In the first video on evolution, I gave the example
of the peppered moth during the Industrial Revolution in
England and how, before the Industrial Revolution, there
were a bunch of moths: some were dark, some were light,
some were in between.
But then once everything became soot filled, all of a
sudden, the dark moths were less likely to be caught by
predators and so all of the white moths were less likely
to be able to reproduce successfully, so the black
moth trait, or that variant, dominated.
And then if you came a little bit later and you saw all the
moths had turned black, you'd say all
these moths are geniuses.
They appear to have somehow engineered their way to stay
camouflaged.
And the point I was making there is that, look, that
wasn't engineered or an explicit move on the part of
the moths or the DNA, that was just a natural byproduct of
them having some variation, and some of that variation was
selected for.
So that example, that was pretty simple: black or white.
But what about more complicated things?
So, for example, here I've got a couple of pictures of what's
commonly called the owl butterfly.
And what's amazing here, and it's pretty obvious, as I
probably don't have to point out to you, is its wing looks
like half of an owl's eye.
I can almost draw a beak here and draw another wing there
and you can imagine an owl staring at us, right?
And here, too, I could imagine a beak here and you would
think an owl there, too.
And so the question is how does something this good show
up randomly, right?
I mean, you could imagine, OK, little spots or black and
white or grey, but how does something that looks so much
like an eye generate randomly?
Now the answer is-- well, there's a couple of answers.
One is why does this eye exist, or this eye-like
pattern or this owl-like eye's pattern?
And there, the jury's still out on that.
I read a little bit about it on Wikipedia and all of these
images I got from Wikipedia.
In Wikipedia, they said, look, there's two
competing theories here.
One theory is that this, even though to us humans, the way
we see things, it looks like an owl's eye, that this is
actually a decoy.
When some predator wants to eat one of these things, they
go for the thing that looks most substantive.
So instead of going for the butterfly's body, which
doesn't look that substantive, they go for
the big, black thing.
They say, oh, that looks like it's protein rich and it'll be
a good meal.
So they try to snap and bite at that, and if they bite at
that, sure, the guy's wing's going to be clipped a little
bit and it's going to suck, but the animal itself, the
actual butterfly, would survive, and maybe it can
repair its swings.
I don't know the actual biology of the owl butterfly.
That's one theory, and then the argument against it goes,
well, no, if that was the case, then you would want the
black spot even further back along its-- you'd want the
spot way far away from the body.
You'd want it back here instead of right here, because
there's still a chance, if something chomps at this
little black spot, that it'll still get the
abdomen of the butterfly.
Now, the other theory as to why this exists-- and, you
know, who knows?
Maybe it's a little bit of both.
Maybe both of these are true.
Maybe this offers two advantages.
The other theory, and this is kind of the one that jumps out
at us when we see this , is, hey, this looks like an owl.
Maybe this is to scare away the things that are likely to
eat this dude.
And it does turn out in my reading that there are lizards
that like to eat these type of butterflies, and those lizards
probably don't like to be around birds or owls because
those owls eat them, so that might be a deterrent.
And then the other example, they said is, look, they tend
to be eaten by this lizard right here-- this is what
Wikipedia told me-- and that this lizard tends to be eaten
by this frog right there, and that the eyes of this
butterfly are not too dissimilar to the
eyes of this frog.
And, you know, we can debate whether or not that's the
case, and if this was the predator we're trying to
mimic, you could make an argument that maybe we would
have had more green on our wing, but that's not the point
of this video.
But it's a fun discussion to have as to what is useful
about this eye.
But let's have the question: How did that eye come about?
And when I say that eye, I mean the pattern on that wing.
What set of events allowed this to happen?
Because when I described evolution, and we know that
everything in our biological kingdom is just a set of
proteins and then stuff that maybe the protein-- but mainly
protein, and that protein's all coded for by DNA.
I'm going to do future videos on DNA, but DNA is just a
sequence of base pairs.
It's a sequence of these molecules.
And we represent adenine, and guanine and
cytosine and thymine.
Then maybe you have a couple of adenines in a row and some
guanine and thymine.
I'll do a lot more on this in the future, but the idea is
it's just coded for by this sequence of these molecules.
How do you go from a butterfly that has no eye to all of a
sudden an eye that goes there?
Obviously, just one change that happens
from a random mutation.
Maybe that G turns into an A or maybe this C and this T get
deleted so everything-- that alone isn't going to develop
this beautiful of a pattern or this useful of a pattern.
So how do the random changes explain
something that's this intricate?
And this is my explanation.
And obviously, I wasn't sitting there watching over
the thousands or millions of years as these owl butterflies
emerged, so this is just my theory of how natural
selection does explain this type of phenomenon.
You have a world where in some environment you have
butterflies, and their wings look like-- let's say you have
some butterflies that are generally like this.
That's their wing, and it's a very bad drawing, but I think
you get the idea, and there's just some general patterns.
We've seen it before.
There's variation.
And the variation does show up from these little random
changes in DNA.
I think we can all believe that, that most of these
changes are kind of benign.
Maybe they just set up differently where a little
pattern will show up or a little speck of pigment will
show up with a slightly different color.
And we even see amongst these owl
butterflies, there is variation.
This dude's wing is different than that guy's wing with the
commonality that they do have these eye-looking shapes.
And there's not just one; there's actually multiple.
This guy has this other thing up here that looks
interesting, and they have multiple things, but the one
really noticeable feature is this eye-looking thing.
So how do we go from this to an eye-looking thing?
So the idea is you have some variation.
One guy might look like that.
Another guy, or gal, might-- just randomly, their dot might
be something like that.
Another gal or guy-- these wings are really badly drawn,
but you get the idea.
This is the butterfly.
This is its antenna right there.
That's its body.
Another butterfly's patterns might look like this, right?
And so, they're just random.
But when they go into a certain environment for
whatever reason, maybe one of its predators-- maybe that
theory that these are supposed to look like eyes is true.
And so, actually, maybe this guy just has a
random pattern here.
And so this guy-- and I'm not saying that it's like
definitely better.
They're both going to be found and killed by predators, but
it's all probablistic, right?
Maybe this guy has a 1% less chance of getting a predator,
because when a predator just looks at him out of the corner
of that eye, that little really hazy region kind of
looks like an eye and the predator would be better off
just not messing with it, and they'd rather go after the
dude that looks like this.
So it's just a slight probability.
Now, you might, say, OK, what's 1% going to do?
But when you compound that 1% over thousands and thousands
of generations, all of a sudden, this trait might
dominate because he's just going to be killed that less
frequently, 1% less frequently.
Now, maybe this guy has a similar trait, but his spot is
closer to the abdomen.
And here, it's a tradeoff, because maybe some predators
get scared away by this concentration of pigment.
And once again, I'm not saying that we're here yet.
We're not at this very advanced, sophisticated
pattern yet.
We're at this random concentration of pigment that
just shows up.
So we see that people who have this concentration of pigment
further away from their abdomen, they do well.
But when it's too close, maybe some predators think that
that's actually an insect and they want to eat it, so that's
actually a bad trait.
So what happens is this guy dominates, and so within this
population, you start having a lot of variation, because he
starts representing-- he's more likely to
pass on these traits.
And I want to make that point very clear.
This isn't what happens over the course
of an animal's lifetime.
It's not like if somehow I experience something, or at
least our current theory if I experience something, that I
could somehow pass on that knowledge to my child.
What it says is if my DNA just happens to have just some
variation that happens to be more useful or more likely for
me to survive to reproduction and for my children to
survive, then that will start to dominate in the population.
So then the population, you're going to have variations
within that.
Maybe some guys, you know, it's going to get a little bit
to look like that.
Maybe another one's going to look a little bit like that.
Maybe it has some spots there.
You can kind of view it as the variation as "exploring." But
I want to be very clear not to use any active verbs here
because this is all being done really as almost a common
sense process, where everything changes.
The changes that are most suited are the ones that are
going to survive more frequently.
And then the next generation's going to have more of that and
then you'll have variation within that change.
And then this one might be like that, and
maybe this is the one.
These were good compared to that, but now when you're
competing amongst themselves, this one is able to reproduce
1% more than this guy or this guy.
And so this guy becomes-- and maybe it's some combination of
all of the above, and they mix and match.
It's a hugely complex system.
But then this guy represents most of the population, when I
say this guy, I'm saying this guy's genetic information, at
least as it pertains to his wings.
And then you get variation amongst that.
Maybe some of it, they have a little small dot and there's
some dots around it.
Maybe it's like this.
Maybe one of them digresses and goes back here, but then
he has trouble competing so he gets knocked out again.
And then some other people have it back here.
I think you get the point that this
isn't happening overnight.
These changes can be fairly incremental, but we're doing
it over thousands of generations.
So when you're talking about thousands of generations, or
even millions of generations, even a 1% advantage can be
significant, and when you accumulate those variations
over a large period of time, you can get to fairly
intricate patterns like this.
So I just wanted to explain that, because this is often
used as, sure, I can believe the butterfly moth or I can
even maybe believe the examples of the antibiotics
and the bacteria or the flu, because those are kind of
real-time examples.
But how does something this intricate show up?
And I actually want to make a point here.
We think this is more intricate because we can
relate to it in our everyday lives.
But if you actually look at a structure of a bacteria and
how it operates or what a virus does to infiltrate an
immune system or a cell, that's actually on a lot more
levels a lot more intricate than a design.
In fact, the whole reason why I'm using this as an example
is because this is a fairly simple example as opposed to
kind of explaining the metabolism of a certain type
of bacteria and how that might change and how it might become
immune to penicillin or whatever else.
But I want to make this very clear that these very
intricate things, they don't happen overnight.
It's not like one butterfly was completely one uniform
hot-pink color and then all of a sudden they have a child
whose wings looked just like this.
No!
It happens over large periods of time, although there might
be some little weird hormonal change that does this, but I'm
not going to go there, but that is possible.
But I just wanted to make this point because I think the more
examples we see, the more it'll kind of hit home that
this is a passive process.
We're not talking about these things happening overnight.
And it's actually really interesting to look at our
world around us and look at ecosystems as they are today
and try to think really hard about how something came to
be, what it's useful for, why it might have
been selected for.
For example, are traits that occur after reproduction
selected for?
Well, probably not unless they affect the reproduction of the
next cycle.
For example, you might say, oh, well, the trait to be
nurturing after your reproductive years, that's
after reproductive years.
No, but it helps your offspring reproduce.
But we already see a lot of diseases, especially once we
get beyond our reproductive and our child-rearing years.
So once we get into our fifties and sixties, the
incidences of diseases increases exponentially from
when we're younger and because they're no longer being
selected for, because it no longer affects our ability to
reproduce, because we've already reproduced.
We've already raised our children so
that they could reproduce.
So the only thing that happens at that point is now not being
selected for.
So anyway, hopefully, this video will give you a little
bit more nuance on evolution, and I want to do a couple of
videos like this, because I really want to make it clear
that it's not making some wild claim that all of a sudden
this appears spontaneously, that it really is a thing that
happens over millennia and eons and very gradually.