Animals and plants flourished on earth for millions of years before humans appeared.
The direct evidence comes from one source only;
from their remains that can be found in rocks, from fossils.
Some are spectacular and dramatic, complete skeletons of huge reptiles.
Others are the merest trace of imprints,
left by such insubstantial creatures as jellyfish.
Many are the remains of creatures quite unlike any that exist today.
Fossils can be found all around us if we know where to look.
The south of England, the Dorset coast, and a world-famous fossil site.
Heavy rains have drenched the clay and limestone cliffs.
The rocks are slipping. New surfaces are being exposed.
Fresh fossils could have been revealed overnight.
Peter Langham regularly patrols this coast searching for them
and he knows that the day after a storm is the best time for finding something interesting.
A couple of likely-looking bits of stone.
Why? They look like all the rest to me.
Really, it's from the right horizon.
It takes a lot of experience to judge which of the many boulders in a cliff like this
is likely to have a fossil inside it.
But, then, Peter has been doing this for years.
Generally, these split fairly easily. They've got good bedding plains.
Let's see what happens.
(LANGHAM) We're in luck. (ATTENBOROUGH) Gosh!
That's one of the most well-known ammonites from Lyme, Asteroceras.
That's beautiful.
Fossils don't always appear every time you hit a nodule of rock with a hammer,
but they do so surprisingly frequently
if you can recognise the right sort of nodule and know where to find it.
I used to come to these old ironstone quarries in Leicestershire as a boy to look for them,
and the moments of success, when the rock fell apart
and revealed a shell that hadn't seen the sun for 200 million years
and that I was the first human being to see,
seemed to me then, as, to be truthful, it still seems to me now, to be moments of magic.
It's a beguiling business, for you know that, even if you've not found anything much so far,
the very next blow of your hammer may suddenly reveal something amazing.
That's not bad, but if I keep looking I should be able to do rather better.
Slowly you begin to get your eye in,
and soon you will start to recognise the particular glint, the tell-tale curve,
the slight change in colour that indicates the tip of a fossil sticking out from the rock.
It doesn't take long to gather quite a varied collection.
They all seem to be the remains of animals that lived in the sea.
But the local people, some at any rate, refused to believe that.
"How could they be?" they would say,
"When we are in the middle of England, far from the sea,
"and when these fossils are buried in the rock,
"far below the surface of the earth. How could that be?"
Instead, they had their own explanations. They said, for example,
that these were the toenails of the devil.
And this, these impressive, bullet-shaped objects,
and there's some in the boulder on which I'm sitting,
those, they said, were thunderbolts, made when lightning struck the earth.
And the most beautiful of them all, these ammonites,
those, they said, were snake-stones,
and they came in two kinds, big ones, like that, and little ones.
Farther north, up in Yorkshire, near Whitby, where exactly the same fossils are found,
the people had a detailed explanation as how that had come about.
They said that back in the seventh century, an early Christian saint, Saint Hilda,
had wanted to found an abbey but discovered the place was infested by snakes,
so miraculously she turned them all to stone.
0f course, there's one problem with that explanation:
None of these so-called snake-stones have heads.
But when the devout pilgrims came to the site of this miracle,
They carved on heads onto the snake-stones, so that they looked rather more convincing.
But there are some fossils that are so perfectly preserved
that their animal origin simply cannot be denied.
These tiny creatures are imprisoned in amber,
a hard, stony substance that's found in lumps in mudstones and sandstones.
Who can doubt that these, so complete in every bristle and antenna,
are truly ants, scorpions and flies?
But how did they get there?
Amber was once liquid and sticky,
resin trickling down the trunks of trees that grew in swamps some 30 million years ago.
Insects were attracted, then as now, by its sweet smell,
and flew or crawled towards it, with fatal results.
The resin gradually hardened into solid lumps.
Eventually, the tree itself died...
... and the long, slow processes that lead to fossilisation began.
Mud and sand washed in by the sea
slowly settled on the resin lumps and buried them.
As millions of years passed,
the layers of sediment were compressed and compacted under their own weight,
and turned into mudstones and sandstones
and then were pushed and buckled by colliding continents to form mountains,
like these in the Dominican Republic on the Caribbean island of Hispaniola.
And since amber is highly valued for making jewellery,
men today burrow deep into the hillsides to look for it.
The shafts are steep and may go as much as a hundred yards into the mountain.
The amber miners have to chisel away tons of stone
before they find the particular layer where the lumps of resin have accumulated.
But once they find that seam, they often discover piece after piece.
(SPEAKS SPANISH)
It's difficult to tell what's inside pieces like this when they've just been dug out,
because the surface is all broken and pitted and dirty.
But when they are polished, they may reveal the most extraordinary things.
Many pieces are quite clear, with nothing whatever in them.
Those are the ones that are valued for jewellery.
But one in every dozen or so has the remains of some kind of creature.
Backboned animals were mostly strong enough to pull themselves free from the resin,
but occasionally they failed, and these are the rarest of all amber fossils.
A tiny lizard.
And a frog.
Insects are the commonest and were sometimes caught in action.
An ant carrying a pupa.
A bug beside a leaf from which it might have been sucking sap.
A beetle apparently walking up a twig.
Flying insects with even their delicate wings undamaged.
And a whole swarm of ants,
so perfectly preserved that you can even see the facets in their 30 million-year-old eyes.
Mud itself doesn't embalm bodies as resin does,
but even mud can preserve an extraordinary amount if it accumulates in a particular way.
It must settle fast before decay dissolves the flesh and sinews that hold a skeleton together
and before the bones are separated, washed away and, perhaps, broken into fragments.
As more mud settles in thicker and thicker layers on the bottom,
so the body beneath is squashed flat.
The mud may be so glutinous that it shuts off oxygen,
and then some relic of the flesh may survive.
But even if that entirely disappears, the scales and bones may remain,
and when the mudstone is cleared away, the fossilised body is revealed in great detail,
sometimes down to the delicate tracery of its fins.
So wherever you find sandstones or shales, mudstones or limestones
that were once sediments at the bottom of a sea or a swamp,
you stand a chance of finding fossils.
And it's not only animals that may be preserved in this way, sometimes even plants are.
Some 220 million years ago,
these logs were part of trees that grew in a great coniferous forest
in this part of Arizona in the United States.
When the trees died, some of them fell into the rivers
and the logs were carried downstream and ultimately buried in these sands and gravels.
And now, although they look exactly like wood, they are, in fact, solid stone.
Because they are no longer flexible wood but brittle rock,
these trunks have broken into segments as if they had been sawn into short lengths.
The bark has been perfectly preserved
so that you can see its grain and the knot-holes from which small branches once sprang.
The wood itself has been replaced by a mineral, quartz,
but the annual growth rings can still be seen,
so that you can calculate just how old each huge tree was before it fell.
In fact, these fossils retain so many of the characters of the original trees
that botanists can work out exactly what kind they were.
They were cypresses, related to the swamp cypresses that still grow 1500 miles to the east
in the flat, waterlogged plains along the coasts of Florida and Louisiana.
These forests give us a very accurate picture of what the trees of the petrified forest were like
when they were alive so long ago.
But conifers were not by any means the first trees to clothe the earth.
150 million years earlier still, there were trees of a very different kind.
These, like giant horsetails, also grew in coastal swamps.
Sometimes there were changes in the level of the sea,
and then water swept into the swamps, bringing with it great quantities of sand and mud,
which settled around the bases of the trees, burying them and killing them.
The outside of these particular trees had extremely tough bark,
but the wood inside was soft and pithy, and when the tree died, it decayed very rapidly.
And as it decayed, so more sand settled in in place of the wood.
But the bark remained for much longer time,
separating the sand inside the trunk from the sand outside.
Over millions of years, the sand compacted and formed sandstone,
and when men came to quarry it, it broke away where the bark had once been,
so revealing these extraordinary trunks.
So although the wood itself has totally disappeared
and these, in effect, are just casts of tree trunks,
they nonetheless give a vivid impression of the forest that grew 350 million years ago
where today the city of Glasgow stands.
But this familiar substance is the actual remains of the plants themselves.
First the rotting plants formed peat, and that in turn was compressed into coal.
Tom Phillips has devoted his life to working out exactly what those plants were.
He's travelled the world collecting specimens,
but most of his research has been done with material he found here,
in the great opencast coal mines of Illinois in North America.
The sand that buried the peat crushed it so severely
that almost all the details of the plants were destroyed.
But within the seam are hard lumps called coal balls, and they are much more interesting.
It's calcium carbonate that has precipitated and filled up all the voids in the plant tissue,
so that as compaction took place and we went from thirty feet down to five feet of coal,
the dimensions of this weren't altered.
So it was a kind of lump in the middle of this peat bog
where there was a lot of calcium carbonate which turned into limestone, forming a ball,
and this didn't squash.
To see just what a coal ball contains, you must first cut it into two.
Then you dip it in a tank of weak hydrochloric acid,
which etches away the calcium carbonate
and leaves the plant remains standing just proud of the surface.
Acetone is poured over it...
... a transparent sheet of acetate is laid on that
and then left to dry to form what is called a peel.
The peels are fairly easily removed.
Like so. You can tell the colours even before we look at them with a microscope.
This is the wood. It has a different colour from the surrounding tissues.
(ATTENBOROUGH) 0h, perfect! (PHILLIPS) Notice what large cells.
(PHILLIPS) Most of the tissues are still intact and preserved to some degree.
(ATTENBOROUGH) So that's a stem there?
(PHILLIPS) It's a rather fancy stem. It has several cylinders of wood inside,
rather than one like most plants.
All of this tissue that extends round the outside, you can see the basket of bundles,
and the dark cells are support cells.
This was a tree, not a very tall tree, maybe 15 feet or so,
and less than a foot in diameter.
As a result of work like this,
we can now picture very precisely the ancient forests which formed coal.
We know the anatomy of the stems in such detail that we can reconstruct individual plants.
Many were like the living horsetail plant, except that these grew to 50 feet high.
This is a section of a cone which produced the male spores and grew on another kind of tree
around the base of its leafy crown.
The female seed-like structures had tiny sails and floated away to other parts of the swamp.
We can deduce all this
only because coal balls have preserved the structure of the plants in microscopic detail.
For a long time it was thought that that kind of perfection of preservation
was to be found only in plant fossils.
But look at this:
This is part of the jaw of that great flesh-eating dinosaur Tyrannosaurus rex.
It used to be said of superb, fossilised bones like this
that in some miraculous way, minerals had replaced the bone molecule by molecule.
But scientists here in the New Mexico Museum of Natural History
have had this bone analysed chemically.
The spaces within the bone have indeed been filled with silica
but the substance of the bone itself is chemically almost identical with modern bone.
Not only that, they have also taken sections from the bone,
and when you look at these under the microscope, this is what you see.
These are grains of the mineral filling, quartz, or silica,
but here are bone cells.
And these, with their cell walls and central spaces,
are almost identical in appearance with the bone cells of living reptiles.
This is the actual substance of a dinosaur.
So fossils can reveal in the most extraordinary detail
the anatomy of long-vanished animals and plants.
But how do you find them? How would you know this bleak spot was a good place to look?
Well, you need a practised eye,
and few are more experienced than those of Stan Wood, a collector from Edinburgh.
He took me to this shore in northern Scotland to look for fossil fish.
(WOOD) Grab that. That's it. Ah, at last.
(ATTENBOROUGH) Gosh.
(WOOD) There she is up there. (ATTENBOROUGH) That's the head, huh?
That's the head. Down here's the tail.
In between, the scales of the body.
They're better preserved down here.
In fact, the body itself is preserved.
If I can just lift that up...
I can actually lift that out
as an ancient kipper.
The scales are on both sides, you see?
It's now carbonised,
but at one time that would have been a nice juicy little salmon of the period.
So fossils up here are relatively common and easy to find.
But sometimes, and often in the places where you'd most like to find them,
they seem so scarce as almost not to exist at all.
This is just one of those places. It's a quarry in Scotland, just outside Edinburgh.
The rocks in it were laid down around 338 million years ago,
at a crucial period in the history of life on earth,
when animals with backbones were, for the very first time, crawling out onto the land.
A few extremely important fossils of these creatures
were discovered in this quarry in the 19th century.
But then, search as people might, they could find no more.
Until, that is, Stan Wood started looking.
Now, Stan, why do you think there's anything in that?
Because I've split it vertically,
that's at right angles to the layers of rock that was laid down,
and when you cut it vertically,
in this case, we're seeing marks along the plane...
- There? ...which indicate bone, yes.
That's bone because I've been working on this kind of rock for a while
and I recognise it as bone.
What I'm hoping, against hope, perhaps, is that there's a little skull in here
of one of these very rare early four-legged animals.
The idea is to now try and split it along the plane that the skull is lying,
taking care to avoid damaging the skull wherever possible.
So I'm placing the chisel to one side.
They're not easy to recognise because they're so small.
There's not that much to see.
Now, what on earth is this?
I'll try and put this together and see...
It is a skull.
I think we have parts of the body running down here at right angles to the skull.
- Do you see that, David? - I do.
Is that the backbone, there?
(WOOD) The skull, as it were, has turned left.
(WOOD) Look. There's one of the eyeballs, you see?
(WOOD) It's shot out... As the skull's been squashed,
the bone surrounding the eye socket has shunted out to the side.
That round hole is actually one of its eyes. The other eye would be over here.
- And what sort of animal do you think it is? - It will be an amphibian.
Stan has now made many new discoveries in this quarry,
but this, one of his most recent, is the most important of all.
Its body is twisted, but it's possible to imagine the bones in a more life-like position
and then to clothe them with muscles and skin.
This seems to be not only a completely new species but, at 380 million years old,
the earliest reptile yet discovered by about 40 million years.
Finding any specimen may be only the beginning of a long process of research.
Preparing it can alone take months, and it's a highly skilled job.
In the Natural History Museum in London, a whole laboratory is devoted to the work.
All kinds of different techniques are used:
air blasting with sand, grinding with dental drills, chipping with chisels.
Sometimes the work is so delicate and detailed,
it has to be done with needles under a binocular microscope,
taking away the matrix grain by grain.
When a lot of rock has to be removed, rather more vigorous techniques can be used.
One whole room is devoted to a method pioneered by the Natural History Museum,
baths of acetic acid.
- What's this? - A block of limestone from Queensland, Australia
which contains the remains of a fossil turtle.
- Can we see it? - Yes.
William Lindsay is an expert in controlling this process.
The acid eats away the limestone
but has little effect on the fossil bones, which are chemically rather different.
The bones of this turtle were already projecting clear of the boulder.
- So how long has it been in here? - It's almost two years.
- What have you got out so far? - We've got some parts of shell already removed.
These look like pieces of vertebra.
They're perfect, aren't they?
The advantage of the acid technique is that it will reveal the most delicate details
that can't be revealed by other methods.
How long will you leave this in this bath?
Possibly almost another year.
Along here we've got a specimen we're about to start.
This is a block of limestone from Australia.
It comes from a locality where there have been finds of fossil fish before.
You can see some very small fragments of bone,
and perhaps after a year we'll be able to reveal something rather more exciting.
OK.
And throughout the next year, we filmed it, one frame every day,
to record the whole process.
After a year, the matrix had almost completely been removed.
This 110 million-year-old fish
had obviously decayed quite considerably before it was covered by the first layers of mud
so that the bones of its skull had slipped apart and become jumbled,
but they all seem to be here.
This is one of the fins on the underside of the body, just behind the head.
Here is the right gill cover.
In front of it, the top of the skull and the brain-case.
And then the snout, complete with all the tiniest bones,
and teeth not only in the jaws but in the palate,
a detail that had not been known before.
The next step is delicately to separate the bones one by one
and then put them back together as they were in life.
That is like working on a jigsaw puzzle with several hundred pieces,
without a pattern and in three dimensions.
Mahala Andrews at the Royal Museum of Scotland
has been doing just this with the skull of a similar fish prepared in an acid bath.
(ANDREWS) The two pieces have a moveable joint... there.
That's its nostril.
And you can see how it could flap its cheeks while it was breathing or eating.
And then underneath there are these deep slots
that go right through to the skin on the outside of its head.
When the lower jaw was in place -
there's the articulation at the back -
these big teeth at the front would bite right through the skull
up to the skin...
...like that.
This lump of rock contains no actual remains at all of an animal,
only the rather baffling spaces where some had once been,
but even here there's a lot that can be discovered using the right techniques.
Alick Walker from Newcastle on Tyne University
carefully fills it with liquid silicone rubber,
pouring steadily and slowly to avoid trapping air bubbles.
It needs an hour or so to set
and, being flexible, can be pulled out of holes in which plaster would have stuck irretrievably.
(WALKER) Now that the cast has been removed from the rock,
one can see a good deal more detail than one could from the natural mould alone.
The cast shows part of the backbone of a reptile.
Here are three vertebrae.
These are ribs, which are slightly displaced,
and here is one of the series of small circular bony plates or scutes
which lay in the skin of the top surface of the animal.
Sometimes you can discover all kinds of information
without even excavating the fossil at all.
This piece of slate, to the naked eye, contains nothing more than a slight bulge.
But Johannes Mehl of the University of Erlangen in Germany uses x-ray techniques
and with them reveals things that can't be seen in any other way.
The equipment he uses is specially modified apparatus
that was originally developed for medical purposes.
(SPEAKS GERMAN)
Ah! Well... Yes, how absolutely perfect.
- A starfish. - Yes, a starfish. Very well preserved.
(ATTENBOROUGH) Perfectly preserved. And you can see all the tiny structures here.
(MEHL) They are not visible without x-ray.
(ATTENBOROUGH) Could you actually dig it out? (MEHL) It's very difficult, I think.
- Because that's very delicate, isn't it? - Yes.
So you can make it only visible by x-raying it.
The next specimen he showed me was particularly interesting
because this fossil, a cephalopod,
was an earlier form of those bullet-like fossils in that quarry in Leicestershire.
It was unusually complete, for it had the remains of some structures at the broad end,
though I couldn't see exactly what they were.
...the radiograph, and it's amazing to see that there are some organs preserved
and even the gills, which are very delicate structures, are seen in the x-ray.
(ATTENBOROUGH) But that's totally new, isn't it? (MEHL) It's totally new.
(MEHL) Let's see an enlarged photograph of this x-ray.
(MEHL) You can very well realise the two gills, they have only two and not four gills,
and this picture shows the first gills known in fossil cephalopods today.
At a hospital in St. Louis in America,
another extremely advanced piece of medical equipment is being used to look at fossils.
This is the skull of a 50-million-year-old badger-like animal.
Computer-aided tomography, or CAT-scanning, as it's called,
is normally used by surgeons to plan intricate head operations.
This fossil head is excellently preserved,
but its interior is filled with stone that neither acid nor anything else can remove,
and it's the internal shape of the brain-case
that researchers Glenn Conroy and Michael Vannier are particularly interested in.
This skull was scanned in two-millimetre thin slices,
and then the computer reconstructs the specimen in three dimensions.
We'll bring up here shortly the four different views of the skull.
As we look on the left side of the screen, we are seeing a 3D computer image
of the top of this skull, with the stone matrix removed.
In this bottom view here, the computer has made the top of the skull disappear,
so that we are now looking down inside the brain-case.
There's no way we could determine that from the original specimen
but the computer can electronically dissect this specimen,
so it's as if the palaeontologist has taken a knife and cut this specimen right in half.
The computer has removed the stone matrix from the brain-case.
Here is a picture of the brain-case of this animal.
We can also see where the spinal cord entered the back of the skull, going up in this direction.
So, in a sense, we have a window into this fossil using this CT technique
that we never would have had previously.
And I imagine you can put them all together to look at it from any point of view you need.
We can take all these views, put them together in three dimensions
and then look at them in any desired plane.
So today we no longer need to appeal to the supernatural
to explain the strange shapes in rocks.
This stone spiral is not, as the people of Arkansas once maintained,
a corkscrew used by the devil,
but the filled-in burrow of an ancient kind of beaver.
Fossil hunters proved that by excavating this one,
which had the chamber at the very bottom still preserved
and in it the bones of the animal that made it.
This is not the devil's toenail, it's an early ancestor of today's oyster.
A thunderbolt? No, the internal skeleton of an animal like a squid,
which had tentacles at one end and, as we now know, two gills.
Stone snakes?
No, shells from a long-vanished sea.
Such revelations are, perhaps, even more astonishing
than the myths people invented to explain the strange shapes they found in rocks.
But finding the remains of animals is only the beginning of this detective story.
Working out how such animals as this lived and breathed,
moved and behaved hundreds of millions of years ago is the next part.
That's what we'll be looking at in the next programme.