Short-tail Alpine garter snake

Transcription

[ Applause ] >> Okay thanks for that. Let's [inaudible] a bit. Okay, the title of the talk is, the "Snails in Art and the Art of Snails." And what I hope I can persuade you, is that it is in fact possible to join science and art together, and each field may be able to learn something from the other. The -- I was looking -- my next book, as you just heard is called "The Serpent's Promise". It's not out yet, but the last one, book three or four is this thing here, still on sale $7.99 on good bookshelves, and it's called "The Single Helix". And I gave it that title because I knew it wasn't half as good as "The Double Helix", but I hoped it would sell half as many copies but it didn't. The helix is not the helix of DNA, but it's the Latin name, or the older Latin name of the snail; I spent for the last 40 years working on, which is called helix or asapere amoralis [phonetic], and that's a picture of the snail's shells. Now it's -- working on snails seems to many people rather eccentric. It isn't really, it's a perfectly sensible thing to do, but I was asked once, at a dinner party some years ago, which a number of Greek people were at, I was asked out of the blue, what do you call somebody who does research on snails. And the correct word is Malachologist, okay? And this caused an alarming response, in that half the audience fell laughing uncontrollably to the ground, because the root of the word, Malachologist in Greek is malaca [phonetic], which means soft and floppy, and I won't go into what it means in Greek slang [laughter]. But actually that's really an introduction of the way that one can use snake - science and art together, because the first piece of artwork I'll show you is this thing here, which is a Dali woman with snail, and Dali - as you will of course know - referred to himself as the "Great Masturbator" and was very much concerned about impotence. And what we've got here is a classic example of impotence hard at work and Dali showing it as a soft and floppy snail. And I hope that actually I'll persuade you that that is actually a bit of an error when it comes to snails and sex. There's one general rule about working on snails and in that very minor way, I suppose, it applies to me. Which is that nobody gets famous until they stop working on snails. And there are a number of extremely good examples of that. In other words, for a snail person -- somebody who works on animals with shells rather than snails or slugs -- is a conchologist, somebody who studies shells. And this is a textbook published in the 19th Century for use in schools, "The Conchologists First Book". And I'll show you the title page. The Conchologist's First Book, blah, blah, blah, testaceous malacology, by Edgar Allan Poe [laughter]. And that was Edgar Allan Poe's first work, was a book about snails. I wonder what happened to him? Okay [laughter]. There he is, Edgar Allan Poe. Another person who was very keen on snails, and I wonder what happened to him, is this chap here, Louis Carroll. And Louis Carroll was a keen amateur malachologist -- in more than one sense of the word no doubt -- and he -- many people will know his famous poem of the - from "Alice in Wonderland", "Beware the Jabberwok, my son! The jaws that bite, the claws that catch! Beware the Jubjub bird, and shun the frumious Bandersnatch!". Now the imagine of the Bandersnatch in this tenial drawing is of course a horrible great monster a bit like a dragon. In fact, I discovered almost by mistake what the Bandersnatch actually was. Here's a paper on snails in German. So our structure -- the diversity and structure of the Polymorphism in the Banderschneck -- Banderschneck -- Banded snail, Cepaea hortensis. Okay? So actually let's track down one of the great literary mysteries of what was the Banderschneck? It was in fact a snail [laughter]. Now there are, indeed, of course many obvious uses of images of snails and mollusks in art; some of which are familiar. Here is the Sagrada Familia, in Barcelona and wonderful cathedral. And you'll see we've got rather fine images of snails crawling up the side there. That's kind of well known. Another well known example of a snail is Matisse's cut and paste snail, which is a snaily -- not a very snaily snail, but at least it's brightly colored. And they are just images of mollusks, and they're pretty things, there's no question of it. But very often -- so often in art -- the use of snails in art does have a symbolic meaning and some of those symbols are rather startling. Some are fairly obvious. If you go to where I come from in West Wales, and you go to a graveyard, very often what you find is there are these plain -- these nice slate gravestones going back to the 18th Century. And many of them are very finely engraved. It was a thing which became popular in the 18th and 19th Century. And among the images you frequently find on gravestones are snails. Why should that be? It seems odd. Well actually, it's an image of the resurrection; of being born again. Because many snails -- and many of you will know this if you've traveled in southern Europe and around the Mediterranean -- many snails in the summer climb away from the ground, of the lair of super hated heat -- super-heated air on the ground -- and I'll come back to that question a little later in the talk. They climb up onto twigs and branches, and they stay there, and many thousands of them, throughout the summer until the first rains fall in the autumn, whereupon miraculously they are born again and they come back and they can start crawling around. And hence that's snails a resurrection. Okay? But then other religious aspects of snail imagery, some which are fairly [inaudible], and here's something which is in the National Gallery, alright? This is Francesco del Cossa's annunciation of the "Virgin Mary". And you'll see for all the conventional diagram, the annunciation; it's very formal. There's the Virgin Mary; there's the various angels rushing about and there's obviously a fine building. If you look carefully, down about 5 o'clock there, you'll see a snail crawling across the front of the painting. Why should that be? It's because snails were seen as an image of the Virgin birth, okay? And because they have this great, horrible thick shell around them, it seemed to the clergy of those days that they must reproduce without sex -- I can tell you they were dead wrong there. But of course they've got this enormous sort of calcareous condom which they wear [laughter]. Then they would actually produce -- magically produce offspring without having sex, and hence the image of the snail as purity. Okay? That isn't true at all because the sex lives of snails are really quite startling things. There's no question about that. Many of them -- not all of them, but many of them are hermaphrodites, okay? They're actually cross -- rather unusual -- they're cross-fertilizing hermaphrodites. Boy/girl meets girl/boy, okay? And they get together. Now in that circumstance, if you're a cross fertilizing hermaphrodite, what you want to be obviously is the boy. You want to be the male. You want to impregnate your partner and then beat it as quickly as you can, because your -- before your partner decides that he/she wants to impregnate you [laughter]. Because in other words, what he can do then is you can have all the joy of sex without any of the costs. You can fertilize your partner and then you can beat it and you don't have to pay university fees for your children and that type of stuff [laughter]. And they do it in very complicated ways. Here's an image -- which seems odd, from a 17th Century manuscript -- of a snail about to shoot an arrow. Now why would he want to do that? He'd want to do that because he actually does that. Snails have things called love dots. They're not really love dots; they're more hate dots. But what they actually do is they fire them at each other. It was originally thought that they fire them at each other -- and they're quite substantial things. If you keep snails in a box, in the spring you'll find them the following morning, numbers of them. They'll fire them on each other; once thought to be a sort of, you know, this is a statement of affection okay? Or I'm giving you a pile of calcium carbonate -- which is what the dot is made of -- and therefore, you know, I'm worth dallying with. The notion got into art. Here's a Boucher -- Cupid and Psyche -- no doubt the island -- the image of Cupid with his arrows, I'm absolutely certain came from the observation of snails copulating -- I'm not that certain but it would be nice if it was true. And here's actually a snail dot. And what actually happens is, and if the dot is dry and clean, it looks like this; it looks like an arrow -- it looks a bit like an arrow. In human terms, it's probably about that big. So, you know, having that shot into you isn't all that much fun. But actually, if you look at it in living animals, it's covered with mucus; it's covered with this sort of snotty type of stuff, which nobody really thought very much about. But in fact it turns out that it's got -- contains a hormone. It's a hormone which is a -- it's a male hormone -- it's a hormone which is produced by the male part. And the female -- in this boy/girl meets girl/boy -- the female part stores sperm. And that's very common in the animal world. Mammals don't do it as far as we know, but lots of insects and snails do. Now they mate -- the female has a special organ into which the sperm is taken, and she lets out a bit whenever she feels like it and she can actually choose what she thinks of -- "thinks" in inverted commas -- as the highest quality sperm from this sperm "store". So if a male mates with a female, the most -- oldest sperm will just be taken in and put on one side until somebody else turns up -- somebody else possibly better turns up. But what this hormone does, it forces the female to open the door of her sperm store so that the male sperm is then immediately reduced -- released into the female reproductive track. Not many people know that when they talk about Cupid's dot; but that's what Cupid's dot was really for. Okay? Well that's a general -- that's a kind of generalization about snails and all the stories about snails. They go further -- many of you -- we talked about snails; let's talk about slugs. Now slugs are something else. Slugs are completely amazing. All slugs were once snails. Hitler once said, "A slug is a degenerate snail." He also said, "A Toad is degenerate frog." And he was wrong about the second but he was right about the first. Slugs are snails who have given up having shells because shells are expensive to make. Okay? And they mate; boy/girl meets girl/boy. And the mating pattern -- I cannot bear to describe in detail because it's a bit eye-watering -- but here's a common British slug, limax [phonetic] whatever it is, and Charles Darwin [inaudible], Darwin's Bunker I'm speaking from quoting in his raw, good French, from Agassiz "Quiconque a eu-" Oh I won't do it in French -- who has the need -- who has the chance to look at the loves of the slugs can have no doubt that the seduction used by the movements and the allure which prepare and accomplish the double embracement of these hermaphrodites. Okay? They embrace each other. And you can see these big white things embracing. They're not embracing they're hitting each other and the big white things are actually the two penis' alright? And they bash each other madly with penises until one of them stuns the other one into submission and mates with them. But they go further than that -- something which we discovered here some years ago -- that actually, the winner bites off the penis of the other one, okay? [Laughter] to stop him from actually using his penis and that's called apophalletaon -- biting off of penis. We made up the word, and that's kind of weird. But that too, very strangely, has a resonance in the work in art. Here's a famous Goya of "Cronos devouring his children." And what Cronos actually did was to devour his children after having castrated his father. And who was his father? His father was Neptune. And what happened with Neptune was castrated? His testicles were thrown into the sea and they turned into foam. And here we have Botticelli, "Venus emerging from the foam". And that's what the foam was, it was the sperm of the -- of Neptune. Again, a slightly unlikely tie, perhaps, between the world of science and the world of art. However, I shall now stop telling snotty stories -- smutty stories and I shall start talking about snail polymorphism, which is of course much, much more interesting, alright? So why work on snails? Well there are many reasons, they're sluggish -- pause for laughter -- okay, they're easy to mark -- and we'll come back to that. The -- most of all though, they're what we call polymorphic, okay? And polymorphism means being different; individual differences. And I started working on these things -- I hate to say it -- in 1965, a long time ago. Oddly enough the guy who won the Nobel Prize just a couple of days ago, a developmental biologist, gave me my first lecture -- not on snails, but it was a long time ago. And in those days, lots of people worked on snails -- this particular snail -- and the reason they did it was they were interested in the central question of evolution -- the central question of genetics, which is why is there so much diversity? Evolution could not happen unless there was lots of inherited diversity. Charles Darwin's machine depends on that. Darwin's Machine; natural selection, consists of inherited differences in the ability to reproduce. That's what it is. Without differences, there could be no evolution; we'd still be sitting in the primeval soup, okay? Where we depend on difference. But way back in the 1960s and indeed until rather later than that -- 1968 it actually happened that the first discovery was made here again. We have to put in by UCL rules an advertising break every 15 minutes, so that was exactly 15 minutes; that wasn't bad [laughter]. But in the 1960s here at UCL, in what was then the Galton Laboratory [phonetic], the discovery was made -- not -- but now, but quite startling at the time -- that if you took a random sample of proteins from the blood of normal human beings -- actually they were medical students, so it's not entirely dependable work -- if you took a random sample of proteins -- of 27 proteins -- and you stand -- you put them on an apparatus that you separate them according to charge and size, an electrophoresis apparatus as it's called -- to everybody's great astonishment, it turned out that something like 13 of those proteins were variable from person to person. And nobody expected that. The absolute expectation was that if somehow magically -- and in those days it was unthinkable -- we could read human DNA, we would find that most people from all over the world were pretty much identical to each other with a few obvious minor differences, perhaps in blood group, skin color, eye color that kind of stuff. And that was the expectation, but it turned out not to be true. But until that technique became available -- and of course the technology now is far, far more sophisticated now that you can sequence an entire genome in a morning -- until that technique became available we didn't have that kind of information. There were some species of; some creatures of, which were visibly variable. You could go out -- we bred these up; these are my snail. This is a sample collected on the Marlborough Downs in southern England. And if you look at them, you'll see an actual riot of individual differences. And if you do crossing experiments -- which we have done -- they turn out to be straight forward genetic differences in color, from like a pale yellow to dark pink or brown, and in number of stripes from 0 to 5 and various other minor things. Okay? Now this is just one population. Almost every individual is different from all the others. And what you can do -- and we've done it mightily on hundreds of thousands of snails -- is to go out and simply go out into nature and count the frequencies of the different variants and how they differ from place to place. And I know I've spent many years -- many happy years -- driving with my hairy, hippie-type friends all over Europe doing that, and we've collected about half a million of them, okay? And you can draw maps of the frequencies of the different types. They vary from extremely light colored to extremely dark colored. And the picture is really quite clear. Here's a recent map. You can -- there's a striking really tendency of the south of Europe to be light colored, and populations in the north of Europe to be dark colored. And what actually happens is that that's a very striking and significant thing between the frequency of the light-colored variants -- pale yellow, let's say, and the amount of bright sunshine and temperature. Okay? so I mean the hotter it is, the more light-colored creature you've got. We know a lot about that, that's kind of been an obvious statement as anybody will find. If you were to sit in shorts on a black, painted park bench on a sunny day, even in London, you'd stand up pretty smartish because dark objects heat up more rapidly to a high temperature in the sun than light objects do. It's physics so it's true, okay? So that's fine. Alright, so that's fine. Now we spent a lot of time doing that, and that's been done in various creatures and we know quite a lot about the behavior implications; it's all very boring. But actually, we weren't asking -- and I think many people weren't asking the interesting question. And the interesting question isn't, why do populations differ from place to place -- as many populations do -- as human populations do, of course there's skin color they'd say, or the ability to drink milk or to metabolize alcohol? Why do we differ from place to place? You can study that quite easily, okay? The more interesting question is, why does there nearly always remain variation differences within a particular place; within a particular population? For example, if you were to -- if you were to go to southern Europe; I've done most of my recent work in the Pyrenees, where it's often hot and sunny, even in the hottest and sunniest parts of the Pyrenees, way up high when there's no cover and the sun comes roaring in and it's really, really -- you can get sunstroke up there quite easily, even there you find mainly light-colored shells; but a few dark ones. I did my undergraduate project on the dunes in Montrose on the east of Scotland. I spent 10 years in Edinburgh; I don't think I saw the sun once in that decade [laughter]. But certainly on the dunes in Montrose, which is where it's cold and not sunny, you'll find 90% of dark colored ones; but still a few light-colored ones. So what's going on? Why do we maintain diversity? And the same is of course, written at large in human genetics. We now know that if you sequence DNA, you find of the 3,000 million base pairs, which go to make human DNA [inaudible] speaking -- and there's a lot of DNA in every one of us, and if any one of you bored by this talk, were to rush into Gower Street, and to be squashed flat by a #29 bus, the DNA in your individual body would reach from that damp patch on the pavement, which used to be you, to the moon and back 8,000 times. So there's a lot of DNA in every one of us. Every cell has got 2 meters of DNA in it; 3,000 billion DNA letters in those two meters. And if you sequence along about 1:1,000 letters from you to the person next to you is likely to be different. And there are various other differences to do with rearranging the order, deletions of letters and that kind of thing. And we know a lot about it, but we don't know why it's there. That's the interesting question. You can find out to some degree, why different places have got different combinations of genes in humans, but why it's still there, we don't know. And the amount of variation in humans and everything else now, makes snails pale into insignificance. It's clearly the case that apart from identical twins -- and my mother, as it happens, was an identical twin although I don't think that's why I became a geneticist -- apart from identical twins, everybody on Earth is different from everybody else. Fair enough. But actually, if you do the sums, the amount of variation means that everybody on Earth is different, not only from everybody alive today, but from everybody who has been alive in the past or will be alive in the foreseeable many thousands of years futures. That's very different. But even more striking -- if you do the sum again -- every sperm and every egg ever made in human history is different from all the others. So that's a massive amount of individual difference and it's surprising to me that there's not more wide-spread interest in why that difference is there. So after having spent many years mapping these genes across Europe, we decided to start asking the questions about why is the variation in these snails, actually [inaudible]. Well, oddly enough the idea -- one of my ideas came once again, from the world of art. Here's a Dutch flower painting -- now many of you will be familiar with Dutch flower paintings. They're very beautiful, intricate and wonderful things worth a huge amount of money; there's some very nice ones in the National Gallery -- a wonderful, beautiful, beautiful pieces. Okay? And people nowadays see them simply as marvelous paintings and something to put in your bank vault and sell and become rich. But actually they had a symbolic meaning when they were painted a lot of them in the 17th Century. They were a reminder of mortality. What you have here are a series of beautiful, beautiful flowers. So that tells you that God is good. God has made the world into a wonderful and attractive place. But look more carefully. Now what happens to flowers? They decay. They get eaten by caterpillars, alright? They get eaten by snails. This is a reminder that nothing will last. These flowers will decay in a day or so and be eaten by insects and snails and worms and that kind of stuff. And you will decay and be eaten in the same way. And this is one of my favorites, this is de Heem. This is the painting. If you look at it more carefully, and I'm not sure how well you can see it here, but if you look there and up there and I've actually made a -- if you look at the bottom left there, you'll see a snail -- one of my snails, alright? In the painting and up there, the top on the right just parallel with it, another one of my snails; they're different from each other. I did think of asking for an NERC research grant to buy lots of Dutch old masters to see if the gene frequencies have changed [laughter], but they turned me down as they invariably do. But it's a statement of difference. Now the odd thing is, unless I pointed those snails out to you, you probably wouldn't notice them; you'd have to look pretty hard. And the reason you can't -- wouldn't notice them is actually, they are very well camouflaged against their background, okay? And that's what I want to go into, the question of the relationship between variation in the genes of creatures we're looking at -- snail shell colors and the like -- and the habitat in which they live, alright? Well we know that natural selection can -- actually climate, can work on a large scale because of this European thing I'm telling you. But snails are also attacked by predators. It's been known for a long time that if you go to southern England, you can often see lots of broken shells around stones, which could be bashed by thrushes and the like. But a snail -- but one of them is what comes from a broken home? [Laughter], yes and another one is, that one's got shell shock. You see it's kind of formal series of jokes. And for many years that was thought to be the major process that drove the system of variation. That isn't true. That's actually only a very local in southern England; it isn't true anywhere else. But it made us think about camouflage. And of course camouflage in the animal worlds -- crypsis as it's known -- is a remarkable thing. Here's a leafy sea dragon, which is a sea horse, against some seaweed and you can see it's really remarkably; reasonably well-hidden. Okay? So we'd began to look at this camouflage and this fit between the scale on which that creature is built, and the scale of the background against which it's found. And they turn out to be very closely related to each other. As I said, there are lots of cases of snails coming from a broken home. Here we'll see some ducks doing the job for us. There's an example of what's called a Thrush Dome, but that's a kind of a minor phenomenon. Now of course camouflage is used in many other contexts too. It's widely used in warfare. Here's a famous Edward Wadsworth print from 1919 of a ship in dry dock at the end of the first World War, and what we've got here is what's called dazzle camouflage, where you break up the dimensions of the ship by painting it in stripes, which are rather like -- the dimensions are the same size -- rather like the dimensions of say, like a breaking wave out at sea. And that's very effective. It's in fact been adopted exactly by zebra's -- as we see here -- which are concealing themselves with stripes which turn out to be almost exactly the dimensions of the trees and the bushes and the trunks against which you see them in the wild. It's been picked up further in art. Here we have some Bridget Riley's. And it's clear -- what's interesting about Briget Riley paintings -- first of all she doesn't paint them, of course, which is very particularly interesting -- but secondly, their scale -- they're always on the same scale. There seems to be some mental statement that's being made that our minds find particular sizes and relationships of size attractive, and they are very beautiful things without question. Well that's the kind of argument we needed -- we wanted to go into. There's a more recent one. There's a Japanese painter who is very, very eccentric. Yayoi Kusama, who does it on a much larger scale where she has these eccentric objects which she puts into a room and it's very, very hard to see them unless you look hard. So what are the -- how are we going to do that in snails? Well one of the many advantages of working on snails is that they only live in national parks. That's kind of a slightly overstatement, but they tend to live in very nice places. And for each of the last 20 summers I've spent -- in fact this summer I only spent a week there -- but at least for the last 20 summers, I usually spend at least a month, sometimes more, in the Pyrenees collecting snails. And here's a shot of the Pyrenees. It's pretty. We work in a place called the Val D'Aran, which is a Spanish valley on the north side of the Pyrenees. And the snails live from about 300 meters above sea level -- which is at the bottom of the Pyrenees, to 2,700 meters which is way up at the top. So there's a huge range of habitats in which they live. And they live in structurally and ecologically very different places. Here's one from lowland -- it's called Aties -- and you can see the bushes in the front there, are -- that's covered with snow. Or we can go up to the top and that's a grey, horrible day, up at the top and that plain -- that short grass, if you go out there on a wet day, there'll be snails crawling all over it. So there's a huge difference in ecology between those two places. And what's interesting is that it's immediately obvious if you collect the animals, that there's a big difference in the kind of sample you collect. Here's a sample from fairly low down that's got both light and dark individuals there. Here's a sample from high up -- and this is a very old picture I took in the 1970s I think -- and that's got nearly all light individuals. So there are big differences over a distance of about 5 or 6 kilometers. So we began to wonder what that was due to. And it wasn't all that easy to do. We spent quite a lot of time learning botany or learning some kind of parody of botany, but we tried to identify the number of species of plant in each place, expecting there'd be far more kinds of plant low down than up on the Alpine pasture. In fact, the opposite is true. One of the most diverse habitats of all is a finely cropped, high up pasture because there are many, many species of grasses and flowers up there. So that didn't fit. So then we began to think, well let's think like a snail. Alright, let's take a snail's eye view. And here's a snail -- if you happen to be a snail and sometimes on a bad day I've began to think I was turning into one now and again. If you think like a snail and you put yourself at the bottom of a bush or, you know, in a forest and you look up, you would see the sky and you would see something like this. This is a fish-eye lens shooting through a forest canopy. And what you would see would be lots of patches of dark and light. And there's a whole field called sun flake ecology, which studies exactly that. And it's tremendously important. It's one of these areas which is hugely important and nobody knows about. UCL certainly doesn't know about because I know plant science has died about 10 years ago in the medical -- they were eaten by the medial school. But it's enormously important because the amount of sun that gets into a crop determines how fast it grows. So there's a huge amount of interest in breeding crops of different shapes and sizes so that you can maximize the amount of solar input. And there's all kinds of extremely sophisticated machinery, electronic apparatus, which will tell you about the patchiness -- the amount of sun that comes in; how broken up it is. And you can buy these things, but they're expensive -- and of course we didn't have any money so we had to think about it, alright? So we defined -- began to define -- how would -- if I was a snail, how would I work out how patchy the [inaudible] in terms of sun flecks, and how much sun is coming in and affecting me. Because we know snails are very susceptible to being overheated, like most creature; like us. They live on the edge of a thermal cliff. If our temperature goes up by 5 -- 3 degrees celsius, you're ill. If a snail's temperature goes up 3 degrees higher than the air temperature on a hot day it's dead. So it has to be very, very careful about how much it -- solar energy it absorbs. Well these machines were expensive, so we couldn't buy them, so we had to think. And after a bit of thought, I came up with a technique, which I've given the rather eccentric name of "Jones' Balls." It involved taking a series of small, plastic spheres and just going to a very -- to a series of habitats and throwing these spheres in to a 1 meter square, and then using the UCL satellite -- otherwise known as a folding ladder -- defining oneself as the sun, and simply climbing up this ladder from the point of sunrise all the way around to the point of sunset and counting how many of these spheres you could see. Now in a place like this, which has got very short vegetation, you'd probably get figures like 3, 3, 4, 7, 10, 10, 10, 10, 4, 7, 3, 2, see. Because you can see most of them. If you go to a much more - into a more vegetational kind of place you'll see fewer. And if you go to a place with a lot more vegetation you'll see fewer again. So what we first did was to say, okay, is there any relationship between the extent of the variation in the population and the amount of diversity in the patchiness of light, and the extent to which the vegetation cuts it off. And the answer is yes. Here we have the amount of genetic variation versus the thermal complexity, as I call it, of the habitat. So that's fine, but what are we actually measuring? How do the snails experience it? Well we tried to ask them, but we don't speak snail particularly well, so after a bit of puzzling -- and I did this some years ago now -- we came up with a method of measuring the extent to which each individual animal was exposed to sunlight. And it sounds eccentric, but it is in fact true. We started off with gene manipulation. And with gene manipulation, I mean we took -- and we're talking early 1970s here -- mid 1970s -- and that means in those days everybody in this room would have been wearing blue jeans, okay? And they would be carefully faded. And I thought, hang on those jeans are faded. Why have they faded? Because the sun has faded the cloth. So I thought, oh we'll cut our little squares of cloth and we'll stick them under snails -- "jean" manipulation [laughter] -- and we'll see whether they fade, alright? And the answer is it didn't bloody well work. It -- they came off basically. But then I thought, ah ha! Just a minute. What is the dye which they put in these jeans? And I found out what it was and it's a commercial dye which fades. So we have a little techno -- piece of technique where we took a -- this blue dye, we mixed it with yellow pain to make a green paint, okay? And if you expose that green pain to sunlight it fades to yellow. Now let me just -- just -- here we go. This is the way it works. Here we've got two snails which have been in the sun for a different amount of time; the same population. You'll see the one on the left has scarcely faded at all; the one on the right has faded more. We can compare it -- and this is a -- the colors are lousy on this but it does work. You can compare it against the scale and you can measure how much time each individual animal has spent in sunlight over a month or so. And we did a lot of work on this. This is an aerial shot of the University College of London Snail Ranch at White and [inaudible] in Oxford, which was 101 meters square; 1 meter circular cages into which we put snails. And we did various things with the paint and we found, indeed they vary in the way they behave. If you go back to the balls experiment, what we did was to take these little circular washers -- which is what they are; we call them spiders -- and we put the spiders in the places where the balls had fallen in these pictures of vegetation. Came back after a day and we found that in some places they'd all gone to yellow and some places they were patchy green and yellow. And if we look at the relationship between the habitat patchiness and the amount of variation, yet again there's a striking fit between the two. So somehow this habitat patchiness is determining the amount of diversity in the population. Well why should that be? It turns out to be -- to depend on something which is becoming very important in understanding genetics and evolution, which is differences in individual behavior. And small differences in behavior have a huge effect on snails, on humans, on everything else. And what we found, indeed, with the snail ranch is that if we take light and dark colored animals and we put them in the snail ranch and we come back after two months in the summer, there's a big difference in the extent to which the un-banded -- that's the light colored individuals having been exposed to sunlight -- versus the bandeds. We can actually do some phenotype manipulation by painting them black and white. We can take light colored ones and paint them black and dark colored ones and paint them white; put this paint on them and we can ask again what happens? They reverse their behavior. We did this in Spain and the Spaniards are an amiable lot, tend to pick these things up and eat them; they cook them. There was one old lady who was doing it who picked up a pile of black ones and she crossed herself and went -- ran away [laughter]. But you can reverse their behavior and that's what happens as you reverse their behavior. Okay. So what we've got here is an ability of individual animals to choose the patch, sunny or dark, in which they'll relatively fit. And they track it very, very carefully. And the more complicated the habitat, the more effective that it is in a way of maintaining polymorphism. And that fits between habitat complexity and genetic complexity is now beginning to suggest that actually that's of general importance. For example, if you look at the variation in diet of different primates, the more variation there is in their diet, the more variation there also is in their genes; particularly in the genes that give taste and smell. So this may be a more general phenomenon than people realize. However, there is -- naturally we need -- we've been talking -- and whether we talk about snails or not, we've been talking largely about old and rather beautiful artworks. Modern artworks are of course much more challenging. Two or three years ago -- more now, four years ago -- I was written to out of the blue by somebody who I didn't know, who was an artist, a guy called Findley Taylor [assumed spelling], who's a print-maker at Goldsmith's College, [inaudible] and he wanted to do an artistic experiment and what he did was to take a copy of Charles Darwin's "Origin of Species", okay? And put it in the garden for several months and -- a very wet summer -- and a copy of my attempt to rewrite the "Origin of Species" -- in 2009, which was called "Almost like a whale". And the artwork was the same, but the snails prefer to eat [laughter]. And I have to tell you, somewhat to my disappointment, they found the origin -- on the right -- much more palatable than my book on the left [laughter]. But as I've killed off nearly half a million animals in my career, I suppose they're entitled to get their home back. I shall stop there. Thank you. [ Applause ]