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In 2009, a new species of spider was identified. | 0:00:23 | 0:00:28 | |
A spider with superpowers. | 0:00:32 | 0:00:35 | |
It was named exactly 150 years | 0:00:44 | 0:00:46 | |
after the publication of Darwin's On The Origin Of Species, | 0:00:46 | 0:00:49 | |
in which he explained why life on Earth is so diverse and so complex. | 0:00:49 | 0:00:56 | |
Darwin's theory of evolution by natural selection | 0:01:02 | 0:01:05 | |
was built on the work of naturalists who were discovering | 0:01:05 | 0:01:09 | |
thousands of new species across the world. | 0:01:09 | 0:01:13 | |
That process of finding species new to science and naming them | 0:01:17 | 0:01:20 | |
continues to this day. | 0:01:20 | 0:01:22 | |
And it's recognised in the name of this newly discovered arachnid. | 0:01:22 | 0:01:25 | |
Darwin's bark spider. | 0:01:28 | 0:01:30 | |
The spider occupies a unique niche. | 0:01:35 | 0:01:38 | |
It can hunt where no other spider can. | 0:01:38 | 0:01:41 | |
That spider creates the largest webs found anywhere on Earth. | 0:01:44 | 0:01:47 | |
In order to do that, it has to produce the strongest silk | 0:01:47 | 0:01:51 | |
of any spider. They can span over 25 metres across lakes and rivers. | 0:01:51 | 0:01:56 | |
And actually, no-one knows how they get their webs | 0:01:56 | 0:01:59 | |
across such a large distance. | 0:01:59 | 0:02:01 | |
But Darwin's bark spider | 0:02:09 | 0:02:10 | |
is one of thousands of unique species of animals and plants | 0:02:10 | 0:02:14 | |
that you find in Madagascar. | 0:02:14 | 0:02:16 | |
The rainforests here are one of the most bio-diverse places | 0:02:20 | 0:02:23 | |
on the planet. | 0:02:23 | 0:02:25 | |
And each year, more discoveries are made | 0:02:31 | 0:02:33 | |
as researchers try to understand why this tiny corner of the universe | 0:02:33 | 0:02:38 | |
is so prolific. | 0:02:38 | 0:02:41 | |
All of these living things were found within a five-minute walk | 0:02:41 | 0:02:44 | |
of this field station. And the diversity is remarkable. | 0:02:44 | 0:02:49 | |
There's a chameleon there. These are orchids. | 0:02:49 | 0:02:53 | |
This big green leaf is a traveller's palm. | 0:02:53 | 0:02:55 | |
There are four species of mushroom on that branch alone. | 0:02:55 | 0:02:59 | |
Across Madagascar, there are over 14,000 species of plants, | 0:03:06 | 0:03:11 | |
there are hundreds of species of mammals, birds and reptiles | 0:03:11 | 0:03:15 | |
and over 90% of them are unique to this island. | 0:03:15 | 0:03:19 | |
How could it be that so many diverse living things, | 0:03:31 | 0:03:35 | |
so beautifully adapted to their environment, could've emerged | 0:03:35 | 0:03:38 | |
from a universe that's governed by a simple set of natural laws? | 0:03:38 | 0:03:43 | |
The fact that we know the answer to that question | 0:03:49 | 0:03:51 | |
is one of the greatest achievements in science. | 0:03:51 | 0:03:55 | |
In this film, I want to explore how these endless forms, most beautiful, | 0:03:55 | 0:04:00 | |
have emerged from a lifeless cosmos. | 0:04:00 | 0:04:03 | |
Africa. A whole continent full of creatures utterly different | 0:04:51 | 0:04:56 | |
from those in Madagascar. | 0:04:56 | 0:04:58 | |
But the diversity of life doesn't stop at what you see. | 0:05:03 | 0:05:08 | |
Because within each individual lies another world of complexity. | 0:05:08 | 0:05:14 | |
This, believe it or not, is the top predator in Africa. | 0:05:41 | 0:05:45 | |
Or she will be when she's older. | 0:05:45 | 0:05:47 | |
She's only about eight weeks old now. | 0:05:47 | 0:05:50 | |
Her body is built from a host of different molecules | 0:05:52 | 0:05:55 | |
and by far the most diverse group are known as proteins. | 0:05:55 | 0:06:00 | |
We can see the proteins here. | 0:06:01 | 0:06:03 | |
Those claws, so vital for a lion's survival, | 0:06:03 | 0:06:08 | |
are made of a protein called keratin. | 0:06:08 | 0:06:10 | |
Her eyes, also absolutely vital for her survival, | 0:06:10 | 0:06:13 | |
have a protein called opsin which is bound to a pigment | 0:06:13 | 0:06:17 | |
to make structures called rhodopsins which allow her to see in colour | 0:06:17 | 0:06:21 | |
and also to allow her to see very well at night when she's hunting. | 0:06:21 | 0:06:25 | |
There are also proteins in her muscles... | 0:06:28 | 0:06:31 | |
..myosin and actin, which are the things that allow her to run away. | 0:06:32 | 0:06:37 | |
The proteins in a lion come in countless different forms. | 0:06:46 | 0:06:50 | |
But they all share something in common. | 0:06:53 | 0:06:56 | |
A backbone of carbon. | 0:06:56 | 0:06:59 | |
An atom that's able to form long, complex molecules. | 0:07:01 | 0:07:05 | |
Of all the 92 elements, there really is only one | 0:07:09 | 0:07:13 | |
which has that appetite for bonding its four electrons - | 0:07:13 | 0:07:19 | |
to share them with other molecules. | 0:07:19 | 0:07:21 | |
Carbon will share those electrons with nitrogen, oxygen, hydrogen, | 0:07:21 | 0:07:27 | |
and critically, with other carbons, | 0:07:27 | 0:07:29 | |
to build up these immensely complex chains, | 0:07:29 | 0:07:32 | |
the amino acids and the proteins | 0:07:32 | 0:07:34 | |
which are the building blocks of life. | 0:07:34 | 0:07:37 | |
So to understand our planet's endless diversity, | 0:07:39 | 0:07:41 | |
we must begin by considering this life-giving element. | 0:07:41 | 0:07:46 | |
I've got a few scratches now because of you! Because of your proteins! | 0:07:47 | 0:07:51 | |
After all, to build a lion, you must first build carbon. | 0:07:54 | 0:07:59 | |
And that's a story that stretches back to a time | 0:07:59 | 0:08:02 | |
long before there were even stars in the universe. | 0:08:02 | 0:08:05 | |
13.5 billion years ago, | 0:08:13 | 0:08:15 | |
just a few hundred million years after the Big Bang, | 0:08:15 | 0:08:18 | |
the universe was a carbon-free zone. | 0:08:18 | 0:08:22 | |
An infinite, sterile gloom of hydrogen and helium clouds. | 0:08:24 | 0:08:29 | |
Until, one day, | 0:08:31 | 0:08:33 | |
those vast clouds began to collapse under the force of gravity. | 0:08:33 | 0:08:36 | |
Long before the solar system, Earth or life existed... | 0:08:42 | 0:08:46 | |
..the first stars were born. | 0:08:47 | 0:08:49 | |
The birth of the first stars | 0:09:08 | 0:09:10 | |
did much more than illuminate the universe, | 0:09:10 | 0:09:13 | |
because that set in train a sequence of events | 0:09:13 | 0:09:16 | |
which is necessary for the existence of life in the universe. | 0:09:16 | 0:09:20 | |
And we can still see that process playing out in the universe today. | 0:09:28 | 0:09:31 | |
This is the brand-new South African Large Telescope. | 0:09:37 | 0:09:41 | |
TECHNICIAN: Number three amps, gear right, gear box. | 0:09:41 | 0:09:44 | |
Its mirror is 11 metres wide, | 0:09:47 | 0:09:50 | |
making it the largest optical telescope | 0:09:50 | 0:09:52 | |
in the southern hemisphere. | 0:09:52 | 0:09:54 | |
And it recently helped to pin down what's happening in an object | 0:09:56 | 0:10:00 | |
some 650 million light years from Earth. | 0:10:00 | 0:10:02 | |
This beautiful, almost lifelike system is known simply as the Bird. | 0:10:09 | 0:10:16 | |
It's the spectacular result | 0:10:17 | 0:10:19 | |
of what we used to think was two galaxies colliding. | 0:10:19 | 0:10:22 | |
It's events happening in the head of the Bird | 0:10:26 | 0:10:29 | |
that are most interesting from a perspective of life in the universe. | 0:10:29 | 0:10:32 | |
Because the head is formed by another galaxy, | 0:10:32 | 0:10:36 | |
a third galaxy, an island of billions and billions of stars, | 0:10:36 | 0:10:40 | |
colliding with two galaxies that form the wings and the body | 0:10:40 | 0:10:44 | |
at a speed of around 250 miles a second. | 0:10:44 | 0:10:48 | |
The turbulence, the disturbance, | 0:10:48 | 0:10:51 | |
that that creates is causing many new stars to be formed. | 0:10:51 | 0:10:55 | |
These stars begin their lives by burning hydrogen, | 0:11:01 | 0:11:05 | |
to produce ever more helium. | 0:11:05 | 0:11:07 | |
But as they age, as the hydrogen runs out, they turn to this helium. | 0:11:09 | 0:11:14 | |
The temperature at their core rises | 0:11:16 | 0:11:19 | |
increasing the chances of three helium nuclei | 0:11:19 | 0:11:22 | |
fusing together to form a new element - carbon. | 0:11:22 | 0:11:26 | |
That process has been going on | 0:11:29 | 0:11:31 | |
for almost the entire history of the universe, | 0:11:31 | 0:11:35 | |
back 13 billion years, and it's the formation of stars | 0:11:35 | 0:11:39 | |
that is the vital first step in the formation of life, | 0:11:39 | 0:11:43 | |
because stars produce the heavy elements in the universe | 0:11:43 | 0:11:47 | |
including carbon. | 0:11:47 | 0:11:49 | |
From the universe's earliest times, | 0:11:56 | 0:11:59 | |
carbon has been created inside ageing stars. | 0:11:59 | 0:12:03 | |
And over time, this carbon has built up, | 0:12:08 | 0:12:11 | |
drifting through the cosmos as dust... | 0:12:11 | 0:12:14 | |
..until some of it was caught up | 0:12:16 | 0:12:18 | |
in the formation of a planet called Earth. | 0:12:18 | 0:12:21 | |
And it's here that we can see this ancient carbon | 0:12:27 | 0:12:30 | |
brought vividly to life. | 0:12:30 | 0:12:32 | |
Today, the universe is old enough | 0:12:47 | 0:12:50 | |
that countless stars have lived and died. | 0:12:50 | 0:12:52 | |
So, there's been plenty of time to synthesise | 0:12:52 | 0:12:55 | |
the primordial hydrogen and helium into the heavy elements. | 0:12:55 | 0:12:59 | |
The question now is, how does that carbon get into the web of life? | 0:13:01 | 0:13:07 | |
Well, today, it enters via one ingredient | 0:13:07 | 0:13:11 | |
and I'm going to measure it using this balloon. | 0:13:11 | 0:13:15 | |
The ingredient is carbon dioxide, | 0:13:22 | 0:13:24 | |
which plays a key role in photosynthesis. | 0:13:24 | 0:13:27 | |
Each night the carbon dioxide concentration increases, | 0:13:30 | 0:13:34 | |
filling the air around the leaves at the top of the trees. | 0:13:34 | 0:13:38 | |
This balloon has a carbon dioxide monitor in it | 0:13:41 | 0:13:45 | |
which is going to measure the change in the levels of CO2 | 0:13:45 | 0:13:48 | |
at the top of the forest canopy as night turns to day. | 0:13:48 | 0:13:52 | |
As the sun rises, the trees begin to photosynthesise. | 0:13:59 | 0:14:04 | |
At 6pm last night, just after sunset, | 0:14:06 | 0:14:09 | |
the concentration was around 350 parts per million. | 0:14:09 | 0:14:13 | |
Around 10pm, around four hours after sunset, | 0:14:14 | 0:14:17 | |
the concentration had risen to about 400 parts per million. | 0:14:17 | 0:14:22 | |
Now, at about midday, the concentration's back down | 0:14:23 | 0:14:27 | |
to about 345 parts per million. | 0:14:27 | 0:14:31 | |
So that's a variation over a period of about 18 hours of 10% | 0:14:31 | 0:14:36 | |
in the concentration of carbon dioxide, | 0:14:36 | 0:14:40 | |
just in that piece of atmosphere at the top of the forest canopy. | 0:14:40 | 0:14:43 | |
What you are seeing there is photosynthesis in action. | 0:14:43 | 0:14:47 | |
Every day, across the planet, | 0:14:52 | 0:14:55 | |
photosynthesis uses sunlight to turn carbon dioxide and water | 0:14:55 | 0:15:00 | |
into simple sugars. | 0:15:00 | 0:15:02 | |
The overwhelming majority of the carbon | 0:15:06 | 0:15:08 | |
is locked up inside long chains of sugar molecules | 0:15:08 | 0:15:12 | |
called cellulose and lignin. | 0:15:12 | 0:15:15 | |
Lignin is the stuff that gives wood its strength. | 0:15:19 | 0:15:24 | |
So, in this form, remember, that is most of it, | 0:15:24 | 0:15:27 | |
it is very difficult indeed for animals to access. | 0:15:27 | 0:15:30 | |
For the energy and nutrients locked away in these long carbon chains | 0:15:35 | 0:15:39 | |
to move through the food web, they must be broken down. | 0:15:39 | 0:15:43 | |
The best place to see that process in action is out on the open plain. | 0:15:48 | 0:15:53 | |
It's one vast larder for all manner of organisms. | 0:15:55 | 0:15:59 | |
By far the most effective harvester of carbon | 0:16:05 | 0:16:08 | |
is actually one of the smallest creatures on the savanna. | 0:16:08 | 0:16:13 | |
Termites are social insects, working together to form | 0:16:18 | 0:16:21 | |
a characteristic sight, seen all over the bush. | 0:16:21 | 0:16:25 | |
That's a termite mound. Actually, it's the tip of the iceberg. | 0:16:25 | 0:16:29 | |
The termite city extends way beyond that underground. | 0:16:29 | 0:16:34 | |
And its function is fascinating. | 0:16:34 | 0:16:37 | |
It's essentially an air-conditioning system. | 0:16:37 | 0:16:40 | |
What it does is maintain specific conditions inside the mound - | 0:16:40 | 0:16:45 | |
the conditions of the rainforest. | 0:16:45 | 0:16:47 | |
When the termites first colonised the savanna 30 million years ago, | 0:16:49 | 0:16:54 | |
they brought the rainforest with them | 0:16:54 | 0:16:57 | |
to support a form of life that was already wonderfully adapted | 0:16:57 | 0:17:01 | |
to living off dead wood. | 0:17:01 | 0:17:03 | |
This is what these termite mounds are all about. | 0:17:03 | 0:17:06 | |
Can you see those structures, those white honeycomb-like structures? | 0:17:06 | 0:17:11 | |
Those are called fungal combs. | 0:17:11 | 0:17:14 | |
They're wood pulp and possibly bits of dead grass | 0:17:14 | 0:17:17 | |
that the termites bring in and build into that structure. | 0:17:17 | 0:17:21 | |
And the reason the conditions have to be the same as the rainforest | 0:17:21 | 0:17:24 | |
is because they grow a particular genus of fungus called termitomyces | 0:17:24 | 0:17:31 | |
around those honeycombs. | 0:17:31 | 0:17:34 | |
The job of that fungus is to break down the lignin | 0:17:38 | 0:17:42 | |
and cellulose inside the wood | 0:17:42 | 0:17:43 | |
and convert it into a form that the termites can eat, | 0:17:43 | 0:17:46 | |
which you can see there, the little white nodules, | 0:17:46 | 0:17:50 | |
just present on the honeycomb structure. | 0:17:50 | 0:17:54 | |
The termites lack the enzymes to break down the wood efficiently, | 0:17:57 | 0:18:02 | |
so they have become farmers, tending to one giant social stomach. | 0:18:02 | 0:18:07 | |
There's a very intense relationship between the termites and the fungus. | 0:18:09 | 0:18:14 | |
You don't find that fungus anywhere else in the world | 0:18:14 | 0:18:18 | |
as far as we know, other than inside termite mounds. | 0:18:18 | 0:18:22 | |
It's thought that up to 90% of the carbon locked up in lignin | 0:18:24 | 0:18:31 | |
in this part of Africa is released back into the food chain again, | 0:18:31 | 0:18:35 | |
solely by those termites | 0:18:35 | 0:18:38 | |
and that fungus. | 0:18:38 | 0:18:39 | |
So the termites deal with most of the lignin, | 0:19:01 | 0:19:04 | |
but that still leaves a vast store of carbon in the form of cellulose. | 0:19:04 | 0:19:09 | |
Across Africa, herds of mammals graze on grasses and leaves, | 0:19:10 | 0:19:15 | |
turning the cellulose into meat. | 0:19:15 | 0:19:18 | |
Many are a type of mammal known as a ruminant... | 0:19:22 | 0:19:24 | |
..the largest of which is one of the easiest animals to spot on safari. | 0:19:25 | 0:19:30 | |
There's a giraffe there as well. | 0:19:30 | 0:19:32 | |
Giraffes live off a diet similar to termites. They eat cellulose. | 0:20:01 | 0:20:07 | |
Primarily the tops of the acacia trees | 0:20:07 | 0:20:10 | |
that you see scattering the African savanna. | 0:20:10 | 0:20:13 | |
And they face that same problem, | 0:20:13 | 0:20:15 | |
they've got to break those difficult carbon bonds down | 0:20:15 | 0:20:19 | |
and they've come up with a very similar solution | 0:20:19 | 0:20:21 | |
which is to cultivate bacteria and fungi. | 0:20:21 | 0:20:25 | |
But they do it inside their stomachs and ruminants like giraffes | 0:20:25 | 0:20:30 | |
have had to build a very complex system in order to do that. | 0:20:30 | 0:20:34 | |
They've got four stomachs, | 0:20:34 | 0:20:36 | |
one of them contains their culture of bacteria and fungi, | 0:20:36 | 0:20:39 | |
and they allow them to digest that difficult cellulose. | 0:20:39 | 0:20:44 | |
Even with all this hardware, | 0:20:48 | 0:20:50 | |
ruminants must feed for over two thirds of the day. | 0:20:50 | 0:20:54 | |
But there are other creatures here that have found a short cut, | 0:20:57 | 0:21:02 | |
after all, if plant fibres are hard to digest, | 0:21:02 | 0:21:06 | |
why not let someone else do the work and simply steal a meal? | 0:21:06 | 0:21:10 | |
It's coming for us. | 0:21:17 | 0:21:20 | |
Oh, my God... | 0:21:20 | 0:21:21 | |
ENGINE STARTS | 0:21:29 | 0:21:31 | |
Look what we've just found. | 0:21:34 | 0:21:37 | |
We were out looking for giraffe this morning, | 0:21:37 | 0:21:39 | |
and we found about ten of them over there, | 0:21:39 | 0:21:42 | |
but in looking for the giraffe, we've just found a leopard. | 0:21:42 | 0:21:45 | |
This is one of the top predators out here. | 0:21:47 | 0:21:50 | |
He's got very little to fear apart from other leopards and maybe lions. | 0:21:50 | 0:21:54 | |
He's having a good look, he certainly doesn't care about us. | 0:21:54 | 0:21:58 | |
He's around two years old and at the moment, | 0:22:03 | 0:22:05 | |
he doesn't have his own territory, he's too young for that. | 0:22:05 | 0:22:10 | |
So he's lying low. | 0:22:10 | 0:22:12 | |
He'll have to make about two kills a week, to stay in good condition. | 0:22:17 | 0:22:22 | |
So, maybe he'll catch an impala every three to four days, | 0:22:22 | 0:22:27 | |
and he's obviously doing that. | 0:22:27 | 0:22:29 | |
Because, look at him! | 0:22:32 | 0:22:34 | |
-He's looking for protein. -He likes your boom. > | 0:22:37 | 0:22:40 | |
And I'm a little bit worried, cos I'm protein! | 0:22:40 | 0:22:43 | |
-Oh, wow. -He's after your boom, George. > | 0:22:45 | 0:22:47 | |
He's coming really close to us | 0:22:49 | 0:22:51 | |
because he's after the sound man's boom pole. | 0:22:51 | 0:22:54 | |
Which is...oh! | 0:22:54 | 0:22:56 | |
-That's incredible. -RUMBLING MICROPHONE DISTORTION | 0:22:56 | 0:22:59 | |
I just... | 0:22:59 | 0:23:01 | |
-HE LAUGHS -He's taken it... | 0:23:01 | 0:23:03 | |
From its origin in the death of stars... | 0:23:19 | 0:23:23 | |
..its capture by plants... | 0:23:29 | 0:23:32 | |
..through insects, mammals and on. | 0:23:37 | 0:23:40 | |
The carbon cycle is the real circle of life. | 0:23:48 | 0:23:52 | |
Out there tonight, the relentless recycling of carbon | 0:23:58 | 0:24:02 | |
through the food chain will continue. | 0:24:02 | 0:24:04 | |
As night falls, you can almost sense it - the change in the sounds | 0:24:06 | 0:24:10 | |
and the atmosphere. | 0:24:10 | 0:24:12 | |
Some will die, so that others can live, | 0:24:15 | 0:24:19 | |
as carbon leaps from branch to branch | 0:24:19 | 0:24:22 | |
across the great tree of life. | 0:24:22 | 0:24:24 | |
And guiding it along its way is just one very special form of chemistry. | 0:24:26 | 0:24:32 | |
Every living thing is just a temporary home | 0:24:32 | 0:24:35 | |
for carbon atoms that existed long before there was life on Earth | 0:24:35 | 0:24:39 | |
and will exist long after Africa and Earth are gone. | 0:24:39 | 0:24:43 | |
But, the pattern of life, | 0:24:49 | 0:24:51 | |
the information needed to build a zebra, or a tree, | 0:24:51 | 0:24:56 | |
or a human being or a lion persists. | 0:24:56 | 0:25:00 | |
It's passed on from generation to generation, in a molecule. | 0:25:00 | 0:25:04 | |
A helical molecule with a backbone of carbon called DNA. | 0:25:04 | 0:25:09 | |
MUSIC: "Atmosphere" by Joy Division | 0:25:29 | 0:25:31 | |
There was a time when Earth appeared empty. | 0:25:35 | 0:25:39 | |
# Walk | 0:25:39 | 0:25:43 | |
# In silence | 0:25:43 | 0:25:46 | |
# Don't walk away | 0:25:46 | 0:25:51 | |
# In silence... # | 0:25:51 | 0:25:52 | |
Yet despite appearances, 3.8 billion years ago | 0:25:52 | 0:25:56 | |
life was already under way, in the form of tiny living specks | 0:25:56 | 0:26:01 | |
that probably all shared the same biochemistry. | 0:26:01 | 0:26:04 | |
We know that every living thing on the planet today - | 0:26:05 | 0:26:08 | |
so every piece of food you eat, every animal you've seen, | 0:26:08 | 0:26:12 | |
everyone you've ever known or will know, | 0:26:12 | 0:26:15 | |
in fact every living thing that WILL ever exist on this planet - | 0:26:15 | 0:26:19 | |
was descended from that one speck. | 0:26:19 | 0:26:22 | |
# Walk | 0:26:23 | 0:26:27 | |
# In silence... # | 0:26:27 | 0:26:31 | |
We call it the last universal common ancestor, or LUCA. | 0:26:31 | 0:26:35 | |
So, just as the universe had its origin at the Big Bang, | 0:26:35 | 0:26:39 | |
all life on this planet had its origin in that one moment. | 0:26:39 | 0:26:44 | |
Less than a billion years after its formation, | 0:26:49 | 0:26:52 | |
there was already life on Earth. | 0:26:52 | 0:26:54 | |
It's possible that some of it used biochemistry | 0:27:00 | 0:27:03 | |
utterly different from the life we see today. | 0:27:03 | 0:27:07 | |
If so, it has long been extinct. | 0:27:07 | 0:27:10 | |
It's also possible that the first life may not have been cellular - | 0:27:13 | 0:27:17 | |
just living chemistry in the porous rocks of some ancient ocean. | 0:27:17 | 0:27:22 | |
We're not sure, but what's certain is that one day, | 0:27:22 | 0:27:27 | |
a population of organisms showed up with biochemistry that we WOULD recognise. | 0:27:27 | 0:27:32 | |
This was LUCA. | 0:27:34 | 0:27:37 | |
The first expression of a form of life that would in time | 0:27:37 | 0:27:41 | |
throw up a group of humans who left their mark in this part of Africa. | 0:27:41 | 0:27:46 | |
Now, we don't know what LUCA looked like, | 0:27:50 | 0:27:53 | |
we don't know precisely where it lived or how it lived. | 0:27:53 | 0:27:57 | |
But we do know this. | 0:27:57 | 0:27:59 | |
If you start to trace my ancestral line back to my parents, | 0:27:59 | 0:28:04 | |
to their parents, to their parents, to their parents, | 0:28:04 | 0:28:08 | |
all the way back through geological timescales | 0:28:08 | 0:28:11 | |
over hundreds of thousands of millions and billions of years, | 0:28:11 | 0:28:15 | |
there will be an unbroken line from me all the way back to LUCA. | 0:28:15 | 0:28:21 | |
We know that, because every living thing on the planet today | 0:28:25 | 0:28:29 | |
shares the same biochemistry. | 0:28:29 | 0:28:32 | |
We all have DNA. It's made of the same bases, A, C, T and G. | 0:28:32 | 0:28:38 | |
They code for the same amino acids. | 0:28:38 | 0:28:40 | |
Those amino acids build the same proteins, which do very | 0:28:40 | 0:28:44 | |
similar jobs, whether you're a plant, a bacterium, or a bipedal hominid, like me. | 0:28:44 | 0:28:50 | |
So all life uses the same fundamental biology... | 0:28:55 | 0:28:59 | |
..those four bases, A, C, T and G, | 0:29:01 | 0:29:04 | |
which code for just 20 amino acids, | 0:29:04 | 0:29:07 | |
which in turn build each and every one of life's proteins. | 0:29:07 | 0:29:12 | |
Be you bacteria, plant, bug or beast, | 0:29:16 | 0:29:20 | |
your design comes from your DNA. | 0:29:20 | 0:29:23 | |
So it's this molecule that must hold the key to understanding why life today is so diverse. | 0:29:25 | 0:29:32 | |
We now know that the answer to the question, | 0:29:35 | 0:29:37 | |
"Why is life on Earth so varied?" is actually the answer to | 0:29:37 | 0:29:41 | |
the question, "Why is the DNA molecule itself so varied?" | 0:29:41 | 0:29:45 | |
What are the natural processes that cause the structure of DNA to change? | 0:29:45 | 0:29:51 | |
Well, part of the answer actually doesn't lie on Earth at all. | 0:29:51 | 0:29:55 | |
It lies up there amongst the stars. | 0:29:55 | 0:29:58 | |
And I can show you what I mean, using this, | 0:29:58 | 0:30:01 | |
which is a cloud chamber, a piece of apparatus that has a unique place | 0:30:01 | 0:30:07 | |
in the history of physics. | 0:30:07 | 0:30:10 | |
I'm going to cool it down using dry ice, frozen carbon dioxide, | 0:30:10 | 0:30:14 | |
just below -70 degrees Celsius. | 0:30:14 | 0:30:17 | |
I'll put the top on. | 0:30:23 | 0:30:25 | |
-HIGH-PITCHED SQUEAKING -Hear that? | 0:30:25 | 0:30:27 | |
That's the metal at the bottom of the tank cooling down very rapidly to -70. | 0:30:28 | 0:30:34 | |
The cloud chamber works by having a super-saturated | 0:30:36 | 0:30:41 | |
vapour of alcohol inside the chamber. | 0:30:41 | 0:30:44 | |
Plenty on there... | 0:30:44 | 0:30:46 | |
Now, I want to get that alcohol, I want to boil it off, | 0:30:47 | 0:30:50 | |
to get the vapour into the chamber. | 0:30:50 | 0:30:52 | |
So I'm going to put a hot water bottle on top. | 0:30:52 | 0:30:54 | |
This is the first genuine particle physics detector. | 0:30:54 | 0:30:58 | |
It's the piece of apparatus that first saw antimatter. | 0:30:58 | 0:31:02 | |
And it really does consist only of a fish tank, some alcohol, | 0:31:02 | 0:31:08 | |
a bit of paper, and a hot water bottle. | 0:31:08 | 0:31:10 | |
There, look at that. Do you see that? | 0:31:32 | 0:31:34 | |
Cloud vapour trail. | 0:31:34 | 0:31:37 | |
That's a cosmic ray. | 0:31:39 | 0:31:41 | |
That was initiated by a particle, probably a proton, | 0:31:41 | 0:31:46 | |
that hit the Earth's atmosphere. | 0:31:46 | 0:31:48 | |
It almost certainly originated outside our solar system | 0:31:52 | 0:31:56 | |
and was accelerated by the magnetic fields of our galaxy. | 0:31:56 | 0:31:59 | |
It may even have begun its life BEYOND our galaxy. | 0:31:59 | 0:32:04 | |
Now, imagine if one of those hits the DNA of a living thing. | 0:32:18 | 0:32:24 | |
What that will do is cause a mutation. | 0:32:24 | 0:32:27 | |
That mutation may be detrimental, or, | 0:32:27 | 0:32:31 | |
very, very occasionally it might be beneficial. | 0:32:31 | 0:32:34 | |
And I think it's quite wonderful to imagine that maybe | 0:32:38 | 0:32:44 | |
one of the key mutations that was selected for over the millennia | 0:32:44 | 0:32:48 | |
that led to some trait in ME | 0:32:48 | 0:32:51 | |
was caused by some particle that began its life perhaps | 0:32:51 | 0:32:55 | |
in a massive supernova explosion, perhaps outside our galaxy | 0:32:55 | 0:33:00 | |
and went and hit the DNA of something | 0:33:00 | 0:33:03 | |
and caused some kind of beneficial mutation. | 0:33:03 | 0:33:07 | |
We don't know, but you can dream, can't you? | 0:33:07 | 0:33:09 | |
Mutations are an inevitable part of living on a planet like Earth. | 0:33:17 | 0:33:21 | |
They're the first hint at how DNA and the genes | 0:33:24 | 0:33:28 | |
that code for every living thing | 0:33:28 | 0:33:30 | |
change from generation to generation. | 0:33:30 | 0:33:34 | |
Mutations are the spring | 0:33:50 | 0:33:52 | |
from which innovation in the living world flows. | 0:33:52 | 0:33:56 | |
But cosmic rays are not the only way in which DNA can be altered. | 0:33:59 | 0:34:05 | |
There's natural background radiation from the rocks, | 0:34:05 | 0:34:08 | |
there's the action of chemicals and free radicals. | 0:34:08 | 0:34:11 | |
There can be errors when the code is copied. | 0:34:11 | 0:34:15 | |
And then all those changes can be shuffled by sex, and indeed | 0:34:15 | 0:34:19 | |
whole pieces of the code can be transferred from species to species. | 0:34:19 | 0:34:24 | |
So, bit by bit, in tiny steps from generation to generation, | 0:34:24 | 0:34:29 | |
the code is constantly randomly changing. | 0:34:29 | 0:34:33 | |
Now, whilst there's no doubt that random mutation does alter DNA, | 0:34:36 | 0:34:41 | |
evolution is anything but random. It can't be, | 0:34:41 | 0:34:46 | |
because the chances of something with DNA as complex as this | 0:34:46 | 0:34:50 | |
appearing by luck alone are vanishingly small. | 0:34:50 | 0:34:53 | |
Imagine you just changed one position in the code at random, | 0:34:54 | 0:34:58 | |
a random mutation. | 0:34:58 | 0:35:00 | |
There are four letters, A, T, C and G, | 0:35:00 | 0:35:02 | |
so there are four possible combinations. | 0:35:02 | 0:35:05 | |
If there are two places in the code, | 0:35:05 | 0:35:07 | |
there are four combinations for each one. So that makes 16. | 0:35:07 | 0:35:12 | |
If there are three, then there are 64 possibilities. | 0:35:12 | 0:35:15 | |
By the time you get to a code with 150 letters in it, | 0:35:15 | 0:35:19 | |
then there are more possible combinations in the code | 0:35:19 | 0:35:23 | |
than there are atoms in the observable universe. | 0:35:23 | 0:35:26 | |
Now, a hippo has a code | 0:35:29 | 0:35:32 | |
with around three billion different letters. | 0:35:32 | 0:35:36 | |
So the number of combinations of those letters, the chances of | 0:35:36 | 0:35:41 | |
producing that code at random, are absolutely, infinitesimally small. | 0:35:41 | 0:35:47 | |
It's impossible. | 0:35:47 | 0:35:48 | |
So there must be a non-random element to evolution... | 0:35:53 | 0:35:57 | |
..a natural process, which greatly restricts this | 0:35:58 | 0:36:02 | |
universe of possibilities, and shapes the outcome. | 0:36:02 | 0:36:05 | |
We call it natural selection. | 0:36:06 | 0:36:09 | |
And to see it in action, let's return to where we began | 0:36:10 | 0:36:14 | |
on the island of Madagascar. | 0:36:14 | 0:36:16 | |
Around 65 million years ago, a group of seafarers were nearing | 0:36:46 | 0:36:49 | |
the end of a long journey across the Indian Ocean. | 0:36:49 | 0:36:53 | |
These were accidental travellers, a group of creatures from Africa, | 0:36:54 | 0:36:58 | |
trapped on a natural raft and carried by the ocean currents. | 0:36:58 | 0:37:03 | |
The land they found was virgin green territory. | 0:37:11 | 0:37:14 | |
Plants, insects, reptiles and birds had established themselves, | 0:37:16 | 0:37:21 | |
but there were none of their own kind. | 0:37:21 | 0:37:23 | |
They were caught up in a saga that tells of the great | 0:37:26 | 0:37:29 | |
shifting of Earth's continental plates. | 0:37:29 | 0:37:32 | |
It's impossible to understand the diversity of life on Earth today | 0:37:38 | 0:37:42 | |
without understanding the shifting geography of our planet. | 0:37:42 | 0:37:46 | |
Here's a map of Earth's southern hemisphere as it was | 0:37:46 | 0:37:50 | |
150 million years ago, and you see | 0:37:50 | 0:37:52 | |
it's dominated by a single landmass called Gondwana. | 0:37:52 | 0:37:56 | |
And then, 90 million years ago, | 0:37:56 | 0:37:59 | |
Gondwana had begun to break up, to separate, | 0:37:59 | 0:38:03 | |
into something that looks quite recognisably like Africa, | 0:38:03 | 0:38:07 | |
and these two islands, Madagascar and India. | 0:38:07 | 0:38:11 | |
Now, subsequently India has drifted northwards | 0:38:11 | 0:38:14 | |
and bumped into Eurasia, raising the Himalayas. | 0:38:14 | 0:38:17 | |
But, crucially, Madagascar has remained isolated. | 0:38:17 | 0:38:22 | |
It's been an island surrounded by ocean for almost 90 million years. | 0:38:22 | 0:38:27 | |
So, when those seafarers arrived on their raft of trees and twigs and leaves, | 0:38:35 | 0:38:41 | |
they had a blank canvas - two, three, | 0:38:41 | 0:38:45 | |
maybe even a single pregnant individual | 0:38:45 | 0:38:48 | |
had a whole island to roam across. | 0:38:48 | 0:38:52 | |
And over 65 million years, they have blossomed into hundreds and | 0:38:52 | 0:38:56 | |
thousands of individuals, and become Madagascar's most iconic animals. | 0:38:56 | 0:39:01 | |
Finding the descendants of those ancient mariners is not easy. | 0:39:43 | 0:39:47 | |
But local guide Joseph has been tracking them for years. | 0:39:48 | 0:39:51 | |
And he's going to help me find them. | 0:39:51 | 0:39:53 | |
There at the top of the tree is an indri, | 0:40:13 | 0:40:15 | |
which is the largest lemur in Madagascar. | 0:40:15 | 0:40:18 | |
He's just sat there watching us quietly at the moment. | 0:40:21 | 0:40:25 | |
This lemur here is a very special lemur. | 0:40:30 | 0:40:32 | |
He has a name, he's called David. | 0:40:32 | 0:40:35 | |
After Sir David Attenborough. | 0:40:37 | 0:40:40 | |
LEMUR SCREECHES | 0:40:48 | 0:40:51 | |
LEMUR SCREECHES | 0:40:57 | 0:40:59 | |
Now, we can only do this because | 0:41:09 | 0:41:11 | |
Joseph has spent a lot of time with these lemurs. | 0:41:11 | 0:41:15 | |
So they trust him. And therefore, it seems, they trust me. | 0:41:16 | 0:41:22 | |
Its enormous hands! | 0:41:35 | 0:41:38 | |
The reason, it's thought, that we find lemurs here in Madagascar and Madagascar alone | 0:41:40 | 0:41:46 | |
is because there are no simians, there are no chimpanzees, | 0:41:46 | 0:41:51 | |
none of my ancestral family, | 0:41:51 | 0:41:55 | |
dating back tens of millions of years, to out-compete them. | 0:41:55 | 0:41:58 | |
So what's thought to have happened is that around 65 million years ago | 0:41:58 | 0:42:04 | |
one of the lemur's ancestors | 0:42:04 | 0:42:09 | |
managed to sail across the Mozambique Channel, and landed here. | 0:42:09 | 0:42:14 | |
There were none of those competitors here, | 0:42:14 | 0:42:17 | |
and so the lemurs have flourished ever since. | 0:42:17 | 0:42:19 | |
There are now over 90 species of lemur, or subspecies, | 0:42:21 | 0:42:25 | |
in Madagascar, | 0:42:25 | 0:42:27 | |
and no species of my lineage, the simians. | 0:42:27 | 0:42:31 | |
LEMUR SCREECHES | 0:42:38 | 0:42:40 | |
Over a vast sweep of time, the lemurs have diversified | 0:42:45 | 0:42:50 | |
to fill all manner of different habitats. | 0:42:50 | 0:42:53 | |
From the arid, spiny forests of the south... | 0:42:55 | 0:42:58 | |
..to the rocky canyons in the north, | 0:42:59 | 0:43:02 | |
there is something about this island | 0:43:02 | 0:43:05 | |
that is allowing the lemur's DNA to change in the most amazing ways. | 0:43:05 | 0:43:10 | |
We're on the hunt for an aye-aye, | 0:43:29 | 0:43:32 | |
the most closely related of all the surviving lemurs | 0:43:32 | 0:43:35 | |
to their common ancestor. | 0:43:35 | 0:43:36 | |
Oh, yes... | 0:43:52 | 0:43:54 | |
Oh, yeah. | 0:43:56 | 0:43:58 | |
Just shone the light up, and we saw these absolutely... | 0:44:04 | 0:44:07 | |
Two bright red eyes, shining out. | 0:44:07 | 0:44:11 | |
She's very high up at the moment. | 0:44:11 | 0:44:14 | |
Don't want to lose sight of her in this forest, | 0:44:17 | 0:44:20 | |
which is very dark and dense. | 0:44:20 | 0:44:22 | |
The team have located a female aye-aye, and her son. | 0:44:25 | 0:44:28 | |
They want to attach radio collars to track their movements, | 0:44:30 | 0:44:33 | |
and better understand how far they range through these forests. | 0:44:33 | 0:44:37 | |
But first, they must sedate them with a dart. | 0:44:39 | 0:44:45 | |
He's waiting for it to come down low enough to get that clean shot - | 0:44:45 | 0:44:48 | |
I mean, how you get a clean shot in this I have no idea. | 0:44:48 | 0:44:54 | |
After two hours of traipsing through the treacherous forest, | 0:44:59 | 0:45:03 | |
the aye-ayes remain at large. | 0:45:03 | 0:45:06 | |
INDISTINCT CHATTER | 0:45:17 | 0:45:20 | |
Well, here is the aye-aye that was tranquillised last night. | 0:45:31 | 0:45:35 | |
They finally got her about half an hour after we left. | 0:45:35 | 0:45:38 | |
I think it was probably because we were disturbing her. | 0:45:38 | 0:45:40 | |
Apparently as soon as we'd gone, she came down the tree | 0:45:40 | 0:45:43 | |
and she was tranquillised. | 0:45:43 | 0:45:45 | |
And as you can see she's pretty well sedated now, | 0:45:45 | 0:45:48 | |
which is fortunate for me | 0:45:48 | 0:45:50 | |
because she has certain adaptations that I wouldn't like to be deployed. | 0:45:50 | 0:45:56 | |
You can see there her teeth. | 0:45:56 | 0:45:58 | |
Her teeth are very unusual for a primate - | 0:45:58 | 0:46:02 | |
in fact, unique, because they carry on growing, | 0:46:02 | 0:46:06 | |
so she's much more like a rodent in that respect. | 0:46:06 | 0:46:08 | |
And that's so she can gnaw into wood. | 0:46:08 | 0:46:11 | |
You see, aye-ayes have filled a unique niche on Madagascar. | 0:46:11 | 0:46:15 | |
It's a niche that's filled by woodpeckers in many other areas of the world. | 0:46:15 | 0:46:19 | |
What she does is she feeds on grubs and bugs inside trees, | 0:46:19 | 0:46:23 | |
and to do that, she has several unique adaptations of which her teeth are one. | 0:46:23 | 0:46:28 | |
The most startling is this central finger here. It's bizarre. | 0:46:29 | 0:46:35 | |
It's got a ball and socket joint, for a start, | 0:46:35 | 0:46:39 | |
so it has complete 360-degree movement. | 0:46:39 | 0:46:42 | |
It feels to me almost as if it's broken, but it isn't, | 0:46:42 | 0:46:45 | |
it's just, you can move it around in any direction. | 0:46:45 | 0:46:48 | |
And she uses that finger initially to tap on the trunk of the tree, | 0:46:48 | 0:46:53 | |
and then, listening to the echo from that tapping, with these huge ears | 0:46:53 | 0:46:58 | |
she can detect where the grubs are. | 0:46:58 | 0:47:01 | |
And then, she gnaws through the wood with those rodent-like teeth, | 0:47:01 | 0:47:05 | |
and then uses this finger again to reach inside the hole | 0:47:05 | 0:47:09 | |
and get the bugs out. | 0:47:09 | 0:47:11 | |
So the question is, why? | 0:47:11 | 0:47:14 | |
How could an animal be so precisely adapted to a particular lifestyle? | 0:47:14 | 0:47:22 | |
She's waking up now! | 0:47:22 | 0:47:24 | |
And the answer is natural selection. | 0:47:24 | 0:47:28 | |
See, what must have happened is way back, | 0:47:28 | 0:47:31 | |
when the ancestors of the lemurs - the Lemuriformes - | 0:47:31 | 0:47:34 | |
arrived in Madagascar, | 0:47:34 | 0:47:36 | |
there must have been a mutation that | 0:47:36 | 0:47:39 | |
lengthened the middle finger ever so slightly of one of those lemurs. | 0:47:39 | 0:47:43 | |
And that must have given it an advantage. | 0:47:43 | 0:47:46 | |
That must have allowed it perhaps | 0:47:46 | 0:47:48 | |
to reach into little holes and search for grubs. | 0:47:48 | 0:47:50 | |
There's some reason why that lengthened middle finger | 0:47:50 | 0:47:53 | |
meant that that gene was more likely to be passed to the next generation | 0:47:53 | 0:47:58 | |
and then down to the next generation. | 0:47:58 | 0:48:00 | |
So that landscape of possibilities is narrowed, | 0:48:00 | 0:48:04 | |
it's narrowed because that gene persists. | 0:48:04 | 0:48:07 | |
And it's persisted now for at least 40 million years, | 0:48:07 | 0:48:11 | |
because this species has been on one branch of the tree of life now | 0:48:11 | 0:48:16 | |
for over 40 million years. | 0:48:16 | 0:48:19 | |
And so, over those years that middle finger | 0:48:19 | 0:48:22 | |
has got more and more specialised. | 0:48:22 | 0:48:24 | |
Natural selection has allowed the aye-aye's wonderfully mutated finger | 0:48:25 | 0:48:30 | |
to spread through the population. | 0:48:30 | 0:48:32 | |
And this same law applies to all life. | 0:48:35 | 0:48:38 | |
If you have a mutation that helps you in the struggle to survive, | 0:48:40 | 0:48:43 | |
you are more likely to leave more offspring. | 0:48:43 | 0:48:47 | |
And in the next generation, that mutation is more likely to survive. | 0:48:47 | 0:48:52 | |
So this animal is a beautiful example, probably one | 0:48:56 | 0:49:00 | |
of the best in the world, of how the sieve of natural selection produces | 0:49:00 | 0:49:06 | |
animals that are perfectly adapted to live in their environment. | 0:49:06 | 0:49:11 | |
Now, there are many reasons to study the aye-aye. But here's a good one. | 0:49:34 | 0:49:39 | |
In the 1970s, it was thought the aye-aye was extinct. | 0:49:39 | 0:49:42 | |
Now, we know there are several thousand in the forests of Madagascar - | 0:49:42 | 0:49:46 | |
5,000, 6,000, 7,000, certainly less than 10,000 - | 0:49:46 | 0:49:50 | |
but over the last 50 years, 50% of this forest has vanished. | 0:49:50 | 0:49:54 | |
This is an animal that's been around as a species for over 40 million years. | 0:50:09 | 0:50:14 | |
So it's important to know how these animals are doing, | 0:50:14 | 0:50:18 | |
and how they're surviving in this diminishing habitat. | 0:50:18 | 0:50:22 | |
Whilst natural selection explains why the aye-aye evolved, | 0:50:38 | 0:50:42 | |
it alone can't explain how a small group of individuals, over 60 million years ago, | 0:50:42 | 0:50:49 | |
gave rise to over 90 different species of lemur today. | 0:50:49 | 0:50:53 | |
But there is another form of life that can offer us a clue. | 0:50:57 | 0:51:00 | |
Up here in the high forest canopy, we're in a very different | 0:51:03 | 0:51:07 | |
environment to the one down there on the forest floor. | 0:51:07 | 0:51:11 | |
It's a more arid environment, it's almost like a desert. | 0:51:11 | 0:51:15 | |
It's exposed to the sun, water is harder to come by. | 0:51:15 | 0:51:18 | |
And so, this is a sea of different niches, | 0:51:18 | 0:51:23 | |
that are able to be occupied and exploited by animals | 0:51:23 | 0:51:26 | |
that are different to the ones you'll find down there on the floor. | 0:51:26 | 0:51:30 | |
So, in a very real sense, this is an island, an island to be colonised. | 0:51:30 | 0:51:35 | |
And sure enough, there are settlers to be found, even here. | 0:51:37 | 0:51:41 | |
You see that thing that looks like a muddy ball there, on the branch? | 0:51:42 | 0:51:46 | |
Well, that's an ants' nest, | 0:51:46 | 0:51:49 | |
it's home to a species of Crematogaster ants | 0:51:49 | 0:51:51 | |
that are unique not only to Madagascar, | 0:51:51 | 0:51:55 | |
but to the forest canopy. | 0:51:55 | 0:51:57 | |
You see, what makes those ants unique is that they can | 0:51:57 | 0:52:00 | |
build their own nests. | 0:52:00 | 0:52:02 | |
There are very few species of ants that can do that. | 0:52:02 | 0:52:05 | |
So that is an island, that is a niche, | 0:52:05 | 0:52:09 | |
and it's allowed that species of ant to develop | 0:52:09 | 0:52:12 | |
because they're isolated from the rest of the ecosystem. | 0:52:12 | 0:52:16 | |
And astonishingly, within this niche, | 0:52:16 | 0:52:20 | |
another form of life new to science has been discovered... | 0:52:20 | 0:52:23 | |
..a beetle that manages to survive here unharmed by the ants. | 0:52:25 | 0:52:30 | |
How it does it is a mystery. | 0:52:31 | 0:52:35 | |
But what IS known is that this particular species has only | 0:52:35 | 0:52:39 | |
ever been found inside these nests. | 0:52:39 | 0:52:42 | |
So, that really is its own mini-ecosystem, | 0:52:43 | 0:52:48 | |
with species living in it that are unique to that island. | 0:52:48 | 0:52:51 | |
We live on an ever-shifting, dynamic world | 0:53:03 | 0:53:07 | |
that creates islands in abundance. | 0:53:07 | 0:53:10 | |
Earth's mountain ranges, river valleys and canyons | 0:53:19 | 0:53:23 | |
all create islands for life. | 0:53:23 | 0:53:26 | |
And it's these islands | 0:53:31 | 0:53:33 | |
that those ancestors of the lemurs found when they arrived in Madagascar. | 0:53:33 | 0:53:37 | |
Empty niches, where populations became isolated, | 0:53:44 | 0:53:48 | |
and over great swathes of time | 0:53:48 | 0:53:52 | |
involved into such wonderfully diverse forms. | 0:53:52 | 0:53:55 | |
150 years on from the Origin Of Species, the subtlety | 0:54:17 | 0:54:22 | |
and beauty of Darwin's insight is still revealing itself to us. | 0:54:22 | 0:54:26 | |
It describes how our beautiful, complex tree of life | 0:54:30 | 0:54:33 | |
has grown from a once desolate universe. | 0:54:33 | 0:54:37 | |
The chemistry of carbon | 0:54:39 | 0:54:41 | |
allows for the existence of a molecule that is able to replicate | 0:54:41 | 0:54:44 | |
itself, and pass information on from generation to generation. | 0:54:44 | 0:54:49 | |
There can be random changes in the structure of that molecule - | 0:54:49 | 0:54:53 | |
mutations - and they are tested by their interaction with | 0:54:53 | 0:54:57 | |
the environment and with living things. | 0:54:57 | 0:54:59 | |
The ones that pass that test survive, | 0:54:59 | 0:55:02 | |
and the ones that fail that test are lost. | 0:55:02 | 0:55:04 | |
The separation and isolation of living things onto islands - | 0:55:09 | 0:55:14 | |
which may be physical, like Madagascar, | 0:55:14 | 0:55:17 | |
or just the single branch of a single tree - | 0:55:17 | 0:55:20 | |
results in speciation, the explosion of living forms | 0:55:20 | 0:55:24 | |
highly specialised to occupy niches within niches. | 0:55:24 | 0:55:29 | |
And this is the explanation for the diversity of life on Earth. | 0:55:29 | 0:55:34 | |
"There is grandeur in this view of life," as Darwin wrote, | 0:55:34 | 0:55:38 | |
and understanding how it happened surely only adds to the wonder. | 0:55:38 | 0:55:43 | |
As precise as Einstein's theories of relativity, and as profound | 0:55:51 | 0:55:56 | |
as thermodynamics, | 0:55:56 | 0:55:59 | |
Darwin has given us another universal law. | 0:55:59 | 0:56:03 | |
Evolution by natural selection. | 0:56:06 | 0:56:09 | |
And if evolution is the law on this island, | 0:56:19 | 0:56:23 | |
then it will apply throughout the cosmos. | 0:56:23 | 0:56:26 | |
Which begs a big question. | 0:56:30 | 0:56:32 | |
Could there be other "trees of life most beautiful" amongst the stars? | 0:56:36 | 0:56:41 | |
In 2011, we discovered a rocky planet | 0:56:49 | 0:56:53 | |
orbiting around a distant star, | 0:56:53 | 0:56:55 | |
with daytime temperatures not too dissimilar to those found on Earth. | 0:56:55 | 0:57:00 | |
Now, there must be millions | 0:57:00 | 0:57:02 | |
if not billions of such planets out there in the universe, | 0:57:02 | 0:57:06 | |
and it's inconceivable to me that none of them | 0:57:06 | 0:57:10 | |
will have trees of life as complex or even more complex than our own. | 0:57:10 | 0:57:15 | |
But that doesn't devalue the existence of OUR tree, | 0:57:15 | 0:57:20 | |
because our tree is unique. | 0:57:20 | 0:57:22 | |
It consists of thousands of branches, | 0:57:22 | 0:57:24 | |
all interdependent on thousands of others, | 0:57:24 | 0:57:27 | |
and the precise structure depends on chance events, like the passage | 0:57:27 | 0:57:32 | |
of the lemurs across the ocean 65 million years ago. | 0:57:32 | 0:57:36 | |
So when you go outside tomorrow, | 0:57:44 | 0:57:46 | |
just take a look at a little piece of your world. | 0:57:46 | 0:57:49 | |
A corner of your garden, or a park, | 0:57:49 | 0:57:52 | |
or even the grass that's growing in a crack in the pavement. | 0:57:52 | 0:57:57 | |
Because there will be life there, and it will be unique. | 0:57:57 | 0:58:01 | |
There will be nowhere like that anywhere else in the universe. | 0:58:01 | 0:58:05 | |
And that makes our tree, from the sturdiest branch to the most | 0:58:05 | 0:58:09 | |
fragile twig, indescribably valuable. | 0:58:09 | 0:58:12 | |
MUSIC: "Underneath the Stars" by Kate Rusby | 0:58:14 | 0:58:18 | |
# Underneath the stars you met me | 0:58:18 | 0:58:23 | |
# And underneath the stars you left me | 0:58:23 | 0:58:29 | |
# I wonder if the stars regret me | 0:58:29 | 0:58:35 | |
# I'm sure they'd like me if they only met me | 0:58:35 | 0:58:40 | |
# They come and go of their own free will | 0:58:40 | 0:58:48 | |
# Go gently... # | 0:58:48 | 0:58:52 | |
Subtitles by Red Bee Media Ltd | 0:58:52 | 0:58:54 |