Evolution and the City: The Beasts

Human cities are the ultimate artificial environments -- and we're not the only organisms to call them home. In this episode of the Stuff to Blow Your Mind podcast, Robert Lamb and Joe McCormick consider some of the adaptive animals that have taken to city life and thrive within its challenging complexity. 

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:03):
Welcome to Stuff to Blow your Mind from how Stuff
Works dot com. Hey, welcome to Stuff to Blow your Mind.
My name is Robert lamp and I'm Joe McCormick. Hey, Robert,
I've got a I've got a quiz question for you.
All right, quiz what do you think is the animal

(00:23):
out there in the world that humans are the most like?
M hmm, Well, I mean we're we're so unlike all
the creatures, but I mean one obviously turns to the
primates for our closest evolutionary relatives. Yeah, I would say physiologically,
if you look at comparative anatomy, and of course genetically,

(00:44):
we are the most similar to primates like chimpanzees and binobo's,
and they actually are known to be our closest relatives
in the animal kingdom. But I think if you look
at humankind in a different light, if you don't just
look at the individual body plans and compare one individual
to another individual, but if you compare the entire species

(01:06):
ecological and trophic profile as a whole population, you can
make a very different case. We're the most like ants,
and we became more like ants starting around ten thousand
and maybe thirteen thousand years ago. Before this time, I
would say, there's really no way to compare us to
ants at all. We just weren't very antlike, except maybe

(01:29):
that you could say we were a social species. But
you know, maybe ten thousand to thirteen thousand years ago
humans first started practicing plant and animal agriculture, and over
the years more people began to transition from a nomadic
hunting and gathering way of life to a settled agricultural
way of life. And of course the introduction of farming,
we know the story. It changed everything. It allowed for

(01:50):
surpluses of food resources, specialization of skills, education, writing, construction, invention,
and so on. And because all of these processes were
made possible by keeping people and resources close together with
continuous interconnected access to one another, this meant the birth
of cities. And I would say ever since then, the

(02:12):
construct of the city, the idea of the city as
a technological thing and as a social organizing principle, has
been one of the biggest influences that has changed the
way human beings relate to the earth. Now, we're all
pretty familiar with this story of of urbanization from a
human point of view, but from a biological or ecological

(02:33):
point of view, It is an extremely strange and interesting
thing for us to do. And it's also extremely similar
to what ants do when they form colonies and build
ant hills. It is yeah, when you when you start
thinking about it, this this artificial habitat that they can
they construct to live in and in, you know, in
in in in some cases, grow their food in, cultivate

(02:57):
their own crops. Yeah, almost all creatures on Earth adapt
to their environment. The environment is one way, and the
animal over time evolves to be a best fit to
the environment around them. But humans and ants and some
other creatures you could argue, like bees and some other
use social insects, termites to some extent, don't adapt to

(03:18):
their ecosystem as much as they build an ecosystem for themselves.
They engineer their own environments in their own ecosystems, and
of course, in both cases ant hills and human cities,
these ecosystems are not hermetically sealed off from the rest
of the world. They're poorous and connected to the rest
of the world. And what this means for ants, of course,

(03:41):
is that they have entire classes of organisms that have
specifically evolved to thrive within the ecosystems created by the ants,
the same way that a fox or wolf, spider or
any other creature would thrive within its natural environment. There
are organisms that that have evolved to thrive within the
ant engineered environments, and these organisms are called myrmica files. Yeah. There.

(04:05):
Then there are a number of different species that the
one could spend time with. Here, Uh, a couple that
that came up from me though, Uh, there's one. Uh.
This is an example of research before the p Favieri deetle.
So it uses a complex dance of both chemical and
auditory mimicry to convince the ant population that it's one

(04:26):
of them, even as it crawls in into their abode
and feeds on their larva and benefits from the colony's protection.
But as Carl Zimmer highlights in his New York Times
piece on a study concerning these beetles, the deceptive beetle
may even mimic the queen from time to time in
order to receive royal treatment, but it otherwise knows to

(04:48):
leave the queen unharmed. It doesn't seek to decimate its
host colony, but rather to thrive within it through perfect mimicry.
Uh and uh. I explored this, by the way, originally
because I was interested the Monster from John Carpenter's The Thing,
because one of the ideas that is explored in the film,
and I think also in like a comic book sequel,

(05:09):
is that if this thing gets gets out, if it
escapes from this frigid base, it's going to just decimate
the world in no time. Right, it will mimic all
life forms and just take over the entire planet. Right.
But would it necessarily do that? Right? I mean, I mean,
you can certainly make a case that it's an alien contamination,
So who knows what it would do to to to

(05:30):
what is to it an alien ecosystem. But I think
if we look to examples like this from our natural world,
we can we can see that, well, maybe it wouldn't
necessarily overrun the planet because it needs to live at
harmony within the host ecosystem. Yeah, it needs an ecosystem
to survive off off of. It can't become the whole
ecosystem itself. Yeah, So it's they're going to be essentially

(05:52):
self imposed limits on what it will take over and destroy. Now,
that's far from the only example of mermai else that
have evolved specifically to survive and thrive within the environments
created and maintained by ants. There are thousands more, right,
One that I ran across that was interesting is the
oak blue butterfly. So these don't reside really within the

(06:15):
colony so much, but the butterfly larvae may chemically mimic
or camouflage themselves and be accepted by the what are
sometimes called the plant ants on their host plant, the
ant plant, or macaranga as it's called. So essentially what's
happening here is the chromato gaster ants. They nest in

(06:38):
the plants hollow stems and then attack anything that climbs
or lights upon their domain, except for the oak blue larvae.
And this is presumably because it has an evolved a
defense that tricks the ants into thinking it's okay for
it to be there. Yeah, so there's protection within the
ants domain, even if ultimately there's no more dangerous place

(06:58):
to be than within an antstone. Right, there's protection if
you have some kind of evolved defense to sneak through
the city walls and say, okay, I'm part of this colony.
Now nobody noticed that I'm not an Aunt. Yes, hello,
fellow ants. Now, Aunts have been engineering their own ecosystems
for millions of years, right, so there has been a
lot of time for these mermica files and these creatures

(07:21):
that infest ant colonies and other AUNT controlled environments to
very tightly hone their their evolved traits, right that, There's
been a lot of time for them to do this. Humans,
on the other hand, have only been engineering their own
environments for much much less time, just thousands of years.
But nevertheless, our human ant hills seem to be in

(07:42):
the early stages of developing Mermica files of our own,
except they wouldn't be Mermica files, they would be creatures
of the city. As we continue to engineer environments around
the concept of the city, more and more forms of wildlife,
we're beginning to show marked adaptations and eventually heritable evolved
traits for specifically surviving in human urban landscapes. This is

(08:07):
urban evolution, and this is gonna be our topic for today.
This is actually going to be the first part of
a multipart episode that we will continue to explore just
because there's so much interesting stuff to talk about, but
it's going to be focused on wild organisms evolving to
survive and even thrive within the ecosystems that humans have
engineered for themselves. And we should go ahead and mention

(08:29):
that we've been wanting to do this episode for a while,
but recently a book came out on this topic and
this became one of our major sources for this episode.
It's a book but the Dutch evolutionary biologist Minnow Skill Tausend,
who is a researcher at the Naturalist Biodiversity Center, which
is a museum in Leiden, Netherlands, and the book is
called Darwin Comes to Town. It was just published by

(08:51):
Pikador just recently. Yeah, I'll include a link to this
book on the landing page for this episode of Stuff
to your Mind dot Com. I want to note that
the cover illustration is fabulous because you have this this
drawing of various animals scaling a zigaratte that it's formed
of all these buildings and skyscrapers. Yeah, it's it really
captures the spirit of the book. I appreciate a good

(09:13):
cover illustration because so many books have bad cover art. Now, yeah,
it seems to be a dying art form. Here's my
cry out there. If you're a publisher of science fiction
or fantasy or something like that. Stop going with the
stop going with the stock art. Get those original illustrated
covers back. Those were great. Yes, And I do not
want to see another minimalist like mock up of a

(09:34):
movie poster or a book cover. I'm done with that.
I want I want to a full visual experience. No.
Back to the subject. Okay, So Skill Tolls and actually
himself makes this comparison between human cities and ant colonies,
and the subsequent comparison between mermenicaphiles and the organisms that
have come to thrive in our cities. And I think

(09:54):
it's a really good comparison, except one difference is that
our cities are actually and much more vast and varied
landscapes than the complex environments that ants create. Right, yeah,
I mean you look at something like say New York City,
right You have the sort of concrete jungle regions of
the city. You have an artificial um wilderness in its center.

(10:19):
You have essentially mountains made out of steel and glass
that alter the flow of air, that alter the weather itself.
You just have so many different elements going on to
warp the natural world into a new form. I tried
to make a short list of just some of the
ways that cities are fundamental departures from what the natural

(10:42):
landscapes around them are like. And I know I didn't
capture everything here, but here just the things that occurred
to me in our research. One of them is habitation surfaces. Right,
not many complex organisms can live on flat concrete without
soil or vegetation. That that's not an environment that occur
is all that much on Earth. And when environments kind

(11:03):
of like that do occur, there aren't a whole lot
of organisms that inhabit them. So much of the plant
and animal life in cities is isolated to or based
in urban islands of vegetation. So they're gonna be things
like parks or small undeveloped areas, or urban trees or
yards or gardens or grassy street medians. We look at
these spaces in our urban areas as kind of blank, right,

(11:26):
Maybe not parks, but a lot of these other things,
like the grassy median between two sides of a highway. Yeah,
we think we might think of that as a place
that is empty, but really, like that's the only place
in your field of vision where there is non human
life taking place at any like real degree. We look
at those places sort of like the margins of of
a page, like that's where nothing's going on. But yeah,

(11:50):
that is in fact like a hot spot. It's a
hotbed of life and activity that is surrounded by these
dead rivers of asphalt, so many feral cats just whooping
it up in there. But there is so much more
than that. So okay, that's the obvious habitation surfaces. But
then there is climate. Actually, the climate of a city

(12:12):
is generally different than the climate of the surrounding area.
We've talked before on the podcast about the idea of
the urban heat island effect and urban rain. Uh. The
the material properties of cities in the way they absorb
and reflect light and retain heat actually affects the temperature
and the weather within the city, usually leading to these
situations where in the middle of a city it's a

(12:33):
lot hotter than the surrounding countryside is on the same day.
An obviously huge factor that makes a city different than
the surrounding environment is what types of food resources are available,
because it's going to be completely different nutritional profiles. Yeah,
outside of the city, a bird has to you know,
hunt around for its h its food, but inside the

(12:54):
city it can just fly into at home depot and
just aisle upon aisle of food awaits it. Now, I
wonder if for birds, home depot eventually becomes a sub
city within a city, where birds will evolve their own
populations within the home depot over that's kind of frightening.
I imagine like large prehistoric carnivorous birds roaming the home
depot picking off humans that are a little too little

(13:16):
too picky in which soil they're going to purchase for
their home garden. Here's another one. You've got very different
kinds of threats in human created environments than you do
have an unspoiled natural landscapes. You have environmental threats, human threats,
and machine threats. I mean, think about try to put
yourself in the mind space of like a fox or

(13:38):
a coyote or raccoon or something, and you're living in
a place where there are these giant mechanical predators constantly
plowing through the city back and forth at high speeds,
and they will kill you. But also they don't really
seem to chase you, and so it's it's you're not
evolved at all to deal with this kind of situation. Yeah,

(14:01):
the Frogger game, that is life for an animal in
the city. Yeah, cars as predators. It's a thing that's
hard to direct wrap your mind around. If you're a fox,
then of course there's a totally different chemical environment than
there is in in unspoiled nature. So you've got pollutants.
Of course, you've got the byproducts of industry and all that.
But then you've got things that people wouldn't even often

(14:22):
tend to think of, Like, how about if you're in
a northern city, what chemically you might you do to
alter the surfaces of the city during the winter. I'm
thinking about spilled hot chocolate for starters. I guess that's
a good one. But how about salting the roads? Oh
my goodness, I mean, yeah, millions of pounds of salt.
You turn it into basically a big salt lick of

(14:43):
death exactly. Yeah, so you're you're fundamentally altering the chemical
profile of the surfaces that these animals dwell upon, and
suddenly all this runoff water that would normally be fresh
water become salt water. And yeah, it's totally strange. Here's
another one. The darkness regime, completely different in cities than
it is in a place that hasn't been colonized by

(15:06):
human beings. That that's a that's a great one. I
mean that in roads are situation like light pollution, and
in roads, of course are everywhere. The roads crisscross human
habitats wherever they occur, and and you know, invite death
for anything that dares to cross it. And then of
course we we've all heard accounts of how dangerous artificial

(15:28):
lighting can be uh into various natural habitats, including beach
habitats for turtles that are returning from the ocean to
lay their eggs. Yeah, and of course a big one
being for insects. The way light affects insects is crazy.
I mean, there's this thing that's the vacuum cleaner effect
that Skill tous And talks about in his book, where
you put say a service station out by a dark

(15:50):
highway in the middle of nowhere, and it's got lights
on at night. And what this is going to do
is act like a vacuum that just sucks in insectual
life from the hire surrounding countryside for a period of
time until it's killed so many millions of insects that
Eventually the density around it just kind of drops off,
and then it stops happening for a while, and then

(16:13):
you have the city which just has that going on
all the time. It's just a center of artificial light
all night. Now, that's by no means all of the
ways that cities change the environment from the natural environment,
but that that's a handful of them to get you
thinking about the ways that these techno beasts that we
inhabit that feel very natural and normal to us are

(16:33):
are aliens sci fi environments for animals that are designed
to live in a meadow or live in the forest
or something like that. And yet at the same time
we know for me and Malcolm that life, uh finds
a way that's right and find a way it does.
And that is what we're going to be focusing on
for the rest of the episode today is many of

(16:55):
the fascinating ways that urban life affects wildlife and that
wildlife apps to it or fails to adapt to it.
All Right, we're gonna take a quick break and when
we come back, we will dive right into the topic.
Thank alright, we're back. You know, Joe, we live in Atlanta,
and certainly especially the portion of Atlanta we reside in

(17:15):
is is far from a like stereotypical concrete jungle. We
have a lot of green trees around, a lot of
these little noman zones of of of of built up
weeds and vegetation for things to live in. What are
some of your your favorite wild animals that you've encountered. Yeah,
Landa actually is sometimes known as the city of Trees,

(17:35):
and I like that about it. I mean, it can
be a problem if a tree falls on your house
or something, but otherwise it's very nice to have all
this urban greenery that we do have. But yeah, as
far as urban wildlife goes, I don't know. I mean,
there's a lot just in my backyard. Like our our
dog Charlie, he loves to chase the squirrels in the backyard.
And there was one night not too long ago, when

(17:58):
he's not a barker, he'dn't bar much, but we let
him out in the backyard one night and suddenly he
started barking, and we're like, what's going on? And we
went out to get him and we realized he was
in a standoff with an opossum. It's perched up on
the fence and not moving. It just was frozen and
staring at him and making the face. And so we
got him inside and the possum never moved. We looked

(18:20):
back out the window like a while later, and it
was still in the exact same place, hadn't moved from
the spot. And I think about adaptations when I see
stuff like that. So, Okay, you've got an urban opossum
and that maybe is getting some tasty trash morsels living
in the city like this, but it's also got a
deal with dogs and backyards and people and animal catchers

(18:41):
and cars and all this stuff that threatens it. And
for some reason, it's it's evolved response to this is
freeze and make the scary face. Why does it do
that and does that usually work or what? What was
that traite evolved as a solution to. You know, the
backyard division of things is really interesting because it does
create these these little sequestered zones where that are protected,

(19:07):
but each one also may contain its own localized predator
in the form of a dog or even you know, cats,
which I guess are gonna be less restricted by the
fences little enclosures with monsters in them. Yeah, it was
very recently It was just last week actually that I
heard this rucus bird rucus in the backyard, and I

(19:27):
went to check it out because I'm thinking about what's
happening in cat that there's a maybe a feral cat
back there messing with some birds. I look back there
the birds were agitated because a wild turkey was in
my backyard. Yeah, so good, I know. It's it's really
kind of a holy experienced to see a creature that's
ultimately so large. If you've not seen one there, it's
a far different animal than the like the Thanksgiving turkey,

(19:49):
but it is it is still a big critter and
seeing it hop up there on the fence and then
uh disappeared into the next yard was pretty pretty awe
inspiring for me. Yeah, my parents actually in Tennessee sometimes
get turkeys in their yard. Well, you know, I don't
know about everyone else, but one animal that instantly came
to mind from me when thinking of of creatures that

(20:10):
thrive in an urban environment is the noble trash panda.
The raccoons. Raccoons, Yeah, they've you know, it makes sense
because raccoons, they've thrived in North America for at least
two point five million years or at least we know
that it's Procyon genus was well established here by that point,
with its ancestry reaching back a good through thirty seven

(20:34):
million years. But their success is due largely to their flexibility.
Oh yeah, there's sort of a jack of all. Yeah, yeah,
they they have They have teeth for both the shearing
of meat and also expanded molars for crushing. They also
have these incredibly sensitive hands which can be used to
manipulate objects and feel without loss of sensitivity for food

(20:57):
and chilly stream beds. You know, that makes me wonder
Sometimes our listeners have asked this fun question before. It
was like, if humans disappeared, what would be the next
creature on Earth to like assume the sort of intelligent
civilization mantlepiece. And of course you want to say, well,
probably great apes or something. Uh. Some people want to
say dolphins or whatever. But you could say, well, I

(21:17):
wonder about raccoons. They've got hands that are really kind
of a hand alike. They can manipulate objects. That seems significant. Yeah,
And I was when I dived a little deeper into this,
I was really impressed by just how sensitive their hands are.
So I want to read a tidbit here. This is
from Northern Woodlands magazine. Quote. There's a myth that raccoons

(21:39):
wash their food, but what they're doing when they wet
and rubn object is seeing it. It's thought that water
contact increases a raccoon's tactile ability. When a raccoon wets
and handles a crayfish, stone worm, or clam, he's gathering information.
Nearly two thirds of the sensory data that he's processed

(22:00):
comes from cells that interpret various types of touch sensation.
In other words, touches as important a sense as hearing, smell,
and sight. I had no idea. That's fascinating, Yeah, I
mean it's it's it's I think it's especially hard for
you know, any of us with with healthy um sight
to really think about that, to think about that sense

(22:20):
of touch as being one of the most important ways
that you interact with your surroundings. Well, there's that, but
there's also the peripheral sort of mentality that comes along
with that, right, the the animal personality that is correlated
with the feeling of touch as an exploratory mechanism, because
it makes you think that this is a creature that's

(22:40):
likely to sample objects in its environment at a high rate. Yeah,
it's it's not enough just to peer at it from
the shrubs. It's got to get up there. It's got
to handle it and see what's what. So you know
what happens when an adaptive creature with marvelous little hands
like this ventures into the city, Well, it thrives. And
raccoons have been of interest to science for over a century.

(23:03):
Because of this, they flourish in human environments. In nineteen seven,
psychologist Lawrence W. Cole and Clark University graduate student Herbert
Burnham Davis both independently studied raccoon intelligence in light of this,
and they concluded that they were smarter than cats and
dogs and were more in the cognitive realm of monkeys.

(23:26):
Now not everyone agrees with that. I should note now,
whatever the baseline level of raccoon intelligence, as far as
object manipulation and all that goes, there is one thing
that has become clear, which is that there's a pretty
large variation in the difference between different populations of raccoons
and their intelligence at say, uh spatial problem solving, right,

(23:47):
the distinction being that of city raccoons and country raccoons,
rural and urban raccoons. Right, it seems like one of
those populations has more incentive to get smart about how
to mess with objects. That's right. So Susan mcdonne, old
comparative psychologist at York University in Toronto. She compared the
problem solving abilities of urban and rural raccoons and found

(24:08):
that urban raccoons win in both intelligence and ability. Yeah.
I was reading about one of these studies, and apparently
it required the raccoon to figure out how to get
into a food baited trash can that had its lid
held shut with a bungee cord. And apparently in the
study I was reading about, none of the rural raccoons
could get into the trash can, but about eighty percent

(24:29):
of the city raccoons did. Yeah. And in a two
thousand and sixteen Nautilus article titled the Intelligent Life of
the City Raccoon, Jude Isabella points out the following uh
in this regarding the study quote. For the past few summers,
she videotaped rural and urban raccoons toying with containers baited
with cat food. While both rural and city raccoons readily

(24:52):
approached familiar containers, they dealt differently with unfamiliar ones. Where
rural raccoons took a long time to approach novel conta
aner's city raccoons would attack them the moment she turned
her back. I like that opportunism, and that's great. Yeah,
so I got one of the ideas here is city raccoons.
They're they're fast to get in there, they're fearless and

(25:12):
approaching a problem. But they also that there they stick
with the problem that they're trying to figure out. They'll
work at it for an hour or more, trying to
figure out how do I get into this, how do
I how do I defeat this problem? That just shows
perseverance pays off. Yeah, and then this also brings us
back just to the idea of a city, like what
does the artificial environment of a city do well? Isabella

(25:35):
cites the work of Harvard economist Edward Glacier Uh, the
author of Triumph of the City uh and Uh. Glacier
argues that cities themselves are machines for learning uh and
if raccoons are innately bold and curious uh, then they
engage with these puzzles more readily. What's more increasingly complex,

(25:55):
latches and and UH and other devices they may be encountering. Quote,
may actually be training raccoons to open them. So the
city itself, as we change it, trains the raccoons and
sort of changes them. Now, an important thing to consider
is that this might be happening at multiple levels of
honing the skills of raccoons. Right, you can imagine on

(26:16):
in one sense, raccoons are just getting better at solving
puzzles within their lives, right, they may to some extent
be learning how to adapt to this. But in another extent,
they may be getting better at solving puzzles across generations. Right.
The ones that solve more of these puzzles tend to
get more food and thus have more offspring. And thus

(26:38):
it's possible we're literally seeing an evolution of the city
raccoon into a baseline smarter animal, or at least an
animal that's better at manipulating these kinds of traps and
foreign objects. Yeah, in a way, it's like the city
raccoons are in more of an arms race with their environment,
whereas the rural raccoons there's their environment is a bit

(26:59):
more static. Now at the same time, I mean, we've
already touched on the growing city and uh and one
of the ramifications of that is that it diminishes the
the rural environments, and that is very evident when it
comes to foxes, especially the foxes of Britain. According to

(27:20):
the two thousand seventeen article and The Guardian, Foxes Surge
into England's towns and Cities by Charlie cuff Um, the
overall number of UK foxes is in decline, but the
number of urban foxes has quadrupled over the past twenty years.
One study estimates that a hundred and fifty thousand foxes
thrive in England one for every three hundred city dwellers.

(27:43):
That's up from thirty three thousand in the nineties. Essentially,
what's happening here is that the foxes are losing their
rural habitats and they're just finding a lot more food,
including garden worms and all those rats and mice, as
well as suitable habitats in the urban environment. Skill tous
And talks about this in his book, mentioning that some

(28:04):
of what drives animals into the city is not just
what's available in the city or the fact that the
city now exists where their home used to be. But
the depletion of the habitability of the surrounding landscape. This
is happening all over the place. Even though cities are
these extremely weird, alien places for animals to try to
survive in, they tend to be more habitable environments than

(28:27):
the waste lands created just outside of cities. I'm reminded
of the witches gingerbread house in the woods. You know,
for a couple of kids who are lost in the woods,
there's no more dangerous place than going into that gingerbread house.
But at the same time, the woods are terrifying and
full of inedible things and berries that will poison you

(28:49):
if you try and eat them, whereas the witches houses
made out of candy. How can you work out a
deal with this witch? That's the challenge. But what if
the candy is just all of the trash that the
wit threw away because she didn't want to eat herself. Well,
so we are on the subject of trash life. Of course,
much of what we're talking about with the raccoons is
how they are affected by by urban trash and what's

(29:13):
trash to us maybe delicious morsels for many scavenging animals,
especially if they're not super picky, and they're smart at
manipulating containers and things like that. But I thought we
should explore some of the more of the ways that
the pervasive presence and endless forms of human garbage, and
I mean the garbage produced by humans, not people who
are garbage, how that shaped urban animal life. So I've

(29:36):
got one, Robert, Do you remember the mcflury hedgehog? I
do not remember the mcflury hedgehog. Have you ever had
mcflury in in the past. I believe I did have
the mcflury or two. Yes, I'm not trying to be
a snob. I can say I've never had one of
these things, so I can't speak from experience, but maybe
you can help guide me on the mcflury ology. Here.
The only thing I remember is that they had a
weird top. Yeah, that's that's the thing. So back in

(29:59):
the mid nineties, McDonald's fast food restaurant introduced the mcflury,
which is it's some kind of ice cream thing, right,
God knows what it's like, hamburger flavored ice cream. So
now you're now you're just trash talking to mcflury. It
was at least it was sweet. It was sweet flavor
does have big MAC sauce in it, No, but it's
it's all I remember, is just an overpowering sweetness. Well,

(30:21):
so this sweet stuff that was in the mcflurry, it
was served out of containers with these weird lids you're
talking about that essentially functioned as a hedgehog trap. So
the way it seemed to work is that you'd be
eating your mcflurry and then you'd throw the container down
on the sidewalk or the parking lot, and then later
a hedgehog would come along and want some of that
delicious reeking sugar stuff inside the cup. But the aperture

(30:45):
in the lid, which would I guess made for spoon access,
so you could use a spoon. It was just big
enough for hedgehogs and some skunks to stick their heads
inside and slurp up some mcmlty. But then, of course
hedgehogs have bines, and the spines are generally oriented to
fold backward from the head, so once the hedgehog's head

(31:06):
is in the hole, it might not be able to
get itself back out of the mcflurry cup. So, on
the one hand, this is funny. I've included an image
for you to look at. It is funny and very
cute and lead too much laughter about little creatures running
around with their heads stuck in cups. But there's a
dark side, right, which is that if nobody helped these
creatures out, nobody saw them, they would probably die right

(31:28):
possibly of starvation, or they might wander into traffic, or
they might wander into a body of water and drown.
Oh yeah, that is terrifying. It At first it's cute,
and then when it it's explained to you, then then
it is a very sad affair. But fortunately there was
a good end to it. After years of complaints from
organizations like the British Hedgehog Preservation Society in two thousand six,

(31:50):
McDonald's eventually changed the design of their lids to make
them too small for hedgehogs to get their heads through
in the first place. So fortunately that had a good resolution.
But that's just one exam ample of the thousands of
ways we can't even predict about how the shape or
chemistry or nutritional profile or whatever of human refuse will
exploit some fatal flaw in another organism. And also you

(32:12):
always have to wonder how if McDonald's had never intervened.
This might have shaped the evolution of city dwelling hedgehogs, right,
would this cause a selection pressure for hedgehogs that were
better at getting their heads out of small holes, or
for hedgehogs with big heads that would never get through
the hole to begin with, or for hedgehogs that didn't
like the smell of dairy products and wouldn't be interested

(32:35):
in ice cream. So let's dig through more trash, Robert,
you're ready to dig through more to do it? What
else is in there that's that's worth eaten? How about
beatles and bottles? Have you ever read this story before, Robert,
I've read Fox in Socks where there's a much discussion
of of beatle battles inside of a bottle. No, no, no,
this is beatle. This is not a battle. This is
a beatle something else outside of a bottle. So I

(32:56):
want to take you to Australia to meet the Julo
Dimorpha bake Welly, which is the Australian jewel beetle. It's
a type of beetle from the boot breasted family found
throughout a lot of parts of Australia, and so in
nineteen eighty three, there were a couple of biologists named
Darryl Quinn and David Rince, and they published some interesting
findings about human trash and its local effects on wildlife

(33:21):
in the Journal of austral Entomology. So here's the story.
Earlier that year, in nineteen eighty three, the authors were
wandering out beside a highway near a town called Donra
in Western Australia, and they noticed something weird. A male
jewel beetle perched on top of a piece of litter,
which was a discarded brown beer bottle. Okay, well, that

(33:42):
in and in and of itself is not that strange. Uh.
Then they got closer and they looked see what's going
on here, and they realized the beetle was trying to
mate with the beer bottle. The authors looked around and
they found two more beer bottles of the same type,
both of which had male bake wellies trying to mate
with them, and the males were either on the side
of the bottle or quote mounted on top with quote

(34:04):
averted genitalia. And I've got a picture here of what
the beetles look like with averted genitalia. Okay, I'm seeing
it now. I don't know if you have any comments
on that, um I do. It does convey the sense
that this, uh, this insect is trying to mate with
the bottle. That's quite averted, So what's going on here? Well,

(34:25):
The authors noted that bake Welly is a species in
which males can fly and the females are ground dwelling,
and the color and texture of these beer bottles in
many ways resembled a giant female of this beetle species.
The author's right quote the shiny brown color of the
glass is similar to the shiny yellow brown electra of J.

(34:47):
Bake Welly and quote rows of regularly spaced small tubercles
around the base of the bottles reflect light in a
similar way to the punctations on the electra of the beetle.
So the brown beer bottles referred to as stubbies in
Australia at the time. We're proving very efficient at setting
off mating behaviors in male beetles, and almost alarmingly so,

(35:09):
because when the author's picked up the bottles, the beatles
would not leave them unless physically removed. And then the
authors also performed an informal experiment where they placed four
stubbies these beer bottles on the ground and watched to
see what happened, and within thirty minutes, two of the
four bottles had male beetles trying to mate with them.
And it gets worse. I want to read a quote

(35:31):
from their paper. Quote. In one of the observations, a
male at the side of the bottle was being attacked
by a number of ants which were biting at the
soft portions of his averted genitalia. A dead male covered
in ants was located a few centimeters away from this
same bottle. So these things are literally dying to mate

(35:51):
with glass bottles because just going off of their genetic
programming like this is their purpose. I have come here
to mate with this. This is glorious and large of females,
and I must do so even as answer tearing me
apart exactly right, ants maybe chewing off my genitals, But
it is worth it because this bottle sets off all
of my internal signals for amazing attractiveness in a female

(36:15):
of my species. So there is another fortunate ending from
the human perspective. I reade a report on NPR that
the bottle designers became aware of this and eventually they
changed the bottle design to remove the small bumps on
the glass. After they did that, the male beetles stopped
caring about them. Oh that's good. But once again, you
can imagine what would have happened if nobody noticed this

(36:35):
and the bottle makers never changed their methods. Will never know,
but one possibility is these beetles could have become endangered
or gone extinct, with all the healthy males refusing to
mate with actual females because they preferred glass bottles. These
bottles were better looking than the real members of the species.
But in other possibilities, the species would have evolved to
favor different sexual preference genes and males. Right that males

(36:59):
would be not attracted to whatever features set off the
extreme bottle desire, but to something else, maybe sent or
something like that. And I mean again, just the crazy
thing about this is that it's not like they were
setting around trying to come up with a bottle design
that would throw off beetle mating in the immediate area.
This was just pure accident, but it could have had

(37:19):
disastrous consequences for the species. All this stuff is pure accident.
Now I want to explore an accident that went a
different way where animals have been found to be adapting
in a positive way to harmful trash being thrown into
their environment. Uh. Do you ever have that friend Robert
who thought it was cool to flick cigarette butts out
into the world when they're done smoking. You know, they're

(37:39):
like the system man, they finished there and just flicked
the butt. I have not, but I will still occasionally
see somebody at like a stoplight that's doing that, and
I judged them rather harshly. Yeah, it's not cool to do.
Don't don't litter the world with your cigarette butts. But
it actually that was not a pun, by the way. Uh,
there's an interest follow up to this. So. Montserrat Suarez

(38:02):
Rodriguez is an ecologist at the National Autonomous University of
Mexico in Mexico City, and she and her colleagues Isabel
Lopez Rule and Constantino Marcius Garcia published some fascinating research
in Biology Letters in and they started by pointing out
something really interesting about the birds of Mexico City. The

(38:24):
birds were putting discarded cigarette butts in their nests. Okay,
well that that in and on itself doesn't sound crazy,
because if they're if there are a lot of these around.
If cigarette butts are more forthcoming than twigs, then why
not put them in your nest? Right? Yeah, they're fiber, right,
So if the cities are full of littered cigarette butts,
maybe the urban birds will just use whatever kind of

(38:45):
fiber is around to be part of the nest that.
You know, there's some cellulose here, I'll put it in
the structure of the nest. But these researchers performed experiments
and they found something pretty amazing. They looked at the
nests of house sparrows, which are passer domestica us and
house finches, which are Carpodacus and mexicanus, and they found
that the more cigarette butts a nest contained, the fewer

(39:08):
parasitic mites could be found in the nest. Now why
would that be, Well, cigarette butts contain a cellulose filter
through which the smoke passes when you smoke a cigarette, right,
and this filter traps all kinds of compounds from the smoke,
including nicotine, the stimulant drug in the tobacco products. So
why do tobacco plants contain nicotine in the first place.

(39:32):
It's because it is a poison designed to deter herbivorous
animals from eating the plants, including insects, and it's even
been used by humans directly as an insecticide. Oh, so
this is a for the birds and naturally occurring insecticide
in their artificial city environment. Exactly, the birds have parasitic

(39:53):
arthropods that attack them in their nests, but if they
line their nests with insecticide traps found among the trap
shin gutters of the city, they can repel these parasites.
And the researchers confirmed this by setting up traps to
attract parasites lined with two types of cigarette butts. They
had smoked butts and unsmoked butts, and the parasites were
much more deterred from the nest that had the smoked

(40:15):
butts in them. Now, why would that be. The smoked
butts contained the nicotine because the smoke had come through them,
while the unsmoked butts didn't contain any they were just
the cellulose. So the researchers determined it was not just
the fiber, really was the nicotine. And now, at the
same time, that's an ingenious adaptation to the available materials
of a city. But we also shouldn't conclude that this

(40:36):
is always going to be good for the birds, because exposure,
of course, could have negative side effects that haven't been
identified yet. We all know what some of the negative
side effects of exposure to tobacco products can be. But
still they've they've essentially made a protective chemical weapon out
of these discarded cigarette butts. Now here's another thing about
the physical environment of cities that most of us probably
wouldn't even stop to think about. But there is an

(40:58):
extremely simple diff friends in the kinds of physical surfaces
one encounters more often in the city versus the country. Right,
what kind of animal is actually evolved to live on hard, flat,
relatively smooth surfaces with no vegetation cover that you can't
dig down into? And that sounds like a nightmare? Right, Yeah? Like,
what kind of creatures do would you typically find scurrying

(41:21):
about on rocks and other flat surfaces? I mean not
that many. I mean you some live on rocks, but
at least then you'd have vegetation nearby, or you could
retreat down into cracks between the rocks. The sort of flat,
unbreakable surfaces of the city are, and especially the smooth
ones are just not great for many animals, but nevertheless,
animals adapt, life finds a way. So another study I

(41:44):
want to mention is that a team led by Kristen
Winchell of the University of Massachusetts, Boston examined males of
the animal lizard which is Enolis christ to tell Us
from a couple of cities in Puerto Rico and compared
them to males of the same species from adjacent four
wrists And was there any biological difference? You bet. They
actually published their results in the journal Evolution in sixteen,

(42:07):
and what they reported was that the city lizards had
both longer legs and they had more lamela, which are
these structures on the toes on the undersides of the
feet that helped the toes stick to surfaces, especially smooth surfaces.
So these traits were probably helping the lizards, helping these
animal lizards evolved to be able to climb smooth walls

(42:30):
and stay attached to these smooth, slippery surfaces, even vertically
aligned ones. Yeah, these these kind of like essentially like
hyper surfaces. Is that you're not going to find something
that is that is that flat, uh and in featureless
that that vertical in the natural environment. Yeah, and so
to test whether this was an actual inherited trait, they
also raised lizards from stock captured in the city and

(42:53):
from stock captured in the forest, and they raised them
both in the lab just to make sure it was
a true genetic difference and not some weird way the
lizards were able to change their bodies during life, and
it turned out it was a true heritable difference. The
city lizards hatched wall climbers with these more lamlay and
the longer legs, and the forest lizards did not. And
you can imagine that so many city species are evolving

(43:15):
along these lines with small changes in their body just
to get a better grip on the surfaces of human
made environments. Right, Yeah, it makes perfect sense. Like this
is the this is the geography you're presented with. Now,
while we're on the subject of crawling reptiles, I want
to know something about city dwelling animals. Is it true
that there are colonies of alligators living in the New

(43:37):
York sewers? Ah, Now, this is a fun, fun topic.
Sometimes they are they're they're reported to be blind like
albino alligators living Yeah, in like thick packs in the
depths of say the New York sewer system. Is this
ever addressed in one of the Blade movies. I don't
think so. Maybe unless they made passing reference to it.

(43:59):
I'd know it shows up in Teenage Mutant Ninja Turtles,
So it would have been a great set piece to have,
like Blade Battle, like an albino crocodile vampire that lives
in the sewers. Well, we have at least one film.
There's a nineteen eighties alligator. Do you remember this one?
I've never seen it. I should have. I don't know
why I haven't seen it. Oh man, I saw it
as a kid. It was It was a lot of fun.
It started Robert Forster, and it takes place in Chicago,

(44:25):
though not in New York City, which is a shame
considering what I'm about to lay on everybody, Well, tell me,
is it real? Okay? It? Well, it's not real. I
think if you were near a New York sewer right now,
do not worry about the blind alligators climbing up after you.
I looked at a nineteen seventy nine paper, Alligators in

(44:46):
the Sewers, A journalistic origin by Lauren Coleman, published in
the Journal of American folklore, and um, she this is interesting.
She points to Thomas Pension, uh, the famed American author
of Gravity's Rainbow, as someone who did not He did
not originate the tale, but he helped to propagate it,

(45:07):
and propel it through his debut nine novel V in
which there's this, uh, this this brief discussion of you know,
the classic trope baby alligators that are acquired at a
carnivore fair or on a trip to Florida. You come
back to New York, they start getting bigger. So what happens?
They get flushed down the toilet or thrown out and

(45:28):
then they wind up in the sewer. That sounds like
a cruel thing to do to a baby alligator, I agree,
But it it's this, you know, this idea that, oh, well,
they wind up here by accident, and then they wind
up down there, and then they thrive quote down there.
God knew how many there were. Some had turned cannibal
because in their neighborhood the rats had all been eaten

(45:48):
or had fled in terror, thanks Thomas Pension. But Coleman
digs deeper than than this. So various authors and even
herpetologist she found, referred to the urban legend, but they
cited it as such. They were not saying this is true.
They were saying, hey, this is crazy story some people
tell um claiming, you know, they grow fat on New

(46:09):
York sewer rats, they and or they grow pale and
blind in the depths. But then she explored more than
seventy reports of just alligator sightings in general in Northern
American climates, such as an eight account of a frozen
gator that's supposedly watched up on the banks of the
Rock River in Wisconsin. But she found just one single

(46:31):
account of a sewer gator that was at the time
actually reported as fact. And she admits that this may
have never taken place. It could be, you know, a
fraudulent story, but the matter of fact reporting style and
the fact that this was a very established paper may
have caused the story to simply explode. Wait what paper
was it? The New York Times, February five. You can

(46:56):
find this full um this full article online either uh
in the New York Times are archives which I believe
you need a membership to access. But then other people
have have have reproduced it elsewhere on the web. This
is the title alligator found an uptown sewer youth shoveling
snow and man hoole see the animal churning and the

(47:16):
icy waters snare it and drag it out reptile, slain
by rescuers when it gets vicious. Whence it came is mystery,
So I'm gonna let everyone else go read this on
their own. I'll include a link to it on the
landing page for this episode of Stuff Toblow your Mind
dot Com. But essentially the idea is, uh, the they

(47:37):
discover this sewer gator and they're frightened by it, and
then they drag it up and onto the onto the snow,
and then beat it to death with snow shovels. Yea, why,
it's just what you do, I guess when you're frightened
of a of a large creature. But then it But again,
I want to stress this doesn't mean this actually happened. Yes,
it made it into the New York Times, but when

(48:00):
you start looking at the evidence that you still have
to doubt that this really occurred. Okay, Well, what about
sewer gators in general? I mean, is there any evidence
that there might be gators living in the sewers underneath
some cities? Well, I looked into this a little bit.
So for one question that immediately came to mind is, Okay,
New York is u is a bit too far north

(48:22):
for alligators to really have a chance. But are alligators
living in sewers in say Florida? And uh and yeah,
you you do see reports of gators winding up in
Florida storm drains or sewers and many of and this
is because many of these waste outlets back out into
the swamps. But New York sewers not really outside of
just pure you know, urban legend. This one story and

(48:46):
also an account from two thousand ten in which a
baby gator was found in a Chinatown sewer, there's not
a lot to go on. And with that baby gator,
it's I'm it seems like it was probably just a
case of somebody through this this creature out into the
sewer and then it was found. This is not the
same as say, adult sewer born alligators popping up in

(49:07):
Times Square. And then I should also mentioned that snopes
dot com has an article on this, and they point
to the writings of nature writer Diane Ackerman. She points
out that the gators would only be able to survive
for a few months at the most. In New York sewers,
I would guess this would probably be the summer months, right, right,
because the big thing is the temperature. They're gonna need

(49:28):
temperatures between eighty seven and ninety degrees fahrenheit. And we're
talking about them living in the sewer. Uh, They're they're
gonna be surrounded by Salmonella E coli, shigela, other sewer
microbes that they're just not going to be able to
live with those. They're going to die in there. A
sewer is just not a suitable habitat for an alligator. Yeah,

(49:51):
And I think this does draw attention to the fact
that while we do see many animals uh coming up
with fascinating adaptations and even evolving to be better fits
for city life, not all animals are good candidates for this,
and certainly not all animals are good candidates for this
in all cities. Yeah, because with the alligator, for instance,
in in Florida, Yes, during the colder months, a storm

(50:15):
drain environment can be actually an excellent place for a
gator to hold up. All right, on that note, we're
going to take another quick break and then we'll be
right back all right, We're back all right. Now we've
been talking about the myth of the New York sewer gators,
which does not turn out to be true, and this
has highlighted some of the ways in which not all
animals are well suited to all city environments. Some are

(50:37):
much more suited to it than others. One animal that
has proven extremely well suited to city environments that is
a larger predator, kind of like an alligator, but very
different type, is the coyote. Yeah. And I've always found
this interesting because when I've lived in very rural environments
and when I've i've lived in urban environments, they're all
essentially all I encounter are mostly tales of the coyote.

(51:00):
It's such a secretive and stealthy animal that it's more
of a It's it's almost supernatural, this this beast that
is there, but you're only aware of it through its
childlike noises from the kud zoo under dark, just you know,
reaching out after you. Yeah, I mean, it's it's haunting.
That's this beautiful image. I don't usually think of coyotes

(51:21):
that way. I guess they're so common in cities. Now
we've started they've started to lose some of their wildlife magic,
and we start to think of them as like, oh,
that's like a city rat or something, you know. But no,
it's a It's a coyote. This is a large, candid predator.
I mean, this is an interesting thing, the fact that
they're colonizing our cities so much so. I found an
interesting Ohio State University news report on the work of

(51:42):
the os U wildlife ecologist stand Girt, who has been
studying urban coyotes, and some interesting facts and observations from
Girt's research. One is that coyotes have colonized pretty much
every big city in the United States. In somebody even
snapped a picture of a coyote standing on the roof
of a bar in Queens. Wow, how did it get there?

(52:07):
I don't know they I think they think maybe it
got out from a window of a building nearby or
something like that. In Queens, there's a coyote on the
roof of a bar. And this actually just isn't all
that weird as weird as it seems, because coyotes are
everywhere in our cities. Gert has observed coyotes adapting to
city traffic, literally pausing at the edge of the street,

(52:28):
looking at the direction that traffic comes from, and checking
for oncoming traffic. Because in an urban environment we've already
talked about the idea of cars as predators. The number
one cause for death for a coyote in a city
is getting hit by a car. But those risks are
paired with big rewards because Girt's research has found that
an average litter size for an urban coyote is nine pups,

(52:50):
which is bigger than the average litter size in rural areas.
And this means city coyotes are fattening up on abundant resources.
And this is possible because coyotes can make you of
all kinds of resources their omnivores. They'll lead almost anything,
and these are the kinds of organisms that tend to
do well in cities. Now, on the other hand, people
have started to see them very much as an urban nuisance.

(53:11):
I even found a New York Times article about the
trend of urban hunters culling city coyote populations. Have you
read about I have not heard about this. I've heard about,
you know, rat hunters, obviously, but this is the first
effort about the coyote hunters. Yeah, so because of this
kind of action and the fact that we will never
seem to get rid of all of them, I wonder
if we may actually be driving a selection regime to

(53:35):
evolve urban coyotes that are guess what, good at hiding
from humans. And there's a cool example of this that's
actually already been reported in places like National Geographic so uh,
to quote from that GEO article on it, quote in
downtown Chicago, one GPS collared coyote pair raised a litter
of five healthy pups inside a secret concrete den in

(53:59):
the parking lot of Soldier Field Stadium, home of the
Chicago bears a high traffic environment, but the signals to
me the emergence of of invisibility traits in these creatures.
You know, they find those places where no one will
look for them. Okay, one last animal to look at.
There are millions of ways we could look at mice,

(54:20):
but there is one way that I think is going
to be particularly interesting. So one of the ways we
don't often think about the effects of the techno ecosystem
of the city is that it creates urban islands. And
this could be counterintuitive to us, because to us, a
city is actually one of the easiest places in the
world to get around. Right, there's no rocky terrain, there's

(54:41):
no forest blocking the way of getting through things. A
city is the place where you can go to somewhere, right, Yeah,
I mean you hear about Oh, this is a very
walkable city. You can just get out and walk wherever
you want. You don't have to cross a river, scale
a mountain. It's just all there. But for many animals,
a city is exactly the opposite. So his book Skill
Tousand points out many ways that cities start to recreate

(55:04):
the principles of island biogeography by allowing small patches of
habitable environment that are separated from one another by all
kinds of virtually impassable barriers, freeways or even small roads.
For some animals, breaks and vegetation cover. There are all
kinds of barriers we wouldn't even think of. So Skill

(55:24):
Tousand mentions a case of something kind of like island
evolution from within New York City, specifically the work of
a zoologist named Jason Munshi south of for Fordham University,
who studies the way that different isolated populations of mice
have evolved for specializations for different parks of New York
City now Munchie South. Research is focused on the white

(55:46):
footed mouse or Paramiscus leucopus, and this mouse inhabited the meadows, swamps,
and forests to the New York City area long before
humans ever settled there, so it's not the kind of
mouse that follows human settlements everywhere. It's a local has
clung onto survival in the city that rose up around it,
and so originally this population of white footed mice would

(56:08):
have been a single combined population with continuous interbreeding throughout.
But the populations that have survived up until now in
New York are isolated from one another on the islands
of New York's parks. So there's a population in Central
Park and one in Prospect Park, and more in smaller
parks around the city. And the mice can do pretty

(56:29):
well in these parks because most of the park's actually
aren't big enough to support natural predators like owls or foxes.
But the different park populations don't tend to interbreed with
one another very much, which means they're free to evolve
independently in different directions, whether through local natural selection or
just through genetic drift. Yeah, because how's a mouse going

(56:50):
to get from say, Washington Square Park all the way
to Central Park. Are they're gonna They're gonna take the train. Now,
I mean some some rodents will be better at traversing
the city in that way than others. These mice are
very shy. They want vegetation cover. They don't want to
come out from under the plants they live beneath. So
unless there was like a land bridge of parks between
the two, right, yeah, they're probably not going to leave

(57:11):
their island. Now. It's not that mixing never happens, but
it's very rare, and rare enough that these populations do
have evolved to become genetically distinct. Munchie South and colleagues have.
They've been tracking the evolution of these different park populations
by trapping mice from each of the parks and performing
cross reference to DNA tests. Now, gene pool fragmentation like

(57:33):
this is generally considered bad for the health of a
species in a long run. This is one of the
reasons you see these wildlife corridors, you know, that are
so important. It's because they help creatures from one side
of a freeway come to the other side so they
can mate and increase the gene flow across the two populations.
But nevertheless, the fragmented populations of white footed mice seem

(57:55):
to be doing pretty well, and they've adapted more and
more to their local conditions in the parks where they live. Now,
you might think, how could the adaptation pressures of one
city park be all that different from the pressures of
another park or another place. I mean, there's some interesting results.
So here here are some adaptations they found that were
specific to Central Park mice. The Central Park mice had

(58:16):
a variation in the a k R seven gene, which
is involved in neutralizing a flat toxin, which is a
toxic compound produced by some molds, as Skill tells and
points out molds that grow on seeds and nuts. Interesting.
So the obvious implication is that the Central Park mice
are more exposed to this kind of toxin, probably in

(58:38):
the foods that they eat. Another one involved in diet
a variation on the f A d S one gene,
which is involved in the metabolism of high fat diets.
This is probably a trash situation, yeah, kind of not
not hard to see what's going on there. But then
there are other mutations found in the city park mice
having to do with diet, metabolism, exposure to pollutants, and

(59:00):
importantly immune function because, as Munchie South says, quote, very
easy to spread disease when you're in a small population. Interesting.
I love this they are since they're evolving to live
on a diet of one dollar pizza slices. Right, Yes,
as are many New Yorkers, And so, I mean fair
is fair, But New Yorkers at least you know, they've

(59:20):
got more ways to get around, right. These mice live
on an island, even in the middle of a city.
It is an island to them. They really can't leave,
so they deal with what imports arrive. That this is
going to be going to think about the next time
you're walking through a city park. Yeah, I mean, it's
kind of crazy to imagine that the types of trash

(59:41):
usually littered in one park versus the types of trash
usually littered in another park. If they're different enough types
of trash, this could literally be shaping the evolution of
the creatures that live in those parks. Oh wow, so
is the human population like that? The details of a
human population change around a certain park, it could have
a drafting even disastrous effect on the mice that reside there. Yes,

(01:00:06):
food trends come and go a nearby restaurants and stuff
like that. It's crazy. Yeah, they depend on the avocado
toast and then what happens when that goes away? Right?
Oh yeah, we we we went all in on evolving
to be avocado toast eaters and now you're into what
grapefruit rice? And I don't want that. Well, I think
we should wrap up today's episode with just one final

(01:00:28):
look at some general trends in urban evolution that have
been observed across many studies and and of course be
reminded that we're going to come back and explore more
examples of urban evolution and adaptation in the next episode here.
But to sum up today, uh, actually, Jason Munchie South,
who were we were just talking about, is one of
the authors of a paper we're about to look at.

(01:00:48):
The other author was Mark T. J. Johnson, and this
was a paper called Evolution of Life in Urban Environments
published in Science in and this is a huge review
of research on urban evolution, observed general trends and what's
been discovered in the literature so far. To discuss one example, uh,
the general trend they've identified as quote, cities elevate the

(01:01:09):
strength of random genetic drift meaning stochastic or random changes
in alleal frequencies, and restrict gene flow meaning the movement
of alleles between populations due to dispersal and mating. And
so this leads to a loss in genetic diversity within
populations and increasing difference between populations, just like we were

(01:01:30):
talking about with the mice, right. Smaller number of studies
they found indicate that urban pollution can increase mutation rates
in urban dwelling animals, which might actually speed up evolution, right,
if you've got more mutations going on. But then also
when it comes to natural selection, cities tend to present
different selection pressures the natural environments, and so they say, quote,

(01:01:53):
adaptations typically evolve in response to pesticide use, pollution, local climate,
or the physic coal structure of cities. And that's not
even counting um canisers of mutagen that are thrown into
the sewer affect the local turtle population. I mean, you
can't even factor that in. That's just anomally. But one
more trade I think would be worth mentioning is something

(01:02:15):
that Skill to House and mentions in his book as
adaptive to many species in cities, and it's what would
be known as neophilia, or an attraction to strange or
familiar or unfamiliar objects. Like if you're an animal, neophilia
obviously cuts both ways. It's a gamble. If you approach
a strange, unfamiliar object, it could turn out to yield

(01:02:35):
big rewards for you might have some good tasty morsels
in there, or it could turn out to injure or
kill you. Nature probably pays many animals to be conservative
and avoid strange stimuli, better not to risk it. Right,
But in the city animals can get big rewards by
approaching a KFC bucket or an ice cream carton or
other objects that would not they would not have natural

(01:02:57):
instincts for or any previous experience with. So there could
be cases in the cities where neophilia is positively selected
for in a strong way, maybe breeding more bold, more
curious animals. Well, I this brings me back to the raccoons.
You know, the idea that the raccoon is bold in

(01:03:17):
its uh, it's experimentation with some sort of a puzzle
before it, you know, such as a KFC bucket. I
mean a KFC buckets probably nothing to a raccoon. I'm
sure they're well, they are well acquainted with the with
the bucket of KFC at this point. Excuse me, Mr Lamb,
we know about those. Um yeah, well, I guess maybe

(01:03:41):
that should be it for today, right, and then we
can explore more when we come back. We haven't even
gotten deep into one of the most fascinating areas of
urban evolution, which is birds. Yes, and then there's the
whole we we talked a little bit about light earlier,
but light pollution is another area with some very surprising
adaptations that are occurring. We will explore all of those

(01:04:01):
fascinating avenues the next time. And uh hey, while you're
waiting for those, uh those new explorations, head on over
to stuff to Blow your Mind dot com. That is
the mothership. That's where you'll find this episode, all other episodes,
including our episode on the London Underground mosquito, which is
a fascinating look at a particular species that has adapted

(01:04:22):
to an artificial human environment, that of the London Underground
train system. Also at stuff to Blow your Mind dot com,
you'll find links out to our various social media accounts
such as Facebook, Twitter, Tumbler, and Instagram. Thanks so much,
as always to our wonderful audio producers, Alex Williams and
Tarry Harrison. If you would like to get in touch
with us directly to let us know feedback on this

(01:04:43):
episode or any other episode, to suggest a future topic,
or just to say hi as always, you can email
us at blow the Mind at how stuff works dot
com For more on this and thousands of other topics.

(01:05:04):
Is it how stuff works dot com