Name: 進化の証拠 (Evidence for Evolution)
Uploaded: 2021-01-14T05:47:18.000Z
Duration: 13 min 4 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Hi. It's Mr. Andersen and welcome to Biology Essentials video number 4. This

is on Scientific Evidence for Evolution. Here is a picture of Charles Darwin much later

程度の副詞

in life. Charles Darwin was a very meticulous scientist. He gathered copious amounts of

data and to show that evolution was true and that his mechanism of natural selection was

right. Unfortunately he did not have a real good understanding of genetics and DNA obviously

was not around back then, but the scientific evidence for evolution right now is pretty

overwhelming. Some of the things he could have pointed to were fossil records. This

is a baleen whale. If you look at the fin of a baleen whale it almost looks exactly

like the bone structure in the human arm, which suggests that both I and the whale have

a common ancestor that had bone structure similar like that. Or you could look at the

rear legs. Why would a whale have rear legs unless at one point it actually walked on

land and evolved from something like that. And so today what I am going to talk about

is evidence for evolution. So what is evolution again? It's just changes in the gene pool.

But specifically here we're not only talking about microevolution but macroevolution as

well. First I'm going to talk about three things that were available to Darwin, and

he talked about. Number one is Biogeography, in other words where living things are found.

I'll talk specifically about the Galapagos Tortoises. Next he talked about fossils. An

example I'll give you is horse evolution over time. Next, homologies or those are characteristics

organisms have that show common ancestry. I'll talk about both homologous structures

and vestigial structures. And then I am going to talk on a few things that Darwin didn't

have available to him. Mainly molecular evidence - DNA is the trump card when it comes to evidence

as far as evolution goes. And finally I am going to show you how we can use mathematical

models to support our models for how evolution actually takes place. So we've got a lot to

do so I better get started. Let's start with where Darwin started, on the Galapagos formulating

his ideas. And I have been here as well. And to see these tortoises the first time is pretty

amazing. Darwin's idea was that the giant tortoises on the Galapagos had moved from

here out to the Galapagos. And so it had to float there, make it someway from the mainland

to the Galapagos. And when he looked at the tortoise in Ecuador it looks very similar.

There's no predators and so they are able to get very, very big. You can see there

are clear differences in the size of the tortoises and more in their structure of their shell.

Tortoises that come from really barren areas actually have a longer neck and what's called

a saddle shape versus a dome shape. This is one from the highlands of Santa Cruz and this

one is from San Cristobal. Now why do we just find tortoises there? Well there was a founding

population that actually moved there. Now before Darwin most scientists at that time

believed in special creation, that God had placed everything specifically on the island

where it was. And Darwin, when he went to the Galapagos and started to see these islands

and the similarities but also differences between those he started to realize that life

and where life is found, we call that biogeography, is big evidence for evolution. Example, South

America used to be connected to Australia. And we had a certain type of mammal there

called marsupial mammals. We had eutherian mammals up here on the top. And when those

two came together there was a war of the mammals. And eutherians really did fairly well and

wiped out a lot of the marsupials that were there. But Australia, as it remained adrift

kept those marsupials there. So it would be another example of biogeography. Next we could

look at the fossils. It's surprising how much fossil evidence we actually have, because

it's hard to create a fossil. The geologic properties required for that are pretty tough.

A great example would be in horse evolution. Through time horses have gotten larger and

larger and larger as their environment has changed and they move from more of a browsing

to more of a grazing kind of animal. But we can see that growth reflected in the change

in the fossil record. In other words the teeth become flatter. They have to run faster when

they're out on the plains. And so they move from many digits to just one digit. And so

we can see this transition. It's not linear, it's branched. In other words if we look at

horse evolution there are many dead ends, there are many branch points. But we can see

that there is a continuous thread all the way from those first horses to the horses

that we have today. So horse evidence, fossil evidence is really good. There's a surprising

amount of data on whale and whale evolution if you are interested in that you can take

a look. Next is, and Darwin talked about this as well. In fact he actually mentioned this

and I've got a big one of these. This is called a Darwin's tubercle, which is like a little,

I do not know if you can see that, where your ear is and what it suggests is that we share

ancestry with other primates who have this bump there as well. Homology or homologous

means that they come from the same ancestry. And so this would be a human arm, this would

be a dog leg, this would be a pigeon wing and this would be a fin of a whale. And if

you look at it you could definitely if you are an engineer design a wing more efficiently

then this wing right here but natural selection started with an organism that had the same

bone structure and so it's used that bone structure and it's manipulated it to make

the appendage that we have today. Vestigial structures are another thing that I could

talk about briefly. Vestigial structures are structures that once had and did something

but don't do anything anymore. An example would be goosebumps. I get goosebumps when

I get scared or when I get cold, but I don't have a lot of fur, so it doesn't make me large

and it doesn't give me much insulation. Wisdom teeth, a primitive tail, all those things

are vestigial structures, an appendix, and they point to an ancestor that actually used

those but has lost them over time. And so anatomy gives us huge pieces of evidence for

evolution. But the one thing that Darwin didn't have was DNA. And so the best way to talk

about DNA to start is to talk about the telephone game. If you've ever played the telephone

game, essentially what you do is you start with a phrase, let's say, "the fat cat ate

the rat". And then this phrase is going to be whispered to the second person in line,

who will whisper it to the third person in line. But let's say the third person in line

here, we'll call this person yellow, makes a mistake. Instead of saying "the fact cate

ate the rat", said "the fat car at the rat". Now that's message, that's the DNA. And so

when that DNA is copied again, that mutation is copied on as well. So "the fat car ate

the rat". So that goes over here to pink. Pink does a nice job of passing it on but

then eventually we get another mutation here. So we get a red mutation. And now it's "the

fat car ate the bat" And now "the fat car ate the bat" and finally "the far car ate

the bat". So when we get to the end the DNA is very similar but it's changed a little

bit. And each of these are a mutation. We could call that the yellow mutation, the red

mutation and then the purple mutation. And so life started with one strand of DNA. And

all living things on our planet have that same DNA but these mutations have accumulated over

time and so they tell us a lot about who's related to whom. In other words if you were

to just tell me what the message is and you had this mutation here in yellow but you didn't

have the red one, I could kind of place where you are and who you were standing next to.

And so if Darwin had evidence related to DNA it would have been a lot, he would have had

a better, an easier job convincing other people that he's right. So let's talk about some

specific DNA evidence. An example I am going to give you here is the Human FGF2 gene. Over

the last 10 years we have started sequencing huge genomes. And a genome, remember is the

sequence of all the DNA inside that one living organism. The one I am going to look at is

one that makes fibroblasts, so it's helpful in healing of wounds. And so we are going

to go to this website (http://uswest.ensembl.org/index.html) right here and we're going to take a look at,

let's go right here, we're going to take a look at this gene. So this is the human gene,

FGF2. It's found on chromosome 4 and you can tell like how many base pairs, it's 6000 letters

long. It tells me where exactly it is. We've learned so much. We could actually look at

all the letters in that gene. Each of these red ones here would be an axon, so not really