Transcript format and synch by Andante
This is a journey of the imagination
that may change your opinion
of who you are and where you come from.
Viruses, once solely thought to be agents of disease and death,
may have actually given rise to our species.
They are our ancestors.
If we respect humans, I think we have to respect the viruses that made them.
Startling discoveries are also revealing that
viruses have left their fingerprints throughout evolution.
They may have sparked the explosion of complex life,
changed the way the young are born, and be responsible for love itself.
The notion that viruses simply be harmful is absurd.
Today, the handiwork of viruses is far from over,
and some even imagine that in the future,
viruses could lead to the emergence of a new human species.
Life on this planet would not be life on this planet without viruses.
Not far from the lights of Hollywood,
a strange story is being written that sounds like a script for a sci-fi movie.
But this tale is real.
Within the dark confines of a cavernous laboratory,
a visionary scientist carefully outlines his plot.
His name, Dr. Luis Villarreal.
At the center of his drama
is a bizarre cast of microscopic creatures
Villarreal calls agents.
To most of us, they are known as viruses.
By definition, viruses are parasites that infect cells and cause disease.
But in this story, they possess far greater power.
Villarreal suspects that if we could go back in evolutionary time,
we would see that every plant, every animal,
and even humans were created in large part by viruses.
According to Villarreal, we are the descendants of these creatures.
When most people think of the word virus,
they have a distinctly negative reaction,
a fearful reaction, because they understand them
to be infectious agents that can make them quite sick,
and therefore there's something to be avoided and feared.
But I think viruses are the leading edge of evolution.
Villarreal's ideas are revolutionary, but they're also controversial.
How could viruses help to create life
when they seem solely built for destruction?
Viruses are best known as microscopic armies
that attack living cells in massive assaults.
Viruses are like tiny robots.
Together, they form a brigade of machine-like invaders.
Their only weapon, a piece of genetic code which many inject into a cell.
Once inside, the code can quickly destroy the cell's DNA and takes control.
Often, the cell is forced to build more viruses until it finally explodes,
releasing a new brigade of replicants.
Villarreal thinks there's more to viruses than replication and death,
and he's not alone.
The story he's weaving is based on evidence being compiled from all over the globe.
It doesn't look like a month of a new route, so...
Nathan Wolf is a virus hunter.
And while you may think viruses are rare
because you seldom get sick,
Wolf knows the true extent of their domain.
At this moment, they're sitting everywhere,
surrounding me, coding me on the inside of my body
throughout my different organ systems.
These things are everywhere,
and they're impacting us in ways that we have really
only just begun to understand.
The jungles of Cameroon are a hot zone for virus hunters like Wolf.
That's because the forest is literally teeming with life,
and viruses infect everything
that walks, flies,
slithers, and crawls.
Although the tropics are known for their animal diversity,
it is the virus that is king of the jungle.
Almost by definition, that makes viruses the most diverse entities on our planet.
Viruses are a vast, unknown world.
Among the legions of viruses that lurk in these jungles,
Wolf is stalking those that jump from animals to humans,
a feat thought to be rare.
But when it does happen, the results can be catastrophic.
It's widely believed that not far from this jungle,
a virus did jump from chimpanzees to people,
a virus known the world over as HIV.
Wolf suspects that there are other viruses
poised to launch further assaults.
When we started our work, I think people pretty much suspected
that we wouldn't see much.
The conventional wisdom was that
these were relatively rare events.
These were not things that were occurring on a regular basis.
On the lookout for viral jumps,
Wolf is monitoring villagers like this tribal chief and his family.
That's because the people living here have near-daily contact with wild animals.
Whether through trapping
or butchering.
This intimate contact can expose people to a myriad of viruses.
Viruses that live on skin, in saliva,
in vital organs,
and to viruses that thrive in blood.
By monitoring viruses
in the blood of the hunted and the hunters,
Wolf made a striking discovery.
Several viruses in the same family as HIV have jumped to humans.
I actually do remember the first time that we actually saw evidence,
and frankly it was a little bit shocking from our perspective,
that this was not something that was rare.
Wolf's initial results revealed that ten people in a thousand he sampled
were clearly exposed to a primate virus.
And ten in a thousand is a significant number.
All you have to do is take one step back and extrapolate that
to how many people are in the country we were looking in, Cameroon.
How many people are in Central Africa?
How many of those people have day-to-day contact with these animals?
And very quickly,
we recognized that probably tens of thousands of people
were infected with these viruses, and frankly it was a shock.
As viruses continually jump from animals to humans,
it's unclear if these new infections will ultimately lead to a pandemic,
like the one caused by HIV.
And Wolf is keeping a watchful eye.
But there's more to this story than a potential health threat.
That's because the viruses Wolf is tracking
have a rare power to rearrange the basic blueprint of life, DNA.
Many viruses attack cells in seek and destroy missions.
Central to their assault is obliterating the cell's DNA
before exploding the cell into oblivion.
The viruses Wolf is investigating rely on a different tactic.
And they are called retroviruses.
Now retroviruses are very interesting,
because what retroviruses do is in order to complete their life cycle,
they actually have to integrate themselves
into the genetic diversity of their host.
After they've entered into a cell,
they actually take their genetic information
and they become part of the genetic information of the host cell.
That cell and all of its progeny are forever changed.
Now that sets up a very interesting situation.
If a retrovirus integrates into a sperm or egg cell,
the genetic changes can become permanent,
passed down from generation to generation.
And if integration like this happens repeatedly,
over evolutionary time,
our basic blueprint could be altered dramatically.
And that's something which is sort of profound if you think about it.
In some ways, you could almost think of it
as this is a moment where a virus and a host merge.
They're not acting like viruses,
but they're a part of our own genetic fabric,
which could affect the future course of evolution.
If retroviruses can change our genetic code,
this raises a provocative question.
How has this rewiring affected our species?
Luis Villareal thinks he knows the answer to this question.
He suspects that retroviruses
can help to explain how primates
evolved into human beings.
If you just looked at the blueprints of the chimpanzees in humans,
our genes are virtually identical,
nearly 99% the same.
So where are the instructions that make us unique?
Villareal is convinced
the answer can be traced back to retroviruses
and something called junk DNA.
Junk DNA is bits and pieces of genetic code that litter the blueprint of chimpanzees.
Junk DNA also plutters our genome.
One of the big surprises when the initial sequencing of the human genome was done
is that somewhere between 93 to 95% of the DNA
was in this junk category.
We are predominantly junk, according to this view.
But this junk, it turns out, isn't junk after all.
A lot of it is the genetic remains of ancient retroviruses.
Villareal imagines that long ago,
as viruses integrated into primates,
they began redrawing their blueprint.
A lot of the changes went nowhere, evolutionary dead ends.
Over time, however, Villareal thinks some changes proved beneficial for survival.
And as they accumulated, primates gave rise to a new species,
human beings.
As humans and chimps went their separate ways,
both species were continually colonized
by their own unique viruses.
So what really marks the distinction
of our evolution from our closest relative
are the viruses that colonized our respective genomes.
The viruses were directly involved
in differentiating our lineage from the chimpanzee lineage.
And in that context, it's not junk, it's who we are.
Villareal realizes that it might be hard to imagine that
viruses led to the emergence of humans.
But this isn't the strangest part of his story.
In piecing together the evolution of life on Earth,
investigators have documented an epic tale
with a cast of incredible animals and surprising twists and turns.
Villareal, however, thinks we've overlooked a major player.
The history of evolution of biology is
basically devoid of considering the consequence of viruses,
especially those that persist and colonize.
But I have concluded that
viruses were involved in all of the major evolutionary transitions.
According to conventional wisdom,
if we could go back in time,
the early chapters of animal life
were suspected to have unfolded something like this.
Hundreds of millions of years ago,
before dinosaurs, chimpanzees and humans,
before animals swam the ocean,
only one group of animals existed.
They were sponges.
Unable to move on their own,
they lacked all but the most basic abilities.
Sponges filtered food particles from the water
by pumping water through their bodies.
They were little more than a loose collection of cells.
Then creatures far more complex came into being and changed the world forever.
These flower-like beings are called cnidarians.
Here was an animal with a mouth, muscles and nerves.
Next came a flatworm-like animal,
the first with a head and eye-like sensors.
Then, in a geological instant,
a great diversity of new body plans emerged and life blossomed,
eventually leading to terrestrial animals
and human beings.
It's an accepted chronology of evolution,
but Villarreal suspects we need to rewrite the first chapter.
In his version of the story,
evolution got jump-started by a virus,
and a recent discovery supports his theory.
Trevor Douglas is a chemist.
Mark Young is a virologist.
Together, they hunt for viruses in extreme environments
that resemble early Earth.
The hot springs that pepper this landscape
are like windows back in time.
Within these scalding waters,
there are ancient microbes,
descendants of the earliest life forms on the planet.
The creatures thrive here in temperatures
that can reach more than 200 degrees Fahrenheit,
in cauldrons of acid that can burn flesh.
And where there's ancient life, there sure to be ancient viruses.
We knew there was life in these hot springs, and we knew it was unusual life.
And so we suspected that the viruses that would be there would be also unusual,
and might give us new insights
into how life evolved on this planet.
Just bring it back slowly, and I'll go ahead and measure the temperature.
The fun part of this is, you know,
you go to weird places, turns out you find weird things.
Well, I think, you know, any time I look at this virus, especially the cryo...
To date, Young and Douglas have unearthed dozens of viruses,
with lineages that can be traced back to the beginnings of life.
Particles that look empty...
But nothing they found prepared them
for an ancient virus that was discovered by accident in Europe.
The year is 2003.
In a lab in France,
Bernard La Scola is examining what he thinks
is an old bacteria sample from the archives.
But as he looks through the lens of his high-powered microscope,
La Scola is shocked.
This is no bacteria.
The sample was misidentified.
This is a monstrous virus.
The virus, later named Mimi,
shattered the view of what a virus could be.
It's long been thought all viruses were tiny,
that they were essentially lifeless,
and that they need cells in order to replicate.
Mimi changed everything.
First of all, it was gigantic.
Mimi is a big kind of overweight virus that's got too much stuff.
And that extra bloatedness comes from the fact that
it's carrying a whole bunch of genes that viruses don't normally carry.
And that makes it start to look like it can do cellular-type functions.
Some of the genes in Mimi are startling.
They suggest that long ago, Mimi might have been able to replicate without a host.
And if that was the case, Mimi wasn't like other viruses.
Maybe it wasn't a machine.
Maybe it wasn't a parasite.
Maybe at one time, it was alive.
Young and Douglas know this is a controversial idea.
Critics claim Mimi simply stole some genes from a cell.
End of story.
Young and Douglas disagree.
They point to evidence that indicates Mimi's genes are simpler,
and therefore could be older.
To many investigators, this means
Mimi didn't steal the genes.
On the contrary, it may have invented them
long before there was complex life.
Young and Douglas imagine that going back in time,
early Earth might have looked something like this.
For eons, the planet was basically mats of simple life, like bacteria.
A world we'd hardly recognize today.
But there were viruses.
Young and Douglas think it's possible
that an ancient Mimi-like virus might have invented the instructions for life
to become more complex, and then inserted them into primitive cells.
They also think that a Mimi-like virus
could have served as the first cellular nucleus.
The command and control center
that enabled life to get more elaborate.
Could viruses really be responsible for injecting code into cells,
paving the way for life to evolve from slime
to the first animals to humans?
Young and Douglas think it's not only possible, but probable.
They point to evidence in labs around the world
that reveals many of the attributes found in cells that exist today
can be traced back to simple viral origins.
There's no question in my mind that a virus
is the precursor for life as we know it now.
Life on this planet
would not be life on this planet
without viruses.
To Villareal, the fingerprints of viruses
can be found everywhere in life's history.
And the more he looks,
the more hidden traces he uncovers.
Not long ago, he heard about a profound discovery
that was unearthed in part by accident.
And it links viruses
to the birth of children.
Tom Spencer never imagined he'd help to unlock a secret power of viruses,
but that's exactly what happened on this farm.
Spencer is a reproductive biologist.
He investigates the mysteries of birth
by studying sheep.
To Tom Spencer, viruses were a common annoyance,
an unwelcome guest in his lab.
Viruses were littering the genetic data he was gathering from pregnant sheep,
making his job more difficult.
Spencer was attempting to isolate genes
that might play an important role in pregnancy.
But throughout his search, again and again,
Spencer kept hitting a motherload of retroviruses.
When we first saw the retrovirus, we really just thought it was junk.
Because you're taught that the DNA of all mammals is
littered with remnants of viruses.
And that they really played no role,
except for maybe a stuffer.
And so we were screening to get rid of it.
In a sense, it was a nuisance.
For years, filtering out the viruses was standard operating procedure.
But that all changed with a phone call.
Hello, this is Tom Spencer.
Spencer got news of some research
that was spreading through his field like wildfire.
We just think it's junk DNA or something like that.
In one study, retroviruses like those Spencer found in sheep...
were discovered somewhere else.
The viruses were found in the wombs of pregnant women.
The viruses, it turns out, were thriving in an organ called the placenta.
The placenta forms during pregnancy,
in part to feed and provide oxygen to the fetus.
What were the viruses doing hunkered down in the placenta?
Spurred on by the findings,
Spencer reviewed the data he'd been collecting on sheep.
Everywhere he looked in the reproductive system,
he saw clear signs of the invaders.
Maybe, just maybe,
these retroviruses weren't junk after all.
Spencer began to suspect
that the retroviruses were playing
an active role in pregnancy.
But how?
Searching for answers in humans was out of the question.
However, at Spencer's field laboratory,
he had the perfect stand-in candidate.
And he began to develop a plan.
Spencer focused his attention
on one of the most dramatic and mysterious events
of a sheep's pregnancy.
Sixteen days after inception,
the round embryo has transformed,
elongated to become more string-like.
Next, the embryo begins generating very special cells,
each with two nuclei that coat the embryo.
These cells connect the embryo to the womb,
and they seed the growth of the placenta,
which fuels fetal development.
Viruses had left fingerprints all over this process,
and Spencer suspected this might not be a coincidence.
Perhaps viruses are critical players in this transformation.
In a novel experiment,
Spencer and his colleagues performed a series of surgeries.
The first focused on recently impregnated sheep
with embryos that had yet to transform.
If the viruses were involved in this process,
what would happen if they were surgically stopped?
With the sheep's vital signs stable,
the operation is set to begin.
Using great care,
Spencer and his team
quickly make their way to the sheep's reproductive organs.
Time is of the essence.
The team doesn't want to keep the animal anesthetized any longer than necessary.
The microscopic embryo resides protected within this fleshy cocoon.
The injection is harmless to the sheep,
but will knock out the virus.
After surgery, the sheep is quickly prepared for recovery.
Now all that's left to do is to wait.
Over the next week,
Spencer monitors the health of his flock,
anxious to know the outcome.
Could viruses really be playing a vital role in healthy pregnancy?
Spencer reassembles the team and leads a second round of surgeries.
When Spencer removes the embryos,
he is amazed by what he finds.
In sheep, when we disable the endogenous retroviruses in the embryo,
then what we fail to see is the
development of these specialized cells of the placenta,
turned by nucleated cells that have two nuclei.
And those cells are needed
so the embryo can implant into the uterus.
And without them, the pregnancy will fail.
Tom Spencer is among a rapidly growing number of biologists
that are reconsidering past prejudices.
He now thinks the placenta of many mammals,
including humans,
can be linked to viral invasion.
The placenta of mammals,
catalyzed by viruses, is like a power plant.
Around 70% of its energy
fuels the growth of one of the most remarkable feats of evolution,
large, powerful brains.
I marvel at the capacity of viruses
to create and destroy together.
They are our ancestors.
They were directly involved
in the development and evolution of our large social brain.
If we respect humans,
I think we have to respect
the viruses that made them.
Villarreal thinks that viruses have done
more than foster the hardware
that is our brain.
We created a mechanism of addiction.
He thinks viruses also played a role
in the evolution of learning and language.
But that's not his boldest assertion.
He's certain that viruses played a role
in the emergence of one of the most
powerful emotions,
love.
Viruses and love?
What role could viruses possibly play
in an emotion that almost defies description?
When I realized I was in love with him, it was not anything subtle.
It was like somebody brought a pile of bricks on my head.
I mean, it's absolutely addictive.
You know, you start to feel it, and then all you want is more of it.
You do things you never thought you would do.
You say things you never thought you would say.
The good part is that you don't really think anymore.
Whatever logic you use to have, those processes stop.
Despite the myriad of complex emotions associated with love,
biologist Larry Young suspects
it might be rooted in some very basic chemistry with a link to viruses.
Love has been the topic of poets and philosophers for thousands of years,
and certainly a favorite topic in every society.
And there's something magical about it,
and that's sort of one emotion that
many people hold onto and think, you know,
this is out of the realm of science.
It's something that we can never understand.
But I don't necessarily think that's true.
In Young's investigation into love and bonding,
he focuses on one of the most primal behaviors,
sex.
So sex is a very pleasurable experience, and this is why people engage in it.
This is what's responsible for the procreation of our species.
The brain is really specialized
to motivate us to engage in that behavior by making it pleasurable.
And so how can that happen?
Young suspects that during sex,
three basic chemicals are released
that bond mates together.
The first is dopamine,
which provides feelings of pleasure and euphoria.
The other two chemicals, oxytocin and vasopressin,
heighten our sensory perceptions,
associating pleasure with our partner.
For example, during mating,
it would help the brain focus in on the
characteristics that make that partner unique.
In other words, the individual says, wow,
that felt really good.
And I was with this individual when it happened,
and therefore I'm going to try to be around this individual more often.
It's hard to imagine that a chemical cocktail of just three hormones
could be the basis of bonding and love,
that complex emotions could have such simple roots.
But Young had a strong hunch,
and in a search for evidence,
he turned his attention to other mammals
in the animal kingdom and to a virus.
Prairie voles are among the most doting mammals on Earth.
Like some humans, males and female prairie voles
form lifelong bonds,
share parenting duties,
and males jealously guard females.
In contrast, a nearly identical cousin
has adopted a more swinging lifestyle.
When the promiscuous cousins have sex,
there are no strings attached,
and no cuddling afterwards.
In fact, if they get too close,
they're more apt to fight than to playfully nibble.
What's driving these two distinct approaches to mating,
and could the answer help us understand human relationships?
When Young peered into the vole brains,
he discovered that both species
were releasing the same love cocktail as humans.
But there was one big difference between the vole species.
Only the monogamous voles had sufficient brain hardware
in the form of receptors that could soak up the bonding chemicals.
Hormones like oxytocin and vasopressin can only act by binding to a receptor.
It's sort of like a key in a lock.
Well, when we looked in the brain of the prairie voles,
we found that these reward areas
were loaded with oxytocin and vasopressin receptors.
The promiscuous voles have fewer receptors,
and Young suspects that could explain
their free-loving lifestyle.
To investigate his theory,
Young turned to a virus.
His plan was simple.
He injected a virus into the brain of a promiscuous vole.
The virus sliced into the vole's DNA
and inserted the instructions
to create more receptors.
Brain scan images revealed success.
But would the new receptors change behavior?
To find out,
Young mated the virally altered vole
with a female.
And then separated the couple.
Next, he tethered the mated female in a box.
At the other end of the box, he tied down a temptress.
And finally, he introduced
the virus-injected vole.
Would the male remember the days in the love nest?
Or would he be back on the prowl?
In an evolutionary flip-flop,
the virally altered vole
returned to dote on his mate.
A virus that altered just one gene
had dramatically changed their behavior.
Again and again,
with dozens of previously promiscuous voles,
Young got the same results.
Young's results are striking
and raise provocative implications.
Perhaps an ancient virus long ago
entered our bodies
and rewired us from monogamy.
Given what we know about viruses
and what we've done in our own laboratory,
I certainly think it's a possibility that
a similar sort of thing may have happened in nature.
And if it did, it could have resulted in changes in behavior,
including the evolution of social bonding,
monogamy, and perhaps even
the emotion that we call love.
People often ask, you know, if we understand
the biochemistry of love,
won't that take away some of the magic?
And I really have to say, I don't think so.
It's not going to ruin my sex life.
To Luis Villarreal,
viruses are more than mere parasites.
Yes, they can cause sickness and even death.
But he's among a growing number of investigators
that suspect there's far more to viruses
than we ever imagined.
The notion that viruses could simply be harmful is absurd.
Let's say you had a switch on the wall,
and if you flip that switch, you can eliminate viruses on the planet.
Many people might think, okay, I would flip that switch.
But the reality is, if you did flip that switch,
many of us who study viruses think that
the world would come to a screeching halt.
Viruses not only are infectious and cause disease,
ultimately what all this work will mean is that
viruses most likely played a fundamental role in evolution.
Villarreal couldn't agree more.
In his story, viruses gave rise
to the first complex cells.
Played a role in the diversification of life.
Changed the way the young are born.
Drove the wedge that separated us from our closest cousins.
And may have given rise to complex emotion.
Given the potential role of viruses in evolution,
many are starting to question
who we really are and where we came from.
I think it's really easy to come to the conclusion,
and I've come there, that we are viruses.
To Villarreal, viruses have clearly shaped our basic blueprint,
and they're not through with us yet.
He knows that viruses are attempting to modify our species
in a way that could lead to new human beings.
It's clear that viruses have had a
major impact on the origin, evolution,
and diversification of all life on this planet,
including primates and including hominids.
And therefore it's not at all difficult
to propose
that this phenomenon could continue.
It could lead to the creation of a new
lineage of humans, a new species of humans.
How will viruses redraw who we are?
What might a new human look like?
How might they construct their societies,
their culture, their art?
What would it mean to be human?
For viruses, the long march goes on.
Transcript format and synch by Andante