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I think what is probably the most misunderstood concept in

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

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of the most contentious concepts, maybe not in

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

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of evolution.

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

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in the biological context, we imagine that something is

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changing, it is evolving.

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And so when people use the word evolution in our everyday

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

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is going to test my drawing ability-- but you

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see an ape bent over.

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

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

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

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Maybe he's also wearing a hat.

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And then they show this picture where he slowly,

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slowly becomes more and more upright, and eventually, he

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

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

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walking completely upright.

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And it's some kind of implication that walking

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upright is better than not walking upright,

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et cetera, et cetera.

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Oh, he doesn't have a tail anymore.

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Let me eliminate that.

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This guy does have a tail.

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Let me do it in an appropriate width.

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

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drawings skills, but we've all seen this.

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

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

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

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the apes somehow changed into a human being.

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

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biology classes and even the scientific community.

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

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

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

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

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human and so on and so forth.

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And I want to be very clear here.

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Even though this process did happen, that you did have

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creatures that over time accumulated changes that maybe

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their ancestors might have looked more like this, and

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eventually they looked more like this, there was no active

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process going on called evolution.

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

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

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DNA to get enough changes to look more like this.

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And it's not like the DNA knew.

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

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be kind of hunchbacked like an ape.

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

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change into this dude.

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That's not what evolution is.

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

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there was a tree.

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

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fruit at the top of the tree.

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Maybe they're apples.

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

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

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

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because they want to get there, maybe the next

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

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after generation after generation, their necks get

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longer and longer, and eventually

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they turn into giraffes.

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

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implies, although sometimes the everyday notion of the

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word seems to make us think that way.

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

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

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Let me write that word down.

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Natural selection.

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

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

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this is an important keyword here.

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

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If you look at the kids in your

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school, you'll see variation.

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

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have blond hair, some people have black hair,

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so on and so forth.

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There's always variation.

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And what natural selection is is this process that sometimes

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environmental factors will select for certain variation.

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Some variations might not matter at all, but some

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variations matter a lot.

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

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

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peppered moth.

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And this was in pre-Industrial Revolution England that these

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

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draw a moth.

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I think you get the idea.

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Let me draw a couple of them.

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Let me draw a few peppered moths.

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A couple of peppered moths there.

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Let me draw one more.

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So most peppered moths, there was just this variation.

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

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than others.

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So some of them might look like this.

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

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Let me do a white.

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So it had spots like that.

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Some of them might have looked more like that.

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

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And then some of them might have been-- just

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barely have any spots.

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You just have this natural variation.

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

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see some variation in colors.

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Now, they were all happy, probably for thousands of

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years, just this natural variation.

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

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

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

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these factories that are running these steam engines

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powered by coal.

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

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

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Let me draw some tree trunks.

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Maybe there were some tree trunks that used

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to look like this.

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

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

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peppered moth would be pretty OK.

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Maybe there are some tree trunks that were pretty dark.

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But all of a sudden, the Industrial Revolution happens.

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Everything gets covered with soot from the coal being

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burned, and then all of a sudden, all the

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trees look like this.

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

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than they were before.

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

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

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select for these moths?

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

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ability of the birds to see the moths.

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

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blacker than it was before, you can guess

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what's going to happen.

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

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

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

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

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

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guy a lot more frequently.

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So you can imagine what happens.

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If the birds start catching these guys before they can

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

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going to happen?

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

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

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lot more moths that look like this.

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

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So what happened here?

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

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of the moths?

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

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thing to do to become black, right?

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Your surroundings became black, and you wait a couple

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

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moths are black.

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

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They all somehow decided to evolve into black moths in

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order to hide from the birds more easily.

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But that's not what happened.

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

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And what happened was that when everything turned darker

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

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lot less success in reproducing.

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These guys just reproduced more and more and more, and

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

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maybe while they were reproducing so that they

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

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just became dominant.

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

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view it as a black moth.

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Now, you might say, OK, Sal.

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That's one example.

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I need more.

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This is natural selection.

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It's purported to apply to everything.

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It purports to explain why we evolved from basic bacteria or

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

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more in the future.

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I need more evidence of this.

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I need to see it in real time.

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And the best example of this is really the flu.

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

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and how they replicate.

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Viruses are actually fascinating, because it's not

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even clear that they're alive.

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They're literally just little buckets of DNA and sometimes

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

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they're just contained in these little protein

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

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all they are.

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They're not like regular living organisms that actively

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move and that actively have metabolisms and all that.

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

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

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that DNA to produce more viruses.

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

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but the flu is a virus.

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

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virus, and they have some variation.

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

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

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

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

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

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a lot of damage.

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

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this is the current flu.

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Let me do all of them.

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

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

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can be recognized.

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

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

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

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

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

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so you have a very strong natural selection once immune

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

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

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start attacking these guys, right?

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

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they're not really tricky.

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

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constantly change.

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

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having a little bit of change.

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So maybe the great majority of them have those two dots, but

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maybe every now and then, one of them has one dot, one of

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them has three dots, and maybe that's just a random mutation.

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This just randomly happened.

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Maybe this is one in every-- I'll make up a number: One in

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every million of these viruses have this only one dot instead

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of two dots.

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But what's going to happen as soon as the human immune

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system gets used to attacking the virus

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with the two red dots?

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Well, then this guy isn't going to have to compete with

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the other virus capsules for infecting people.

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He's going to have people's DNA all to himself.

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And so he or she, or whatever you want to call this virus,

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is then going to be more successful.

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So by next year's flu season when people start sneezing and

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are able to spread it on doorknobs and whatever else

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again, this guy's going to be the new flu virus.

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So when you see this process of every year there's a new

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flu virus, that is evolution and natural

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selection in real time.

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It is happening.

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It isn't this thing that only happens over eons and eons of

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time, although most of the kind of the substantial things

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that we see in our lives or even ourselves are based on

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these things that happened over eons and eons of time,

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but it happens on a yearly basis.

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Another example is if you think about

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antibiotics and bacteria.

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Bacteria are these little cells that move around, and

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we'll talk more about them.

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They actually are definitely living.

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They have metabolisms and whatever else.

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And this is just a nice note.

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When people talk about infections, it could either be

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a viral infection, which are these things that go and

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infect your DNA and then use your cell mechanisms to

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reproduce, or it could be a bacterial infection, which are

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literally little cells that move around and they release

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toxins that make you sick and whatever else.

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So bacteria, these are what antibiotics kill.

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Actually, I don't think there's a hyphen.

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They attack bacteria.

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They kill them.

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If you know a couple of doctors or whatever and you

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say, hey, I'm sick.

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I think I have a bacterial infection.

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Give me some antibiotics.

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A responsible doctor says no, I won't give you antibiotics

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just willy-nilly, because what happens is, the more

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antibiotics you use, you're more likely to create

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versions-- and I want to be very careful about the word

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create, because you're not actively creating them.

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But let's say-- and let me finish my sentence.

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You're very likely to help select for

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antibiotic-resistant bacterias.

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Now, how does that work?

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Let's say that these are all bacteria and you have

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gazillions of them, right?

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Every now and then, you get one that's

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slightly different, right?

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Now in a population of bacteria, these all will make

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you equally sick, and this is just some random difference in

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the bacteria.

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Maybe on its DNA some slight different changes happened,

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but whatever happened, these all are a kind of bacteria.

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You don't want to get a lot of them in your system.

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Your immune system can attack them and fight them off, but

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if you get a lot of them, then they might kill you or make

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you sick or whatever else.

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Now, if everyone just starts using antibiotics when they're

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not sick or when they don't really need to in a

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life-or-death situation, you might have an antibiotic that

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is really good at killing the green bacteria.

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But what happens if you all of a sudden kill a

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lot the green bacteria?

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Well, now the blue bacteria have the whole ecosystem that

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before it was competing with all these green dudes to get

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at all the good stuff inside of your body, but now he's all

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alone, and now he can replicate willy-nilly.

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So now he's going to replicate willy-nilly, and obviously--

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once again, it wasn't like there was any design, there

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was any intelligent process here that said look, this

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bacteria should-- some bacteria said, oh, I'm going

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to be little bit smarter and design myself to resist this

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antibiotic threat.

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No!

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There's just these random changes that happen, and

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mutations and viruses and bacteria happen frequently and

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these random changes that happen, and this might be a

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one in one billion change, right?

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But all of a sudden, if you start killing off all of the

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people it's competing with, this guy can start replicating

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really fast and then become the dominant bacteria.

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And then all of a sudden, that antibiotic that you had

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developed very carefully to destroy the green dudes is

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useless, and you have this superbug.

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You might have heard the word superbug.

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That's what a superbug is.

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It's not like it designed itself somehow.

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It's just that we got very good at killing its

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competition, and so we allowed it to take over, and we can't

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kill it, because all of the drugs were just good at

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killing its competition.

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These bacteria just keep mutating and keep mutating,

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and if we use these antibiotics a little bit too

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heavily, we'll always be selecting for the things that

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won't be affected by the antibiotics.

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Well, anyway, I think I've spoken long enough, but this

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is a fascinating, fascinating topic.

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And I really wanted to make this my very first video or

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lecture if you will, on biology, because if you really

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went to-- you know, biology is the study of life, and we can

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talk about what life is, whether

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viruses are living, whatnot.

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But if you really want to study living systems, you

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really can't make any assumptions other

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than natural selection.

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We could go to another planet where the creatures don't have

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DNA, or maybe they have some other type of hereditary

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information stored in their cells, or they replicate some

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other way, or they're not even carbon based.

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Maybe they're silicon based.

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And if we went to that type of a planet in order study the

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biology on that planet, everything else we know about

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biology, about viruses and DNA, would be useless.

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But if we do understand this one concept, this one concept

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of natural selection, that your environment will select,

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and it's not-- you know, there's no

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active process here.

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It's just random stuff happened and they randomly

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select for random changes.

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And over large swaths of time, and these are unimaginably

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large swaths of time, those changes essentially

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accumulate, and they might accumulate into fairly, fairly

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significant things.

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We'll talk more about this in another video.

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See you soon.