The theory of evolution by natural selection
was put forward in the 1850s independently by two men.
One was Charles Darwin,
who lived in this house, in the village of Downe in Kent.
The other was Alfred Russel Wallace.
Both men had some scientific background, of course.
But at heart, both men were naturalists.
(Birdsong)
The fact is that there are two traditions of explanation
that march side by side in the ascent of man.
One is the analysis of the physical structure of the world.
The other is the study of the processes of life:
Their delicacy, their diversity,
the wavering cycles from life to death in the individual and in the species.
And these traditions do not come together until the theory of evolution.
Because, until then, there is a paradox which cannot be resolved,
which cannot be begun, about life.
We see it about us in the birds, the trees, the grass, the snails - in every living thing.
The manifestations of life, its expressions, its forms,
are so diverse that they must contain a large element of the accidental.
And yet, the nature of life is so uniform
that it must be constrained by many necessities.
So it's not surprising that biology, as we understand it,
begins with naturalists in the 18th and 19th centuries.
Observers of the countryside, birdwatchers, clergymen,
doctors, gentlemen of leisure in country houses -
I'm tempted to say gentlemen in Victorian England.
Because it cannot be an accident that the theory of evolution is conceived twice
by two men living at the same time, in the same culture -
the culture of Queen Victoria in England.
Charles Darwin was in his early twenties
when the admiralty was about to send out a survey ship
to map the coast of South America, called the Beagle.
And he was offered the post of Naturalist.
The five years that he spent on the ship transformed him.
He had been a sympathetic, subtle observer of birds, flowers...
life in his own countryside.
But South America exploded all that for him.
He came home convinced that species are taken in different directions
when they are isolated from one another.
Species are not immutable.
But when he came back,
he could not think of any mechanism that drove them apart.
That was in 1836.
At that time, Wallace was a boy in his teens.
He was born in 1823.
That makes him 14 years younger than Darwin.
WALLACE: "Had my father been a moderately rich man,
my whole life would have been differently shaped.
And though I should, no doubt, have given some attention to science,
it seems very unlikely that I should have ever undertaken a journey
to the almost unknown forests of the Amazon,
in order to observe nature and make a living by collecting."
So Wallace wrote about his early life,
when he had had to find a way to earn his own living in the English provinces.
He took up the profession of land surveying, which did not require a university education.
It was an open -air life, and Wallace became interested in plants and insects.
When he was working at Leicester,
he met a man with the same interests, who was rather better educated.
[Skipped item nr. 60]
~ ERIK SATIE: Embryons Desseches
His new friend astonished Wallace
by telling him that he had collected several hundred different species of beetles
in the neighbourhood of Leicester,
and that there were more to be discovered.
It was a revelation to Wallace, and it shaped his life and his friend's.
The friend was Henry Bates,
who later did famous work on mimicry among insects.
Meanwhile, the young men had to make a living.
Fortunately, it was a good time for a land surveyor,
because the railway adventurers of the 1840s needed him.
Wallace was employed to survey a possible route
for a line in the Neath Valley in south Wales.
Wallace was a conscientious technician, as Victorians were.
But he suspected, rightly, that he was only a pawn in a power game.
Most of the surveys were only meant to establish a claim
against some other railway robber baron.
Wallace calculated that only a tenth of the lines surveyed that year were ever built.
(Train whistle)
The Welsh countryside was a delight to the Sunday naturalist.
Now Wallace observed and collected for himself,
with a growing excitement in the variety of nature
that affectionately remained in his memory all his life.
~ Monastery Bells
WALLACE: "Even when we were busy, I had Sundays perfectly free,
and used them to take long walks over the mountains with my collecting box,
which I brought home full of treasures.
At such times, I experienced the joy
which every discovery of a new form of life gives to the lover of nature.
Almost equal to those raptures which I afterwards felt
at every capture of new butterflies on the Amazon."
He found a cave on one of his weekends where the river ran underground,
and decided then and there to camp overnight.
It's as if unconsciously he was already preparing himself for life in the wild.
WALLACE: "I wanted for once to try sleeping out of doors,
with no shelter or bed but what nature provided.
I think I had determined purposely to make no preparation,
but to camp out just as if I had come accidentally to the place in an unknown country,
and had been compelled to sleep there."
In fact, he hardly slept at all.
When he was 25,
Wallace decided to become a full-time naturalist.
It's an odd Victorian profession.
It meant that he would have to keep himself by collecting specimens in foreign parts,
to sell to museums and collectors in England.
And Bates would come with him.
So, the two of them set off in 1848 with a hundred pounds between them.
They sailed to South America and then 1,000 miles up the Amazon
to the city of Manaos, where the Amazon is joined by the Rio Negro.
(Squawking)
Wallace had never been further than Wales,
but he was not overawed by the exotic.
From the moment of arrival, his comments were firm and self-assured.
For example, on the subject of vultures...
WALLACE: "The common black vultures were abundant,
but were rather put to it for food
being obliged to eat palm fruits in the forest, where they could find nothing else.
I am convinced, from repeated observations,
that the vultures depend entirely on sight, and not at all on smell, in seeking out their food."
The friends separated at Manaos and Wallace set off up the Rio Negro.
He was looking for places that had not been much explored by earlier naturalists.
If he was going to make a living by collecting,
he needed to find specimens of unknown or, at least, of rare species.
(Birdsong)
The river was swollen with rain,
so that Wallace and his Indians were able to take the canoe right into the forest.
The trees hung low over the water.
Wallace, for once, was awed by the gloom.
But he was also elated by the variety in the forest.
WALLACE: "What we may fairly allow of tropical vegetation
is that there is a much greater number of species and a greater variety of forms
than in the temperate zones.
Perhaps no country in the world contains such an amount of vegetable matter on its surface
as the valley of the Amazon.
Its entire extent, with the exception of some very small portions,
is covered with one dense and lofty primeval forest,
the most extensive and unbroken which exists upon the earth."
~ WAGNER: Das Rheingold
"The whole glory of these forests could only be seen by sailing gently in a balloon
over the undulating, flowery surface above.
Such a treat is, perhaps, reserved for a traveller of a future age."
He was excited when, for the first time, he went into a native Indian village.
WALLACE: "The most unexpected sensation of surprise and delight
was my first meeting and living with a man in a state of nature,
with absolute uncontaminated savages.
They were all going about their own work or pleasure,
which had nothing to do with white men or their ways.
They walked with the free step of the independent forest dweller,
and paid no attention whatever to us, mere strangers of an alien race.
In every detail, they were original and self-sustaining,
as are the wild animals of the forest.
Absolutely independent of civilisation.
And who could, and did, live their own lives in their own way,
as they had done for countless generations, before America was discovered."
~ SAINT-SAENS: Carnival Of The Animals
It turned out that the Indians were not fierce, but helpful.
Wallace drew them into the business of collecting specimens.
WALLACE: "During the time I remained here, 40 days,
I procured at least 40 species of butterflies quite new to me,
besides a considerable collection of other orders.
One day, I had brought me a curious little alligator of a rare species,
which I skinned and stuffed, much to the amusement of the Indians,
half a dozen of whom gazed intently at the operation."
Like Darwin, Wallace was struck by the difference between neighbouring species.
And, like Darwin, he began to wonder how they had come to develop so differently.
WALLACE: "There is no part of natural history more interesting or instructive
than the study of the geographical distribution of animals.
Places not more than 50 or 100 miles apart
often have species of insects and birds at the one which are not found at the other.
There must be some boundary which determines the range of each species,
some external peculiarity to mark the line which each one does not pass."
Wallace is as acute an observer of men as of nature.
In an age in which Victorians called the people of the Amazon "savages,"
he has a rare sympathy with their culture.
He understands what language, what invention, what custom means to them.
He is perhaps the first person to seize the fact
that the distance between that civilisation and ours is much shorter than we think.
WALLACE: Natural selection could only have indulged savage man
with a brain a few degrees superior to that of an ape,
whereas he actually possesses one very little inferior to that of a philosopher.
With our advent, there had come into existence a being
in whom the subtle force we term "mind"
became of far more importance than mere bodily structure."
At this point, Wallace's journal breaks into poetry.
Well, into verse.
WALLACE: "There is an Indian village;
all around the dark eternal boundless forest spreads its varied foliage.
Here I dwelt a while.
The one white man among perhaps 200 living souls.
Each day, some labour calls them.
Now they go to fell the forest's pride, or in canoe,
with hook and spear and arrow, to catch fish.
A palm tree's spreading leaves supply a thatch,
impervious to the winter's storms and rain.
The women dig the mandioca root,
and with much labour, make of it their bread.
And all each morn and eve wash in the stream.
And sport like mermaids in the sparkling wave.
The children of small growth are naked and the boys and men wear but a narrow cloth.
How I delight to see those naked boys!
Their well-formed limbs, their bright, smooth, red-brown skin,
and every motion full of grace and health.
And as they run and race and shout and leap,
or swim and dive beneath the rapid stream,
I pity English boys,
their active limbs cramped and confined in tightly-fitting clothes.
But how much more I pity English maids,
their waist and chest and bosom all confined by that vile, torturing instrument called 'stays."'
(Plays traditional tune)
"I'd be an Indian here and live content to fish and hunt, and paddle my canoe,
and see my children grow like young, wild fawns
in health of body and in peace of mind.
Rich without wealth,
and happy without gold."
The sympathy is different from the feelings
that South American Indians aroused in Charles Darwin.
When Darwin met the natives of Tierra del Fuego, he was horrified.
That's clear from his own words
and from the drawings in his book on the voyage of the Beagle.
No doubt the ferocious climate had an influence on the custom of the Fuegians,
but 19th-century photographs show that they did not look as beastly as they seemed to Darwin.
Wallace spent four years in the Amazon basin,
then he packed his collections and started home.
WALLACE: "The fever and ague now attacked me again
and I have passed several days very uncomfortably.
And to attend to my numerous birds and animals was a great annoyance,
owing to the crowded state of the canoe
and the impossibility of properly cleaning them during the rain.
Some died almost every day.
And I often wished I had had nothing whatever to do with them.
Though, having once taken them in hand, I determined to persevere.
Out of 100 live animals which I had purchased or had had given to me,
there now only remain 34."
The voyage went badly from the start.
Wallace was always an unlucky man.
WALLACE: "On the 10th June, we left Manaos,
commencing our voyage very unfortunately for me.
For, on going on board, after bidding adieu to my friends,
I missed my toucan,
which had, no doubt, flown overboard and, not being noticed by anyone, was drowned."
His choice of a ship was most unlucky.
She was carrying an inflammable cargo of resin.
Three weeks out, on August 6th, 1852, the ship caught fire.
WALLACE: "I went down into the cabin, now suffocatingly hot and full of smoke,
to see what was worth saving.
I got my watch and a small tin box containing some shirts
and a couple of old notebooks with some drawings of plants and animals,
and scrambled up with them on deck.
Many clothes and a large portfolio of drawings and sketches remained in my berth,
but I did not care to venture down again
and, in fact, felt a kind of apathy about saving anything that I can now hardly account for.
The captain at length ordered all into the boats and was himself the last to leave the vessel.
With what pleasure had I looked upon every rare and curious insect
I had added to my collection.
How many times, when almost overcome by the ague,
had I crawled into the forest and been rewarded with some unknown and beautiful species?
How many places, which no European foot but my own had trodden,
would have been recalled to my memory by the rare birds and insects
they had furnished to my collection?
And now...
...everything was gone.
And I had not one specimen to illustrate the unknown lands I had trod,
or to call back the recollection of the wild scenes I had beheld.
But such regrets, I knew, were vain.
And I tried to think as little as possible about what might have been,
and to occupy myself with the state of things which actually existed."
Alfred Wallace returned from the tropics, as Darwin had done,
convinced that related species diverge from a common stock...
...and nonplussed as to why they diverged.
What Wallace did not know
was that Darwin had hit on the explanation two years after he returned to England.
Darwin recounts that in 1838
he was reading the Essay On Population, by the Reverend Thomas Malthus...
..."for amusement," says Darwin, meaning it was not part of his serious reading.
And he was struck by a thought in Malthus.
Malthus had said that population multiplies faster than food.
If that's true of animals, then they must compete to survive.
So that nature acts as a selective force,
killing off the weak and forming new species from the survivors
who are fitted to their environment.
"Here, I had at last got a theory by which to work," says Darwin.
And you'd think that a man who said that
would set to work, write papers, go out and lecture.
Nothing of the kind.
For four years, Darwin did not even commit the theory to paper.
Only in 1842, he wrote a draft of 35 pages in pencil.
And two years later, he expanded it to 230 pages in ink.
And that draft, he deposited with a sum of money
and instructions to his wife to publish it if he died.
We feel that Darwin would really have liked to die before he published the theory,
provided after his death the priority should come to him.
That's a strange character.
It speaks for a man who knew that he was saying something deeply shocking to the public,
certainly deeply shocking to his wife.
And who was himself, to some extent, shocked by it.
The hypochondria. Yes, he had some infection from the tropics.
The bottles of medicine...
the enclosed, somewhat suffocating atmosphere of his house and study...
the afternoon naps...
the delay in writing...
the refusal to argue in public...
All those speak for a mind that did not want to face the public.
The younger Wallace, of course, was held by none of these inhibitions.
Brashly he went off, in spite of all adversities, to the Far East.
And there, on a night of fever, he recalled the same book by Malthus,
and had the same explanation flash on him that had struck Darwin.
(Thunderclap)
(Rumble of thunder)
WALLACE: "It occurred to me to ask the question:
Why do some die and some live?
The answer was suddenly clear.
From the effects of disease, the most healthy escaped.
From enemies, the strongest, the swiftest, or the most cunning.
From famine, the best hunters, or those with the best digestion.
Then I at once saw that the ever present variability of all living things
would furnish the material from which,
by the mere weeding out of those less adapted to the actual conditions,
the fittest alone would continue the race."
~ MENDELSSOHN: On Wings Of Song
"The more I thought it over, the more I became convinced
that I had, at length, found the long sought for law of nature
that solved the problem of the origin of species.
I waited anxiously for the termination of my fit
so that I might at once make notes for a paper on the subject.
The same evening, I did this pretty fully.
And on the two succeeding evenings, wrote it out carefully
in order to send it to Darwin by the next post, which would leave in a day or two."
Darwin received Wallace's paper
here in his study at Down House, in June of 1858.
He was at a loss to know what to do.
But friends arranged that Wallace's paper and one by Darwin should be read,
in the absence of both, at the next meeting of the Linnean Society in London, next month.
The papers made no stir at all.
But Darwin 's hand had been forced.
Wallace was, as Darwin described him, "generous and noble."
And so, Darwin wrote The Origin Of Species and published it at the end of 1859.
And it was instantly a sensation.
And a bestseller.
The theory of evolution by natural selection
was certainly the most important single scientific innovation in the 19th century.
Every generalisation about biology is a slice in time,
and it's evolution which is the real creator of originality and novelty in the universe.
And if that is so,
then each one of us traces back through that evolutionary process
right to the beginnings of life.
Darwin, of course, and Wallace looked at behaviour,
they looked at bones, at fossils.
And today, we look even more deeply...
...at the chemistry that we all share.
The blood in my finger at this moment has come...
...by some millions of steps...
...from the very first primeval molecules that were able to reproduce themselves
oh, perhaps 3,000 million years ago.
That is evolution in its contemporary conception.
The processes by which this has happened in part depend on... heredity...
...which neither Darwin nor Wallace really understood...
...and in part on chemical structure which, again, was the province of French scientists,
rather than of British naturalists.
But one thing they all had in common.
From that moment, it was no longer possible to believe any story which supposed
that at any time now there could be created once again the beginning of life.
Most people believed that creation had not stopped with the Bible.
They thought that the sun breeds crocodiles from the mud of the Nile.
Mice were supposed to grow of themselves in heaps of dirty, old clothes.
And it was obvious that the origin of bluebottles is bad meat.
Maggots mst be created inside apples. How else did they get there?
All these creatures were believed to come to life spontaneously, without the benefit of parents.
Fables about creatures that come to life spontaneously are very ancient
and are still believed.
Although Louis Pasteur disproved them beautifully in the 1860s.
He did much of that work here, in the house that he loved to come back to every year,
in Arbois, in the French Jura.
This is the wine cellar of his house.
Arbois is a wine-growing district.
Pasteur had done work on fermentation before that.
The fermentation of milk.
The word "pasteurisation" reminds us of that.
But he was at the height of his power.
In 1863, he was 40 when the Emperor of France asked him
to look into what goes wrong with the fermentation of wine.
And he solved that problem in two years.
It's ironic to remember that they were among the best wine years that there have ever been.
To this day, 1864 is remembered as being like no other year.
"The wine is a sea of organisms,"...
...said Pasteur.
"By some it lives, by some it decays."
There are two things... striking in that thought.
One is that Pasteur found organisms that live without oxygen.
At the time, that was just a nuisance to wine growers.
But since then, it's turned out to be crucial to the understanding of the beginning of life...
...because then, the earth was without oxygen.
And second,
Pasteur had a remarkable technique...
...by which he could see the traces of life in the liquid.
In his twenties, he had made his reputation...
...by showing... that there are molecules that have a characteristic shape.
And he had since shown
that that is the thumbprint of their having been through the process of life.
That has turned out to be so profound and so puzzling a discovery
that it's right to look at it in Pasteur's own laboratory upstairs.
PASTEUR: "How does one account for the working of the vintage in the vat...
...of dough left to rise...
...or the souring of curdling milk...
...of dead leaves and plants buried in the soil and turning to humus?
I must, in fact, confess that my research has long been dominated by the idea that
the structure of substances,
from the point of view of left-handed and right-handedness,
if all else is equal,
plays an important part in the most intimate laws of the organisation of living beings...
...and enters into the most obscure corners of their physiology."
Right hand...
...left hand.
That was the deep clue that Pasteur followed in his study of life.
The world is full of things...
...whose right-hand version is different from a left-hand version.
A right-handed corkscrew, as against a left-handed.
A right snail, as against a left one.
Above all, the two hands.
They can be mirrored one in the other...
...but they cannot be turned in such a way
that the right hand and the left hand become interchangeable.
That was known in Pasteur's time to be true also of some crystals,
whose facets are so arranged that there are right-hand versions... and left-hand versions.
Pasteur made wooden models of such crystals.
In his first piece of research, he had hit on the notion
that there must be right-handed and left-handed molecules too,
and what is true of the crystal must reflect a property of the molecule itself.
And that must be displayed by the fact that when you put them into solution,
and shine polarised light through them,
the right-hand molecules must turn the light to the right,
and the left-hand molecules must direct the light to the left.
A solution of crystals, all of one shape, will behave unsymmetrically in a polarimeter.
As the polarising disc is turned,
the solution will look alternately dark...
...and light,
and dark... and light again.
And a chemical solution from living cells does just that.
For the first time, Pasteur had linked life with chemical structure.
From that powerful thought,
it follows that we must be able to link evolution with chemistry.
The theory of evolution is no longer a battleground.
That's because the evidence for it is so much richer and more varied now
than it was in the days of Darwin and Wallace.
The most interesting and modern evidence comes from our body chemistry.
Let me take a practical example.
I'm moving my hand at this moment because the muscles contain a store of oxygen.
And that's been put there by a protein called myoglobin.
That protein has just over 150 amino acids to make it up.
The number is the same in me and all the other animals that use myoglobin.
But the amino acids themselves are slightly different.
Between me and the chimpanzee, there is just one difference in an amino acid.
Between me and the bushbaby, which is a lower primate,
there are several amino acid differences.
And then, between me and the sheep, the mouse,
the number of differences increases.
It's the number of amino acid differences
which is a measure of the evolutionary distance between me and the other mammals.
It's clear that we have to look for the evolutionary progress of life
in a build-up of chemical molecules.
~ PROKOFIEV: Love For Three Oranges
And that build-up must begin from the materials that boiled on the earth at its birth.
To talk sensibly about the beginning of life, we have to be very realistic.
We have to ask a historical question.
4,000 million years ago,
before life began, when the earth was very young,
what was the surface of the earth, what was its atmosphere like?
Well, it was like a volcanic neighbourhood anywhere,
a cauldron of steam and ammonia and gases.
What gases?
One gas was absent.
There was no free oxygen.
That's crucial, because oxygen is produced by the plants
and did not exist before life existed in a free state.
These gases in their reducing atmosphere, dissolved weakly in the oceans,
how would they react now, under the action of lightning, electric discharges,
under the action of ultraviolet light,
which is very important in every theory of life,
and which could penetrate in the absence of oxygen.
That question was answered by a beautiful experiment by Stanley Miller in America,
round about 1950.
He put the atmosphere in a flask.
The methane,
the hydrogen cyanide,
the ammonia, the water,
the oxides of carbon...
and went on for day after day after day,
boiled and bubbled them up,
put an electric discharge through them, to simulate lightning and other violent forces.
~ PROKOFIEV: Love For Three Oranges
And visibly, the mixture darkened.
Why?
Because, on testing, it was found that amino acids had been formed in it.
That's a crucial step forward,
because amino acids are the building blocks of life.
From them, the proteins are made.
And proteins are the constituents of all living things.
~ PROKOFIEV: Love For Three Oranges
We used to think that life had to begin in those sultry, electric conditions.
Until a few years ago.
And then, it began to occur to a few scientists
that there is another set of extreme conditions which may be as powerful.
That is the presence of ice.
It's a strange thought.
But ice has two properties which make it very attractive
in the formation of simple, basic molecules.
First of all, the process of freezing concentrates the material
which, at the beginning of time, must have been very dilute in the oceans.
And secondly, the crystalline structure of ice makes it possible for molecules to line up
in a way which is certainly important at every stage of life.
At any rate, Leslie Orgel did a number of elegant experiments
of which I will describe the simplest.
He took some of the basic constituents
which were sure to be present in the atmosphere of the earth at an early time.
Hydrogen cyanide is one.
Ammonia is another.
He made a dilute solution of them in water
and then froze the solution over a period of several days.
The time-lapse photographs show what happens.
The concentrated material is pushed into a sort of tiny iceberg to the top,
and there, the presence of a small amount of colour
reveals that organic molecules have been formed.
Some amino acids, no doubt.
But most important,
Orgel found that he had formed one of the four fundamental constituents
in the genetic alphabet which directs all life.
He had made adenine, one of the four bases in DNA.
It may indeed be that the alphabet of life in DNA
was formed in these sorts of conditions and not in tropical conditions.
Were the chemicals here on earth at that time unique to us?
We used to think so.
But the most recent evidence is different.
Within the last years, there have been found the spectral traces
in the interstellar spaces of molecules
which we never thought could be formed out in those frigid regions.
Hydrogen cyanide...
...cyanoacetylene...
...formaldehyde.
Those are molecules which we had not supposed to exist elsewhere than on earth.
It may turn out that life had more varied beginnings
and has more varied forms.
It doesn 't at all follow that the evolutionary path which life,
if we discover it elsewhere, took resembles ours.
It doesn 't even follow that we shall recognise it as life.
Or that it will recognise us.