all of science, and as we all know is now turning into one

of the most contentious concepts, maybe not in

science, but in our popular culture, and that's the idea

of evolution.

Whenever we hear this word, I mean, even if we don't hear it

in the biological context, we imagine that something is

changing, it is evolving.

And so when people use the word evolution in our everyday

context, they think of this notion of change, that-- this

is going to test my drawing ability-- but you

see an ape bent over.

We've all seen this picture at the natural museum, and he's

walking hunchback like that, and his head's bent down and--

oh, I'm doing my best. That's the ape.

Maybe he's also wearing a hat.

And then they show this picture where he slowly,

slowly becomes more and more upright, and eventually, he

turns into some dude, who's just walking on his way to

work, also just as happy, and now he's

walking completely upright.

And it's some kind of implication that walking

upright is better than not walking upright,

et cetera, et cetera.

Oh, he doesn't have a tail anymore.

Let me eliminate that.

This guy does have a tail.

Let me do it in an appropriate width.

This guy has a tail, so you're going to have to excuse my

drawings skills, but we've all seen this.

If you've ever gone to a natural history museum, and

they'll just make more and more upright apes, and

eventually you get to a human being, and it's this idea that

the apes somehow changed into a human being.

And I've seen this in multiple contexts, even inside of

biology classes and even the scientific community.

They'll say, oh, the ape evolved into the human or the

ape evolved into the pre-human, the guy that almost

stood upright, the guy that was a little bit hunchback, so

he looked a little bit like an ape and a little bit like a

human and so on and so forth.

And I want to be very clear here.

Even though this process did happen, that you did have

creatures that over time accumulated changes that maybe

their ancestors might have looked more like this, and

eventually they looked more like this, there was no active

process going on called evolution.

It's not like the ape said, gee, I would like my kids to

look more like this dude, so somehow, I'm going to get my

DNA to get enough changes to look more like this.

And it's not like the DNA knew.

The DNA didn't say, hey, it is better to be walking than to

be kind of hunchbacked like an ape.

And so therefore, I'm going to try to somehow spontaneously

change into this dude.

That's not what evolution is.

It's not like-- you know, some people imagine that maybe

there was a tree.

There's a tree, and on that tree, there's a bunch of good

fruit at the top of the tree.

Maybe they're apples.

And then maybe you have some type of cow-like creature, or

maybe it's some type of horse-like creature that says,

gee, I would like to get to those apples, and that just

because they want to get there, maybe the next

generation-- they keep trying to raise their neck, and then

after generation after generation, their necks get

longer and longer, and eventually

they turn into giraffes.

That is not what evolution is and that's not what it

implies, although sometimes the everyday notion of the

word seems to make us think that way.

What evolution is-- and actually, this is the word

that I prefer to use-- it's natural selection.

Let me write that word down.

Natural selection.

And literally, what it means is that in any population of

living organisms, you're going to have some variation, and

this is an important keyword here.

Variation just means, look, there's just some change.

If you look at the kids in your

school, you'll see variation.

Some people are tall, some people are short, some people

have blond hair, some people have black hair,

so on and so forth.

There's always variation.

And what natural selection is is this process that sometimes

environmental factors will select for certain variation.

Some variations might not matter at all, but some

variations matter a lot.

One example that's given in every biology book, but it

really is interesting is-- I believe they're called the

peppered moth.

And this was in pre-Industrial Revolution England that these

moths-- some of the moths were-- let me see if I can

draw a moth.

I think you get the idea.

Let me draw a couple of them.

Let me draw a few peppered moths.

A couple of peppered moths there.

Let me draw one more.

So most peppered moths, there was just this variation.

Some of them were-- I guess we could call them more peppered

than others.

So some of them might look like this.

You know, they had-- let me do other colors.

Let me do a white.

So it had spots like that.

Some of them might have looked more like that.

And, of course, they had some black spots on them.

And then some of them might have been-- just

barely have any spots.

You just have this natural variation.

Like you'd see in any population of animals, you'll

see some variation in colors.

Now, they were all happy, probably for thousands of

years, just this natural variation.

It was a non-important trait for these peppered moths.

But then, all of a sudden, the Industrial Revolution happens

in England, and all this soot gets released from all of

these factories that are running these steam engines

powered by coal.

And so, all of a sudden, a lot of the things that once were

grey or white, for example, maybe some tree trunks.

Let me draw some tree trunks.

Maybe there were some tree trunks that used

to look like this.

You know, maybe it looked like a-- maybe it kept a-- maybe

some tree trunks used to look something like this, and a

peppered moth would be pretty OK.

Maybe there are some tree trunks that were pretty dark.

But all of a sudden, the Industrial Revolution happens.

Everything gets covered with soot from the coal being

burned, and then all of a sudden, all the

trees look like this.

They're just completely pitch black or they're a lot darker

than they were before.

Now, all of a sudden, you've had a major change to these

moths' environment, and you have to think what is going to

select for these moths?

Well, one thing that might get these moths are birds and the

ability of the birds to see the moths.

So all of a sudden, if the environment became a lot

blacker than it was before, you can guess

what's going to happen.

The birds are going to see this dude a lot easier than

they're going to see this dude, because this dude on a

black background, he's going to be a lot harder to see.

And it's not like the birds won't catch this guy.

They'll catch all of them, but they're going to catch this

guy a lot more frequently.

So you can imagine what happens.

If the birds start catching these guys before they can

reproduce, or maybe while they're reproducing, what's

going to happen?

This guy, the darker dudes, are going to reproduce a lot

more often, and all of a sudden, you're going to have a

lot more moths that look like this.

You're going to have a lot more of these dudes.

So what happened here?

Was there any design or was there any active change by any

of the moths?

Did any of the moths-- I mean, it looks like a really smart

thing to do to become black, right?

Your surroundings became black, and you wait a couple

of generations of these moths, and now all of a sudden, the

moths are black.

And you might say, wow, those moths are geniuses.

They all somehow decided to evolve into black moths in

order to hide from the birds more easily.

But that's not what happened.

You had a lot of variation in your peppered moth population.

And what happened was that when everything turned darker

and darker, these dudes right here-- and dudettes-- had a

lot less success in reproducing.

These guys just reproduced more and more and more, and

these guys got eaten up before they were able to reproduce or

maybe while they were reproducing so that they

couldn't produce as many offspring, and then this trait

just became dominant.

And then the peppered moth just became-- you can kind of

view it as a black moth.

Now, you might say, OK, Sal.

That's one example.

I need more.

This is natural selection.

It's purported to apply to everything.

It purports to explain why we evolved from basic bacteria or

maybe even self-replicating RNA, which I will talk about

more in the future.

I need more evidence of this.

I need to see it in real time.

And the best example of this is really the flu.

And I'll do other videos in the future on what viruses are

and how they replicate.

Viruses are actually fascinating, because it's not

even clear that they're alive.

They're literally just little buckets of DNA and sometimes

RNA, which we'll learn is genetic information, and

they're just contained in these little protein

containers that are these neat geometrical shapes, and that's

all they are.

They're not like regular living organisms that actively

move and that actively have metabolisms and all that.

What they do is they take that little DNA, and they inject it

into other things that can process it, and then they use

that DNA to produce more viruses.

But anyway, we can do a whole series of videos on viruses,

but the flu is a virus.

And what happens every year is you have a certain type a

virus, and they have some variation.

I'll just make the variation by how many dots they have.

And they infect-- let's say it's a human flu.

They infect humans, and slowly our immune systems, which we

can make a whole set of videos on as well, start to recognize

the virus and are able to attack them before they can do

a lot of damage.

So now you can imagine what happens if, let's say, that

this is the current flu.

Let me do all of them.

They all have these little two dots and that's how-- and

we'll talk in the future what these dots are and how they

can be recognized.

But let's say that's how our immune system recognizes them.

They start realizing, oh, any time I get this little green

dude with two dots on it's, that's not a good thing to

have around so I'm going to attack it in some way and

destroy it before he infects my DNA and all the rest. And

so you have a very strong natural selection once immune

systems learn what this virus is-- and we'll talk more about

what learning means for an immune system-- that they'll

start attacking these guys, right?

But flu, you can kind of think of them as being tricky, but

they're not really tricky.

They're not sentient objects, but what they do do is they

constantly change.

So what you have is, in any flu population, you're always