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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)