but many end up being given away because their presence
can bring out an allergic reaction in their owners.
It's the cat saliva which is responsible, or rather a protein within it called Fel d 1.
The American scientists isolated two cats which were low in Fel d 1
and bred them over several generations until the protein had virtually been eliminated.
In doing so, they created cats which don't bring out allergies.
The RSPCA has criticised the development saying selective
breeding undermines the value of animal life.
The company responsible is emphasising the benefits to people.
I know how pet owners really are and in times of need and passion,
whether it's depression or something traumatic, nothing
substitutes the love of a pet.
You can't put a price and it.
But in fact they have. A moggy like this will set you back more than £2,000.
There's already a long waiting list.
Some living animals are so bizarre they seemed hard to explain by Darwin's theory.
How can a tail like this evolve when it seems sure to slow its owners escape from predators?
And wouldn't the same apply to the great cumbersome jaws of this stag beetle?
Surely these are exactly the sort of things
that would be weeded out in the struggle for life.
Darwin said these kind of exaggerated features evolved by what he called sexual selection.
"This form of selection depends on a struggle between the individuals
"of one sex, generally the males, for the possession of the other sex.
"The result isn't death, but few or no offspring."
The struggle isn't violent.
The males gather to show off their tails and the females choose which males to mate with.
If, even with such long tail feathers, a male peacock is still strong enough
to escape from predators then such feathers are a sure sign of a healthy male.
From an ancestral form of peacock with short tail feathers,
the females of each generation would have chosen the longest feathered males to mate with.
In time, the feature would have become exaggerated
to produce today's peacocks with their spectacular tails.
Such a process would also explain the famous displays of male birds of paradise.
But sexual selection isn't just about show.
"In many cases victory depends on having a special weapons."
Male stag beetles actually fight other males.
The winner gets the female.
So the biggest jawed males of each generation beat their rivals and have big-jawed offspring.
The adding up of tiny advantages leads to animals superbly adapted to their own way of living.
Given the number of offspring every living thing is able to produce,
it's actually a good thing life is a struggle.
"There's no exception to the rule that every organic being naturally increases at so high a rate
"that if not destroyed the earth would soon be covered by the progeny of a single pair."
The result of just a few successive generations, in which all offspring
from one original pair survive to breed, would be dramatic.
Temporary outbreaks of mice in Australia when food is abundant
and predators scarce are living proof of that.
The hard times will return, then the struggle will begin again
and many animals will die before they can breed.
The first challenge to overcome is the intense and unrelenting heat.
Red kangaroos deal with the worst of this by finding shade
and digging to find cooler earth below the sun-baked ground.
Another trick is to conserve as much water as possible.
When resting, they don't sweat.
Instead, they lick their forearms so that saliva cools blood vessels close to the surface.
Emus also cool down using surface blood vessels,
increasing the flow to their long necks, long legs and big feet.
Their flightless wings have unique double quilled feathers that
protect them from the burning heat so they can brave the midday sun without shade.
The second problem desert dwellers face here,
unlike their rainforest past, is finding water.
Emus are often forced to walk huge distances to find water
as they need to drink every day.
Red kangaroos can memorise pools they visited before,
but they're better adapted to cope without a drink.
They store more water in their bodies, in the muscles and their guts, than other mammals.
And can withstand water loss that would easily kill a human.
If there are plenty of green plants, the kangaroos' sole diet, they don't need to drink at all.
But they can't always count on that.
Red kangaroos have evolved broad padded feet designed not to damage new shoots,
but still their biggest problem is finding enough to eat.
They're experts in saving energy.
They can survive on the bare minimum of food.
Kangaroos, and all of Australia's marsupials,
have a much lower metabolism than mammals in other parts of the world.
This means they use less energy, whether resting or on the move,
so they can live on less food than other mammals of their size.
A vital adaptation to desert life.
Today, they number 10 million.
But the kangaroos' ability to scrimp and save is nothing
compared to their neighbours.
In nearby creeks and billabongs, freshwater crocodiles have barely
changed since their rainforest days 50 million years ago.
They feed on fish, insects, crustaceans and the occasional unwary bird.
When times are good, they lay down fat in special stores along their tails.
This, combined with an exceptionally low metabolism,
far lower than the kangaroos', allows them to survive up to two years without a single meal.
Among the towering cliffs, peaks and ridges of Ethiopia's Semien highlands,
the so-called roof of Africa,
Walia Ibex - Ethiopia's national symbol.
They can exist in these precarious places and they do.
But that's mainly because they have to.
The cliffs are something like a kilometre high
and they're almost sheer.
That's where the Walia Ibex live
and to see them in this enormous distance
on these sheer cliffs is truly spectacular.
I tried to film them years and years ago for another series and they proved too difficult.
The Walia Ibex were much wider spread at one time throughout the mountains of Ethiopia
and are related to the Ibexes of Europe.
But as humans have spread through Ethiopia
and the environment has dried out, the Walia Ibex has
been pushed into the most marginal habitats it can find and some
of the last remaining places humans can't get to
are these incredible sheer cliffs
and it's only just been with a lot of warfare
in the last century in Ethiopia, the Italian invasion
and then a big civil war, that the Walia Ibex became favourite food for soldiers.
The Semien mountains saw a huge amount of fighting
through the 1970s and 1980s and in that period
the easiest food for a very cold soldier would have been to take a shot at one of the Walia Ibex.
We saw the numbers decimated.
The one thing the Walia has going for it is the habitat it lives in.
These sheer, sheer cliffs.
There are very few animals in the world that could live on precipices like the Walia.
It has a little niche it can cling to,
but it's such a fragile situation.
600 animals for a large mammal is nothing.
When you've no other habitats to spread in to, no other populations to interbreed with,
no Walia Ibex in captivity,
you'd better be sure you can protect that one last piece of cliff they have.
Aborigines survive by their exceptional knowledge of the land
and its secret sources of food and water.
This priceless knowledge is inherited through storytelling.
Stories that relate to the magical dream time are passed from generation to generation.
They retrace the journeys of the ancestral beings as they wandered
over the empty continent creating the world.
In doing so, every feature of the land and its invaluable resources
are recounted to enable future generations to survive here, too.
But even if you know what food you're looking for,
how do you find enough?
The best strategy is to keep on the move and eat
from a wide variety of sources - to avoid any becoming depleted.
And an intimate knowledge of wildlife is essential.
Eggs from the freshwater crocodile are usually laid in the holes within ten metres of water.
After laying, the female leaves them unguarded, only returning when the baby has hatched.
So with the right knowledge, it's safe to raid her nest.
By breaking open the roots of certain bushes and trees, witchety grubs can be found.
These plump white insects are larvae of the ghost moth -
an important source of protein, said to taste like almonds.
They're usually cooked in ashes but can easily be eaten raw.
The trail of a certain ant leads to a sweeter delicacy.
Digging a hole as deep as herself,
this Aboriginal woman can access the underground nest of the honey ant.
Some of the worker ants are fed on nectar by other members of the colony
until their abdomens are so swollen they can barely move.
They become living storage vessels, tucked away deep in the nest where
other ants can feed on them in times of drought.
By easing them gently out with a stick, others can feed on this sugar sauce too.
As women are traditionally gatherers, it's their task
to collect plant food which makes up half of their diet.
They have a special technique to help it grow.
Firestick farming, as it's called, works in two ways.
First, it burns off the tall, dominant grasses
allowing a range of edible plants to grow in their place.
So there is not only in more food to eat, but it's easier to find.
The Aborigines rely on their detailed knowledge of the land to see them through.
Just like their predecessors 40,000 years ago, they know
how to find water underground when their usual water holes dry up.
The desert sand protects this water from evaporating and the grass acts as a filter.
So, digging in the right place can produce a life-saving drink.
And in desperate times, every drop of water helps.
Burrowing frogs can shut down body systems and live dormant underground for seven years.
Even in the hottest months, they don't dry out because layers of dead skin act like cocoon.
They stay alive this long by using water stored in their bladders after previous rains.
And Aborigines know how to access this in an emergency.
As temperatures in Australia rose, most of the rainforest trees died out,
but one, the eucalyptus, adapted well to the new dry conditions
and seized its chance to spread.
There are now over 700 species of eucalypts in Australia's dry, dusty earth.
To save precious nutrients, they grow fibrous leaves full of poisons
so that like the Spinifex grass, nothing can eat them.
But one animal has broken through its defences...
In fact, it eats nothing else.
Koalas have very long digestive tracts,
full of specialised bacteria,
which must be passed on to their young through their faeces.
They carefully select leaves with the fewest tannins and the highest oil content.
But despite munching through a kilo a day,
they still gain very little energy.
The price they pay for this poor diet is to sleep
an epic 19 hours a day.
Since they spend five hours feeding,
there is little time for anything else.
Koalas have another way to save energy.
They are bears of very little brain.
The brain consumes more energy than any other organ,
so if all you do is eat and sleep, a small brain probably makes sense.
But there is an upside to this poor diet.
The chemicals in the pungent leaves means koala flesh is not popular to eat.
So despite their sluggish way of life,
koalas can still sleep away their days in relative peace.
In the High Arctic, the Planet Earth team saw
polar bears behaving in ways they'd
never seen before.
Get your eye behind the viewfinder, the adrenalin starts rushing.
You know you're recording something so unusual, something so amazing
that very few people have ever seen before.
But you have to focus.
It is very rare to see a bear go after walruses
and to actually physically
jump on them and attack them, stalk them, hunt them.
Ten years ago, at the same time of year and at the same latitude,
this, as filmed in a BBC Wildlife Special
was what polar bears were doing.
The sea was frozen and the bears were hunting
less intimidating prey.
Not enormous walruses in defensive herds on dry land,
but small ring seals out on the ice.
We are rapidly losing ice cover.
It's happening as we speak.
The ice cap is getting thinner and in its extent, is greatly reduced,
and that icecap is the home of the polar bear.
So, they're finding the places they're accustomed to breeding and hunting are disappearing.
There's no doubt, people can see the ice breaking up,
they can see the glaciers retreating.
That's a real problem for the polar bears.
Polar bears are in deep trouble and there's lots of research to show that.
There are two possibilities, one, they go extinct
as they try desperately to find ice.
Or, they may go further south and come on to firm land.
Of course, their habits will have to change greatly.
Maybe they will evolve to do that?
It's got a very short time in which to do this,
if the projection is that
the polar icecap will have disappeared within 50 years,
we are expecting an awful lot
in the way of habitat change, annual movement change,
feeding habits, hunting techniques of a bear.
I think it's going to be very interesting to see if it can do that.
The estimates we have is that we might lose 35% of them over the next 50 years.
As that population starts to go down and their prey species move out,
it's going to be a tough adaptation for the polar bear.
No part of the Earth is more hostile to life than the frozen wastes around the Poles.
850 miles north of the Arctic Circle, this is Ellesmere Island.
No animal can live permanently on these ice fields.
And even plants face almost insuperable problems,
for the four things they must have are in cripplingly short supply.
Water, it's true there is a lot of frozen water all around me,
but water has to be liquid for plants to make any use of it.
Nutrients, there's virtually none in this frost-shattered rock.
Warmth and light,
for six months of the year it's dark,
and in the brief summer as now,
the sun doesn't rise high in the sky and devastating winds
can carry away what little warmth it brings.
And yet, there are plants here.
actually inside the rock.
This thin green line is made by algae, microscopic plants.
They're so small they can live actually between the grains of the sandstone.
And there at least, they're out of this desiccating wind.
On the surface of the rocks there are lichens.
They grow incredibly slowly and may take 50 years to cover a square centimetre.
But they can survive even if there are only two days in the year when it's warm enough for them to grow.
In spite of these bleak conditions, there are in fact flowers to be found here.
But you have to look hard to find them.
It's a kind of mustard,
but it's much smaller than its more southerly relatives.
But by being so small, it manages to keep out of the crippling wind.
In mid-summer, for a few weeks, enough water melts from the glaciers
for streams to flow, then, miniature gardens burst into bloom.
The searing wind compels them all to keep close to the ground.
None keeps closer than this.
It is in fact a tree, a willow.
These are its catkins.
But the trunk grows horizontally instead of vertically
and it can stretch almost as far along the ground
as its more southerly relatives stand up above it.
Even so, it still produces enough leaves to sustain a few grazers -
The Arctic poppy, like all plants needs warmth to grow,
but it's unusually efficient at collecting it.
As the mid-summer sun skims round the horizon, all 360 degrees
in 24 hours without setting,
the poppy turns its flowers to track it.
The slanting sun may not be strong,
but it is at least continuous during the few weeks of high summer.
The heat of the poppy gathers by staring continuously at the sun enables it to develop the seeds
in the centre of each flower before summer comes to an end
and the sun disappears below the horizon for months.
On the high peaks of the Alps,
spring brings a greater benefit than it does in the Arctic.
The sun rises higher in the sky and is warm enough to melt all but the highest snowfields.
As it melts, it reveals the snow bell, already in flower.
The plant formed its flower buds last autumn,
before the increasing cold shut down all its activities for the winter.
The buds remained dormant until the spring sunshine filtering down through the snow triggered
them into action and they opened even before
the snowy blanket above them had melted.
In summer, the high meadows,
newly freed from snow, fill with flowers.
Because for so much of the time it's so cold,
the vegetation here decays only very slowly.
So a peaty soil forms, but it's only a thin layer over solid rock
and boulders and trees find it difficult to get root.
Not only that, but avalanches regularly sweep these slopes,
carrying away saplings before they can get firmly established.
So, shallow-rooted plants have these parts of the mountains
largely to themselves, and in summer they bring a rich display of colour.
But, for every 1000 ft you climb,
the average temperature drops by about three degrees.
Plants living in the high mountains
have to be able to survive extreme cold.
It's very important to keep out of the worst of the chilling winds,
and many plants here form small, rounded humps
and that brings them a number of advantages.
Growing into the shape of a cushion
is an excellent way of conserving heat.
And no plants do it more spectacularly than these growing
high in the mountains of Tasmania.
These are the largest cushion plants in the world.
They grow to over 12 ft across.
Any one square yard contains over 100,000 shoots.
So I guess this one cushion around me contains several million.
This rounded shape does more than just reduce wind chill.
The air temperature around me here at about 3,500 ft high
is only a degree or so above freezing.
But if I take this temperature probe, put it on the surface of this cushion,
I can see that there, it is several degrees warmer.
The cushion in fact acts as a solar panel,
absorbing heat directly from the sun.
So that even on very cold days, providing it's not covered with snow
and is exposed to direct sunshine, it can photosynthesise and grow.
The plants that form these spectacular cushions
come from several different families.
Sedges and rushes, daisies and dandelions.
One cushion may contain several species tightly packed together
and growing to exactly the same height.
For one kind to grow higher than those around it would be suicidal.
In the New Zealand Alps, one of these cushion-forming species
also protects itself by developing a blanket of hair.
This tall pillar growing on Mount Kenya
also covers itself in a blanket.
It's a giant lobelia.
Its long leaves are fringed with dense hairs.
Its flowers are hidden away from the frost beneath this downy covering.
There's no point in having bright petals if they can't be seen, and these are just simple tubes.
But the lobelia's pollinator, a sunbird, knows where they are
and how to reach them.
During the day, it can get quite warm.
For Mount Kenya stands almost exactly on the equator.
But up here, at 14,000 ft, once the sun goes down it gets bitterly cold,
and then the lobelia will have real need of its hairy blanket.
There are other giants here, too.
Tree groundsels, relatives of the little yellow weed that grows in European gardens.
They have a different way of dealing with the cold nights.
Their dead leaves remain attached
to the stem so that they act like lagging and prevent the liquids
in the pipes running up inside the trunk from freezing solid.
Conditions here can change with extraordinary speed.
One moment the equatorial sun is blazing down from a cloudless sky,
the next, a chilling wind begins to blow and the great mountain
collects a cloud cover.
As well as the tree groundsel, there's another member of the family
that grows close to the ground like a cabbage.
As night falls,
it makes its own preparations for surviving the bitter cold.
The most precious and vulnerable part of the plant is the bud
in its centre, from which all growth comes.
That must be protected at all costs and folding the thick leaves over it does the trick.
The birdcage plant lives in California.
But the desert dunes are always moving and a sheltered site
can suddenly become intolerably exposed -
so the plant must find a new place.
This plant is now dead.
But within it, there is still life.
These tiny particles are the next generation.
Each is a miracle of packaging because each, after all, contains
complete genetic instructions for rebuilding an adult plant like this.
And it's precisely because these grains are so small
that it is in this form that most plants do most of their travelling.
Some of these genetic particles, in fact, are microscopic.
The smallest of all belong to fungi.
Fungi are not, to be accurate, plants at all. They belong to a kingdom all their own.
But the particles they produce, called spores, are in many ways similar to seeds.
A single puffball produces so many that someone has calculated that if,
for two generations, every spore
grew into an adult, the resultant mass of puffballs would be 800 times
the volume of the Earth.
Like the birdcage plant, a puffball can be carried along by the wind.
But the real long-distance travelling is done by the spores
that are knocked from it in clouds, like smoke.
In autumn, other, smaller fungi appear on the woodland floor.
Their appearance, just after they have emerged above ground,
gives little hint of how complex they will become.
As the damp autumn airs blow through the leafless woods,
the earth stars begin to transform themselves.
They open at this time of year to take advantage of the falling rain.
A drip gives them all the energy they need
to propel their spores into the air.
A snow leopard, the rarest of Himalayan animals.
The Planet Earth team spent months
just trying to glimpse a snow leopard, and more months to film one.
How do you conserve a creature that you're lucky even to see?
How do these scientists, or how do these conservationists know
where this animal is, how many there are, and what their behaviour is?
Someone told me that there were 3000 between China and Afghanistan.
Now, I mean, we've had a very tough time identifying three.
There is a threat to its existence,
simply because not enough is known about it.
We really don't know where it thrives.
Because it's isolated, you expect that a lot of wildlife is there.
How much of it and what are the elements affecting it are unknown.
In the distant reaches of Outer Mongolia,
one of the planet's great migrations is underway.
Few people ever see this extraordinary annual event.
Mongolian gazelle. 2 million are thought to live here.
But what will happen to the gazelle in 15 years?
And if they go the way of the saiga, will it matter?
Should we concentrate only on the most important species?
If so, which ones are the most important?
We need every species.
We need a great diversity of species.
We need every species
when you start decreasing the numbers of species,
especially in an environment
which has adapted to a high level of diversity,
you'll start reducing the stability of the area.
I think any extinction that is before its time matters.
If one was to pick two groups, it's at the very top and the very bottom.
You know, the creatures that keep the planet going
and the big organisms that keep our souls and imaginations on fire.
The tiger, probably the best known poem in the English language,
Blake's Tiger Tiger, which
every child can recite and every child understands what it means.
"Tiger Tiger, burning bright, In the forests of the night."
They know that it's not just dark forest.
It's to do with the pulse of life.
If we lose these majestic creatures,
with their sense of power and ancestry and their possibility
of power over us sometimes, then I think
we are diminished by that, as well as the ecosystem.
If you go to a village in India
and you start talking to them about saving the tiger,
people will say to you, "How can you talk about saving the tiger when
"we've got starving people here?"
I think the way conservation was developed over the last 50 years,
we have focused our energy into trying to convince people
that things like tigers are inherently important.
Ultimately, if our movement is not relevant to the lives of real people
dealing with real issues, we're just going to be preaching to the choir.
My concern is the great indifference that most people have toward
the species of lesser creatures
that they'd never noticed or dismissed as bugs and weeds.
That's where the bulk of life on Earth exists.
When you magnify one of these organisms
to human size and approach it as an independent,
highly-complicated entity on Earth,
then you see it as the equal of a large mammal.
The organisms that matter, perhaps most of all, are the plants.
Many of them very unglamorous, hard-working, fantastically common.
Of course, without which,
there would be no way in which the energy of the sun
was translated into available energy for all other organisms.
Each of these creatures plays a role in its ecosystem.
Some of those roles quite important.
If you think in terms of a brick wall,
we are systematically knocking out bricks.
Sooner or later the wall collapses.
This is biodiversity.
The planet's full wide range of life-forms.
And it benefits every single species, including the human one.
The whole planet Earth is a system
and we, human species,
are only a very small part of the system.
There are literally millions of species out there.
We may not know them.
We may not know their value.
But we want to conserve them.
There are a very wide range of practical reasons
as to why we need to conserve this planet's biodiversity.
For a start, all our food ultimately derives from biological systems.
So do a lot of our medicines.
A lot of our industrial products are based upon chemicals
we've taken from nature, for example.
Biodiversity is very much part, therefore, of the global economy.
Very much part of our wellbeing.
I don't think there's a single compelling
reason of an economic kind
that compels us to preserve biological diversity.
Insofar as there are reasons, one says, we want to preserve all this
gene pool because maybe we can use it.
Maybe we can be clever enough to just understand the molecules ourselves.
The second says, we depend on the services ecosystems give - pollinating,
and as we reduce the number of species, we can't be sure they will continue to deliver those services.
Maybe we could be clever enough to live in an impoverished world.
The third reason is a straight ethical reason that says we have a responsibility of stewardship.
And how strong that is depends on the luxury you have to enjoy it.
The head count of the Amur leopard is disturbing.
Because of habitat loss and poaching,
there are just 30 left in the wild.
With extinction so close, conservation becomes desperate.
Here in New Orleans, the Audubon zoo, we have a pair of the Amur leopards.
Our long-term strategy with them is to work with what we call
the species survival plan.
The Amur leopard is one of the high-priority animals.
What's happened recently, and some of the work we're doing involving cloning, has allowed
us to now not necessarily take eggs and sperm but we're able
to take tissue samples from these animals.
Put this tissue sample in a culture and where it was once maybe 100 cells,
we can now grow thousands of cells.
Each one of those cells contains the complete copy of DNA of this animal.
So we can freeze these cells.
Let's say 50 years from now, scientists go into those liquid nitrogen containers and they
pull out the DNA from tigers, Amur leopards, rhinos.
That DNA is alive and it's able to be used to produce
embryos that then could result in babies - in offspring.
So, what I'm hoping we leave in our lifetime is this living library for the future.
50 years from now, the scientists can say, "Oh my gosh, we're about to lose
"this little rusty-spotted cat from Sri Lanka or the Amur leopard, but do you know what? We have the DNA.
"We have the science to at least be able to bring the numbers up of the species so they won't go extinct."
We have to be careful about producing
something which is a facsimile of a wild animal,
from something which is able to exist in the wild.
One of the problems of keeping animals in conventional zoos, the
selective pressures are very great
and you're actually moving that animal towards domestication.
It may look the same, but it may not have the skills
or the behavioural attributes or physiology to survive in the wild.
You know it's funny when people say, we may be playing God, we may be
controlling and taking charge of kind of these species' destinies.
But you know, man played God a long time ago.
I think, and I believe, God gave us stewardship over these animals.
What we're doing is using the capabilities that we have
as humans to not destroy animals any longer but to try to protect them,
to preserve them and bring them back.
Subtitles by Red Bee Media Ltd
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A selection of clips taken from BBC programmes about Darwin and evolutionary biology. The programme includes material on adaptation and natural selection.