[MUSIC PLAYING] SEAN CARROLL: After
four arduous years of collecting animals
in the Amazon jungle, Alfred Russel Wallace is
finally heading back to England. Sailing with him are the
rewards of a long journey-- thousands of specimens he will
sell to museums and collectors. Exhausted from his
travels, Wallace is looking forward to
the comforts of home. [SHOUTING IN THE DISTANCE] SPEAKER 1: I'm afraid
the ship's on fire. SEAN CARROLL: Every one
of Wallace's specimens is destroyed. His hard-earned records
of which animals live where in South
America are also lost. These notes contain
clues to the question that Wallace risked
so much to answer. It was the greatest scientific
mystery of his time. Where do species come from? But now, Wallace's thoughts must
turn to a more urgent concern-- survival. His hands are burned raw
from sliding down a rope. His lifeboat is leaking badly. The castaways have
little food or water and are 700 miles from
the nearest shore. Wallace vows that
if he survives, he will never sail again. This is the story of the search
for the origin of species, and of the epic adventures
of the two explorers who found the answer. Alfred Wallace
might have avoided his predicament had someone
else not been keeping a secret. Another British
naturalist had already answered the question
of the origin of species years earlier, but he had dared
to share his ideas with only a few trusted friends. [MUSIC PLAYING] Charles Darwin set
sail on his own voyage 20 years before
Wallace's shipwreck. He was an unlikely
revolutionary. He lived in a time when
most scientists believed that each species
was specially created by God, in its present
form and constant, and not somehow the product of
natural laws, and changeable. At the age of 22, Darwin also
believed in special creation. He was even planning
to become a clergyman. But then he got a
surprising offer. Darwin jumped at the
chance to sail around the world on a British
Naval vessel, the Beagle. The offer was more about his
pedigree than his resume. Darwin could be cheerful
upper class company for the captain,
no small task given that the Beagle's previous
captain became despondent and shot himself. The lure for Darwin, he was a
passionate amateur naturalist, and now he'd have the
chance to see and collect animals, plants, and
rocks around the globe. [MUSIC PLAYING] Early in the voyage, he
examined plankton with his state-of-the-art microscope,
an instrument that only the son of a wealthy family
could have afforded. Darwin was perplexed. Why was there so much beauty in
the middle of the ocean where no one was around to enjoy it? Why were these forms created
for so little apparent purpose? But for every moment
of joy or discovery, Darwin experienced
100 of suffering. He was often seasick-- [MUSIC PLAYING] --not merely queasy, but
desperately, violently ill. His adventure came
at a high price. Darwin's curiosity was
not limited to science. On the coast of Argentina, he
sampled the local delicacy-- roast armadillo. He thought it tasted like duck. [MUSIC PLAYING] Not far from this
barbecue, Darwin found an interesting fossil. It was a small
piece of an extinct creature called glyptodon. It was part of its
protective covering. Darwin had seen a
similar bony shell on the armadillo
he had just eaten. But this fossil
came from a giant. The animal he discovered would
have been dinner for 1,000. Darwin found several
more fossils nearby, including ground
sloths, like this one. They were all enormous
compared to living species. Darwin would ponder the
geological relationship between the extinct
and the living. Darwin didn't yet understand
why fossils of extinct animals turn up where similar
animals live today. [MUSIC PLAYING] After nearly four years
at sea, twice as long as Darwin had signed
up for, the Beagle arrived in a remote Spanish
colony, the Galapagos. It would have been the
dream of most any naturalist to explore these islands. But when Darwin arrived, he was
more exhausted than excited. If Hell had a garden,
he thought, this is what it would look like. The black volcanic
rocks felt as if they'd been baked in an oven. The plants stank. He didn't see a single
beautiful flower. The Darwin that arrived here
was not the great theorist that we know today. He was a 26-year-old collector,
collecting, really almost at random, any kind of
plants, any kind of animals, any kind of rocks. He didn't even know the
meaning of what he was collecting until much later. [MUSIC PLAYING] He thought the island's
seagoing iguanas looked dim-witted and hideous. But he did like a different
Galapagos reptile-- the tortoises. He even took a ride on one. You magnificent beast. [MUSIC PLAYING] (WHISPERING) When Darwin
was here in the Galapagos, he was given an important clue. The Spaniards told
him that they could tell which island a
tortoise came from just from the shape of its shell. [MUSIC PLAYING] Why would tortoises
on nearby islands look so different
from one another? The island's mockingbirds also
caught Darwin's attention. He focused on their
subtle differences. One kind of mockingbird
had smudges on its breast. Another had a large dark
patch under each eye. A third had a pure white breast. Darwin was astonished
when he realized that, just like the tortoises,
each kind of mockingbird lived on a different island. So even though he stayed
here just five weeks out of the whole
five-year voyage, it's what he saw here in
these five weeks that left the greatest
impression on Darwin and will lead into
his greatest ideas. After stops in Australia and
Africa, and as the Beagle turned home to England,
Darwin had the chance to reflect on what
he'd been seeing. [MUSIC PLAYING] In his cabin, Darwin puzzled
over the Galapagos animals. It was remarkable that
similar but distinct creatures lived on such nearby islands. What would explain this fact. According to special creation,
God made a different species for each island. But another possibility
occurred to Darwin. Perhaps one species might
have come from the mainland, and then changed in different
ways on different islands. The Galapagos animals were
raising a radical idea. Species might change. [MUSIC PLAYING] After Darwin
returned to England, he starts thinking
about everything he saw on this five-year voyage. And he's thinking back to
the geology, the fossils, the animals that he'd seen. He's in this process he
calls mental rioting, just letting every
thought stream to him, until finally, he
has his big idea. Rioting was the right word. His ideas were doing violence
to the established order. The best explanation for what
Darwin saw in the Galapagos was that species changed
into new species. Over time, one
kind of mockingbird somehow became three. Tortoises multiplied
into different forms. And what did it mean that
armadillos and sloths live today where extinct
giant versions once roamed? Maybe, Darwin thought,
today's species are descended from
older extinct types. If so, then all species are
connected to one another in a family tree. It is a simple, crude
sketch, but Darwin's drawing is a radical new
picture of life. Any species can give rise to new
and slightly different species. As generations
pass, grand-species arise, and then
great grand-species. Darwin's bold idea was that
species come from other species just as naturally as
children come from parents. There was a word for
this kind of thinking-- heresy. So the origin of species
was natural, not divine. It was a revolutionary idea
that overthrew special creation. It ran against church
teachings and what most Europeans believed,
including most scientists. Still a young man, Darwin
couldn't reveal his great idea. He would be attacked and ruined. [MUSIC PLAYING] Many years later, Darwin's
popular account of his voyage is a big success. He's published six books and
has become England's most prominent naturalist. But he is still keeping
his biggest idea secret. Darwin is gathering
yet more evidence for his theory,
when at a museum, he encounters an
earnest young man. ALFRED RUSSEL WALLACE:
I've read your work, Voyage of the Beagle. It is excellent and inspiring. Thank you very much. SEAN CARROLL: Wallace had
survived his ordeal at sea. ALFRED RUSSEL WALLACE:
--to do some research. SEAN CARROLL: After 10
miserable days in a lifeboat, he'd been rescued
by a passing ship. ALFRED RUSSEL WALLACE: I'll post
you my notes before I leave. CHARLES DARWIN: Ah, excellent. SEAN CARROLL: Wallace and Darwin
are meeting for the first time. The two explorers share a
great passion for nature, but they are in very
different situations. ALFRED RUSSEL WALLACE: I'm
headed to the Malay Archipelago to do some research. CHARLES DARWIN: Excellent ALFRED RUSSEL
WALLACE: I'm here to-- SEAN CARROLL:
Wallace is single . He has to collect for a
living, and he has yet to make his mark. CHARLES DARWIN: Yes, no,
I've never been there. Are you collecting? ALFRED RUSSEL WALLACE: Yes. SEAN CARROLL: Darwin is
married and has a family. He is financially well-off and
has a scientific reputation to protect. Wallace is as open as Darwin
is secretive about his interest in the origin of species. Little does Darwin know that
this young man will soon force his hand. ALFRED RUSSEL WALLACE: I could
send you back some specimens if you'd like. CHARLES DARWIN: Oh,
very much so, yes. Thank you. But please, no barnacles. I've just finished a
work on barnacles that-- SEAN CARROLL: And Wallace
doesn't have a clue that Darwin has already scooped him. CHARLES DARWIN: Have you
written anything yourself? SEAN CARROLL: Believing
that the question of the origin of species
is still wide open, and despite having nearly
lost his life at sea, Wallace sets out
on a new voyage. [MUSIC PLAYING] He travels to the region
between the Pacific and Indian oceans,
the Malay Archipelago. For the next eight years
he will collect and study animals, as he hops from island
to island in a 14,000 mile journey. Wallace is captivated
by butterflies. His favorite group
is called birdwings after their shape
and large size. They command a high price
for their striking colors. He finds birdwing butterflies
throughout the archipelago. He identifies new
species, some that are slightly different from
those on nearby islands. The Malay butterflies suggest
to Wallace what the Galapagos animals revealed to Darwin-- species change. But Wallace, too, seeks to
understand the bigger picture. Having explored jungles on
opposite sides of the globe, he can compare where different
groups of animals live, and ask why they are
found where they are. Wallace the collector now
becomes Wallace the theorist. Birdwings occur near other
species of bird wings in the Malay Archipelago. Across the globe in the Amazon
lived different families of butterflies. Bird families also
clustered geographically. Cockatoos live only in the
Malay Archipelago and Australia, whereas the Americas are home
to macaws and hummingbirds. Around the globe, the more
similar two species are, the closer they tend to live. Why is this so? Wallace formulates
a new law of nature. It's about where
new species arise. They don't appear
in random places. They arise near similar species. [MUSIC PLAYING] He realizes the
profound implication that species are
connected to one another, like the branches of a tree. On his own, Wallace arrives
at Darwin's still secret tree of life. Wallace finds more
evidence that all species are related by considering
some intriguing creatures. Manatees are mammals that
live entirely in the sea. But inside their flippers
are finger bones. Similar apparently useless bones
are inside whale flippers, too. If God had created these
animals from scratch, wouldn't he have
skipped the fingers? Imperfections such as
these vestigial structures make it clear that every species
is a modified form of an older species. Zig-zagging across
the Malay Archipelago, Wallace gathers critical
evidence for his law. On the island of Borneo, he
sees monkeys and orangutans. But elsewhere in the
archipelago, in New Guinea, the mammals are
strikingly different. [MUSIC PLAYING] No monkeys here-- instead,
up in the branches are tree kangaroos, marsupials
whose young grow up in pouches. Island by island,
Wallace notes which of the two groups of
mammals lives there-- those with pouches
and those without. Animals on the eastern islands
resemble those of Australia, animals to the
west, those of Asia. It as if a line splits
the archipelago. It will be dubbed
the Wallace Line. Why would God draw a boundary
through these islands and put monkeys in
the trees on one side and put kangaroos in the
trees on the other side? This made no sense. Special creation couldn't
explain the line, but Wallace's earlier
law could, that species come from pre-existing
nearby species. [MUSIC PLAYING] The eastern islands of
the Malay archipelago, Wallace surmised, were
once connected by land to New Guinea and Australia. So animals like kangaroos
could hop on over. The Western islands were never
connected to the eastern ones, but they were connected
to Asia, so the west had different mammals, ones with
placentas instead of pouches. It's the history of the
planet, not special creation, that explains the
distribution of species. In Wallace's time,
geologists understood that natural processes, such
as volcanism and erosion, could change the shape of
islands and continents. But what about species? How do they change? That is Wallace's next question. As a collector, he has
a great eye for detail, as he chooses specimens
to sell to his customers. He knows that among
all living things, from butterflies to snails,
individuals within a given species usually
vary in small ways. But what does that
variation have to do with how species change? The answer comes to Wallace
during a high fever. He must have been thinking
about the very real chance that he would die. [MUSIC PLAYING] He recalled the
English economist Thomas Malthus, who noted
that human populations are held in check by famine,
disease, and death. Wallace realized that was
even more the case in nature. Without death, any species
would quickly overrun earth. But animal populations
tend to hold steady. That's because huge numbers
of young die every generation. Two facts now snap together-- massive death plus variation. ALFRED RUSSEL WALLACE: [COUGHS] SEAN CARROLL: Wallace now
sees how species could change. Those individuals
with variations that give them
even a slight edge will survive,
reproduce, and in time, outnumber those
without the advantage. [MUSIC PLAYING] His is a fundamentally
new picture of nature, of intense, even
violent competition. Wallace thinks he might
have an important new idea, but he wants a second
opinion before publishing. He knows just the
right person to ask, thousands of miles
away in England. SPEAKER 2: Excuse me, sir. This just came for you. CHARLES DARWIN: Ah, yes. Thank you. SPEAKER 2: Sir. SEAN CARROLL: Darwin is shocked. He couldn't have
written a better summary of his own theory
of how species change-- he called it natural
selection-- than what had just arrived from Wallace. How could this happen? Both men observed
slightly different species on nearby islands and
concluded that species could change over time. Both had collected huge
numbers of specimens and realized that individuals
vary within species. And both had witnessed
nature up close and realized it
was a battlefield with massive casualties. Same fact patterns, same
explanation, great minds think alike. [MUSIC PLAYING] Darwin now worries that he
will lose all the credit for his original idea. Darwin turned
Wallace's manuscript over to two close colleagues
who had been privy to Darwin's ideas on natural selection. They decided that Wallace's
manuscript and some excerpts from Darwin should be
read aloud together on the same day in London. The idea was to
share the credit, although everyone involved,
including Wallace, agreed that Darwin got there first. [MUSIC PLAYING] Darwin published his own
masterful full-length account in 1859. On the Origin of Species became
one of the most influential books ever published. It was an instant
sensation that signaled the birth of modern biology. Wallace eventually wrote
a book on evolution. He gave it the title Darwinism. Darwin and Wallace,
who framed a new view of life driven by competition,
did not compete, themselves. Instead, they became
lifelong friends, bound by their shared
hard-earned insight into how evolution
shaped the living world. [MUSIC PLAYING]
The video is about origin of species and when the past. A theory of evolutionary of life. Most of these people are here because of homework.