0:00:00.000,0:00:01.575
When I go to parties,

0:00:01.575,0:00:03.359
it doesn't usually take very long

0:00:03.359,0:00:04.399
for people to find out

0:00:04.399,0:00:07.507
that I'm a scientist and I study sex.

0:00:07.507,0:00:12.408
And then I get asked questions.

0:00:12.408,0:00:15.575
And the questions usually have a very particular format.

0:00:15.575,0:00:16.807
They start with the phrase,

0:00:16.807,0:00:18.708
"A friend told me,"

0:00:18.708,0:00:20.608
and then they end with the phrase,

0:00:20.608,0:00:22.525
"Is this true?"

0:00:22.525,0:00:23.911
And most of the time

0:00:23.911,0:00:26.030
I'm glad to say that I can answer them,

0:00:26.030,0:00:27.877
but sometimes I have to say,

0:00:27.877,0:00:29.010
"I'm really sorry,

0:00:29.010,0:00:30.194
but I don't know

0:00:30.194,0:00:33.278
because I'm not that kind of a doctor."

0:00:33.278,0:00:35.194
That is, I'm not a clinician,

0:00:35.194,0:00:38.385
I'm a comparative biologist who studies anatomy.

0:00:38.385,0:00:41.318
And my job is to look at lots of different species of animals

0:00:41.318,0:00:44.635
and try to figure out how their tissues and organs work

0:00:44.635,0:00:46.136
when everything's going right,

0:00:46.136,0:00:47.754
rather than trying to figure out

0:00:47.754,0:00:49.337
how to fix things when they go wrong,

0:00:49.337,0:00:50.538
like so many of you.

0:00:50.538,0:00:52.937
And what I do is I look for similarities and differences

0:00:52.937,0:00:55.204
in the solutions that they've evolved

0:00:55.204,0:00:56.788
for fundamental biological problems.

0:00:56.788,0:00:58.637
So today I'm here to argue

0:00:58.637,0:01:02.503
that this is not at all

0:01:02.503,0:01:04.404
an esoteric Ivory Tower activity

0:01:04.404,0:01:05.721
that we find at our universities,

0:01:05.721,0:01:07.704
but that broad study

0:01:07.704,0:01:10.656
across species, tissue types and organ systems

0:01:10.656,0:01:12.291
can produce insights

0:01:12.291,0:01:15.675
that have direct implications for human health.

0:01:15.675,0:01:18.173
And this is true both of my recent project

0:01:18.173,0:01:19.897
on sex differences in the brain,

0:01:19.897,0:01:21.816
and my more mature work

0:01:21.816,0:01:24.650
on the anatomy and function of penises.

0:01:24.650,0:01:27.280
And now you know why I'm fun at parties.

0:01:27.280,0:01:28.248
(Laughter)

0:01:28.248,0:01:30.531
So today I'm going to give you an example

0:01:30.531,0:01:32.248
drawn from my penis study

0:01:32.248,0:01:33.865
to show you how knowledge

0:01:33.865,0:01:35.632
drawn from studies of one organ system

0:01:35.632,0:01:38.613
provided insights into a very different one.

0:01:38.613,0:01:41.631
Now I'm sure as everyone in the audience already knows --

0:01:41.631,0:01:45.147
I did have to explain it to my nine-year-old late last week --

0:01:45.147,0:01:48.898
penises are structures that transfer sperm

0:01:48.898,0:01:50.198
from one individual to another.

0:01:50.198,0:01:51.698
And the slide behind me

0:01:51.698,0:01:53.431
barely scratches the surface

0:01:53.431,0:01:55.396
of how widespread they are in animals.

0:01:55.396,0:01:57.381
There's an enormous amount of anatomical variation.

0:01:57.381,0:02:01.255
You find muscular tubes, modified legs, modified fins,

0:02:01.255,0:02:05.101
as well as the mammalian fleshy, inflatable cylinder

0:02:05.101,0:02:06.736
that we're all familiar with --

0:02:06.736,0:02:09.018
or at least half of you are.

0:02:09.018,0:02:11.419
(Laughter)

0:02:11.419,0:02:14.157
And I think we see this tremendous variation

0:02:14.157,0:02:17.308
because it's a really effective solution

0:02:17.308,0:02:19.474
to a very basic biological problem,

0:02:19.474,0:02:21.957
and that is getting sperm in a position

0:02:21.957,0:02:24.509
to meet up with eggs and form zygotes.

0:02:24.509,0:02:28.458
Now the penis isn't actually required for internal fertiliztion,

0:02:28.458,0:02:30.924
but when internal fertilization evolves,

0:02:30.924,0:02:32.924
penises often follow.

0:02:32.924,0:02:37.341
And the question I get when I start talking about this most often is,

0:02:37.341,0:02:40.257
"What made you interested in this subject?"

0:02:40.257,0:02:44.207
And the answer is skeletons.

0:02:44.207,0:02:46.774
You wouldn't think that skeletons and penises

0:02:46.774,0:02:48.625
have very much to do with one another.

0:02:48.625,0:02:50.757
And that's because we tend to think of skeletons

0:02:50.757,0:02:52.407
as stiff lever systems

0:02:52.407,0:02:54.090
that produce speed or power.

0:02:54.090,0:02:57.657
And my first forays into biological research,

0:02:57.657,0:03:00.475
doing dinosaur paleontology as an undergraduate,

0:03:00.475,0:03:02.026
were really squarely in that realm.

0:03:02.026,0:03:05.143
But when I went to graduate school to study biomechanics,

0:03:05.143,0:03:07.608
I really wanted to find a dissertation project

0:03:07.608,0:03:10.507
that would expand our knowledge of skeletal function.

0:03:10.507,0:03:12.309
I tried a bunch of different stuff.

0:03:12.309,0:03:13.957
A lot of it didn't pan out.

0:03:13.957,0:03:15.791
But then one day I started thinking

0:03:15.791,0:03:17.573
about the mammalian penis.

0:03:17.573,0:03:21.591
And it's really an odd sort of structure.

0:03:21.591,0:03:24.408
Before it can be used for internal fertilization,

0:03:24.408,0:03:25.891
its mechanical behavior has to change

0:03:25.891,0:03:27.608
in a really dramatic fashion.

0:03:27.608,0:03:30.206
Most of the time it's a flexible organ.

0:03:30.206,0:03:31.490
It's easy to bend.

0:03:31.490,0:03:33.484
But before it's brought into use

0:03:33.484,0:03:34.702
during copulation

0:03:34.702,0:03:36.460
it has to become rigid,

0:03:36.460,0:03:38.475
it has to become difficult to bend.

0:03:38.475,0:03:40.492
And moreover, it has to work.

0:03:40.492,0:03:43.242
A reproductive system that fails to function

0:03:43.242,0:03:46.557
produces an individual that has no offspring,

0:03:46.557,0:03:49.728
and that individual is then kicked out of the gene pool.

0:03:49.728,0:03:52.189
And so I thought, "Here's a problem

0:03:52.189,0:03:55.437
that just cries out for a skeletal system --

0:03:55.437,0:03:58.649
not one like this one,

0:03:58.649,0:04:01.706
but one like this one --

0:04:01.706,0:04:04.123
because, functionally,

0:04:04.123,0:04:05.690
a skeleton is any system

0:04:05.690,0:04:08.722
that supports tissue and transmits forces.

0:04:08.722,0:04:11.072
And I already knew that animals like this earthworm,

0:04:11.072,0:04:12.518
indeed most animals,

0:04:12.518,0:04:13.811
don't support their tissues

0:04:13.811,0:04:15.605
by draping them over bones.

0:04:15.605,0:04:18.438
Instead they're more like reinforced water balloons.

0:04:18.438,0:04:22.305
They use a skeleton that we call a hydrostatic skeleton.

0:04:22.305,0:04:24.371
And a hydrostatic skeleton

0:04:24.371,0:04:26.289
uses two elements.

0:04:26.289,0:04:28.439
The skeletal support comes from an interaction

0:04:28.439,0:04:30.213
between a pressurized fluid

0:04:30.213,0:04:31.819
and a surrounding wall of tissue

0:04:31.819,0:04:36.290
that's held in tension and reinforced with fibrous proteins.

0:04:36.290,0:04:38.538
And the interaction is crucial.

0:04:38.538,0:04:41.906
Without both elements you have no support.

0:04:41.906,0:04:43.188
If you have fluid

0:04:43.188,0:04:45.222
with no wall to surround it

0:04:45.222,0:04:46.656
and keep pressure up,

0:04:46.656,0:04:48.560
you have a puddle.

0:04:48.560,0:04:50.660
And if you have just the wall

0:04:50.660,0:04:52.394
with no fluid inside of it to put the wall in tension,

0:04:52.394,0:04:54.344
you've got a little wet rag.

0:04:54.344,0:04:56.976
When you look at a penis in cross section,

0:04:56.976,0:04:59.409
it has a lot of the hallmarks

0:04:59.409,0:05:01.459
of a hydrostatic skeleton.

0:05:01.459,0:05:02.968
It has a central space

0:05:02.968,0:05:04.488
of spongy erectile tissue

0:05:04.488,0:05:07.066
that fills with fluid -- in this case blood --

0:05:07.066,0:05:09.465
surrounded by a wall of tissue

0:05:09.465,0:05:13.316
that's rich in a stiff structural protein called collagen.

0:05:13.316,0:05:15.816
But at the time when I started this project,

0:05:15.816,0:05:19.017
the best explanation I could find for penal erection

0:05:19.017,0:05:23.301
was that the wall surrounded these spongy tissues,

0:05:23.301,0:05:25.000
and the spongy tissues filled with blood

0:05:25.000,0:05:28.268
and pressure rose and voila! it became erect.

0:05:28.268,0:05:32.233
And that explained to me expansion --

0:05:32.233,0:05:35.800
made sense: more fluid, you get tissues that expand --

0:05:35.800,0:05:38.817
but it didn't actually explain erection.

0:05:38.817,0:05:42.708
Because there was no mechanism in this explanation

0:05:42.708,0:05:45.675
for making this structure hard to bend.

0:05:45.675,0:05:48.391
And no one had systematically looked at the wall tissue.

0:05:48.391,0:05:50.993
So I thought, wall tissue's important in skeletons.

0:05:50.993,0:05:53.359
It has to be part of the explanation.

0:05:53.359,0:05:55.894
And this was the point

0:05:55.894,0:05:58.491
at which my graduate adviser said,

0:05:58.491,0:06:01.874
"Whoa! Hold on. Slow down."

0:06:01.874,0:06:05.242
Because after about six months of me talking about this,

0:06:05.242,0:06:06.558
I think he finally figured out

0:06:06.558,0:06:09.607
that I was really serious about the penis thing.

0:06:09.607,0:06:12.654
(Laughter)

0:06:12.654,0:06:14.703
So he sat me down, and he warned me.

0:06:14.703,0:06:16.879
He was like, "Be careful going down this path.

0:06:16.879,0:06:19.646
I'm not sure this project's going to pan out."

0:06:19.646,0:06:22.178
Because he was afraid I was walking into a trap.

0:06:22.178,0:06:26.995
I was taking on a socially embarrassing question

0:06:26.995,0:06:29.330
with an answer that he thought

0:06:29.330,0:06:31.712
might not be particularly interesting.

0:06:31.712,0:06:33.245
And that was because

0:06:33.245,0:06:34.763
every hydrostatic skeleton

0:06:34.763,0:06:36.831
that we had found in nature up to that point

0:06:36.831,0:06:38.628
had the same basic elements.

0:06:38.628,0:06:39.845
It had the central fluid,

0:06:39.845,0:06:41.645
it had the surrounding wall,

0:06:41.645,0:06:44.781
and the reinforcing fibers in the wall

0:06:44.781,0:06:47.199
were arranged in crossed helices

0:06:47.199,0:06:49.256
around the long axis of the skeleton.

0:06:49.256,0:06:50.577
So the image behind me

0:06:50.577,0:06:52.206
shows a piece of tissue

0:06:52.206,0:06:54.231
in one of these cross helical skeletons

0:06:54.231,0:06:56.764
cut so that you're looking at the surface of the wall.

0:06:56.764,0:06:58.482
The arrow shows you the long axis.

0:06:58.482,0:07:00.332
And you can see two layers of fibers,

0:07:00.332,0:07:02.033
one in blue and one in yellow,

0:07:02.033,0:07:04.831
arranged in left-handed and right-handed angles.

0:07:04.831,0:07:07.080
And if you weren't just looking at a little section of the fibers,

0:07:07.080,0:07:09.781
those fibers would be going in helices

0:07:09.781,0:07:11.531
around the long axis of the skeleton --

0:07:11.531,0:07:13.664
something like a Chinese finger trap,

0:07:13.664,0:07:15.565
where you stick your fingers in and they get stuck.

0:07:15.565,0:07:18.648
And these skeletons have a particular set of behaviors,

0:07:18.648,0:07:20.680
which I'm going to demonstrate in a film.

0:07:20.680,0:07:21.831
It's a model skeleton

0:07:21.831,0:07:24.014
that I made out of a piece of cloth

0:07:24.014,0:07:26.567
that I wrapped around an inflated balloon.

0:07:26.567,0:07:28.265
The cloth's cut on the bias.

0:07:28.265,0:07:31.014
So you can see that the fibers wrap in helices,

0:07:31.014,0:07:35.326
and those fibers can reorient as the skeleton moves,

0:07:35.326,0:07:36.755
which means the skeleton's flexible.

0:07:36.755,0:07:39.228
It lengthens, shortens and bends really easily

0:07:39.228,0:07:42.775
in response to internal or external forces.

0:07:42.775,0:07:44.071
Now my adviser's concern

0:07:44.071,0:07:46.437
was what if the penile wall tissue

0:07:46.437,0:07:48.111
is just the same as any other hydrostatic skeleton.

0:07:48.111,0:07:50.038
What are you going to contribute?

0:07:50.038,0:07:51.505
What new thing are you contributing

0:07:51.505,0:07:53.153
to our knowledge of biology?

0:07:53.153,0:07:56.571
And I thought, "Yeah, he does have a really good point here."

0:07:56.571,0:07:58.321
So I spent a long, long time thinking about it.

0:07:58.321,0:08:00.455
And one thing kept bothering me,

0:08:00.455,0:08:02.905
and that's, when they're functioning,

0:08:02.905,0:08:04.838
penises don't wiggle.

0:08:04.838,0:08:07.177
(Laughter)

0:08:07.177,0:08:10.078
So something interesting had to be going on.

0:08:10.078,0:08:13.379
So I went ahead, collected wall tissue,

0:08:13.379,0:08:14.978
prepared it so it was erect,

0:08:14.978,0:08:17.177
sectioned it, put it on slides

0:08:17.177,0:08:19.829
and then stuck it under the microscope to have a look,

0:08:19.829,0:08:24.865
fully expecting to see crossed helices of collagen of some variety.

0:08:24.865,0:08:27.263
But instead I saw this.

0:08:27.263,0:08:30.264
There's an outer layer and an inner layer.

0:08:30.264,0:08:32.814
The arrow shows you the long axis of the skeleton.

0:08:32.814,0:08:35.383
I was really surprised at this.

0:08:35.383,0:08:36.328
Everyone I showed it

0:08:36.328,0:08:37.528
was really surprised at this.

0:08:37.528,0:08:39.065
Why was everyone surprised at this?

0:08:39.065,0:08:42.049
That's because we knew theoretically

0:08:42.049,0:08:44.864
that there was another way

0:08:44.864,0:08:47.898
of arranging fibers in a hydrostatic skeleton,

0:08:47.898,0:08:50.169
and that was with fibers at zero degrees

0:08:50.169,0:08:54.035
and 90 degrees to the long axis of the structure.

0:08:54.035,0:08:57.597
The thing is, no one had ever seen it before in nature.

0:08:57.597,0:09:00.297
And now I was looking at one.

0:09:00.297,0:09:03.031
Those fibers in that particular orientation

0:09:03.031,0:09:06.246
give the skeleton a very, very different behavior.

0:09:06.246,0:09:07.431
I'm going to show a model

0:09:07.431,0:09:09.376
made out of exactly the same materials.

0:09:09.376,0:09:11.434
So it'll be made of the same cotton cloth,

0:09:11.434,0:09:14.723
same balloon, same internal pressure.

0:09:14.723,0:09:17.190
But the only difference

0:09:17.190,0:09:19.572
is that the fibers are arranged differently.

0:09:19.572,0:09:22.223
And you'll see that, unlike the cross helical model,

0:09:22.223,0:09:25.173
this model resists extension and contraction

0:09:25.173,0:09:26.624
and resists bending.

0:09:26.624,0:09:27.658
Now what that tells us

0:09:27.658,0:09:29.754
is that wall tissues are doing so much more

0:09:29.754,0:09:32.257
than just covering the vascular tissues.

0:09:32.257,0:09:35.751
They're an integral part of the penile skeleton.

0:09:35.751,0:09:38.288
If the wall around the erectile tissue wasn't there,

0:09:38.288,0:09:40.453
if it wasn't reinforced in this way,

0:09:40.453,0:09:41.605
the shape would change,

0:09:41.605,0:09:43.989
but the inflated penis would not resist bending,

0:09:43.989,0:09:46.036
and erection simply wouldn't work.

0:09:46.036,0:09:48.637
It's an observation with obvious medical applications

0:09:48.637,0:09:50.419
in humans as well,

0:09:50.419,0:09:53.354
but it's also relevant in a broad sense, I think,

0:09:53.354,0:09:55.786
to the design of prosthetics, soft robots,

0:09:55.786,0:09:56.853
basically anything

0:09:56.853,0:10:00.171
where changes of shape and stiffness are important.

0:10:00.171,0:10:01.919
So to sum up:

0:10:01.919,0:10:03.136
Twenty years ago,

0:10:03.136,0:10:04.886
I had a college adviser tell me,

0:10:04.886,0:10:06.937
when I went to the college and said,

0:10:06.937,0:10:08.086
"I'm kind of interested in anatomy,"

0:10:08.086,0:10:09.970
they said, "Anatomy's a dead science."[br]

0:10:09.970,0:10:12.587
He couldn't have been more wrong.

0:10:12.587,0:10:15.320
I really believe that we still have a lot to learn

0:10:15.320,0:10:18.453
about the normal structure and function of our bodies.

0:10:18.453,0:10:21.267
Not just about its genetics and molecular biology,

0:10:21.267,0:10:24.666
but up here in the meat end of the scale.

0:10:24.666,0:10:26.101
We've got limits on our time.

0:10:26.101,0:10:28.366
We often focus on one disease,

0:10:28.366,0:10:29.550
one model, one problem,

0:10:29.550,0:10:31.124
but my experience suggests

0:10:31.124,0:10:32.902
that we should take the time

0:10:32.902,0:10:35.467
to apply ideas broadly between systems

0:10:35.467,0:10:37.341
and just see where it takes us.

0:10:37.341,0:10:40.941
After all, if ideas about invertebrate skeletons

0:10:40.941,0:10:42.407
can give us insights

0:10:42.407,0:10:44.492
about mammalian reproductive systems,

0:10:44.492,0:10:48.541
there could be lots of other wild and productive connections

0:10:48.541,0:10:50.990
lurking out there just waiting to be found.

0:10:50.990,0:10:52.842
Thank you.

0:10:52.842,0:10:56.230
(Applause)