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How animals, bugs and plants are evolving in cities

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    This is where I grew up.
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    A small village near the city of Rotterdam
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    in the Netherlands.
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    In the 1970s and 1980s,
    when I was a teenager,
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    this area was still a quiet place.
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    It was full of farms and fields
    and swampland,
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    and I spent my free time there,
    enjoying myself,
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    painting oil paintings like this one,
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    collecting wildflowers, bird-watching
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    and also collecting insects.
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    And this was one of my prized finds.
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    This is a very special beetle,
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    an amazing beetle called an ant beetle.
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    And this is a kind of beetle
    that lives its entire life
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    inside an ant's nest.
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    It has evolved to speak ant.
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    It's using the same chemical signals,
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    the same smells as the ants do,
    for communicating,
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    and right now, this beetle
    is telling this worker ant,
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    "Hey, I'm also a worker ant,
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    I'm hungry, please feed me."
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    And the ant complies,
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    because the beetle is using
    the same chemicals.
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    Over these millions of years,
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    this beetle has evolved a way
    to live inside an ant society.
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    Over the years,
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    when I was living in that village,
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    I collected 20,000 different beetles,
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    and I built a collection
    of pinned beetles.
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    And this got me interested,
    at a very early age, in evolution.
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    How do all those different forms,
    how does all this diversity come about?
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    So I became an evolutionary biologist,
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    like Charles Darwin.
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    And like Charles Darwin,
    I also soon became frustrated
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    by the fact that evolution is something
    that happened mostly in the past.
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    We study the patterns that we see today,
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    trying to understand the evolution
    that took place in the past,
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    but we can never actually see it
    taking place in real time.
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    We cannot observe it.
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    As Darwin himself already said,
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    "We see nothing of these slow
    changes in progress,
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    until the hand of time
    has marked the lapse of ages."
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    Or do we?
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    Over the past few decades,
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    evolutionary biologists
    have come to realize that sometimes,
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    evolution proceeds much faster
    and it can actually be observed,
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    especially when the environment
    changes drastically
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    and the need to adapt is great.
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    And of course, these days,
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    great environmental changes
    are usually caused by us.
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    We mow, we irrigate, we plow, we build,
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    we pump greenhouse gases
    into the atmosphere
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    that change the climate.
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    We release exotic plants and animals
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    in places where they didn't live before,
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    and we harvest fish and trees and game
    for our food and other needs.
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    And all these environmental changes
    reach their epicenter in cities.
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    Cities form a completely new habitat
    that we have created.
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    And we clothe it in brick and concrete
    and glass and steel,
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    which are impervious surfaces
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    that plants can only root in
    with the greatest difficulty.
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    Also in cities, we find
    the greatest concentrations
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    of chemical pollution,
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    of artificial light and noise.
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    And we find wild mixtures
    of plants and animals
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    from all over the world
    that live in the city,
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    because they have escaped
    from the gardening
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    and aquarium and pet trade.
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    And what does a species do
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    when it lives in a completely
    changed environment?
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    Well, many, of course, go, sadly, extinct.
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    But the ones that don't go extinct,
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    they adapt in spectacular ways.
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    Biologists these days
    are beginning to realize
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    that cities are today's
    pressure cookers of evolution.
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    These are places
    where wild animals and plants
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    are evolving under our eyes very rapidly
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    to suit these new, urban conditions.
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    Exactly like the ant beetle did
    millions of years ago,
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    when it moved inside an ant colony.
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    We now find animals and plants
    that have moved inside the human colony
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    and are adapting to our cities.
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    And in doing so,
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    we're also beginning to realize
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    that evolution can actually
    proceed very fast.
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    It does not always take
    the long lapse of ages;
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    it can happen under our very eyes.
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    This, for example,
    is the white-footed mouse.
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    This is a native mammal
    from the area around New York,
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    and more than 400 years ago,
    before the city was built,
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    this mouse lived everywhere.
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    But these days, they are stuck
    in little islands of green,
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    the city's parks, surrounded by a sea
    of tarmac and traffic.
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    A bit like a modern-day version
    of Darwin's finches on the Galapagos.
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    And like Darwin's finches,
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    the mice in each separate park
    have started evolving,
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    have started to become
    different from each other.
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    And this is my colleague,
    Jason Munshi-South,
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    from Fordham University,
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    who is studying this process.
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    He is studying the DNA
    of the white-footed mice
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    in New York City's parks,
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    and trying to understand
    how they are beginning to evolve
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    in that archipelago of islands.
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    And he's using a kind of
    DNA fingerprinting, and he says,
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    "If somebody gives me a mouse,
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    doesn't tell me where it's from,
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    just by looking at its DNA,
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    I can tell exactly
    from which park it comes."
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    That's how different they have become.
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    And Jason has also discovered
    that those changes,
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    these evolutionary changes,
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    are not random, they mean something.
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    For example, in Central Park,
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    we find that the mice have evolved genes
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    that allow them to deal
    with very fatty food.
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    Human food.
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    Twenty-five million people
    visit Central Park each year.
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    It's the most heavily visited park
    in North America.
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    And those people leave behind snack food
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    and peanuts and junk food,
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    and the mice have started feeding on that,
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    and it's a completely different diet
    than what they're used to,
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    and over the years,
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    they have evolved to suit
    this very fatty, very human diet.
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    And this is another city slicker animal.
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    This is the European garden snail.
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    A very common snail,
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    it comes in all kinds of color variations,
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    ranging from pale yellow to dark brown.
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    And those colors are completely determined
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    by the snail's DNA.
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    And those colors also determine
    the heat management of the snail
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    that lives inside that shell.
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    For example, a snail
    that sits in the sunlight,
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    in the bright sun,
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    if it has a pale yellow shell,
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    it doesn't heat up as much as a snail
    that sits inside a dark brown shell.
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    Just like when you're sitting
    in a white car, you stay cooler
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    than when you're sitting
    inside a black car.
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    Now there is a phenomenon called
    the urban heat islands,
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    which means that in the center
    of a big city,
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    the temperature can be
    several degrees higher
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    than outside of the big city.
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    That has to do with the fact
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    that you have these concentrations
    of millions of people,
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    and all their activities
    and their machineries,
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    they generate heat.
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    Also, the wind is blocked
    by the tall buildings,
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    and all the steel and brick
    and concrete absorb the solar heat
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    and they radiate it out at night.
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    So you get this bubble of hot air
    in the center of a big city,
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    and my students and I figured
    that maybe those garden snails,
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    with their variable shells,
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    are adapting to the urban heat islands.
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    Maybe in the center of a city,
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    we find that the shell color is evolving
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    in a direction to reduce
    overheating of the snails.
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    And to study this, we started
    a citizen-science project.
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    We built a free smartphone app,
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    which allowed people
    all over the Netherlands
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    to take pictures of snails
    in their garden, in their street,
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    also in the countryside,
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    and upload them to a citizen
    science web platform.
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    And over a year, we got 10,000 pictures
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    of snails that had been photographed
    in the Netherlands,
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    and when we started analyzing the results,
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    we found that indeed,
    our suspicions were confirmed.
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    In the center of the urban heat islands,
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    we find that the snails have evolved
    more yellow, more lighter-colored shells.
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    Now the city snail and the Manhattan mouse
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    are just two examples
    of a growing list of animals and plants
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    that have evolved to suit
    this new habitat,
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    this city habitat that we have created.
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    And in a book that I've written
    about this subject,
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    the subject of urban evolution,
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    I give many more examples.
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    For example, weeds that have evolved seeds
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    that are better at germinating
    on the pavement.
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    Grasshoppers that have evolved a song
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    that has a higher pitch
    when they live close to noisy traffic.
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    Mosquitoes that have evolved
    to feed on the blood of human commuters
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    inside metro stations.
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    And even the common city pigeon
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    that has evolved ways to detox themselves
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    from heavy-metal pollution
    by putting it in their feathers.
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    Biologists like myself,
    all over the world,
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    are becoming interested
    in this fascinating process
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    of urban evolution.
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    We are realizing that we're really
    at a unique event
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    in the history of life on earth.
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    A completely new ecosystem
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    that is evolving and adapting
    to a habitat that we have created.
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    And not just academics --
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    we're also beginning to enlist
    the millions of pairs of hands
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    and ears and eyes
    that are present in the city.
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    Citizen scientists, schoolchildren --
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    together with them,
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    we are building
    a global observation network
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    which allows us to watch this process
    of urban evolution taking place
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    in real time.
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    And at the same time,
    this also makes it clear to people
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    that evolution is not
    just some abstract thing
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    that you need to travel
    to the Galapagos to study,
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    or that you need to be a paleontologist
    to understand what it is.
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    It's a very ordinary biological process
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    that's taking place
    all the time, everywhere.
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    In your backyard,
    in the street where you live,
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    right outside of this theater.
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    But there is, of course,
    a flip side to my enthusiasm.
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    When I go back to the village
    where I grew up,
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    I no longer find those fields and swamps
    that I knew from my youth.
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    The village has now been absorbed
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    by the growing
    conglomeration of Rotterdam,
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    and instead, I find shopping malls
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    and I find suburbs and bus lanes.
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    And many of the animals and plants
    that I was so accustomed to
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    have disappeared,
    including perhaps that ant beetle.
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    But I take comfort in the fact
    that the children growing up
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    in that village today
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    may no longer be experiencing
    that traditional nature
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    that I grew up with,
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    but they're surrounded
    by a new type of nature,
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    a new type of ecosystem,
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    that, to them, might be just as exciting
    as the old type was to me.
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    They are living in a new,
    modern-day Galapagos.
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    And by teaming up with citizen scientists
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    and with evolutionary
    biologists like myself,
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    they might become the Darwins
    of the 21st century,
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    studying urban evolution.
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    Thank you.
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    (Applause)
Title:
How animals, bugs and plants are evolving in cities
Speaker:
Menno Schilthuizen
Description:

In cities, evolution occurs constantly, as countless plants, animals and insects adapt to human-made habitats in spectacular ways. Evolutionary biologist Menno Schilthuizen calls on peculiar beings such as fast food-loving mice and self-cooling snails to illustrate the ever-transforming wonders of urban wildlife -- and explains how you can observe this phenomenon in real-time, thanks to a global network of enthusiastic citizen scientists.

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Video Language:
English
Team:
TED
Project:
TEDTalks
Duration:
12:07

English subtitles

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