[narrator] This seedling might not look like much now,
but it will grow into one of the most notorious plants in human history:
cannabis.
It's the world's most popular illicit drug,
more prevalent than all the other ones combined.
Marijuana today is a highly manicured product,
glistening with sticky, psychoactive resin.
This is not your mother's weed.
This was more like your mother's weed.
The top strains from a 1977 issue of High Times magazine.
Today's is a lot stronger.
Confiscated marijuana is more than three times as potent
as it was in the mid-'90s
when the US government started keeping track.
And the same trend has been observed in other countries,
like the Netherlands, the United Kingdom, and Italy.
Cannabis also grows smaller and faster,
and in hundreds of strains,
offering all different kinds of flavors and highs.
But an unregulated product with rapidly changing genetics means
that a lot of people don't know what they're really buying
and that there are health consequences we're only starting to understand.
For millennia now, marijuana has been seen as mysterious and sacred
and even demonic.
But now humans have learned to engineer it.
So what exactly have humans done to this plant?
And what does that mean for the people who use it?
[man] Marijuana is an intoxicating, mind-muddling drug.
Marijuana is probably the most dangerous drug in the United States.
Come on, one drag won't hurt you.
That's not what I heard.
[man] Oh, the days of the mild drug that everybody uses...
It's more potent now than ever.
One of these days they're gonna change the stupid law,
and it'll be just as legal to have grass in your pocket
as it is to have beer in the refrigerator.
[narrator] This is 2,700-year-old psychoactive resin from a cannabis plant.
It was found in a grave in Central Asia,
and it's the oldest evidence of cannabis being used as a drug.
Cannabis is a domesticated species.
It's one of the species that we've been co-evolving with for a very long time.
And to say you co-evolve is to say you're changing it
and presumably it's changing you as well.
[narrator] As humans spread across the continents, so did cannabis.
But in colder climates, a different version of the plant developed: hemp.
It couldn't get you high, but it was just as valued
for other reasons.
[man] Long ago when these ancient Grecian temples were new,
hemp was already old in the service of mankind.
[narrator] Hemp was used to make clothes, rope,
sails, paper, food, fuel, and construction materials.
Hemp farming was so important in early America
that towns across the country named themselves after it.
This was the cannabis most Europeans and North Americans knew.
But warmer climates, they got the psychoactive kind of cannabis.
It spread to the Middle East,
where hashish, a paste made of cannabis resin,
became a popular edible intoxicant.
From there, it spread to India, where it became a holy drink.
Then into Africa, where it was used as medicine
and to boost courage before battle.
And then transatlantic slave traders carried it to the Americas.
And what had been as the same plant,
one path selected for length and strength of fibers,
and the other paths selected for psychoactive potency.
[narrator] In 1753, Carl Linnaeus,
a Swedish botanist who created the modern system of classifying organisms,
named the plant cannabis sativa.
These plants grew tall and had thin leaflets.
Later on, a variety of the plant found in the cool mountain climates of India
with darker, thicker leaves was labeled cannabis indica.
And then there's this little guy, cannabis ruderalis,
small plants found in Russia.
Linnaeus noticed something unusual about cannabis.
While most plants have flowers with both male and female parts,
with cannabis, some plants only produced seeds and others only produced pollen.
In other words, they were male and female.
Linnaeus isolated some of the female plants on his windowsill
and got pretty excited about what happened next.
[Chong] "It was certainly a beautiful and truly admirable spectacle
to see the unimpregnated female flourishing,
till they had been for a very considerable time
exploded in vain
to access the male pollen."
Wow, he's really into this weed, isn't he?
[narrator] Because female cannabis plants produce bigger psychoactive flowers,
they're much better for getting you high.
Flower has the most resin in it, the most of the oil.
[narrator] The leaves and stems contain some psychoactives, but not that much.
The main psychoactive chemical is called THC, or tetrahydrocannabinol.
The second major active chemical is cannabidiol, or CBD,
which reduces anxiety.
But cannabis has more than 100 compounds that affect the human body,
called cannabinoids.
A few decades ago, researchers discovered
that we produce a lot of these same chemicals naturally
and have receptors for them sprinkled all around our bodies.
It's involved with food regulation.
It's involved in cognition.
It's involved with fine motor movement.
It's everywhere.
[narrator] Endocannabinoid systems are present in every animal
except for insects.
We still don't fully understand why they're there,
but there's evidence that they play a key evolutionary role
in regulating appetite, helping us forget, and reducing stress.
And they might be the chemicals behind the euphoria you feel after exercise.
But cannabis isn't just cannabinoids.
There are over 400 active compounds
that give each plant a unique chemical profile.
Oh, hello, Pineapple OGs.
Think of it like a graphic equalizer on a stereo.
Imagine a graphic equalizer with over 400 dials on them. THC, cannabidiol, CBG, CBN.
A lot of these things are psychoactive.
A lot of these cannabinoids are non-psychoactive.
Terpenes are basically aroma molecules.
Flavonoids are flavor molecules.
And all of these things are mediated...
by the cannabinoid profile, is what we call it.
[narrator] The popular strain Sour Diesel gets its peppery note
from the chemical caryophyllene,
which is also found in black pepper, cloves, and cinnamon.
While Super Lemon Haze contains limonene, a major component of the peels of citrus fruit.
By selecting the right combination of cannabinoids
over several plant generations,
growers can create an iconic name brand product,
like the famous strain in the movie Pineapple Express.
This is like if that Blue Oyster shit met that Afghan Kush I had
and they had a baby,
and then meanwhile, that crazy Northern Lights stuff I had
and the Super Red Espresso Snowflake met and had a baby,
and by some miracle, those two babies met and fucked...
"...this would be the shit
they birthed." [chuckles]
Now that may not sound super scientific,
but that's basically how it works.
[narrator] Today, Pineapple Express
is one of hundreds and hundreds of unique marijuana strains on the market, some with advertised THC potencies upward of 25%.
That dramatic evolutionary change happened because of one thing:
the American war on drugs.
[Nixon] Marijuana is a weed and spreads like crabgrass once it goes to seed.
In order to fight and defeat this enemy,
it is necessary to wage a new all-out offensive.
[man] But we need to concentrate on the organizations,
we need to concentrate on who's financing them, who's setting them up,
-and we need to cut the heads off there. -[police radio chat]
[narrator] For the majority of the 20th century,
most of the marijuana consumed in the US came from Mexico.
It was terrible stuff.
Marijuana was the...
mostly the leaves...
occasionally the flowers if the dealer was feeling in a good mood.
Frequently the stems or the seeds if the dealer was feeling in a bad mood.
And of course that was garbage that you paid for.
[narrator] Today's growers mostly sell flowers, or bud.
But the Mexican growers sold the whole plant: leaves, seeds, stems, and all.
And the result was a product that probably averaged about 3% THC content by weight.
[narrator] To cut off the flow of cannabis across the border,
the US started paying Mexico
to spray their marijuana fields with herbicide in 1975,
so Americans started making a lot more of it themselves.
But marijuana could only grow in the sunny US states like California,
because the only marijuana we had was cannabis sativa.
That changed in the late 1970s,
when Americans brought back the shorter cold-resistant cannabis indica
from the Hindu Kush mountains.
And we came up with hybrids.
[narrator] Crossbreeding frost-resistant indica
with existing sativa plants
allowed cannabis to grow in every single state in America.
And when the Reagan Administration started using spy planes
to search for marijuana farms from the air,
indica's smaller size allowed growers to hide their plants indoors.
And remember cannabis ruderalis?
Crossbreeding with it allowed for shorter flowering times,
so plants could sprout faster.
And these hybrids were now able to be grown indoors.
And they didn't take 12 weeks to grow,
and they didn't grow eight and ten and 12 feet tall.
[narrator] But the biggest transformation to the plant
was the rediscovery of an ancient breeding method
based on the same phenomenon Carl Linnaeus had observed on his windowsill.
It turns out that process makes flowers ooze psychoactive resin.
One day somebody said to me, "Hey, there's this new kind of weed.
It's called Sinse."
Sinsemilla. It's basically Spanish for "seedless."
[narrator] When female plants are pollinated,
their THC production slows to produce seeds.
But if you keep female plants away from male plants,
they never get pollinated, never produce seeds,
and their THC production never slows down.
Basically, a process of producing
a bunch of sexually frustrated female marijuana plants.
[narrator] And by clipping from those females,
growers could clone a new generation of genetically identical plants,
skipping the pollination process altogether.
Unfortunately, these plants are never going to get to have sex.
So they're just going to keep creating more and more resin,
trying to attract that pollen so that they can make seeds.
And if you think about it, the modern cannabis plant
that's been bred to be all flowers is really kind of a botanical freak.
And the flowers are huge,
totally out of proportion to the plant itself.
It's kind of grotesque actually.
[narrator] The average THC content of Sinsemilla
was several times higher than normal cannabis.
But the THC content for both hasn't changed much over the last couple decades.
Weed, on average, has gotten so much more potent
because Americans started buying a lot more of the stronger version.
But that resulted in another change.
THC, the psychoactive compound, and CBD, the relaxing one, are connected.
The more THC there is in a plant, the less CBD.
Even back in the 1990s,
the ratio of THC to CBD in the plant was about 11 to one.
Today, you know, 30 years later nearly,
we have THC to CBD ratios on the order of 250 to one.
And so you get stuff with more and more THC and less and less CBD.
There's gonna be a higher rate of people getting freaked out.
And that appears to be true.
They run the risk of having increased anxiety, paranoia,
maybe thinking that they're losing their mind.
Those are the major sort of concerns that I worry about
when people with lack of tolerance use high THC-containing products.
[narrator] Legal pot shops will usually label
the THC and CBD levels of different strains,
along with a couple other key descriptors.
There's just one problem:
the words we use to classify this plant don't actually mean anything.
If you shop for marijuana,
chances are you're familiar with these names.
Indica or sativa?
Indica and sativa.
Indica versus sativa.
[inhales]
Indica and sativa.
And I just basically call it "daytime pot" and "nighttime pot."
[narrator] The sativa-indica binary
has been the basis for how most marijuana is sold.
Sativas provide an energetic high feeling,
while indicas give a lethargic stoned feeling.
But much of what we think of these things are just myths.
[narrator] Because of extensive crossbreeding,
how a plant today looks
doesn't necessarily have anything to do with how it makes you feel.
It used to be very easy to visually identify.
And it was that broad-leafed varieties were indica
and thin-leafed varieties were sativa.
And now, because they've been so intercrossed and interbred so much,
you can have a broad-leafed variety that is straight-up sativa in its effects.
[narrator] And we can't do a genetic test for indica or sativa
because there's no genetic sample of pure indica or sativa.
And we're not sure that there ever was.
When you have people labeling something 70% sativa, 70% indica,
it's 100% subjective.
It's done by somebody smoking it
and deciding that they are getting either an indica or a sativa effect from it.
Indica dominant to indica-sativa hybrid
sounds really technical and scientific even though it's complete nonsense.
So people say it.
I think we're going to look back at this period
and laugh at those hipsters in the legal stores
selling us sativa and indica
and telling us what it does and all this hokey shit.
I think we're going to laugh at that.
[narrator] Even if the sativa-indica labels are meaningless,
you would assume at least the strain names mean something.
When you purchase wine by name,
you expect a genetically consistent product.
A Merlot can't be sold as a Cabernet.
That's because governments regulate them,
but that's not true with cannabis strains.
People have absolutely no idea what they're smoking.
The strain names are not reliable.
You can call anything you want Purple Urkle.
[narrator] Improving that labeling is especially important,
because we don't know what a standard unit of marijuana looks like.
We do not have the cannabis equivalent of a drink,
and we really need to get there
so that people can start thinking seriously about,
"Well, you know, how stoned do I want to get?
Do I want to get one puff or two puffs or three puffs worth stoned?"
But that doesn't make any sense until we've standardized the puff.
[narrator] But standardizing a puff requires one big first step:
legal regulated marijuana.
Countries all over the world are starting to loosen laws on cannabis.
And that can mean more accurate labeling.
In the Netherlands, where medical marijuana production is legal,
a company called Bedrocan
closely tests the cannabinoid profile of their products to ensure consistency.
They've done away with the hippie strain names
in favor of more official titles, like Betica and Bedrobinal.
When researchers tested them,
their chemical profiles were extremely consistent.
But White Widow and Amnesia samples bought from different Amsterdam stores
were all over the place.
If the legal weed market grows, we might see more of that consistency.
Bedrocan's parent company, Canopy Growth,
got a widely publicized investment and a historic one.
The investor was the alcohol giant Constellation Brands.
You may not have heard of them,
but you've probably heard of some of their products.
[glass clinks]
That raises the question:
What does the Corona of weed look like?
That depends on the market.
It's estimated that in Colorado's legal pot market,
near daily or daily users make up the biggest share of demand,
almost 67%.
And the percentage of users who consume that heavily
keeps going up in the US.
They're gonna be driven by profits.
If most of their goods are sold to regular and heavy users,
that's who they're gonna market their products to,
and they're going to be working aggressively
at developing new regular and heavy users.
But as long as somebody has a bottom line that's driven by drug abuse,
they're gonna promote drug abuse.
It's not rocket science.
[narrator] Because those heavy users have a greater tolerance
and are constantly pursuing a better high,
they also drive the average demand toward high-potency products.
Everybody I know my age who still smokes complains.
You know, why can't you get the mellow stuff anymore?
And the answer is the people who want the mellow stuff...
don't buy enough to matter.
[narrator] Legal stores now sell edibles, vapor pens, and extracts,
some with concentrations of THC close to 100%.
But you can now also buy those kinds of products with only CBD and no THC at all,
which claim to reduce anxiety without getting you high.
Understanding how these diverse new products
affect the human body is important,
because marijuana isn't totally harmless.
Studies show it can raise the risk of schizophrenia and psychosis.
And there's still a lot we don't know about its long-term health impacts.
But every day also seems to bring
new stories about marijuana's possibilities as a medicine.
[man] Another study found that people with chronic pain reported
they reduce the amount of opioids they use. [woman] Its effectiveness in treating glaucoma
and alleviating the side effects of chemotherapy is unrivaled.
Many patients insist pot helped where other medications failed.
[man] This week's study of 120 children with a rare form of epilepsy
found those who are given CBD along with their standard medications
had a nearly 40% reduction in the frequency of seizures.
[narrator] In the years to come, engineering this plant
will help us tailor those possible treatments
and it will open up a whole new field of medicine.
We've changed plants dramatically before.
Corn, peaches, and watermelon were once inedible, tiny fruits.
Over thousands of years, we bred them to fit our desires.
With cannabis, underground growers made a similar transformation happen
in just a few decades.
And modern agricultural engineering is about to transform it again.
In the long natural history of cannabis,
which has been going on for thousands of years
and has had these very important peak moments,