All language subtitles for Evolution.Im.Grosstadtdschungel.2020.1080p.WEBRip.x264.AAC-[YTS.MX]

(elegant piano music)

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- In a lot of ways you can think

of cities as one of the
largest unplanned experiments

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of all time.

(elegant piano music)

- There can be really small differences

that have very large
biological significance.

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- Cities are places, we call
them extreme habitats really.

They are places where there
is a lot of opportunity.

And at the same time,
there's also challenges.

- [Narrator] As our city
spread, how will nature respond?

Will plants and animals dwindle,

or will they adapt to urban life?

And what kind of new encounters
will we see in the city?

In the historic French town of Albi,

biologist Frederic Santoul
keeps an eye on his catfish.

In 1983, fishermen released
these Eastern European fish

into the Riverton.

Today, they're at the top
of the river's food chain.

(Frederic speaking in foreign language)

- [Voiceover] This is
a fascinating species

because we know so little about them.

There are many myths that people believe,

even that they eat dogs.

There are many stories.

- [Narrator] The biologist is interested

in the behavior of the large fish

that circle the reservoir's basins.

(mysterious music)

(Frederic speaking in foreign language)

- [Voiceover] We work with
fishermen to tag the fish.

They contacted us after
observing very strange behavior

in the fish here in Albi.

- [Narrator] The man-made landscape

of the city fosters new
encounters of species.

(Frederic speaking in foreign language)

- [Voiceover] The pigeons have
never had to face predators

from the water.

Instead, they scan the
sky for birds of prey.

- [Narrator] The pigeons
approach the water

to bathe and drink.

Sometimes a bird misses the
narrow strip of safe ground

and touches down in open water.

(Frederic speaking in foreign language)

- [Voiceover] The catfish
don't really see the pigeons,

but once they sense the birds' movements

in the water with their
bobbles, then they strike.

- [Narrator] This new hunting behavior

of the catfish was
observed by the biologists

for the first time in 2010.

(whimsical music)

For some catfish here,

pigeons now account for
up to 40% of their prey.

- There's suddenly this
ecological interaction

which allows for evolution to start

to improve the bird-catching
ability of the catfish

and also to improve the
escape ability of the pigeons.

So you can expect that all
these new interactions are

also causing new evolutionary dynamic.

- [Narrator] Dutch evolutionary biologist

Menno Schilthuizen
researches the adaptation

of wildlife to the city.

Darwin's theory, he
believes, has gone urban.

- Urban evolution is evolutionary change.

So really genetic change in wild animals

and plants in cities.

It's all about understanding
how species will be able

to survive in this very
human-dominated context.

- [Narrator] Cities are homosapiens'

most extreme intervention in nature.

With concrete and steel,
we create new landscapes

and alter the face of the earth.

Already, most people live in cities,

rather than in the countryside.

How does this influence evolution?

The development of new species?

What selection pressures
does the city create?

A summit evening in the
Dutch capital of Amsterdam,

in the Vondelpark in
the center of the city,

Biologist Menno Schilthuizen
uses a light trap

to catch insects.

He's leading a citizen science project

to explore urban nature.

- For insects and for some smaller plants,

the diversity today in
cities seems to be higher

than in intensively
managed agricultural areas.

Today, agricultural land
is so intensively managed

and every last bit of
production is squeezed out

of every square meter of surface area

that there's no space for nature
anymore in the countryside.

And at the same time, cities get more,

they get greener, people
pay more attention to nature

and to urban nature.

So it's actually becoming
a very rich environment

with a higher biodiversity
than outside of the city.

(uneasy music)

- [Narrator] But overall, we're
rapidly losing biodiversity,

both within and outside our cities.

For insects, the declines
are particularly severe.

In the Swiss Alps near Zurich,

Scientist Florian Altermatt
has set up his light traps.

Ever since humans began
to light up the night,

billions of nocturnal insects

have been dying off every year.

(Florian speaking in foreign language)

- [Voiceover] For such a
species it's problematic

if it's attracted by light

because then it cannot use
the few short days it has

as a moth to lay eggs.

- [Narrator] Light pollution is one

of the major threats to moths.

Scientists are now even speaking
of an insect apocalypse.

(Florian speaking in foreign language)

- [Voiceover] I think the
declines we're now seeing

are already quite worrying.

Studies show a 60 to
80% decline in biomass,

sometimes even in nature reserves.

These are incredibly large numbers.

In my childhood, I used to
observe moths like these.

I would set up this trap
next to my parents' house

and attract moths, actually,
in quite large numbers.

I don't think I'd find many today.

- [Narrator] But might insects be capable

of adapting to life in the
perpetual light of our cities?

That's what Florian
Altermatt wanted to find out.

His test subject, the spindle ermine moth,

whose caterpillars develop
on the European spindle tree.

(bird singing)

(Florian speaking in foreign language)

- [Voiceover] Actually,
it was a coincidence.

While I was working on my PhD thesis,

every day I walked through a park

which had those Europeans spindle bushes.

And I noticed that there
were these caterpillars,

these moths which must
have lived there for years

in a city park with
permanent light pollution.

And then I thought I could
just collect them, raise them,

and test how much the adult
moths are attracted by light.

- [Narrator] With his experiments in 2006,

Altermatt pioneered research
into urban evolution.

He released the moths in a darkened room.

The next morning, he
counted how many had flown

into the light trap.

(Florian speaking in foreign language)

- [Voiceover] The results
showed a difference.

About 20% fewer urban
moths flew into the trap.

I was very surprised.

It was widely known that
moths attracted by light,

some more than others,

but these differences
have always been observed

between different species.

Seeing variations within a single species,

that we'd never seen before.

- [Narrator] The experiment
clearly demonstrated

a hereditary adaptation
to life in the city,

direct proof of urban evolution.

For Dutch biologist Menno Schilthuizen,

the findings confirm a larger picture.

In Amsterdam, he and his group
of citizen scientists debate

whether we might soon observe even more

and greater adaptations of
animals and plants to this city.

- We see that evolutionary
processes are starting

which will eventually

or could eventually produce new species

that are specialized
on living in the city.

- [Narrator] For Menno
Schilthuizen, it's not if, but when.

- Every organism that lives

in the city will show
this urban evolution.

These rapid changes in their behavior,

in their physiology, in their appearances

to optimize their life
in an urban environment.

- [Narrator] But what elements

of urban landscapes
prompt wildlife to adapt?

Evolutionary biologist Jason Munshi-South

is an expert on animals found
in the parks of New York City.

For years, he's been studying
how rodents adapt to the city.

Along with human immigrants from Europe,

rats also voyage to the New World.

Today, they roam the
city in subway tunnels.

Most native rodent species, however,

don't dare try their luck crossing town.

This distinction sparked
the scientist's interest.

- I used to be a tropical biologist,

but then I moved to New York City

for my first academic job
after graduate school.

And I decided I wanted
to do some local work

that would be interesting to
the people of New York City

and to my myself.

And I found out that there
was these small mammals living

in essentially islands
of forest in the city,

and I thought, you know,
that's interesting.

Nobody's really ever looked at these.

Are they becoming genetically different

from mice outside of the city?

Are they adapting? And
that's how it all started.

- [Narrator] Central Park opened in 1873.

It still hosts animal species

that lived here long
before the city was built.

- Right now we're in the
middle of Central Park.

We're gonna be traveling to
the north end of the park

where there's a very nice
forest called the North Woods.

And there we'll be
setting up traps hopefully

to capture white-footed mice.

One of the things that inspired me

when I first started this work is

if you look at a New York City subway map,

you see the subway lines,

but then there are these
large green shapes,

rectangles, and ovals, and so
forth that are the parklands.

And they put those on the map
so you know where they are,

but you also see that they
are almost like a chain

of islands that are scattered

in this sea of concrete and
roads and buildings and,

you know, 8.5 million people.

So in a sense, if it's
a species like a mouse

that can't leave the forest, cross,

you know, neighborhoods
and buildings and roads

and make it to the other patch,

it is essentially the same biologically

as if they were on an island

in terms of them not being able to move

and spread their genes
with the other patches.

And these urban patches,

once they become sufficiently isolated,

operate like a mini Galapagos

and may be driving the
evolution of many species

that are, you know, stuck there now.

- [Narrator] The evolutionary
biologist is investigating

whether the white-footed
mice actually develop

in distinct ways in each
of the various parks.

- Yeah.

So this would be a really nice
spot for white-footed mice.

They like to move next to logs

so they're not completely out in the open.

They might actually even
be living inside this log

where it's rotting or in
holes underneath the log.

So this is pretty much the ideal spot.

- [Voiceover] This forest is
encircled by the Big Apple.

Have the mice already adapted
to this unique environment?

What traits do they need to survive here?

- No shortage of good trapping spots.

Later I'll be going to
one of our more suburban,

almost rural sites with the
larger, more intact forests,

lesser urbanization,
and I'll be setting out,

you know, an equal number of traps

with the hope that we
catch mice there as well.

- [Narrator] Jason
Munshi-South will search

within the animal's genetic
codes for the markers of life

in the big city.

(soft music)

- I think what's been most interesting

to me is thinking about how the things

that we are all doing in our daily lives,

where we put our garbage,

what we're choosing to eat
and what we generate as waste,

where we choose to live,

how we choose to go to work

or out to a restaurant or something,

all of these things we are doing

are now influencing other species

in a way that we're just
starting to understand.

- [Narrator] Though it's not only animals

that adapt to human intervention
in the natural world.

So do plants.

In Southern France, the
yellow-flowered Crepis sancta

is being studied by Biologist
Pierre-Olivier Cheptou.

- [Voiceover] Crepis sancta
is a very common species

in the Mediterranean region,

a kind of Mediterranean
dandelion from the same family.

And its essential advantage as a model is

that it produces two types of seeds,

large ones and small ones.

- [Narrator] The small wildflower produces

both lighter seeds with
parachutes allowing them to glide

and heavier seeds that
simply fall to the ground.

(Pierre speaking in foreign language)

- [Voiceover] I'm interested
in the process of adaptation

to an urban environment.

And in particular, what happens

when a species first arrives a city.

It has recently colonized
certain areas of Montpellier.

And in my comparison between
rural and urban populations,

I focus on the traits related to seeds.

- [Narrator] The idea of
studying the adaptation

of the modest plant of the city came

to Cheptou to almost by chance.

When he came back from abroad,

he noticed the inconspicuousness
flowers growing

in the city.

(Pierre speaking in foreign language)

- [Voiceover] I had left Montreal

in the middle of a blizzard.

I got the plane to Paris.

And when I took the bus
to Downtown Montpellier,

it was sunny with a pristine blue sky.

And then I noticed there
were Crepis sancta flowers

everywhere in those tiny urban patches.

It was then the intuition hit me.

I knew there was something
to discover here,

something to uncover.

- Was the plant already
adapting to the city?

Which aspects of the city
would drive that change?

(Pierre speaking in foreign language)

- [Voiceover] The predominant
mineral in cities,

especially in European
cities, is concrete.

Concrete exerts a powerful
fragmenting force on plants,

driving them to ever-shrinking
refuges in these habitats.

- [Narrator] Sometimes
the city's constraints

on a plant's habitat can be extreme.

How will evolution respond?

(Pierre speaking in foreign language)

- [Voiceover] I'm looking at

how urban fragmentation will modify

the dispersal traits of this species.

I expect plants that produce more

of the larger seeds
will be more successful

at reproduction in urban areas

than they would be in the countryside.

- [Narrator] The heavier
seeds face less risk

of being swept onto the asphalt.

And indeed, the biologist
discovered that far more plants

in the city produced the heavier seeds

and are thus better able to survive.

A difference of 15%.

But what most stands out is
the speed of this adaptation.

(Pierre speaking in foreign language)

- [Voiceover] The evolution
we have seen has taken

about 15 years.

This is extremely brief.

It was the first demonstration

of such a rapid evolution
of seed traits for plants.

And that's due to this
highly fragmented composition

of the urban environment.

- [Narrator] Genetic changes occurring

at such a rate have long
been considered unlikely,

even impossible by science.

- I think Darwin would have
been amazed by the fastness

by which these changes take place.

He was sort of underestimating the power

of natural selection himself.

He said that you could never see any

of these changes in progress.

You cannot actually observe them,

you can only deduce them from the fossils,

from the patterns that you see in nature.

You said evolution is too slow

to see it happening in real time.

And the fact that now
today, especially in cities,

we see these changes taking place

under our eyes in the streets
where we live right around us,

I think Darwin would have
been thrilled by that.

- In Los Angeles, the UCLA
campus also nurtures species

that have migrated from
surrounding areas to the city.

Evolutionary biologist Pamela Yeh studies

the dark-eyed junco.

The mountain bird has only been settled

in California cities for a few decades.

Pamela Yeh began her research

in San Diego more than 20 years ago.

Today, she's investigating
how the once shy bird manages

to survive in bustling Los Angeles.

- So this is a junko nest.

Typically in the mountains they make all

of their nests on the ground,

but up here, we have a good
percentage of our nests

that are up in the middle of, you know,

branches of trees or up on the buildings,

higher up off the ground.

- [Narrator] Darwin himself was fascinated

by the evolution of birds,

but until now, biologists
couldn't observe their adaptation

to new habitats in real time.

- They have this very famous
study on Darwin's finches

in the Galapagos,

and they can show really
large biological differences

in terms of like mortality,

like who's surviving and who's dying,

by like a millimeter
or less of a beak depth

or a beak length or beak width, right?

And so I think there can
be really small differences

that have very large
biological significance.

- [Narrator] To track such subtle changes.

Pamela Yeh and her team led

by PhD candidate Ellie Diamant first have

to catch the birds.

- So the nest is just over here.

Can you see it in the grate?

There are five chicks
up there, nine days old,

and the parents are going
back and feeding them.

- [Narrator] Might recorded
birdsong jolt the bird

into rash action?

- So we're gonna play a playback,

like a territorial junko song.

And it's going to go
to that speaker there.

And hopefully the male

who seems like he's feeding
his chicks right now

is gonna fly over, try to check it out,

maybe go for the speaker,

and hopefully get caught
in this net or in this net.

We'll see.

Okay.

(junko chirping)

- [Narrator] The call of a rival bird.

The male, intent on driving
it off, rushes over.

- [Ellie] Oh, there is a junco in the net.

Guys, that was easy.

- [Narrator] The team
tags and measures the bird

and collects DNA samples.

Back in San Diego in 2003,

Professor Yeh had discovered a change

in the appearance of the
city junco's tail feathers.

Now her team wants to see

if something similar is going on here.

- [Ellie] Spreading his tail
so you can see the white

on his tail there.

- One of the main
differences that we found is

that urban juncos had much
less white in the tail feather

than the populations
in the local mountains,

which had a lot of white.

And what we wanted to know was then, well,

why is it there's this huge difference

that we're finding between the mountains

and the city juncos?

What's the reason for that?

- [Narrator] Evidence suggests
the white tail feathers serve

an important signaling
function in competition

and partner selection by the birds.

- Cool. Success.

All right.

- [Narrator] What new demands
does life between motorways

and buildings make on birds

to change their mating and
territorial preferences?

The case of a species adapting its color

to man-made environments
was first observed

by natural scientists
during industrialization,

even before Darwin put forward his theory

on the origin of species.

- The peppered moth is a species of moth

that comes in two forms,

a light-colored form with light wings

and one with dark wings.

And the dark-winged form
was only first found

in England in the Industrial Revolution.

In the middle of the 19th century,

it began to appear and suddenly
it started to become more

and more common over a
relatively short period of time

in areas where there was
a lot of air pollution.

- [Narrator] The smoke
from the chimneys coated

the white birch bark with dark soot.

The white moths thus
became easy prey for birds.

The new darker moths
enjoyed superior camouflage.

- People didn't really
understand what was going on.

They thought that the
female moths maybe saw

that the environment was getting darker

and somehow that became
imprinted on their offspring.

I mean, that's the way people thought

about genetics and heredity in those days.

- [Narrator] The conclusive
evidence connecting the spread

of the dark moths to coal soot
was only found in the 1980s.

The air was getting cleaner again,

and the white moths returned.

- Evolution can proceed fast

if the environment
changes very dramatically,

which means that a lot
of individuals will die

and a few will survive,

the ones that have some
genetic characteristic

that makes them survive better.

And they will then produce
the next generation.

And they may also have some adaptations

which then spread so that
evolution can proceed faster.

- [Narrator] The color change was a simple

but effective adaptation.

It only required a
mutation of a single gene.

But what if man-made pollutants
substantially distort

the biochemistry of organisms?

In the 1970s, the water at
New Bedford Harbor near Boston

was severely polluted with PCBs.

The US Environmental
Protection Agency, EPA,

wanted to know just how bad
the pollution really was.

- The original focus was
on what must be wrong

with all the fish that live in that harbor

because of the toxic chemicals.

Instead, we came here looking trying

to understand what must
be right about those fish

that could survive here.

So they've become a
natural experiment for us

to study how animals can adapt

to toxic human-made pollutants.

Terrific. Just what we're looking for.

Let's get 'em into a net,
bring 'em back to the lab.

- [Narrator] Diane Nacci heads the EPA lab

in Narragansett Rhode Island.

(mysterious music)

In the breeding facility,

the scientists want to
unravel the mechanism

that allows this population
of a killifish species

to survive in the PCB-polluted
water of New Bedford Harbor.

- [Diane] So let's see if
they left any eggs for us.

- [Narrator] They plan to compare eggs

from the New Bedford Harbor fish

with those of a fish
population from a cleaner site.

- Let's start a test and see what

they do when we expose 'em to chemicals.

- This killifish species occurs all

along the North American Atlantic coast.

- The killifish has been a favorite

of biology literally for centuries.

That they are quite common,
they are non-migratory,

so they reflect their local environment,

and each population is unique in

that it is genetically different.

It is adapted to its local environment.

So it gives us opportunity
for lots of studies.

- [Narrator] The researchers
need to observe the development

of the fish embryos in the
egg in order to understand

at which stages the
environmental toxin disrupts

the animal's biochemistry or not.

- So we'll look at the rate at
which the embryo is developed

and certain features that we
know that PCBs fees can disturb

like a proper development of the heart,

evidence of proper development
of the circulatory system,

and proper body size.

- [Narrator] Why are
these particular fish able

to resist deadly environmental toxins?

- It's important to
understand which species can

and which cannot adapt
because we want to forecast.

We want to predict what the
environment will look like

in the future, whether
the ecosystem surfaces

that we rely on today like pollination,

clean water, et cetera,
can still be relied on.

And for that, we're
going to need adaptation

of all kinds of animals and plants

to this new world that we are creating.

- [Narrator] In California,
some city juncos have less white

in their tail feathers
than their mountain peers.

Which selection pressures
are driving this evolution?

What is the function of this pigmentation?

- And one of the main purposes appears

to be in dominance interactions

between individuals where
typically the more white

that you have, the more dominant

and the more aggressive you are,

and your successful at
winning competitions.

If you're fighting with another one,

often the one that has more white wins.

- So we're gonna do some
aggression playbacks

around Dickson Court.

- All right. Good luck today.

- All right.
- Okay. Yeah.

Thank you so much today, Pam.

- Okay. See you soon.
- We'll keep you up-to-date.

- Okay. Bye-bye.

- [Narrator] To learn
more about the adaptation

of the birds to the city,

PhD student Ellie Diamant aims

to scientifically measure
their aggression levels here

in Los Angeles.

- So we're essentially setting up an arena

to watch the bird.

While they're in the car, it's fine.

This is a Boris the fake junko,

and it's the visual stimulus for the bird.

He's just gonna sit here

and there's gonna be a
song playing from there,

and the bird is going to think
that this is a real junco

and it's gonna hear the
song that it's singing,

and then hopefully come and think

that there is an intruding
bird on the territory.

And we'll see how it reacts to that bird.

- [Narrator] Juncos are territorial birds.

from a male's response to a
stranger in his territory,

the researchers can
gauge his aggressiveness.

- Ready?

- [Researcher] Yeah. All right.

Starting now.

- [Ellie] Okay.

(junco chirping)

I think I hear him.

Oh.
- Oh.

- He's there. Yeah, that's him.

He's in the tree.

- This angle you can.

- Yeah, let me try. He's still singing.

- [Researcher] He turned around.

- Where is he? Oh.

- [Researcher] He's down. Oh.

- He's entering.
- He's entered.

- [Narrator] Shortly before the end

of the 15-minute trial period,

the male stalks the intruder closely.

- He's hiding behind some grass.

Is he gonna knock it over?

- [Narrator] The researchers
stop the playback

to end the experiment.

The male displayed some
aggression, but not a great deal.

Why do the city birds seem

to lose their drive for competition?

- What we think is happening is

that there's selection towards
for less aggressive birds

who are better mates, the better parents,

because you can likely
increase your fitness

so much more by taking care of
the chicks that you do have,

rather than looking for
extra pair copulation

and extra pair fertilizations.

- [Narrator] With the
longest summers in the city

and abundant food from watered greens,

the birds can maintain more nests per year

than in the mountains.

Competition for additional mates

and territories no
longer seems worthwhile.

- There's a lot of reasons why these birds

shouldn't be successful in urban areas,

and yet they are.

So I think understanding why they

are and understanding the mechanisms,

the processes underlying
that can tell us something

about how do we encourage other species

to also be successful.

(elegant piano music)

- [Narrator] What are the factors

that allow individual
species to adapt to the city?

Are parallel developments taking
place in cities worldwide?

At the University of Toronto Mississauga,

evolutionary biologist Marc
Johnson pursues these questions.

- In a lot of ways you can think of cities

as one of the largest unplanned
experiments of all time.

The problem is, is
there's very few organisms

where you could study adaptation

to urban environments on a global scale.

And white clover is one of
those very few organisms

where you can actually do that.

And so now this then becomes the model

to understand whether
organisms in general can adapt

to the convergent
environmental change associated

with cities throughout the world.

- [Narrator] Researchers across the globe

are working together in this study.

Evolutionary biologist Stephan Greiner

and his team are collecting
white clover in Berlin.

In cities, the plant
faces a different habitat.

Temperatures are higher than

in the suburbs and the countryside.

(Stephan speaking in foreign language)

- [Voiceover] What you can expect is that

as humans create new
environmental conditions,

life will adapt.

And to be able to show
that on a global scale,

that's a real scientific benefit.

It has to be done.

That's why we're dedicating
our free time to this project.

- [Narrator] As they
proceed from the countryside

to the city center of Berlin,

Greiner and his team collect
specimens at 30 locations.

That means the data will
be broad enough to compare

with that from other global cities.

In the shadow of the Television Tower,

they find their final samples.

- [Voiceover] That's it. All done.

- In all, we have 168 cities right now,

and over 250 collaborators all working

on the same project together.

There's never been a collaborative project

on evolutionary biology of this scale.

And so this is the largest
collaborative project

in evolutionary biology ever.

- [Narrator] So is clover
developing in the same way

all over the world into a
kind of global city clover?

From the vast set of data,

the researchers hope to find an answer.

In the grounds of a research
institute north of New York,

geneticist Jason Munshi-South wants

to catch white-footed
mice to compare their DNA

with that of those in the city,

but it's not easy.
- Go to the labs.

- [Researcher] It's good.

- Okay.

So this is a trap that was open

that didn't catch anything obviously.

Wow, that's a toad.

I thought it was a mouse.

Nice day for other wildlife, I guess.

We were really surprised

that almost every park was
different from every other park.

It's almost to the point
where you can take a mouse

from one park, give it to our lab,

and we could just look at a
small segment of its genome

and tell you where it came from.

That's how much they had
changed just randomly

over time from being isolated.

And that's when we started
our current studies looking

at over 20,000 genes to see what genes

and potentially what functions change

when they adapt to living
in inside of New York City.

(rich thrumming music)

Oh, there's one.

The first white-footed mouse of the day.

- [Narrator] For the new study,

Jason Munshi-South and his
team have already caught more

than 100 mice and analyzed
their genetic compositions.

They try to take their
samples as gently as possible

so they don't hurt the animals.

- And we take a genetic sample.

In this case, we will be
using this small tool.

It's like a paper punch, but for tissue.

And we store that for a genetic analysis.

And we want to be able to tie

that tissue sample to a location

because that's important for understanding

how they vary when they're

in a more urban or a
less urban population.

So now they're pretty immobile.

This is a male.

It's a young male.

All right, why don't we take the ear punch

and we'll start on the other one.

(rich thrumming music)

- [Narrator] Hair isn't suitable

for comprehensive genetic analysis.

(thoughtful music)

After collecting the samples
and some measurements,

the scientists release the mice.

Genetic analysis can reveal
the evolutionary trajectories

of the mice.

They point to a variety of physical

and behavioral changes
spreading among the animals,

each of them unique to the challenges

of each city park environment.

(thoughtful music)

- So we're starting to fill
in our gradient really nicely.

So here are the mice we have
today from the Calder Center,

and you can see it's right

in between highly urbanized New York City.

And then all these sites we
have up here and went out here.

So Central Park seems

to be our most distinct population

to date.
- We tested it.

- It makes sense. Yeah.

- Yeah.

- Most urban, probably the most isolated.

So if you took a mouse from Central Park,

some of its genes will be
different from a mouse outside

in the countryside in
a big park somewhere.

Right, so for this one in particular-

- [Narrator] The food
supply in Central Park,

much of it human food waste,

might've triggered a genetic response.

- Other places in the
city near Central Park.

And then once you get,

so what we've learned so
far is that one set of genes

that are changing in the city
have to do with metabolism.

So these white-footed
mice are eating things,

then they have to digest them
and assimilate the nutrients.

And we know it's evolution
because a heritable change

in DNA sequence is evolution.

- [Narrator] Central Park mice seem

to have genetically
altered their metabolism

to better digest fast food.

- It raises several like broader questions

about what we are doing as a species.

As we modify the Earth's
habitat for our needs,

how are we changing the
future of other species?

Not only are we affecting them,

but we're changing what they
will become in the future.

- [Narrator] And Narragansett, Diane Nacci

and her team are investigating

how the different fish embryos exposed

to the toxic PCBs have developed.

- So, come in.

Hi, how's it going?
- Hi.

Really well.

So this is the study that's
comparing Scorton Creek

and New Bedford Harbor exposed to PCB 126.

So this one is the group
that was treated with PCBs,

also from the clean site, Scorton Creek.

And as you can see,

the PCBs have had a pretty dramatic effect

on the development,
which is what we expect

with these very toxic chemicals.

- Yeah.

And in my experience, when I see this,

this constellation of anomalies,
it's absolutely lethal.

There's no way that an
animal would even hatch,

nevermind survive, after hatching

if the heart is not functional

and the blood is
essentially not circulating

around the body.

So let's take a look at
that biochemical endpoint

to see if they are also responsive
at the biochemical level.

- [Narrator] Using a
special contrast agent,

the scientists can trace enzyme activity

in the unhatched fish.

- So you can see that the
substrate is fluorescing

in the bladder, showing that
this enzyme system is working

and we're getting the expected
metabolites in the bladder.

- [Diane] That's a very
dramatic demonstration

of enzyme activity in a living organism.

- Mm-hmm.

- [Narrator] The active enzymes reveal

how the organism tries
to break down the toxin,

but parishes in the process.

Then the team observes how
the offspring of the fish

from New Bedford Harbor have developed.

- Okay, so these are fish
from New Bedford Harbor

that were exposed to the same level of PCB

that we were just looking at.

As you can see with this embryo,

it doesn't seem to have any effect.

The heart is still beating
normally and healthy

and it's developed really well.

- That looks like an embryo
that's about ready to hatch.

- [Researcher] Some of them
actually already hatched.

- [Narrator] These fish should be dead,

poisoned by one of the most
lethal environmental toxins.

But life, it seems, has found a way.

- One thing we know about
this class of chemicals is

that in all vertebrates, including people,

it turns on a certain enzyme pathway.

So a normally responsive person,

or in this case, of fish,

should have that enzyme system turned on

if they were exposed to PCBs.

- [Narrator] The
contrast-enhanced image shows

how the enzymes that normally respond

to the toxin remain silent.

- So in this case,

I see very little that's glowing brightly.

It is a dramatic visual
difference that suggests

that that enzyme system is
broken in the New Bedford fish.

- [Narrator] The killifish
from New Bedford Harbor

have changed their metabolism.

The poison can no longer harm them.

But which genetic modifications lead

to the fish's toxin resistance?

That's what geneticist Mark Hahn

of Woods Hole Institute wants to find out.

Could this be a key to understanding

how nature might resist
human interference?

In the laboratory, he uses
the CRISPR-Cas method.

- It's an incredibly powerful way

to modify the genetics of an
experimental fish like this,

to ask questions about the
roles of certain genes,

and, in fact, the roles
of even single amino acids

in the protein can be investigated

with this CRISPR-Cas method.

- [Narrator] To test their assumptions

about the resistant killifish,

Mark Hahn and his team
experiment with zebrafish.

- I want to find out
exactly what are the changes

in those genes, and to
be able to actually zero

in on the specific molecular changes

that are responsible for the resistance,

and to be able to recreate
that in the laboratory

to actually prove that that's
the mechanism of resistance.

- [Narrator] They're inserting
portions of DNA taken

from the resistant killifish
into embryos of zebrafish.

- Hey, Mark.
- Hey, Neil.

- How are you?

- Good.

- [Mark] Which ones are these?

- [Neil] I'm injecting AIP exon two.

- [Narrator] If the zebrafish growing

from these eggs exhibit
the same resistance,

they will have found
the responsible genes.

- Here we are interested
to study a function

of a gene known as AIP.

So we are trying to delete this gene

in this particular species

and then try to study what's
the function of this gene

and however that will alter
the resistance to PCBs.

- [Narrator] With these experiments,

science is venturing deep into
the source code of creation.

The scientists believe
this research could yield

the secret of life's ability to adapt

to the most extreme conditions.

And this knowledge could
also help other creatures

to adapt and survive in
a rapidly changing world.

- I think we will understand the extent

to which we can extrapolate our knowledge

from the killifish system out beyond

to other fish and even other vertebrates.

So a broader understanding of
the toxicology of pollutants

and how that will impact
the natural world.

How we can understand what will be

the most vulnerable species.

(mysterious music)

- [Narrator] At the Max
Planck Institute in Potsdam,

the research team processes
the clover samples from Berlin.

Their goal, to find cyanide.

Clover plants that produce cyanide

are better protected against predators,

but are less able to tolerate cold.

It's warmer in city centers,

so this clover might be more common there.

(Stephan speaking in foreign language)

- [Voiceover] This is a qualitative test.

We use it to indirectly
detect a specific gene

that generates this cyanide.

- [Voiceover] So these are both rural?

- [Voiceover] Yeah,
they're both still rural.

- [Narrator] Greiner and
his team send their results

and other clover specimens to Marc Johnson

in his Toronto lab.

- [Marc] Hey gang, how's it going?

- Good.

- Bita, how did that
extraction go yesterday?

- It was good. Yeah.
- Yeah.

So remind me, this is
Berlin and Buenos Aires.

- [Narrator] The team prepares the clover

for gene sequencing,

but the cyanide values taken by the team

in Germany should show

whether the clover has adapted
an urban existence already.

- Okay, Bita. Did we get
the data from Berlin?

- [Bita] Yes, we did.

And this screen here it is.

So I think it's really good.
- Great.

Okay.

James, have you had a chance to look

at the data from Berlin

so we can understand how
the environment's changing

from Downtown Berlin through the suburbs

and into the rural areas?

You got it.

- All right. So let's take a look at.

So Berlin is one of the cities

where we see white clover
adapting to urban rural gradients.

- [James] Yeah.

- [Marc] Nice.

And so now we're at about 33% of cities

where white clover adapts?

- Maybe 33.29.

(Marc laughs)

But yeah.
- Fair enough.

- [James] It's about 33%.

- Okay.

So then next I think what we're gonna have

to do is figure out what are the drivers,

the environmental drivers
of this adaptation.

So that's really cool.

- [Narrator] In Berlin, plants
from downtown a more likely

to produce cyanide, as
is the case in a third

of the city surveyed so far.

An indication of parallel evolution?

- Some of the preliminary
insights are fascinating.

So it really looks like,

regardless of where you are in the world,

whether you're in Europe,
North America, Japan,

China, Australia, New Zealand,

we see the ability for
this humble white clover

to adapt to these cities.

- [Narrator] In the warmth of the city,

cyanide-producing clover stands
a better chance of survival.

But to survive in the city,

all organisms must adapt
to higher temperatures.

What scientists call "heat islands."

- In cities, humans and
their machinery creates

a lot of heat, and we
have a bubble of hot air

in large cities.

A city of more than a
million people can be seven,

eight degrees Celsius hotter

in the center of the city
than outside of the city.

- [Narrator] This, Menno
Schilthuizen believes,

also influences the evolution
of the white-lipped snail.

Their shells come in many shades

from brown to pale yellow.

A single gene determines the color.

- So they basically carry
their genes on their back.

The shell color determines
the internal temperature

of the snail to some extent.

The difference in temperature
inside can be two degrees

under the same conditions.

And that could be just the difference

between life or death.

On a hot summer day,

you know it was 40 degrees
in Amsterdam a few weeks ago,

it could be that some of
these yellow snails survived,

but many of the brown ones
died because they got too hot,

they overheated, and they died.

- [Narrator] But will statistics
confirm this hypothesis?

- Snails are evolving
towards more yellow shelling.

So the plan is now to just
add some data to the dataset.

So let's go.

- [Narrator] In order
to collect and evaluate

as many snails as possible
throughout Europe,

Menno Schilthuizen is
helped by volunteers.

- You know, you don't have
to go to the Galapagos

to study evolution or
become a paleontologist.

It's happening everywhere all the time.

It's a continuous, very
normal biological process.

- [Narrator] This time
the volunteers find only

a few life snails,

but empty snail shells
can also provide data.

The snail shells are photographed

and added to the database with an app

that anyone can install
on their mobile phone.

- If we're looking at the adaptations

of urban animals and plants
to the urban heat islands,

which, of course, is happening,

has been happening more rapidly
than global climate change,

we can probably predict what's
going to happen globally

in response to climate change.

- [Narrator] With
temperatures rising globally,

our cities become a window

into nature's future transformations.

Every October in Mexico's Sierra Nevada,

monarch butterflies
gather in their millions.

They traverse the whole of
the North American continent

to spend winter down south.

But our growing cities make

their journey ever more perilous.

- Monarch butterflies are
these really great insects.

Unfortunately, right
now they're in decline.

In the United States,

they've experienced 80%
population declines.

There we go.

- In this industrial area of Toronto,

monarch butterflies take a
rest stop before flying on.

They also take the opportunity
to mate and reproduce.

- Ooh, it's a really big caterpillar.

This is the baby monarch.

This one's probably a day or two away

from going into its chrysalis

and then becoming a monarch butterfly.

- [Narrator] While other
species have the ability

to switch to other food sources,

monarch butterflies remained
dependent on a single plant.

- [Man] I got one.

- Let's check it out. You found a monarch.

- [Narrator] The butterflies
lay their eggs on the milkweed.

Their caterpillars feed
exclusively on this plant.

And in many cities,

the land on which milkweed
can grow is disappearing.

- Unfortunately, a lot of
the cities are providing

these barriers that just
don't have the resources

that they need.

And so it would basically be

if you're driving along the road

and you have any fuel stations

and you run out of gas, you're stuck,

then that's what's happening
with these butterflies.

- [Narrator] Not all species can adapt.

As our cities continue to expand,

accommodating wildlife might be crucial.

How we shape our cities in
the future may prove decisive

for the course of life on earth.

- Biodiversity helps us
with the food that we eat.

It helps us with the air that we breathe.

So if we continue along
the path that we have,

many different populations,
including human populations,

will start to crash.

- Urban evolution can help
us design green cities

in a Darwinian way.

- As humans become more urban,
we have the potential to,

you know, allow some
species to live in the city

and adapt to our cities,

but then put less pressure
on the other habitats,

which would allow, you know,

the species that can't survive in the city

to continue to thrive.

- We're going to see more
and more the realization

that we are part of nature,

and that is actually probably
going to help us survive.

(elegant music)