Episode 2 David Attenborough's Natural Curiosities

How did two small animals from opposite ends of the world

upset the reputations of leading scientists

and change our understanding of evolution?

I've been lucky enough, one way or another,

to meet some of our planet's most enchanting creatures.

But some I find particularly intriguing.

We've known about some of these creatures for centuries.

Others we have discovered more recently.

In this series, I share their stories

and reveal why they really are natural curiosities.

In this programme, we explore the stories of two animals

that sent shock waves through the scientific world and beyond.

One is a toad that became the centre of a scientific storm

and caused accusations of fakery in the early part of the 20th century.

The other is an Australian animal

that baffled the greatest thinkers of Victorian Europe

and caused many to question whether it was even real.

When the first Europeans arrived in Australia,

they were shocked by the animals they found there.

Nothing in Europe could compare with the bizarre upright grazers

hopping across the grassland landscape,

carrying their young in pouches.

Kangaroos were obvious oddities, but another even stranger creature

also caught the attention of early settlers.

It lived along river banks and swam in the water.

Those first Europeans who saw it called it a water mole,

but that name didn't last long.

Inside this box is one of the first specimens of platypus

ever to be seen outside Australia.

It was sent to England in 1798 by Captain John Hunter,

the governor of New South Wales.

This one small animal would take the scientific world by storm

and transform the careers and reputations

of some of the leading thinkers of the time.

The platypus seemed to be a concoction of different animals.

Part-bird, with its bill, and part mammal, with its furry body.

When Charles Darwin first encountered one in the wild,

it baffled even him.

"Surely," he wrote, "two distinct creators must have been at work."

The task of describing the first platypus specimen

fell to naturalist George Shaw,

who worked in the department of natural history

in the British Museum.

He viewed this remarkable specimen with a fair degree of caution.

This is a first edition of a journal called A Naturalist's Miscellany,

which was published a few years after his examination.

It contains not only an article by him,

but a nice picture of the animal concerned.

At the end, he says, "On a subject so extraordinary as the present,

"a degree of scepticism is not only pardonable but laudable.

"I ought, perhaps, to acknowledge that I almost doubt the testimony

"of my own eyes with respect to the structure of this animal's beak."

It's said that Shaw was so determined to make sure

that he was not a victim of some elaborate hoax

that he actually cut behind the bill

to make sure that it hadn't been sewn on

by some mischievous forger.

In the late 18th century, the world was opening up.

Travellers were returning from overseas with all kinds of wonders.

Among them were specimens of creatures

that people had come to think of as being myths,

such as mermen and mermaids.

These were, of course, hoaxes,

put together with parts from different animals.

So it's understandable that Shaw had doubts about the authenticity

of his new furry specimen.

Despite his misgivings, he decided to give it a scientific name -

platypus, which means flat-footed.

He didn't know, however,

that a beetle had already been given this name.

Some years later, another taxonomist very properly gave it a new one -

Ornithorhynchus, which means bird snout.

But platypus is still the name that most people use.

But what type of creature was it?

George Shaw believed it to be a mammal because of its furry body.

All mammals feed on milk during the first part of their lives.

Milk that is produced by their mother's mammary glands.

But could an animal with a large, flat bill really suckle?

Some scientists thought that was impossible.

And, anyway, they couldn't believe the platypus and the monkey

could belong to the same group of animals.

But that view was to change.

Some 30 years after George Shaw described the platypus,

a German naturalist, Johann Meckel,

produced this wonderful collection of anatomical studies.

Meckel's meticulous and detailed work would help identify

the true nature of this animal.

Here...

..we can see his drawing of a male platypus,

showing clearly the claw.

Meckel also reported the existence of simple glands

beneath the thick fur of the female platypus,

glands that he suggested secreted milk.

There could be little doubt that these glands produced something.

But even then, several scientists doubted Meckel's claims,

and suggested rather desperately

that the glands secreted not milk but a lubricant.

Today we know that Meckel was right.

I was once able to use an optical probe

to peer into a platypus's burrow

and see a female platypus nurturing her single baby.

Yes. There it is. It's milk.

Milk is the perfect food.

It provides the growing youngster with everything it wants.

Only mammals produce milk.

In most mammals, of course, it comes from a nipple.

But in this very primitive mammal,

it simply oozes through the skin.

But 19th-century biologists had no such tricks to help them.

They had to unravel the strange biology of Australian mammals

from just a few shrivelled remains of long-dead specimens.

40 years after their discovery of the platypus,

a brilliant young anatomist -

who was to become a giant to 19th-century science -

joined the debate.

This is a statue of Richard Owen.

Owen was a formidable man.

The founding director of the Natural History Museum in Britain,

he was once described as having so much brain as to require two hats.

The platypus would become a central character in Owen's career.

His worked on this small creature

would help him secure election

to the prestigious Royal Society,

an exclusive group of scientists and thinkers.

Owen had an advantage over his European colleagues.

Australia was a British colony,

and Owen used his contacts

to supply him with specimens.

Eventually, two baby platypuses arrived

and it was obvious to him

that they would have no difficulty in suckling.

They'd not yet developed the bill

that would have made it awkward.

So he accepted the platypus babies,

like other mammal babies,

were indeed raised on milk.

But the biggest mystery of the platypus was still unsolved.

Did this animal lay eggs,

just like reptiles or birds,

or did it give birth to live young?

Owen was at the heart of that debate.

These jars contain the bodies of several platypus

that were shot and sent back here to the museum

for Richard Owen to examine.

His determination to prove whether or not they laid eggs

was going to cause the death of quite a number of platypus.

The Australian aborigines were absolutely clear they did lay eggs,

but that was not good enough for Owen.

He knew better than any Australian aboriginal.

He did concede that it might be

that the eggs were retained inside the body and hatched there,

so that the young were born live -

but that's as far as he'd go.

Eggs were also sent back.

Some of them were fake,

and some of them belonged to snakes.

It was going to be some decades

before the puzzle of the platypus

was finally solved.

The platypus now became embroiled

in the greatest scientific debate

of the Victorian era.

Did species evolve,

or were they created?

Darwin's Theory of Evolution

suggested that species could change over time,

so an intermediate form that laid eggs

but had fur like a mammal, was to be expected -

but that was too much of an stretch,

even for Owen's great brain.

In 1884,

more than 80 years after this first platypus specimen

had been examined by George Shaw,

William Hay Caldwell arrived in Australia

funded by a Royal Society scholarship.

One of his main aims was to solve the platypus egg question

once and for all.

After several months in Queensland

and with the help of the local aborigines,

he finally got the answer.

He shot a female platypus

soon after she had laid an egg in her nest burrow,

with a second egg about to emerge from her vent.

And they look like this.

It was, at last, visible evidence

that this animal did indeed lay eggs.

He sent a telegram to a scientific gathering in Montreal.

It was brief and to the point.

"Monotremes oviparous,

"ovum meroblastic."

These four words, to the scientifically initiated,

meant that the platypus laid eggs

and that the eggs consisted of an undivided large yolk,

just like a bird's egg.

The mystery was, at last, solved.

Richard Owen, who had refused to believe a mammal could lay an egg,

was by now 80 years old

and he was no longer held in the same esteem

as in the early part of his career.

The platypus had helped establish his reputation

but now the riddle of this creature's reproduction

had proved him wrong.

It's extraordinary to think

that this small animal fooled and confounded

many of the great scientific minds of 19th century Europe.

Not a hoax,

but a true curiosity,

and one like no other.

The egg-laying platypus was hardly believable

to Victorian researchers...

..but evolution has thrown up many unusual mating strategies

and, in the earlier part of the 20th century,

the anatomy of a particular amphibian started an argument that,

like the platypus,

led to accusations of forgery.

This is the curious tale of the midwife toad.

Midwife toads are not native to Britain.

They were introduced about a century ago and since then

have been slowly spreading over England.

Their natural home is Europe,

from Germany to Spain.

And in the 1920s, their mating habits caused a media sensation.

Investigations into the way the body of the male toad changed

according to its environment

led some to believe it might be possible

to breed a race of superhumans.

To understand why,

we must first know what makes the midwife toad so different

from any other frog or toad.

Amphibians were among the first backboned animals

to take to the land.

Since then, they've colonised most habitats,

from rainforests to deserts and mountains.

Despite spending much of their lives on land,

most frogs and toads need water to reproduce,

whether it be in a small vase plant or a large lake.

But mating in water is a slippery business.

Male toads, however, have a special adaptation.

Black warty swellings on their wrists, called nuptial pads,

which enable them to grip their partner securely during sex.

Once the female produces her eggs,

the male releases his sperm

and then lets go. His job is done.

But midwife toads are different.

The male does not have nuptial pads on his wrists.

And that's because he doesn't mate in water.

He mates on land.

The female produces her eggs

and then he takes them around his legs

with an action that has been compared

to a man trying to put on his trousers without using his hands.

And so it is the male toad that is the actual midwife,

not the female.

Midwife toads tend to live in places where open water is scarce.

Once the male has successfully

wrapped a string of eggs around his legs,

he usually hides under a rock, where it's suitably damp.

He may have as many as 150 eggs

and he hides away for up to two months while they develop.

Then, just before the eggs hatch,

he sets off to find water for his emerging tadpoles.

Now, the tadpoles of most frogs and toads

turn into the adult form within a matter of weeks,

but not so the midwife toad - it takes much, much longer.

In fact, sometimes, they may even overwinter

in the form of a tadpole,

which is why perhaps midwife toad tadpoles are such whoppers!

Frogs and toads are widely used in biological studies,

because they're easy to keep

and the different stages of their life cycles are easy to observe.

So it's no surprise that the unusual behaviour

of the midwife toad should attract the attention of many biologists.

One was an Austrian scientist called Paul Kammerer,

who worked in Vienna in the early part of the 20th century.

And his discoveries quickly brought him great fame.

But the toad would become a curse

that would haunt him until the end of his life.

Kammerer was greatly influenced

by the great French zoologist Jean Baptiste Lamarck,

who in 1799 published his theory that characteristics acquired

by an animal during its life could be inherited by its offspring.

That a giraffe, for example,

reaching upwards to nibble the topmost shoots of trees, would

over time lengthen its neck muscles and that this increase would then be

inherited by its offspring, and so on, for generation after generation.

Lamarck's theory was largely rejected after Charles Darwin

proposed a different mechanism for evolution,

based on changes to an animal's genetic make-up.

Kammerer was keen to prove that Lamarck was right after all.

But giraffes are not the ideal experimental animal,

so he needed one he could keep in a lab and that would

reproduce quickly, and his attention fell on the midwife toad.

Kammerer became fascinated

with the unusual nature of the midwife toad's reproduction.

Why did males, like this one, carry eggs around his legs?

And could this be changed?

He wondered if their biology might be related

to their unnatural environment, which is largely arid.

Kammerer decided to see what would happen if he kept the toads

in a warm, humid tank with access to pools of cool water.

His work with the toads would last many years

and involve several generations, but eventually, he noticed changes.

Some male toads abandoned carrying the eggs

and instead, the females laid them directly in water.

Over several generations,

Kammerer had managed to change the midwife toad

from being a land-breeding animal to one that bred in water.

But the most extraordinary discovery

came as he continued breeding these toads.

He noticed that the wrists of some of the males

developed warty-looking structures,

just like the nuptial pads of other frogs and toads, which are normally

used by males to grip females when fertilising her eggs.

His work suggested that somehow, by altering

the environment in which they lived, a toad's body could be changed.

And that change was then passed on to future generations.

Kammerer's work was taking place at the end of the First World War

and political movements on the left and the right

were then keen to exploit scientific discoveries.

Despite his subject being a small toad,

some saw a opportunity to extend his findings beyond the laboratory.

He was hailed as a second Darwin in the New York Times.

Some newspapers got carried away

and suggested that Kammerer's discoveries could apply to humans.

His work could help, in other words, to breed a race of superhumans.

Whether he liked it or not, Kammerer was now in the spotlight.

He set off on a lecture tour across Europe and America.

In Cambridge, the Professor of Zoology hailed his achievements

and put one of Kammerer's toads on display.

But not everyone was convinced.

An American zoologist by the name of GK Noble wrote a damning article

in the prestigious scientific journal Nature.

Noble examined one of Kammerer's toads and declared that

its black nuptial pads were fakes, produced by injecting a black dye.

Kammerer denied this.

Someone, he said, had interfered with his specimens

and was trying to ruin him.

But the damage to his name was done.

Six weeks after the Nature article accusing him of forgery,

Kammerer wrote a letter to another leading scientific journal.

This is an extract of what it said.

"On the basis of this state of affairs, I dare not -

"although I myself have had no part

"in these falsifications of my prior specimens -

"any longer consider myself a proper man to accept your call.

"I see that I am also not in a position to endure

"this wrecking of my life's work and I hope I shall gather together

"enough courage and strength to put an end of my wrecked life tomorrow."

Soon after writing that letter,

he walked into the hills around his home and shot himself.

Whether or not Kammerer's suicide was purely down to the fallout

from his midwife toad experiments, we can't be sure.

There were many other problems in his personal life.

But there can be little doubt that the scandal surrounding his work

would've weighed heavily on his mind.

Since Kammerer's death, a specimen of male midwife toad

with nuptial pads has been found in the wild.

Some scientists now believe that environmental influences

CAN change the way some genes behave,

and that these changes can indeed be passed on to the next generation.

Perhaps midwife toads possess the gene to grow these structures,

but it's only switched on in certain situations.

Does this prove Kammerer was right?

No-one has been able to repeat

Kammerer's experiments with midwife toads.

So we don't know for sure if he falsified his findings or whether

he had stumbled upon a quirk of inheritance ahead of its time

and beyond the understanding of scientists of his era.

What is certain is that the nature

of how species inherit their characteristics

is more complex than he or others at the time originally thought.

The curious lives of the midwife toad and the duckbilled platypus

perplexed and wrong-footed science for some considerable time.

But in the end, both of these creatures helped us

to better understand the way animals evolve.