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Sharks Aren't Fish | Hank Green | YouTubeToText
YouTube Transcript: Sharks Aren't Fish
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Core Theme
The definition of "fish" has evolved from a common-sense, intuitive understanding to a complex scientific classification, revealing that our everyday language often fails to align with biological reality, especially concerning evolutionary lineage.
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So this is going to start out kind of
philosophical with the fact that words
have meanings all of them and those
meanings mean something in our heads and
this is fine. That is where meaning
begins. But it is not where meaning
always ends. Now the crazy thing is that
as we pass words around they mostly mean
the same thing in your head as they do
in my head. If that's not the case then
conversation becomes weird and hard. And
I see this happen all the time,
especially on the internet where
different groups of people have
different. It doesn't matter. The way
that we actually imagine and use words,
what the definition of a word is is the
thing that it means when you think of
it. And that's a fine kind of
definition. When it comes to that kind
of definition, there is obviously a
thing that fish are. This is a fish. And
this is a fish. This is definitely a
fish. Why is a bass to me like the most
fishlike fish? I don't know. But is this
a fish? I mean, yeah. It's not really
fish shaped. What about this? That's a
horse, but is also a fish. So, as
always, things are a bit of a mess on my
we never left the water shirt here.
There's There's like weird fish here.
There's a orfish. That's like a long
fish. There's a whale shark. What's that
even? Mao. What? What? But
interestingly, this used to be a fish.
And this also used to be a fish. This as
well. This is a silverfish. And
interestingly, it was never a fish. It
just reminded people of fish. We've had
words related to fish for a very long
time. And mostly what they meant was the
thing that you think of as a fish. Not
anymore though. And how we ended up
there is very interesting. Now the thing
that means fish is kind of not what you
think of as a fish. Or it is. It still
is. But there also it isn't. There's a
fight going on. And I'm in it. I'm in
the fight. And I want to be in the
fight. I like it here. But how we ended
up in that situation is very
interesting. And also it leads me to
believe that maybe sharks aren't fish or
whales are. What people think of as a
fish has changed over time as our
language has gotten more specific. Used
to be anything moving around in the
water was a fish. Starfish, jellyfish,
cuttlefish, whales, seals, and penguins
were not considered fish because they
spent a lot of time on land. And people
messed around with this. Like Aristotle
was like a bunch of these things are
pretty different. As early as that era,
we started separating out things that
didn't have internal structures. So
sharks and bass and whales, fish, but
squid and octopuses and and snails and
jellyfish and starfish, different things
that got different words. He had a whole
system for dividing things up. Did they
have blood? Did they have bones? Etc.
But that was very different from what
people thought of as fish. And people
kept thinking of squids as fish, even
though Aristotle was like, "No, no, no.
They're a different thing." When I was
in school, people were still a little
unclear on whether whales were fish.
That was the '9s. In the Middle Ages,
for weird logistical reasons, fish
started to be redefined for a lot of
people because you could eat fish during
meat fasts, like during Lent. And some
people didn't have access to like not
just fish, but like any food that wasn't
meat. And so they started looking at
different animals and being like, maybe
that's a fish. I don't know. Ended up
beavers definitely considered fish and
could be eaten during Lent. Same thing
goes for barnacle geese, which people of
the time thought grew on driftwood, like
popped out of barnacles. You could see
how maybe that would be a fish. Also,
puffins lived a lot of their lives in
water, so they were considered fish.
Now, the jury is out on whether people
actually thought these things were fish,
but it really does feel like they did.
Like they looked at beavers and they
were like, "Their tails are scaly. They
live in the water. I don't know. Kind of
fishy." Now, if you look up the
definition of fish in the dictionary and
the words there were just like that
thing you think of as a fish, that would
be a bad definition. That would not be
satisfying. It's almost weird that there
has to be a definition of fish. Like, I
don't know the history of dictionaries,
but there must have been a time when
they were like, I guess we got to
include all the words, even fish, which
everyone knows what a fish is. Like, I
don't have to define fish to people.
Children around fish, no fish. But like,
I guess we got to do it. But before
dictionaries, like the thing you think
of when I say fish is mostly what we
were going with. That was most of human
history. And what definitions today
mostly do with fish is that they try to
describe what you think of when you
think of a fish. Cambridge dictionary.
An animal that lives in water is covered
with scales and breathes by taking water
through its mouth or the flesh of these
animals eaten as food. I mean, no, like
catfish don't have scales. Mudskipppers
are evolved to not live entirely in the
water. But whatever. Google a limbless,
cold-blooded vertebrate animal with
gills and fins and living wholly in
water. Again, muds skippers, but also
tuna. Maybe not coldblooded. It turns
out also lots of fish don't have fins.
So, this is a bad one. Miriam Webster is
improving any of numerous cold-blooded
strictly aquatic cranate vertebrates
that include the bony fishes and usually
the cartilagynous and jawless fishes.
So, those are actually the that's a
little bit of foreshadowing for you. and
that have typically typically also you
should have put typically on
cold-blooded Miriam Wikipedia. A fish is
an aquatic amniotic gilbearing
vertebrate animal with swimming fins and
a hard skull but lacking limbs with
digits. This is the best one, but it
still isn't quite there. There are some
fish that don't have fins. What all of
these things are is an attempt to create
a line that you can draw around all fish
that excludes all things that aren't
fish. Some of them do better jobs than
others. But wildly this is a very
difficult thing to do. There are a lot
of fish. The world is large. There's a
great diversity of life. But you can see
how these definitions are just an
extension of what do I think of as a
fish. Create a list of attributes that
draws a line perfectly including all
things that I think are fish and no
things that I don't think are fish. And
this is fine. Definitions are for humans
to use. And absolutely, even though a
manta ray isn't really very fishshaped
and hagfish don't have fins and catfish
don't have scales, I feel like they
should all be included. But you get the
idea. A fish is like a thing that you
think of when you think of a fish. And
that is often what definitions do. But
there is another thing definitions can
do. If I ask you to define a car, you
will have to give me a list of
attributes. I just don't actually see
another way. He got tires, an engine,
carrying a smallalish number of people,
doesn't have a flatbed, and that's
imperfect, but we're kind of stuck with
that. This is not the case with life. In
the late 1800s, after people realized
that animals evolved from one another,
it started to be pretty clear that there
was actually a reason why fish tended to
have all of these common properties.
Upright tail fins, amniotic,
two-chambered hearts, pumping blood,
gills, and hard skulls. And instead of a
list, we could have a definition that
told us something new because it brought
the definition outside of our minds,
outside of the vibes, outside of what we
think of as a fish and into the real
world, not in here, out there. This
conversation, which has now been going
on for decades, is like a thing that's
happening and you're in the middle of
it. When we moved from defining fish as
the thing that feels like a fish to me
to instead a list of things that include
all of the things I think of as a fish
and none of the things that I don't.
That wasn't actually that much of a
leap. That definition was still inside
of us. A much better definition, but one
that no one currently uses and is part
of this fun, I think fun discourse. No
one's actually mad here, but a much
better definition is when it actually
describes something that exists in the
real world. And the lineage of fish,
starting with the first common ancestor,
a vertebrate with fins and scales and
blood and a two-chambered heart and a
hard head, is a real thing that existed
in the real world. And that is the
common ancestor of all fish. But
interestingly, no current definitions of
fish discuss lineage because they
cannot. And I will now explain that
there was one common ancestor that gave
rise to all of the fish. sharks and
manta rays and bass and marlin. But that
common ancestor also gave rise to
beavers and birds and the prop comedian
Carrot Top. And this would actually be
fine. Birds have a single common
ancestor. They are a group that just
includes birds. Dinosaurs have a single
common ancestor. They are a group that
just includes dinosaurs. And tetropods,
the land vertebrates, all have a single
common ancestor. They are a group that
just includes tetropods. The fish group
includes three different groups. The
bony fish like bass and marlin, the
cartilagynous fish like sharks and rays,
and the jawless fish like hagfish and
lamp rays. But cartilagynous fish and
bony fish split off from each other 420
million years ago, while tetropods and
bony fish split from each other 380
million years ago. 40 million years is a
long time in evolution, and we are way
more closely related to bass than bass
are to sharks. So here's the problem. We
are comfortable with the line that we
drew around fish. Unfortunately, that
line is drawn in such a way that it
cannot line up with the definition of
fish that is created when we remove
ourselves from the equation and seek a
definition that is about more than just
vibes. And so, if we want a definition
of fish that is about reality rather
than vibes, and I understand that we may
not want that, sometimes you just want
to say fish are the things that are like
fish. But in that case, you do have to
accept that whales only got brought out
of that definition through careful
science. But that's fine. But if we want
a definition of fish that is about
reality rather than vibes, that pulls
the definition outside of us and into
the actual biological reality of life on
Earth, you can absolutely do that. We
could create a group that includes all
of the fish, including the tetropods.
The problem is we already have a name
for that group. It's the cranates. Any
animal that has a skull is a fish or
descended from a fish. There are no fish
that are not descended from the first
cranate ancestor all those hundreds of
millions of years ago. But I actually
don't like that as a classification cuz
it's just too broad and we already have
that. We've got craniates. But also
hagfish that are cranates but not
vertebrates are so different from all
the other fish that I will happily call
them not fish. Like the hagfish, maybe
they're like cuttlefish and jellyfish,
just something named fish but not
actually a fish. No one is making them
be fish. They don't have to be fish.
However, this doesn't actually solve our
problems. If we cut the hagfish off and
say, "Okay, fish is everything descended
from the ancestor of all the other fish,
we also have a name for that. That is a
group that already exists as well.
That's the vertebrates." And so, if we
want fish to actually be a thing, we
have to go one step further. Perhaps the
cartilagynous fish aren't fish either.
Perhaps sharks and rays are just sharks
and rays. And if we carve them off too,
we would actually be left with a group
that are fish and are not represented by
anything else. This is the bony fish.
The group that includes all of the fish
descended from the first bony fish,
which has pretty much everything you
think of as a fish in it except for the
sharks and rays and hagfish and
lamprays, but also does include the
tetropods. So, this doesn't solve the
second problem, which is that tetropods
would still be in the group. But here's
the thing. I don't think this is a
problem because I think I'm a fish. In
order to make fish a useful category
that we don't already have a very large
encompassing name for, we have to narrow
it down. But it's literally impossible
to narrow it down so far that it doesn't
include humans without arbitrarily
drawing a line at the shore. And this
division in which only bony fish are
true fish makes sense to me because it
highlights how extremely different
sharks and rays are from bony fish,
which we don't think about. Like we
can't hold it in our brains, but it's
really true. And that's to say nothing
of the hagfish which are I mean just
look at them like that's that's a fish.
The most likely outcome however because
fish aren't that important to us like we
don't spend that much time around them
the way that we do like like we see a
reptile and we see a bird and because
we're land animals we see those things
as very different from each other even
though they are much more closely
related than a shark is to a bass but
because we are what we are we just
continue to operate on fire. This is
what's going to happen. It just means
that I get to keep telling you that
while the things you think of as fish
definitely exist, there is no actual
thing in the real world outside of our
minds that the word fish describes.
There is no such thing as a fish. Thank
you to everybody in the comments of my
video about fish who encouraged me to
make this video about why whales are
fish or maybe they aren't and sharks
aren't fish. I don't know. My point is,
thank you. I had a good time making
this, especially because of the the
point here that definitions can be two
things. They can be our mind's version
of what something is, but they can also
be like the real outside of our mind
version of what something is. And I
think that that's fascinating. And also,
I really want to have that conversation
about life because I hate the current
definitions of life that are it's just a
line drawn around something rather than
actually trying to name what it is. But
regardless, the We never left the water
shirt designed by Matias Ball is still
available, but only for the next week.
After that, we will take the exact
number ordered and print that exact
number of them and ship them out so that
we don't accidentally make too many or
too few. So, if you, an organism that
brought water out of the water and onto
the land and kept it inside of your body
with gratinous skin, want this shirt,
you can get it, but only for another
week. All right, that's the end of the video.
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