WEBVTT 00:00:00.000 --> 00:00:01.575 When I go to parties, 00:00:01.575 --> 00:00:03.359 it doesn't usually take very long 00:00:03.359 --> 00:00:04.399 for people to find out 00:00:04.399 --> 00:00:07.507 that I'm a scientist and I study sex. 00:00:07.507 --> 00:00:12.408 And then I get asked questions. 00:00:12.408 --> 00:00:15.575 And the questions usually have a very particular format. 00:00:15.575 --> 00:00:16.807 They start with the phrase, 00:00:16.807 --> 00:00:18.708 "A friend told me," 00:00:18.708 --> 00:00:20.608 and then they end with the phrase, 00:00:20.608 --> 00:00:22.525 "Is this true?" 00:00:22.525 --> 00:00:23.911 And most of the time 00:00:23.911 --> 00:00:26.030 I'm glad to say that I can answer them, 00:00:26.030 --> 00:00:27.877 but sometimes I have to say, 00:00:27.877 --> 00:00:29.010 "I'm really sorry, 00:00:29.010 --> 00:00:30.194 but I don't know 00:00:30.194 --> 00:00:33.278 because I'm not that kind of a doctor." NOTE Paragraph 00:00:33.278 --> 00:00:35.194 That is, I'm not a clinician, 00:00:35.194 --> 00:00:38.385 I'm a comparative biologist who studies anatomy. 00:00:38.385 --> 00:00:41.318 And my job is to look at lots of different species of animals 00:00:41.318 --> 00:00:44.635 and try to figure out how their tissues and organs work 00:00:44.635 --> 00:00:46.136 when everything's going right, 00:00:46.136 --> 00:00:47.754 rather than trying to figure out 00:00:47.754 --> 00:00:49.337 how to fix things when they go wrong, 00:00:49.337 --> 00:00:50.538 like so many of you. 00:00:50.538 --> 00:00:52.937 And what I do is I look for similarities and differences 00:00:52.937 --> 00:00:55.204 in the solutions that they've evolved 00:00:55.204 --> 00:00:56.788 for fundamental biological problems. NOTE Paragraph 00:00:56.788 --> 00:00:58.637 So today I'm here to argue 00:00:58.637 --> 00:01:02.503 that this is not at all 00:01:02.503 --> 00:01:04.404 an esoteric Ivory Tower activity 00:01:04.404 --> 00:01:05.721 that we find at our universities, 00:01:05.721 --> 00:01:07.704 but that broad study 00:01:07.704 --> 00:01:10.656 across species, tissue types and organ systems 00:01:10.656 --> 00:01:12.291 can produce insights 00:01:12.291 --> 00:01:15.675 that have direct implications for human health. 00:01:15.675 --> 00:01:18.173 And this is true both of my recent project 00:01:18.173 --> 00:01:19.897 on sex differences in the brain, 00:01:19.897 --> 00:01:21.816 and my more mature work 00:01:21.816 --> 00:01:24.650 on the anatomy and function of penises. 00:01:24.650 --> 00:01:27.280 And now you know why I'm fun at parties. NOTE Paragraph 00:01:27.280 --> 00:01:28.248 (Laughter) NOTE Paragraph 00:01:28.248 --> 00:01:30.531 So today I'm going to give you an example 00:01:30.531 --> 00:01:32.248 drawn from my penis study 00:01:32.248 --> 00:01:33.865 to show you how knowledge 00:01:33.865 --> 00:01:35.632 drawn from studies of one organ system 00:01:35.632 --> 00:01:38.613 provided insights into a very different one. 00:01:38.613 --> 00:01:41.631 Now I'm sure as everyone in the audience already knows -- 00:01:41.631 --> 00:01:45.147 I did have to explain it to my nine-year-old late last week -- 00:01:45.147 --> 00:01:48.898 penises are structures that transfer sperm 00:01:48.898 --> 00:01:50.198 from one individual to another. 00:01:50.198 --> 00:01:51.698 And the slide behind me 00:01:51.698 --> 00:01:53.431 barely scratches the surface 00:01:53.431 --> 00:01:55.396 of how widespread they are in animals. 00:01:55.396 --> 00:01:57.381 There's an enormous amount of anatomical variation. 00:01:57.381 --> 00:02:01.255 You find muscular tubes, modified legs, modified fins, 00:02:01.255 --> 00:02:05.101 as well as the mammalian fleshy, inflatable cylinder 00:02:05.101 --> 00:02:06.736 that we're all familiar with -- 00:02:06.736 --> 00:02:09.018 or at least half of you are. NOTE Paragraph 00:02:09.018 --> 00:02:11.419 (Laughter) NOTE Paragraph 00:02:11.419 --> 00:02:14.157 And I think we see this tremendous variation 00:02:14.157 --> 00:02:17.308 because it's a really effective solution 00:02:17.308 --> 00:02:19.474 to a very basic biological problem, 00:02:19.474 --> 00:02:21.957 and that is getting sperm in a position 00:02:21.957 --> 00:02:24.509 to meet up with eggs and form zygotes. 00:02:24.509 --> 00:02:28.458 Now the penis isn't actually required for internal fertiliztion, 00:02:28.458 --> 00:02:30.924 but when internal fertilization evolves, 00:02:30.924 --> 00:02:32.924 penises often follow. NOTE Paragraph 00:02:32.924 --> 00:02:37.341 And the question I get when I start talking about this most often is, 00:02:37.341 --> 00:02:40.257 "What made you interested in this subject?" 00:02:40.257 --> 00:02:44.207 And the answer is skeletons. 00:02:44.207 --> 00:02:46.774 You wouldn't think that skeletons and penises 00:02:46.774 --> 00:02:48.625 have very much to do with one another. 00:02:48.625 --> 00:02:50.757 And that's because we tend to think of skeletons 00:02:50.757 --> 00:02:52.407 as stiff lever systems 00:02:52.407 --> 00:02:54.090 that produce speed or power. 00:02:54.090 --> 00:02:57.657 And my first forays into biological research, 00:02:57.657 --> 00:03:00.475 doing dinosaur paleontology as an undergraduate, 00:03:00.475 --> 00:03:02.026 were really squarely in that realm. NOTE Paragraph 00:03:02.026 --> 00:03:05.143 But when I went to graduate school to study biomechanics, 00:03:05.143 --> 00:03:07.608 I really wanted to find a dissertation project 00:03:07.608 --> 00:03:10.507 that would expand our knowledge of skeletal function. 00:03:10.507 --> 00:03:12.309 I tried a bunch of different stuff. 00:03:12.309 --> 00:03:13.957 A lot of it didn't pan out. 00:03:13.957 --> 00:03:15.791 But then one day I started thinking 00:03:15.791 --> 00:03:17.573 about the mammalian penis. 00:03:17.573 --> 00:03:21.591 And it's really an odd sort of structure. 00:03:21.591 --> 00:03:24.408 Before it can be used for internal fertilization, 00:03:24.408 --> 00:03:25.891 its mechanical behavior has to change 00:03:25.891 --> 00:03:27.608 in a really dramatic fashion. 00:03:27.608 --> 00:03:30.206 Most of the time it's a flexible organ. 00:03:30.206 --> 00:03:31.490 It's easy to bend. 00:03:31.490 --> 00:03:33.484 But before it's brought into use 00:03:33.484 --> 00:03:34.702 during copulation 00:03:34.702 --> 00:03:36.460 it has to become rigid, 00:03:36.460 --> 00:03:38.475 it has to become difficult to bend. 00:03:38.475 --> 00:03:40.492 And moreover, it has to work. 00:03:40.492 --> 00:03:43.242 A reproductive system that fails to function 00:03:43.242 --> 00:03:46.557 produces an individual that has no offspring, 00:03:46.557 --> 00:03:49.728 and that individual is then kicked out of the gene pool. NOTE Paragraph 00:03:49.728 --> 00:03:52.189 And so I thought, "Here's a problem 00:03:52.189 --> 00:03:55.437 that just cries out for a skeletal system -- 00:03:55.437 --> 00:03:58.649 not one like this one, 00:03:58.649 --> 00:04:01.706 but one like this one -- 00:04:01.706 --> 00:04:04.123 because, functionally, 00:04:04.123 --> 00:04:05.690 a skeleton is any system 00:04:05.690 --> 00:04:08.722 that supports tissue and transmits forces. 00:04:08.722 --> 00:04:11.072 And I already knew that animals like this earthworm, 00:04:11.072 --> 00:04:12.518 indeed most animals, 00:04:12.518 --> 00:04:13.811 don't support their tissues 00:04:13.811 --> 00:04:15.605 by draping them over bones. 00:04:15.605 --> 00:04:18.438 Instead they're more like reinforced water balloons. 00:04:18.438 --> 00:04:22.305 They use a skeleton that we call a hydrostatic skeleton. 00:04:22.305 --> 00:04:24.371 And a hydrostatic skeleton 00:04:24.371 --> 00:04:26.289 uses two elements. 00:04:26.289 --> 00:04:28.439 The skeletal support comes from an interaction 00:04:28.439 --> 00:04:30.213 between a pressurized fluid 00:04:30.213 --> 00:04:31.819 and a surrounding wall of tissue 00:04:31.819 --> 00:04:36.290 that's held in tension and reinforced with fibrous proteins. 00:04:36.290 --> 00:04:38.538 And the interaction is crucial. 00:04:38.538 --> 00:04:41.906 Without both elements you have no support. 00:04:41.906 --> 00:04:43.188 If you have fluid 00:04:43.188 --> 00:04:45.222 with no wall to surround it 00:04:45.222 --> 00:04:46.656 and keep pressure up, 00:04:46.656 --> 00:04:48.560 you have a puddle. 00:04:48.560 --> 00:04:50.660 And if you have just the wall 00:04:50.660 --> 00:04:52.394 with no fluid inside of it to put the wall in tension, 00:04:52.394 --> 00:04:54.344 you've got a little wet rag. NOTE Paragraph 00:04:54.344 --> 00:04:56.976 When you look at a penis in cross section, 00:04:56.976 --> 00:04:59.409 it has a lot of the hallmarks 00:04:59.409 --> 00:05:01.459 of a hydrostatic skeleton. 00:05:01.459 --> 00:05:02.968 It has a central space 00:05:02.968 --> 00:05:04.488 of spongy erectile tissue 00:05:04.488 --> 00:05:07.066 that fills with fluid -- in this case blood -- 00:05:07.066 --> 00:05:09.465 surrounded by a wall of tissue 00:05:09.465 --> 00:05:13.316 that's rich in a stiff structural protein called collagen. NOTE Paragraph 00:05:13.316 --> 00:05:15.816 But at the time when I started this project, 00:05:15.816 --> 00:05:19.017 the best explanation I could find for penal erection 00:05:19.017 --> 00:05:23.301 was that the wall surrounded these spongy tissues, 00:05:23.301 --> 00:05:25.000 and the spongy tissues filled with blood 00:05:25.000 --> 00:05:28.268 and pressure rose and voila! it became erect. NOTE Paragraph 00:05:28.268 --> 00:05:32.233 And that explained to me expansion -- 00:05:32.233 --> 00:05:35.800 made sense: more fluid, you get tissues that expand -- 00:05:35.800 --> 00:05:38.817 but it didn't actually explain erection. 00:05:38.817 --> 00:05:42.708 Because there was no mechanism in this explanation 00:05:42.708 --> 00:05:45.675 for making this structure hard to bend. 00:05:45.675 --> 00:05:48.391 And no one had systematically looked at the wall tissue. 00:05:48.391 --> 00:05:50.993 So I thought, wall tissue's important in skeletons. 00:05:50.993 --> 00:05:53.359 It has to be part of the explanation. NOTE Paragraph 00:05:53.359 --> 00:05:55.894 And this was the point 00:05:55.894 --> 00:05:58.491 at which my graduate adviser said, 00:05:58.491 --> 00:06:01.874 "Whoa! Hold on. Slow down." 00:06:01.874 --> 00:06:05.242 Because after about six months of me talking about this, 00:06:05.242 --> 00:06:06.558 I think he finally figured out 00:06:06.558 --> 00:06:09.607 that I was really serious about the penis thing. NOTE Paragraph 00:06:09.607 --> 00:06:12.654 (Laughter) NOTE Paragraph 00:06:12.654 --> 00:06:14.703 So he sat me down, and he warned me. 00:06:14.703 --> 00:06:16.879 He was like, "Be careful going down this path. 00:06:16.879 --> 00:06:19.646 I'm not sure this project's going to pan out." 00:06:19.646 --> 00:06:22.178 Because he was afraid I was walking into a trap. 00:06:22.178 --> 00:06:26.995 I was taking on a socially embarrassing question 00:06:26.995 --> 00:06:29.330 with an answer that he thought 00:06:29.330 --> 00:06:31.712 might not be particularly interesting. 00:06:31.712 --> 00:06:33.245 And that was because 00:06:33.245 --> 00:06:34.763 every hydrostatic skeleton 00:06:34.763 --> 00:06:36.831 that we had found in nature up to that point 00:06:36.831 --> 00:06:38.628 had the same basic elements. 00:06:38.628 --> 00:06:39.845 It had the central fluid, 00:06:39.845 --> 00:06:41.645 it had the surrounding wall, 00:06:41.645 --> 00:06:44.781 and the reinforcing fibers in the wall 00:06:44.781 --> 00:06:47.199 were arranged in crossed helices 00:06:47.199 --> 00:06:49.256 around the long axis of the skeleton. NOTE Paragraph 00:06:49.256 --> 00:06:50.577 So the image behind me 00:06:50.577 --> 00:06:52.206 shows a piece of tissue 00:06:52.206 --> 00:06:54.231 in one of these cross helical skeletons 00:06:54.231 --> 00:06:56.764 cut so that you're looking at the surface of the wall. 00:06:56.764 --> 00:06:58.482 The arrow shows you the long axis. 00:06:58.482 --> 00:07:00.332 And you can see two layers of fibers, 00:07:00.332 --> 00:07:02.033 one in blue and one in yellow, 00:07:02.033 --> 00:07:04.831 arranged in left-handed and right-handed angles. 00:07:04.831 --> 00:07:07.080 And if you weren't just looking at a little section of the fibers, 00:07:07.080 --> 00:07:09.781 those fibers would be going in helices 00:07:09.781 --> 00:07:11.531 around the long axis of the skeleton -- 00:07:11.531 --> 00:07:13.664 something like a Chinese finger trap, 00:07:13.664 --> 00:07:15.565 where you stick your fingers in and they get stuck. NOTE Paragraph 00:07:15.565 --> 00:07:18.648 And these skeletons have a particular set of behaviors, 00:07:18.648 --> 00:07:20.680 which I'm going to demonstrate in a film. 00:07:20.680 --> 00:07:21.831 It's a model skeleton 00:07:21.831 --> 00:07:24.014 that I made out of a piece of cloth 00:07:24.014 --> 00:07:26.567 that I wrapped around an inflated balloon. 00:07:26.567 --> 00:07:28.265 The cloth's cut on the bias. 00:07:28.265 --> 00:07:31.014 So you can see that the fibers wrap in helices, 00:07:31.014 --> 00:07:35.326 and those fibers can reorient as the skeleton moves, 00:07:35.326 --> 00:07:36.755 which means the skeleton's flexible. 00:07:36.755 --> 00:07:39.228 It lengthens, shortens and bends really easily 00:07:39.228 --> 00:07:42.775 in response to internal or external forces. NOTE Paragraph 00:07:42.775 --> 00:07:44.071 Now my adviser's concern 00:07:44.071 --> 00:07:46.437 was what if the penile wall tissue 00:07:46.437 --> 00:07:48.111 is just the same as any other hydrostatic skeleton. 00:07:48.111 --> 00:07:50.038 What are you going to contribute? 00:07:50.038 --> 00:07:51.505 What new thing are you contributing 00:07:51.505 --> 00:07:53.153 to our knowledge of biology? 00:07:53.153 --> 00:07:56.571 And I thought, "Yeah, he does have a really good point here." 00:07:56.571 --> 00:07:58.321 So I spent a long, long time thinking about it. 00:07:58.321 --> 00:08:00.455 And one thing kept bothering me, 00:08:00.455 --> 00:08:02.905 and that's, when they're functioning, 00:08:02.905 --> 00:08:04.838 penises don't wiggle. 00:08:04.838 --> 00:08:07.177 (Laughter) 00:08:07.177 --> 00:08:10.078 So something interesting had to be going on. NOTE Paragraph 00:08:10.078 --> 00:08:13.379 So I went ahead, collected wall tissue, 00:08:13.379 --> 00:08:14.978 prepared it so it was erect, 00:08:14.978 --> 00:08:17.177 sectioned it, put it on slides 00:08:17.177 --> 00:08:19.829 and then stuck it under the microscope to have a look, 00:08:19.829 --> 00:08:24.865 fully expecting to see crossed helices of collagen of some variety. 00:08:24.865 --> 00:08:27.263 But instead I saw this. 00:08:27.263 --> 00:08:30.264 There's an outer layer and an inner layer. 00:08:30.264 --> 00:08:32.814 The arrow shows you the long axis of the skeleton. NOTE Paragraph 00:08:32.814 --> 00:08:35.383 I was really surprised at this. 00:08:35.383 --> 00:08:36.328 Everyone I showed it 00:08:36.328 --> 00:08:37.528 was really surprised at this. 00:08:37.528 --> 00:08:39.065 Why was everyone surprised at this? 00:08:39.065 --> 00:08:42.049 That's because we knew theoretically 00:08:42.049 --> 00:08:44.864 that there was another way 00:08:44.864 --> 00:08:47.898 of arranging fibers in a hydrostatic skeleton, 00:08:47.898 --> 00:08:50.169 and that was with fibers at zero degrees 00:08:50.169 --> 00:08:54.035 and 90 degrees to the long axis of the structure. 00:08:54.035 --> 00:08:57.597 The thing is, no one had ever seen it before in nature. 00:08:57.597 --> 00:09:00.297 And now I was looking at one. NOTE Paragraph 00:09:00.297 --> 00:09:03.031 Those fibers in that particular orientation 00:09:03.031 --> 00:09:06.246 give the skeleton a very, very different behavior. 00:09:06.246 --> 00:09:07.431 I'm going to show a model 00:09:07.431 --> 00:09:09.376 made out of exactly the same materials. 00:09:09.376 --> 00:09:11.434 So it'll be made of the same cotton cloth, 00:09:11.434 --> 00:09:14.723 same balloon, same internal pressure. 00:09:14.723 --> 00:09:17.190 But the only difference 00:09:17.190 --> 00:09:19.572 is that the fibers are arranged differently. 00:09:19.572 --> 00:09:22.223 And you'll see that, unlike the cross helical model, 00:09:22.223 --> 00:09:25.173 this model resists extension and contraction 00:09:25.173 --> 00:09:26.624 and resists bending. NOTE Paragraph 00:09:26.624 --> 00:09:27.658 Now what that tells us 00:09:27.658 --> 00:09:29.754 is that wall tissues are doing so much more 00:09:29.754 --> 00:09:32.257 than just covering the vascular tissues. 00:09:32.257 --> 00:09:35.751 They're an integral part of the penile skeleton. 00:09:35.751 --> 00:09:38.288 If the wall around the erectile tissue wasn't there, 00:09:38.288 --> 00:09:40.453 if it wasn't reinforced in this way, 00:09:40.453 --> 00:09:41.605 the shape would change, 00:09:41.605 --> 00:09:43.989 but the inflated penis would not resist bending, 00:09:43.989 --> 00:09:46.036 and erection simply wouldn't work. NOTE Paragraph 00:09:46.036 --> 00:09:48.637 It's an observation with obvious medical applications 00:09:48.637 --> 00:09:50.419 in humans as well, 00:09:50.419 --> 00:09:53.354 but it's also relevant in a broad sense, I think, 00:09:53.354 --> 00:09:55.786 to the design of prosthetics, soft robots, 00:09:55.786 --> 00:09:56.853 basically anything 00:09:56.853 --> 00:10:00.171 where changes of shape and stiffness are important. NOTE Paragraph 00:10:00.171 --> 00:10:01.919 So to sum up: 00:10:01.919 --> 00:10:03.136 Twenty years ago, 00:10:03.136 --> 00:10:04.886 I had a college adviser tell me, 00:10:04.886 --> 00:10:06.937 when I went to the college and said, 00:10:06.937 --> 00:10:08.086 "I'm kind of interested in anatomy," 00:10:08.086 --> 00:10:09.970 they said, "Anatomy's a dead science." 00:10:09.970 --> 00:10:12.587 He couldn't have been more wrong. 00:10:12.587 --> 00:10:15.320 I really believe that we still have a lot to learn 00:10:15.320 --> 00:10:18.453 about the normal structure and function of our bodies. 00:10:18.453 --> 00:10:21.267 Not just about its genetics and molecular biology, 00:10:21.267 --> 00:10:24.666 but up here in the meat end of the scale. 00:10:24.666 --> 00:10:26.101 We've got limits on our time. 00:10:26.101 --> 00:10:28.366 We often focus on one disease, 00:10:28.366 --> 00:10:29.550 one model, one problem, 00:10:29.550 --> 00:10:31.124 but my experience suggests 00:10:31.124 --> 00:10:32.902 that we should take the time 00:10:32.902 --> 00:10:35.467 to apply ideas broadly between systems 00:10:35.467 --> 00:10:37.341 and just see where it takes us. 00:10:37.341 --> 00:10:40.941 After all, if ideas about invertebrate skeletons 00:10:40.941 --> 00:10:42.407 can give us insights 00:10:42.407 --> 00:10:44.492 about mammalian reproductive systems, 00:10:44.492 --> 00:10:48.541 there could be lots of other wild and productive connections 00:10:48.541 --> 00:10:50.990 lurking out there just waiting to be found. NOTE Paragraph 00:10:50.990 --> 00:10:52.842 Thank you. NOTE Paragraph 00:10:52.842 --> 00:10:56.230 (Applause)