0:00

The story starts with a student

0:02

in my lab. His name is

0:04

Beau Shia. Beau got

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injured while sitting in

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a car, so he moved over and

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he sat, unfortunately, on a belt buckle,

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and he injured his tailbone. It

0:16

all sort of culminated in a very

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simple question. How did we

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lose our tail? The

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chimpanzee, they don't have a tail. The

0:25

gorilla doesn't have a tail.

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But if you go to more distantly

0:29

related, like the macaque monkey, the macaque

0:31

monkey, of course, still has a tail.

0:34

Is one way to try and find out why

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we even had a tail historically,

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and how these other animals have a tail? Is it

0:42

you go and look at them and ask, well, what

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genes have they got that might make them have a

0:47

tail? Because then you can ask, well, are

0:49

they different in us? Right. So

0:51

what Beau did is he

0:53

studied the genome using a genome

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browser that allows him to see

0:58

very conveniently what does our

1:00

genome look like, and particularly what does it

1:02

look like when you compare it to the

1:04

genomes of other animals like the macaque monkey,

1:07

like the gorilla, and the chimpanzee.

1:10

And what he saw

1:12

is that there is a

1:14

particular element that's in

1:17

a region that doesn't look like it would

1:19

be important. It doesn't look like

1:21

it would be very disruptive. However,

1:23

it had three interesting

1:25

things about it. One,

1:28

it was in this gene that was known

1:30

for a very long time that it's

1:33

responsible for the tail. Two,

1:36

it's an element that we could see

1:38

is at the right time. Why is

1:40

it at the right time? Because all

1:42

the animals that have this change don't

1:45

have a tail, and all the animals

1:47

that do still have a tail lack

1:50

this element. So it was the right

1:52

pattern. And three,

1:55

knowing molecular biology, Beau could see

1:57

that that actually would be highly

1:59

disruptive. So now Bo had a hypothesis.

2:02

This change, that

2:04

is how we lost our tail. So

2:07

in summary then, you home in on this region

2:09

of the DNA which we know is linked

2:12

to animals having tails or

2:15

tail function. And

2:17

in animals that appear not to have

2:19

a tail, there is a region of

2:21

that gene which has a change in

2:23

it. And it's

2:26

in all the animals that don't

2:28

have a tail. And it appears

2:31

in such a way that it would disrupt or

2:33

affect how that gene would work, which that does

2:35

look like a smoking gun genetically then. Exactly.

2:38

So now the question is, what do you

2:40

do with this? Bo and

2:42

I sat down together and we designed this

2:44

experiment where we

2:46

would generate mice that

2:48

have exactly the same

2:51

kind of mutation that we saw

2:53

that we have. And the

2:55

prediction would be that if you make

2:58

mice like that, they would also lose

3:00

their own tail. And

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do they? If you introduce this same

3:04

change into a mouse, do you end

3:06

up with mice with truncated or absent

3:08

tails? You know they do.

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And I still get goosebumps every

3:12

time I think about it. They do.

3:14

They're born without a tail. And although

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it took years of work, four years

3:19

of generating mice and studying them, what

3:22

we saw was that

3:24

there's a correspondence between how much

3:26

disruption we put in and the

3:29

length of the tail. Now

3:32

most things that get fixed in evolution confer

3:35

some kind of advantage.

3:37

So on the one hand we lose a

3:39

tail and gain tail-less-ness.

3:42

So what would have been the advantage

3:44

that would have meant this was so

3:46

strongly selected for in the group of

3:49

animals that were our ancestors back in

3:51

history. It was 25 million years

3:53

ago, so we'll never know for

3:55

sure. The way we speculate it is that

3:57

actually it could very well be the...

4:00

this mutation was the

4:02

fundamental mutation that led

4:05

to us sitting down here and

4:07

talking on the Naked Scientists podcast

4:09

that facilitated us to come down

4:12

from the trees and have

4:14

a life on the ground

4:16

where we now stand on our two feet.

4:20

One issue though is that that part

4:22

of the body, how we form the

4:24

backbone and the spinal cord that overlays

4:26

it, there is a

4:28

small group of unfortunate people in

4:30

the population who suffer neural tube

4:33

defects, the conditioned spina bifida, where

4:35

the tube that forms the spinal

4:37

column doesn't close up properly at

4:39

one end, the tail end. Now

4:41

does this link up with or

4:44

is that associated with this particular gene and

4:46

is there therefore a risk if you disrupt

4:48

it that you're going to get more of that

4:50

happening? Yeah, you know this

4:52

was a completely unexpected

4:55

aspect of this project

4:57

that when we made the mice

5:00

with those mutations, some of them

5:02

were born with a

5:04

condition that looked remarkably similar to

5:06

the human condition that you mentioned

5:08

with neural tube defects. And

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I think now it

5:13

could lead to a series of

5:16

new studies that promise to

5:18

make some kind of advancements on how we

5:20

treat this disease. And yet that's the magic

5:23

of science that if you

5:25

let people follow their curiosity,

5:27

it will lead

5:29

to interesting places that are just unpredictable.