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{\an8}Transcript format and synch by Andante

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This is a journey of the imagination

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that may change your opinion

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of who you are and where you come from.

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Viruses, once solely thought to be
agents of disease and death,

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may have actually given rise to our species.

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They are our ancestors.

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If we respect humans, I think we have to
respect the viruses that made them.

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Startling discoveries
are also revealing that

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viruses have left their fingerprints
throughout evolution.

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They may have sparked
the explosion of complex life,

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changed the way the young are born,
and be responsible for love itself.

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The notion that viruses simply be harmful
is absurd.

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Today, the handiwork
of viruses is far from over,

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and some even imagine that in the future,

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viruses could lead to the emergence
of a new human species.

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Life on this planet would not be
life on this planet without viruses.

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Not far from the lights of Hollywood,

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a strange story is being written that
sounds like a script for a sci-fi movie.

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But this tale is real.

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Within the dark confines
of a cavernous laboratory,

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a visionary scientist
carefully outlines his plot.

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His name, Dr. Luis Villarreal.

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At the center of his drama

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is a bizarre cast of microscopic creatures

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Villarreal calls agents.

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To most of us, they are known as viruses.

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By definition, viruses are parasites that
infect cells and cause disease.

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But in this story, they possess
far greater power.

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Villarreal suspects that if we could
go back in evolutionary time,

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we would see that every plant, every animal,

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and even humans were created
in large part by viruses.

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According to Villarreal, we are the
descendants of these creatures.

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When most people think of the word virus,

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they have a distinctly negative reaction,

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a fearful reaction,
because they understand them

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to be infectious agents that
can make them quite sick,

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and therefore there's something
to be avoided and feared.

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But I think viruses are the leading edge
of evolution.

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Villarreal's ideas are revolutionary,
but they're also controversial.

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How could viruses help to create life

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when they seem solely built for destruction?

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Viruses are best known as microscopic armies

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that attack living cells
in massive assaults.

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Viruses are like tiny robots.

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Together, they form a brigade of
machine-like invaders.

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Their only weapon, a piece of genetic code
which many inject into a cell.

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Once inside, the code can quickly destroy
the cell's DNA and takes control.

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Often, the cell is forced to build more
viruses until it finally explodes,

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releasing a new brigade of replicants.

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Villarreal thinks there's more to viruses
than replication and death,

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and he's not alone.

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The story he's weaving is based on evidence
being compiled from all over the globe.

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It doesn't look like a month of
a new route, so...

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Nathan Wolf is a virus hunter.

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And while you may think viruses are rare

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because you seldom get sick,

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Wolf knows the true extent of their domain.

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{\an8}At this moment, they're sitting everywhere,

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{\an8}surrounding me, coding me
on the inside of my body

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{\an8}throughout my different organ systems.

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These things are everywhere,

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and they're impacting us in ways
that we have really

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only just begun to understand.

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The jungles of Cameroon are a hot zone
for virus hunters like Wolf.

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That's because the forest is
literally teeming with life,

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and viruses infect everything

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that walks, flies,

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slithers, and crawls.

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Although the tropics are known
for their animal diversity,

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it is the virus that is king of the jungle.

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Almost by definition, that makes viruses
the most diverse entities on our planet.

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Viruses are a vast, unknown world.

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Among the legions of viruses
that lurk in these jungles,

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Wolf is stalking those that jump
from animals to humans,

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a feat thought to be rare.

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But when it does happen,
the results can be catastrophic.

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It's widely believed that
not far from this jungle,

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a virus did jump from chimpanzees to people,

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a virus known the world over as HIV.

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Wolf suspects that there are other viruses

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poised to launch further assaults.

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When we started our work,
I think people pretty much suspected

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that we wouldn't see much.

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The conventional wisdom was that

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these were relatively rare events.

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These were not things that were occurring
on a regular basis.

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On the lookout for viral jumps,

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Wolf is monitoring villagers
like this tribal chief and his family.

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That's because the people living here have
near-daily contact with wild animals.

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Whether through trapping

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or butchering.

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This intimate contact can expose people to
a myriad of viruses.

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Viruses that live on skin, in saliva,

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in vital organs,

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and to viruses that thrive in blood.

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By monitoring viruses

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in the blood of the hunted and the hunters,

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Wolf made a striking discovery.

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Several viruses in the same family as HIV
have jumped to humans.

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I actually do remember the first time
that we actually saw evidence,

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and frankly it was a little bit
shocking from our perspective,

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that this was not something that was rare.

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Wolf's initial results revealed that
ten people in a thousand he sampled

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were clearly exposed to a primate virus.

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And ten in a thousand is
a significant number.

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All you have to do is take one
step back and extrapolate that

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to how many people are in the
country we were looking in, Cameroon.

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How many people are in Central Africa?

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How many of those people have day-to-day
contact with these animals?

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And very quickly,

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we recognized that probably
tens of thousands of people

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were infected with these viruses,
and frankly it was a shock.

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As viruses continually jump
from animals to humans,

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it's unclear if these new infections
will ultimately lead to a pandemic,

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like the one caused by HIV.

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And Wolf is keeping a watchful eye.

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But there's more to this story
than a potential health threat.

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That's because the viruses Wolf is tracking

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have a rare power to rearrange
the basic blueprint of life, DNA.

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Many viruses attack cells
in seek and destroy missions.

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Central to their assault is
obliterating the cell's DNA

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before exploding the cell into oblivion.

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The viruses Wolf is investigating
rely on a different tactic.

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And they are called retroviruses.

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Now retroviruses are very interesting,

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because what retroviruses do is
in order to complete their life cycle,

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they actually have to integrate themselves

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into the genetic diversity of their host.

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After they've entered into a cell,

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they actually take their genetic information

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and they become part of the
genetic information of the host cell.

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That cell and all of its progeny
are forever changed.

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Now that sets up
a very interesting situation.

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If a retrovirus integrates
into a sperm or egg cell,

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the genetic changes can become permanent,

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passed down from generation to generation.

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And if integration like this
happens repeatedly,

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over evolutionary time,

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our basic blueprint could be
altered dramatically.

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And that's something which is sort of
profound if you think about it.

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In some ways, you could almost think of it

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as this is a moment
where a virus and a host merge.

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They're not acting like viruses,

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but they're a part of
our own genetic fabric,

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which could affect
the future course of evolution.

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If retroviruses can change
our genetic code,

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this raises a provocative question.

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How has this rewiring affected our species?

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Luis Villareal thinks he knows
the answer to this question.

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He suspects that retroviruses

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can help to explain how primates

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evolved into human beings.

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If you just looked at the blueprints
of the chimpanzees in humans,

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our genes are virtually identical,

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nearly 99% the same.

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So where are the instructions
that make us unique?

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Villareal is convinced

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the answer can be traced back
to retroviruses

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and something called junk DNA.

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Junk DNA is bits and pieces of genetic code
that litter the blueprint of chimpanzees.

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Junk DNA also plutters our genome.

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One of the big surprises when the initial
sequencing of the human genome was done

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is that somewhere between
93 to 95% of the DNA

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was in this junk category.

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{\an8}We are predominantly junk,
according to this view.

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But this junk, it turns out,
isn't junk after all.

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A lot of it is the genetic remains
of ancient retroviruses.

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Villareal imagines that long ago,

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as viruses integrated into primates,

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they began redrawing their blueprint.

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A lot of the changes went nowhere,
evolutionary dead ends.

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Over time, however, Villareal thinks some
changes proved beneficial for survival.

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And as they accumulated, primates gave
rise to a new species,

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human beings.

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As humans and chimps
went their separate ways,

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both species were continually colonized

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by their own unique viruses.

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So what really marks the distinction

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of our evolution from our closest relative

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are the viruses that colonized
our respective genomes.

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The viruses were directly involved

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in differentiating our lineage
from the chimpanzee lineage.

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And in that context, it's not junk,
it's who we are.

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Villareal realizes that it might be
hard to imagine that

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viruses led to the emergence of humans.

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But this isn't the
strangest part of his story.

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In piecing together the evolution of life
on Earth,

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investigators have documented an epic tale

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with a cast of incredible animals
and surprising twists and turns.

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Villareal, however, thinks
we've overlooked a major player.

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The history of evolution of biology is

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basically devoid of considering
the consequence of viruses,

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especially those that persist and colonize.

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But I have concluded that

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viruses were involved in all of
the major evolutionary transitions.

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According to conventional wisdom,

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if we could go back in time,

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the early chapters of animal life

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were suspected to have unfolded
something like this.

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Hundreds of millions of years ago,

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before dinosaurs, chimpanzees and humans,

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before animals swam the ocean,

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only one group of animals existed.

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They were sponges.

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Unable to move on their own,

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they lacked all but
the most basic abilities.

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Sponges filtered food particles
from the water

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by pumping water through their bodies.

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They were little more than
a loose collection of cells.

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Then creatures far more complex came
into being and changed the world forever.

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These flower-like beings
are called cnidarians.

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Here was an animal with a mouth,
muscles and nerves.

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Next came a flatworm-like animal,

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the first with a head and eye-like sensors.

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Then, in a geological instant,

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a great diversity of new body plans
emerged and life blossomed,

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eventually leading to terrestrial animals

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and human beings.

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It's an accepted chronology of evolution,

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but Villarreal suspects we need to rewrite
the first chapter.

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In his version of the story,

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evolution got jump-started by a virus,

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and a recent discovery supports his theory.

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Trevor Douglas is a chemist.

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Mark Young is a virologist.

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Together, they hunt for viruses
in extreme environments

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that resemble early Earth.

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The hot springs that pepper this landscape

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are like windows back in time.

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Within these scalding waters,

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there are ancient microbes,

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descendants of the earliest life forms
on the planet.

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The creatures thrive here in temperatures

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that can reach more than
200 degrees Fahrenheit,

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in cauldrons of acid that can burn flesh.

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And where there's ancient life,
there sure to be ancient viruses.

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We knew there was life in these hot
springs, and we knew it was unusual life.

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{\an8}And so we suspected that the viruses
that would be there would be also unusual,

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{\an8}and might give us new insights

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{\an8}into how life evolved on this planet.

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Just bring it back slowly, and I'll go
ahead and measure the temperature.

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The fun part of this is, you know,

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you go to weird places,
turns out you find weird things.

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Well, I think, you know, any time I look
at this virus, especially the cryo...

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To date, Young and Douglas
have unearthed dozens of viruses,

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with lineages that can be traced
back to the beginnings of life.

248
00:19:36,910 --> 00:19:38,320
Particles that look empty...

249
00:19:38,321 --> 00:19:40,459
But nothing they found prepared them

250
00:19:40,483 --> 00:19:45,125
for an ancient virus that was
discovered by accident in Europe.

251
00:19:49,566 --> 00:19:51,766
The year is 2003.

252
00:19:52,509 --> 00:19:54,090
In a lab in France,

253
00:19:54,114 --> 00:19:56,963
Bernard La Scola is examining what he thinks

254
00:19:56,987 --> 00:20:00,461
is an old bacteria sample from the archives.

255
00:20:02,486 --> 00:20:05,807
But as he looks through the lens of
his high-powered microscope,

256
00:20:05,831 --> 00:20:07,827
La Scola is shocked.

257
00:20:08,780 --> 00:20:10,492
This is no bacteria.

258
00:20:10,779 --> 00:20:13,199
The sample was misidentified.

259
00:20:14,080 --> 00:20:17,095
This is a monstrous virus.

260
00:20:20,495 --> 00:20:22,640
The virus, later named Mimi,

261
00:20:22,664 --> 00:20:26,475
shattered the view of
what a virus could be.

262
00:20:29,172 --> 00:20:32,974
It's long been thought
all viruses were tiny,

263
00:20:32,998 --> 00:20:35,808
that they were essentially lifeless,

264
00:20:35,832 --> 00:20:39,103
and that they need cells
in order to replicate.

265
00:20:42,390 --> 00:20:44,960
Mimi changed everything.

266
00:20:48,077 --> 00:20:52,336
First of all, it was gigantic.

267
00:20:53,729 --> 00:20:59,369
{\an8}Mimi is a big kind of overweight virus
that's got too much stuff.

268
00:20:59,689 --> 00:21:03,134
And that extra bloatedness
comes from the fact that

269
00:21:03,158 --> 00:21:06,714
it's carrying a whole bunch of genes
that viruses don't normally carry.

270
00:21:06,739 --> 00:21:11,988
And that makes it start to look like
it can do cellular-type functions.

271
00:21:13,370 --> 00:21:16,855
Some of the genes in Mimi are startling.

272
00:21:17,203 --> 00:21:23,991
They suggest that long ago, Mimi might
have been able to replicate without a host.

273
00:21:24,910 --> 00:21:29,287
And if that was the case,
Mimi wasn't like other viruses.

274
00:21:30,170 --> 00:21:32,060
Maybe it wasn't a machine.

275
00:21:32,243 --> 00:21:34,741
Maybe it wasn't a parasite.

276
00:21:35,650 --> 00:21:39,061
Maybe at one time, it was alive.

277
00:21:42,256 --> 00:21:45,476
Young and Douglas know this is
a controversial idea.

278
00:21:46,076 --> 00:21:50,069
Critics claim Mimi simply stole
some genes from a cell.

279
00:21:50,136 --> 00:21:51,609
End of story.

280
00:21:52,670 --> 00:21:54,705
Young and Douglas disagree.

281
00:21:56,849 --> 00:22:00,892
They point to evidence that indicates
Mimi's genes are simpler,

282
00:22:00,916 --> 00:22:03,457
and therefore could be older.

283
00:22:04,683 --> 00:22:06,677
To many investigators, this means

284
00:22:06,701 --> 00:22:08,848
Mimi didn't steal the genes.

285
00:22:09,750 --> 00:22:12,906
On the contrary, it may have invented them

286
00:22:12,930 --> 00:22:15,510
long before there was complex life.

287
00:22:24,103 --> 00:22:27,231
Young and Douglas imagine
that going back in time,

288
00:22:27,255 --> 00:22:31,242
early Earth might have
looked something like this.

289
00:22:37,039 --> 00:22:42,321
For eons, the planet was basically
mats of simple life, like bacteria.

290
00:22:45,059 --> 00:22:48,036
A world we'd hardly recognize today.

291
00:22:50,926 --> 00:22:53,328
But there were viruses.

292
00:22:55,519 --> 00:22:57,563
Young and Douglas think it's possible

293
00:22:57,587 --> 00:23:02,903
that an ancient Mimi-like virus might
have invented the instructions for life

294
00:23:02,927 --> 00:23:08,164
to become more complex, and then
inserted them into primitive cells.

295
00:23:09,059 --> 00:23:11,671
They also think that a Mimi-like virus

296
00:23:11,695 --> 00:23:15,542
could have served as
the first cellular nucleus.

297
00:23:16,273 --> 00:23:18,230
The command and control center

298
00:23:18,254 --> 00:23:21,193
that enabled life to get more elaborate.

299
00:23:25,802 --> 00:23:31,033
Could viruses really be responsible
for injecting code into cells,

300
00:23:31,057 --> 00:23:35,190
paving the way for life to evolve from slime

301
00:23:35,214 --> 00:23:39,383
to the first animals to humans?

302
00:23:42,106 --> 00:23:46,486
Young and Douglas think it's not only
possible, but probable.

303
00:23:46,975 --> 00:23:50,247
They point to evidence
in labs around the world

304
00:23:50,271 --> 00:23:55,326
that reveals many of the attributes
found in cells that exist today

305
00:23:55,350 --> 00:23:59,427
can be traced back to simple viral origins.

306
00:24:00,263 --> 00:24:03,822
There's no question in my mind that a virus

307
00:24:03,846 --> 00:24:08,313
is the precursor for life as we know it now.

308
00:24:08,400 --> 00:24:10,233
Life on this planet

309
00:24:10,257 --> 00:24:12,013
would not be life on this planet

310
00:24:12,037 --> 00:24:14,745
without viruses.

311
00:24:24,660 --> 00:24:27,284
To Villareal, the fingerprints of viruses

312
00:24:27,308 --> 00:24:30,525
can be found everywhere in life's history.

313
00:24:30,550 --> 00:24:31,755
And the more he looks,

314
00:24:31,779 --> 00:24:34,694
the more hidden traces he uncovers.

315
00:24:35,876 --> 00:24:39,118
Not long ago, he heard
about a profound discovery

316
00:24:39,142 --> 00:24:42,477
that was unearthed in part by accident.

317
00:24:43,443 --> 00:24:45,365
And it links viruses

318
00:24:45,389 --> 00:24:47,823
to the birth of children.

319
00:25:11,307 --> 00:25:17,334
Tom Spencer never imagined he'd
help to unlock a secret power of viruses,

320
00:25:17,358 --> 00:25:20,692
but that's exactly what
happened on this farm.

321
00:25:21,660 --> 00:25:24,334
Spencer is a reproductive biologist.

322
00:25:25,673 --> 00:25:28,333
He investigates the mysteries of birth

323
00:25:28,357 --> 00:25:30,197
by studying sheep.

324
00:25:45,606 --> 00:25:48,911
To Tom Spencer, viruses were
a common annoyance,

325
00:25:48,935 --> 00:25:52,016
an unwelcome guest in his lab.

326
00:25:54,113 --> 00:25:58,978
Viruses were littering the genetic data
he was gathering from pregnant sheep,

327
00:25:59,002 --> 00:26:01,262
making his job more difficult.

328
00:26:02,692 --> 00:26:05,433
Spencer was attempting to isolate genes

329
00:26:05,457 --> 00:26:08,457
that might play an important role
in pregnancy.

330
00:26:08,823 --> 00:26:11,718
But throughout his search, again and again,

331
00:26:11,742 --> 00:26:16,046
Spencer kept hitting
a motherload of retroviruses.

332
00:26:17,220 --> 00:26:20,720
When we first saw the retrovirus,
we really just thought it was junk.

333
00:26:20,953 --> 00:26:25,287
Because you're taught that
the DNA of all mammals is

334
00:26:25,311 --> 00:26:27,732
{\an8}littered with remnants of viruses.

335
00:26:27,899 --> 00:26:30,590
{\an8}And that they really played no role,

336
00:26:30,614 --> 00:26:32,694
{\an8}except for maybe a stuffer.

337
00:26:32,900 --> 00:26:35,840
And so we were screening to get rid of it.

338
00:26:36,605 --> 00:26:38,834
In a sense, it was a nuisance.

339
00:26:40,533 --> 00:26:45,387
For years, filtering out the viruses
was standard operating procedure.

340
00:26:46,119 --> 00:26:49,374
But that all changed with a phone call.

341
00:26:54,120 --> 00:26:56,009
Hello, this is Tom Spencer.

342
00:26:56,176 --> 00:26:58,544
Spencer got news of some research

343
00:26:58,568 --> 00:27:01,736
that was spreading through his field
like wildfire.

344
00:27:01,969 --> 00:27:03,962
We just think it's junk DNA or something
like that.

345
00:27:03,987 --> 00:27:09,196
In one study, retroviruses like those
Spencer found in sheep...

346
00:27:09,221 --> 00:27:11,455
were discovered somewhere else.

347
00:27:13,467 --> 00:27:18,367
The viruses were found
in the wombs of pregnant women.

348
00:27:21,793 --> 00:27:27,926
The viruses, it turns out, were thriving
in an organ called the placenta.

349
00:27:28,186 --> 00:27:30,559
The placenta forms during pregnancy,

350
00:27:30,583 --> 00:27:34,827
in part to feed and provide oxygen
to the fetus.

351
00:27:38,690 --> 00:27:42,810
What were the viruses doing
hunkered down in the placenta?

352
00:27:47,350 --> 00:27:49,214
Spurred on by the findings,

353
00:27:49,238 --> 00:27:52,900
Spencer reviewed the data
he'd been collecting on sheep.

354
00:27:53,643 --> 00:27:56,841
Everywhere he looked
in the reproductive system,

355
00:27:56,865 --> 00:28:00,089
he saw clear signs of the invaders.

356
00:28:03,708 --> 00:28:05,658
Maybe, just maybe,

357
00:28:05,682 --> 00:28:09,569
these retroviruses weren't junk after all.

358
00:28:13,463 --> 00:28:15,610
Spencer began to suspect

359
00:28:15,634 --> 00:28:17,770
that the retroviruses were playing

360
00:28:17,794 --> 00:28:20,475
an active role in pregnancy.

361
00:28:20,663 --> 00:28:21,775
But how?

362
00:28:22,036 --> 00:28:25,416
Searching for answers in humans was
out of the question.

363
00:28:25,870 --> 00:28:28,391
However, at Spencer's field laboratory,

364
00:28:28,415 --> 00:28:30,898
he had the perfect stand-in candidate.

365
00:28:31,290 --> 00:28:33,664
And he began to develop a plan.

366
00:28:40,093 --> 00:28:41,805
Spencer focused his attention

367
00:28:41,829 --> 00:28:44,733
on one of the most dramatic and
mysterious events

368
00:28:44,757 --> 00:28:46,584
of a sheep's pregnancy.

369
00:28:48,813 --> 00:28:51,115
Sixteen days after inception,

370
00:28:51,151 --> 00:28:53,868
the round embryo has transformed,

371
00:28:53,892 --> 00:28:56,779
elongated to become more string-like.

372
00:28:57,980 --> 00:29:02,439
Next, the embryo begins
generating very special cells,

373
00:29:02,463 --> 00:29:06,041
each with two nuclei that coat the embryo.

374
00:29:07,540 --> 00:29:10,633
These cells connect the embryo to the womb,

375
00:29:10,657 --> 00:29:13,102
and they seed the growth of the placenta,

376
00:29:13,126 --> 00:29:15,754
which fuels fetal development.

377
00:29:17,633 --> 00:29:21,242
Viruses had left fingerprints
all over this process,

378
00:29:21,266 --> 00:29:25,000
and Spencer suspected
this might not be a coincidence.

379
00:29:25,299 --> 00:29:30,270
Perhaps viruses are critical players
in this transformation.

380
00:29:43,346 --> 00:29:44,921
In a novel experiment,

381
00:29:44,945 --> 00:29:49,267
Spencer and his colleagues
performed a series of surgeries.

382
00:29:52,147 --> 00:29:55,153
The first focused on
recently impregnated sheep

383
00:29:55,177 --> 00:29:58,548
with embryos that had yet to transform.

384
00:30:00,919 --> 00:30:03,786
If the viruses were
involved in this process,

385
00:30:03,810 --> 00:30:06,869
what would happen
if they were surgically stopped?

386
00:30:09,586 --> 00:30:11,742
With the sheep's vital signs stable,

387
00:30:11,766 --> 00:30:13,846
the operation is set to begin.

388
00:30:15,119 --> 00:30:16,366
Using great care,

389
00:30:16,390 --> 00:30:18,049
Spencer and his team

390
00:30:18,073 --> 00:30:21,797
quickly make their way
to the sheep's reproductive organs.

391
00:30:23,086 --> 00:30:24,460
Time is of the essence.

392
00:30:24,600 --> 00:30:29,174
The team doesn't want to keep the animal
anesthetized any longer than necessary.

393
00:30:31,520 --> 00:30:36,700
The microscopic embryo resides
protected within this fleshy cocoon.

394
00:30:45,780 --> 00:30:48,007
The injection is harmless to the sheep,

395
00:30:48,031 --> 00:30:50,118
but will knock out the virus.

396
00:31:00,233 --> 00:31:03,929
After surgery, the sheep is quickly
prepared for recovery.

397
00:31:05,147 --> 00:31:08,724
Now all that's left to do is to wait.

398
00:31:16,807 --> 00:31:17,980
Over the next week,

399
00:31:18,005 --> 00:31:20,228
Spencer monitors the health of his flock,

400
00:31:20,252 --> 00:31:22,211
anxious to know the outcome.

401
00:31:24,290 --> 00:31:29,212
Could viruses really be playing
a vital role in healthy pregnancy?

402
00:31:35,837 --> 00:31:40,404
Spencer reassembles the team and
leads a second round of surgeries.

403
00:31:41,743 --> 00:31:44,279
When Spencer removes the embryos,

404
00:31:44,303 --> 00:31:47,204
he is amazed by what he finds.

405
00:31:48,522 --> 00:31:54,683
In sheep, when we disable the endogenous
retroviruses in the embryo,

406
00:31:54,707 --> 00:31:57,250
then what we fail to see is the

407
00:31:57,274 --> 00:32:01,944
development of these
specialized cells of the placenta,

408
00:32:01,968 --> 00:32:05,448
turned by nucleated
cells that have two nuclei.

409
00:32:05,923 --> 00:32:08,678
And those cells are needed

410
00:32:08,702 --> 00:32:12,300
so the embryo can implant into the uterus.

411
00:32:12,628 --> 00:32:15,346
And without them, the pregnancy will fail.

412
00:32:18,489 --> 00:32:22,583
Tom Spencer is among a rapidly
growing number of biologists

413
00:32:22,607 --> 00:32:25,695
that are reconsidering past prejudices.

414
00:32:26,048 --> 00:32:28,862
He now thinks the placenta of many mammals,

415
00:32:28,892 --> 00:32:30,625
including humans,

416
00:32:30,649 --> 00:32:33,490
can be linked to viral invasion.

417
00:32:43,060 --> 00:32:45,014
The placenta of mammals,

418
00:32:45,038 --> 00:32:48,560
catalyzed by viruses,
is like a power plant.

419
00:32:53,143 --> 00:32:55,738
Around 70% of its energy

420
00:32:55,762 --> 00:33:00,231
fuels the growth of one of the
most remarkable feats of evolution,

421
00:33:00,255 --> 00:33:02,969
large, powerful brains.

422
00:33:06,959 --> 00:33:09,271
I marvel at the capacity of viruses

423
00:33:09,295 --> 00:33:11,739
to create and destroy together.

424
00:33:11,999 --> 00:33:13,689
{\an8}They are our ancestors.

425
00:33:14,289 --> 00:33:16,803
{\an8}They were directly involved

426
00:33:16,827 --> 00:33:20,581
{\an8}in the development and evolution
of our large social brain.

427
00:33:21,240 --> 00:33:23,483
If we respect humans,

428
00:33:23,507 --> 00:33:24,908
I think we have to respect

429
00:33:24,933 --> 00:33:27,194
the viruses that made them.

430
00:33:28,846 --> 00:33:31,260
Villarreal thinks that viruses have done

431
00:33:31,284 --> 00:33:33,429
more than foster the hardware

432
00:33:33,453 --> 00:33:35,107
that is our brain.

433
00:33:35,134 --> 00:33:37,261
We created a mechanism of addiction.

434
00:33:37,293 --> 00:33:39,588
He thinks viruses also played a role

435
00:33:39,612 --> 00:33:42,383
in the evolution of learning and language.

436
00:33:42,679 --> 00:33:45,563
But that's not his boldest assertion.

437
00:33:46,386 --> 00:33:48,907
He's certain that viruses played a role

438
00:33:48,931 --> 00:33:50,927
in the emergence of one of the most

439
00:33:50,951 --> 00:33:53,160
powerful emotions,

440
00:33:53,184 --> 00:33:54,351
love.

441
00:34:09,707 --> 00:34:12,013
Viruses and love?

442
00:34:12,686 --> 00:34:15,462
What role could viruses possibly play

443
00:34:15,486 --> 00:34:18,920
in an emotion that almost
defies description?

444
00:34:20,012 --> 00:34:23,111
When I realized I was in love with him,
it was not anything subtle.

445
00:34:23,136 --> 00:34:26,022
It was like somebody brought
a pile of bricks on my head.

446
00:34:26,047 --> 00:34:28,829
I mean, it's absolutely addictive.

447
00:34:29,386 --> 00:34:33,859
You know, you start to feel it,
and then all you want is more of it.

448
00:34:34,075 --> 00:34:36,209
You do things you never thought
you would do.

449
00:34:36,234 --> 00:34:38,442
You say things you never thought
you would say.

450
00:34:38,479 --> 00:34:42,669
The good part is that
you don't really think anymore.

451
00:34:42,760 --> 00:34:47,949
Whatever logic you use to have,
those processes stop.

452
00:34:49,919 --> 00:34:54,149
Despite the myriad of complex
emotions associated with love,

453
00:34:54,173 --> 00:34:56,431
biologist Larry Young suspects

454
00:34:56,455 --> 00:35:02,364
it might be rooted in some very
basic chemistry with a link to viruses.

455
00:35:03,040 --> 00:35:08,027
{\an8}Love has been the topic of poets and
philosophers for thousands of years,

456
00:35:08,052 --> 00:35:11,448
{\an8}and certainly a favorite topic
in every society.

457
00:35:11,583 --> 00:35:14,044
And there's something magical about it,

458
00:35:14,068 --> 00:35:16,564
and that's sort of one emotion that

459
00:35:16,588 --> 00:35:18,437
many people hold onto and think, you know,

460
00:35:18,461 --> 00:35:20,589
this is out of the realm of science.

461
00:35:21,112 --> 00:35:23,047
It's something that
we can never understand.

462
00:35:23,573 --> 00:35:25,887
But I don't necessarily think that's true.

463
00:35:31,737 --> 00:35:34,545
In Young's investigation
into love and bonding,

464
00:35:34,569 --> 00:35:38,153
he focuses on one of the
most primal behaviors,

465
00:35:38,177 --> 00:35:39,544
sex.

466
00:35:40,831 --> 00:35:44,857
So sex is a very pleasurable experience,
and this is why people engage in it.

467
00:35:44,882 --> 00:35:48,837
This is what's responsible for
the procreation of our species.

468
00:35:49,640 --> 00:35:51,538
The brain is really specialized

469
00:35:51,562 --> 00:35:55,556
to motivate us to engage in that
behavior by making it pleasurable.

470
00:35:56,173 --> 00:35:57,921
And so how can that happen?

471
00:36:03,399 --> 00:36:06,056
Young suspects that during sex,

472
00:36:06,080 --> 00:36:08,229
three basic chemicals are released

473
00:36:08,253 --> 00:36:10,787
that bond mates together.

474
00:36:12,186 --> 00:36:14,205
The first is dopamine,

475
00:36:14,229 --> 00:36:17,489
which provides feelings
of pleasure and euphoria.

476
00:36:20,179 --> 00:36:24,042
The other two chemicals,
oxytocin and vasopressin,

477
00:36:24,066 --> 00:36:26,421
heighten our sensory perceptions,

478
00:36:26,445 --> 00:36:29,406
associating pleasure with our partner.

479
00:36:31,138 --> 00:36:32,870
For example, during mating,

480
00:36:32,894 --> 00:36:35,670
it would help the brain focus in on the

481
00:36:35,694 --> 00:36:38,254
characteristics that
make that partner unique.

482
00:36:39,729 --> 00:36:42,163
In other words, the individual says, wow,

483
00:36:42,187 --> 00:36:43,802
that felt really good.

484
00:36:44,008 --> 00:36:46,828
And I was with this individual
when it happened,

485
00:36:46,852 --> 00:36:50,860
and therefore I'm going to try to be
around this individual more often.

486
00:36:52,568 --> 00:36:56,898
It's hard to imagine that a chemical
cocktail of just three hormones

487
00:36:56,922 --> 00:36:59,989
could be the basis of bonding and love,

488
00:37:00,013 --> 00:37:04,147
that complex emotions
could have such simple roots.

489
00:37:04,716 --> 00:37:07,115
But Young had a strong hunch,

490
00:37:07,139 --> 00:37:09,044
and in a search for evidence,

491
00:37:09,068 --> 00:37:11,179
he turned his attention to other mammals

492
00:37:11,203 --> 00:37:14,661
in the animal kingdom and to a virus.

493
00:37:18,573 --> 00:37:22,391
Prairie voles are among the most
doting mammals on Earth.

494
00:37:23,620 --> 00:37:26,994
Like some humans,
males and female prairie voles

495
00:37:27,018 --> 00:37:29,016
form lifelong bonds,

496
00:37:29,040 --> 00:37:30,827
share parenting duties,

497
00:37:30,851 --> 00:37:33,805
and males jealously guard females.

498
00:37:41,285 --> 00:37:44,145
In contrast, a nearly identical cousin

499
00:37:44,169 --> 00:37:47,764
has adopted a more swinging lifestyle.

500
00:37:49,120 --> 00:37:51,229
When the promiscuous cousins have sex,

501
00:37:51,253 --> 00:37:53,326
there are no strings attached,

502
00:37:53,350 --> 00:37:55,571
and no cuddling afterwards.

503
00:37:55,979 --> 00:37:57,771
In fact, if they get too close,

504
00:37:57,795 --> 00:38:01,283
they're more apt to fight
than to playfully nibble.

505
00:38:06,329 --> 00:38:10,496
What's driving these two
distinct approaches to mating,

506
00:38:10,520 --> 00:38:15,061
and could the answer help us
understand human relationships?

507
00:38:16,669 --> 00:38:19,062
When Young peered into the vole brains,

508
00:38:19,086 --> 00:38:20,982
he discovered that both species

509
00:38:21,006 --> 00:38:24,230
were releasing the same love cocktail
as humans.

510
00:38:24,783 --> 00:38:28,841
But there was one big difference
between the vole species.

511
00:38:29,577 --> 00:38:33,027
Only the monogamous voles
had sufficient brain hardware

512
00:38:33,051 --> 00:38:37,621
in the form of receptors that could
soak up the bonding chemicals.

513
00:38:39,050 --> 00:38:43,905
Hormones like oxytocin and vasopressin
can only act by binding to a receptor.

514
00:38:44,617 --> 00:38:46,676
It's sort of like a key in a lock.

515
00:38:46,950 --> 00:38:49,954
Well, when we looked in the brain
of the prairie voles,

516
00:38:49,978 --> 00:38:52,413
we found that these reward areas

517
00:38:52,437 --> 00:38:55,424
were loaded with oxytocin
and vasopressin receptors.

518
00:38:56,180 --> 00:38:59,604
The promiscuous voles have fewer receptors,

519
00:38:59,628 --> 00:39:02,032
and Young suspects that could explain

520
00:39:02,056 --> 00:39:04,504
their free-loving lifestyle.

521
00:39:06,237 --> 00:39:08,096
To investigate his theory,

522
00:39:08,120 --> 00:39:10,333
Young turned to a virus.

523
00:39:11,149 --> 00:39:12,708
His plan was simple.

524
00:39:13,489 --> 00:39:17,604
He injected a virus into the brain
of a promiscuous vole.

525
00:39:18,695 --> 00:39:21,395
The virus sliced into the vole's DNA

526
00:39:21,419 --> 00:39:23,335
and inserted the instructions

527
00:39:23,359 --> 00:39:25,756
to create more receptors.

528
00:39:27,350 --> 00:39:30,449
Brain scan images revealed success.

529
00:39:31,823 --> 00:39:34,906
But would the new receptors
change behavior?

530
00:39:36,247 --> 00:39:37,258
To find out,

531
00:39:37,282 --> 00:39:40,242
Young mated the virally altered vole

532
00:39:40,266 --> 00:39:41,680
with a female.

533
00:39:47,816 --> 00:39:50,942
And then separated the couple.

534
00:39:57,329 --> 00:40:00,872
Next, he tethered the mated female
in a box.

535
00:40:04,216 --> 00:40:08,583
At the other end of the box,
he tied down a temptress.

536
00:40:10,756 --> 00:40:12,646
And finally, he introduced

537
00:40:12,670 --> 00:40:15,344
the virus-injected vole.

538
00:40:18,103 --> 00:40:21,739
Would the male remember the days
in the love nest?

539
00:40:22,649 --> 00:40:25,173
Or would he be back on the prowl?

540
00:40:39,040 --> 00:40:41,172
In an evolutionary flip-flop,

541
00:40:41,196 --> 00:40:43,039
the virally altered vole

542
00:40:43,063 --> 00:40:45,344
returned to dote on his mate.

543
00:40:46,580 --> 00:40:49,535
A virus that altered just one gene

544
00:40:49,559 --> 00:40:52,286
had dramatically changed their behavior.

545
00:40:59,814 --> 00:41:01,396
Again and again,

546
00:41:01,420 --> 00:41:04,929
with dozens of previously promiscuous voles,

547
00:41:04,953 --> 00:41:07,704
Young got the same results.

548
00:41:09,813 --> 00:41:11,986
Young's results are striking

549
00:41:12,010 --> 00:41:15,082
and raise provocative implications.

550
00:41:15,359 --> 00:41:18,797
Perhaps an ancient virus long ago

551
00:41:18,821 --> 00:41:20,728
entered our bodies

552
00:41:20,752 --> 00:41:23,302
and rewired us from monogamy.

553
00:41:24,886 --> 00:41:26,734
Given what we know about viruses

554
00:41:26,758 --> 00:41:29,601
and what we've done in our own laboratory,

555
00:41:29,625 --> 00:41:32,073
I certainly think it's a possibility that

556
00:41:32,097 --> 00:41:35,212
a similar sort of thing may have
happened in nature.

557
00:41:35,357 --> 00:41:39,366
And if it did, it could have resulted
in changes in behavior,

558
00:41:39,390 --> 00:41:41,704
including the evolution of social bonding,

559
00:41:41,728 --> 00:41:44,057
monogamy, and perhaps even

560
00:41:44,081 --> 00:41:46,035
the emotion that we call love.

561
00:41:49,652 --> 00:41:52,518
People often ask, you know, if we understand

562
00:41:52,542 --> 00:41:54,598
the biochemistry of love,

563
00:41:54,622 --> 00:41:56,596
won't that take away some of the magic?

564
00:41:56,852 --> 00:41:59,572
And I really have to say,
I don't think so.

565
00:41:59,940 --> 00:42:01,836
It's not going to ruin my sex life.

566
00:42:08,288 --> 00:42:09,830
To Luis Villarreal,

567
00:42:09,854 --> 00:42:12,781
viruses are more than mere parasites.

568
00:42:13,579 --> 00:42:16,788
Yes, they can cause sickness
and even death.

569
00:42:17,175 --> 00:42:20,457
But he's among a growing
number of investigators

570
00:42:20,481 --> 00:42:23,013
that suspect there's far more to viruses

571
00:42:23,037 --> 00:42:24,898
than we ever imagined.

572
00:42:27,159 --> 00:42:30,639
The notion that viruses could
simply be harmful is absurd.

573
00:42:30,760 --> 00:42:32,933
{\an8}Let's say you had a switch on the wall,

574
00:42:32,957 --> 00:42:36,680
{\an8}and if you flip that switch,
you can eliminate viruses on the planet.

575
00:42:37,553 --> 00:42:40,442
Many people might think, okay,
I would flip that switch.

576
00:42:41,012 --> 00:42:43,629
But the reality is,
if you did flip that switch,

577
00:42:43,653 --> 00:42:45,489
many of us who study viruses think that

578
00:42:45,513 --> 00:42:48,134
the world would come to a screeching halt.

579
00:42:50,753 --> 00:42:55,697
Viruses not only are
infectious and cause disease,

580
00:42:55,721 --> 00:42:58,625
ultimately what all this work
will mean is that

581
00:42:58,649 --> 00:43:03,517
viruses most likely played a
fundamental role in evolution.

582
00:43:06,033 --> 00:43:08,394
Villarreal couldn't agree more.

583
00:43:08,700 --> 00:43:11,338
In his story, viruses gave rise

584
00:43:11,362 --> 00:43:13,895
to the first complex cells.

585
00:43:20,207 --> 00:43:23,712
Played a role
in the diversification of life.

586
00:43:31,386 --> 00:43:34,255
Changed the way the young are born.

587
00:43:39,086 --> 00:43:43,475
Drove the wedge that separated us
from our closest cousins.

588
00:43:47,870 --> 00:43:50,948
And may have given rise to complex emotion.

589
00:43:57,703 --> 00:44:00,802
Given the potential role
of viruses in evolution,

590
00:44:00,826 --> 00:44:02,575
many are starting to question

591
00:44:02,599 --> 00:44:06,260
who we really are
and where we came from.

592
00:44:07,003 --> 00:44:09,329
{\an8}I think it's really easy
to come to the conclusion,

593
00:44:09,353 --> 00:44:12,113
{\an8}and I've come there, that we are viruses.

594
00:44:12,783 --> 00:44:18,236
To Villarreal, viruses have clearly
shaped our basic blueprint,

595
00:44:18,260 --> 00:44:20,561
and they're not through with us yet.

596
00:44:21,030 --> 00:44:25,564
He knows that viruses are
attempting to modify our species

597
00:44:25,588 --> 00:44:29,411
in a way that could lead
to new human beings.

598
00:44:30,215 --> 00:44:33,383
It's clear that viruses have had a

599
00:44:33,408 --> 00:44:36,143
major impact on the origin, evolution,

600
00:44:36,174 --> 00:44:38,984
and diversification of
all life on this planet,

601
00:44:39,008 --> 00:44:43,224
including primates and including hominids.

602
00:44:43,535 --> 00:44:45,803
{\an8}And therefore it's not at all difficult

603
00:44:45,828 --> 00:44:47,789
{\an8}to propose

604
00:44:47,813 --> 00:44:49,649
{\an8}that this phenomenon could continue.

605
00:44:49,674 --> 00:44:52,679
{\an8}It could lead to the creation of a new

606
00:44:52,703 --> 00:44:56,024
{\an8}lineage of humans, a new species of humans.

607
00:45:01,300 --> 00:45:05,132
How will viruses redraw who we are?

608
00:45:06,447 --> 00:45:09,084
What might a new human look like?

609
00:45:11,187 --> 00:45:13,831
How might they construct their societies,

610
00:45:13,855 --> 00:45:15,789
their culture, their art?

611
00:45:18,146 --> 00:45:21,285
What would it mean to be human?

612
00:45:23,339 --> 00:45:27,526
For viruses, the long march goes on.

613
00:45:33,236 --> 00:45:35,236
{\an8}Transcript format and synch by Andante