The team explores studies on the academic differences between boys and girls, the discovery of the oldest turtle specimen that has turned turtle science on its head, the discovery of an enormous plume of water vapour on Enceladus, how calving of ice shelf gives an insight into icebergs and climate change, how robot lizards help us learn more about how lizards get themselves noticed, and the link between serotonin and osteoporosis.
Plus, in 'Stuff and Non-Science', are crowds as volatile and unruly as we think?
Chris Smith: Hello, welcome to The Naked Scientists: Up All Night, which is produced in association with the Open University. I’m Chris Smith. In this week’s show, the new fossil that’s got scientists talking.
Helen Scales: It’s thought to be the ancestor of all living turtles that we see today. And that’s turtles, tortoises and terrapins. And it’s really turned the world of turtle science upside down and left it rolling around on its shell, wiggling its legs in the air, because it suggests that, contrary to what we really thought before was that turtles evolved on land, it now seems they may have actually started off in an aquatic environment around 220 million years ago.
Chris Smith: And Helen Scales will be telling us how the turtle grew itself a shell in just a moment, when we’ll also be hearing from a scientist who’s shedding some more light on a phenomenon that’s quite literally out of this world.
Candice Hansen: We discovered a huge plume of water vapour coming from the south pole. And this of course was a big surprise. The moon is 500 kilometres in diameter. And this plume of water vapour goes out thousands of kilometres. It’s actually bigger than the moon itself.
Chris Smith: Candice Hansen. And that plume of water is so powerful that it actually contributes to one of Saturn’s rings, but where does it come from and what else is in it? We’ll be finding out shortly in this week’s Naked Scientists: Up All Night.
First, let’s take a look at some of this week’s top science news stories from around the globe, and our news hunter this week is Helen Scales. So Helen, first up, something that everyone argues about, who’s better academically, boys or girls?
Helen Scales: Yes, the question is, do boys or girls do better at school? Well, it’s something that we’ve had on our minds for a long time, and it’s raised all sorts of heated debates. But this week there is a study that has definitely added to this discussion. And that’s because it could be that boys are much more variable in their performance in tests at schools, compared to girls. Some of them do very well and others less so. While girls, on the whole, seem to be a bit more consistent. And that’s not just in the US, where most of the studies on the differences between girls and boys at school have come from in the past, but now that seems to go for kids in schools all around the World.
Chris Smith: Now when I’ve had my experience of marking exam papers and things, we see quite a characteristic emerging between boys and girls, which is boys tend to go for the smash-and-grab approach; they’ll learn a few things selectively to a really high standard, whereas the girls tend to learn more things to have a sort of fair representation of the whole exam arena. And what that means is that the boys, if their questions they’ve revised for come up, they do really, really well, or if they don’t get the questions they wanted, they do really, really badly, and then the girls tend to do pretty well across the board. Is that sort of what they found?
Helen Scales: That actually is. That could actually be a really nice explanation of what these guys seem to have found in this study. And it’s a study that came out this week in the journal, Science, and it was by Stephen Machin and Tuomas Pekkarinen, and they looked at the boy-girl differences in test scores of 15-year-olds, and that was from the kids in 41 different industrialised countries. And they looked in particular at the results of mathematics and reading tests, and these are two really important subjects that tend to actually predict how you do later on in life.
And what they found was that there was definitely variation in who did better. But, on the whole, boys did better at maths, girls were better at reading. But perhaps, more interesting, was that, like you say, the boys were coming out as being much more variable. So there was, if you looked at a kind of graph of distribution of the test scores of all the boys, it was much wider with more at either end of the very high scores and very low scores, compared to the girls that are in the middle. And I think, like you say, maybe that could be an explanation for that.
Chris Smith: How does this reflect the exam system though? Because it’s well-known that boys do better at certain types of exam; multi-choice, for instance, is much better for boys than it is for girls, because girls find it harder sometimes to make their mind up about, and that’s at least in our experience at university level, about what they think the correct answer is, whereas boys tend to be much more, “Well, it’s that!” and they slam down an answer. And it seems to favour the men over the women.
Helen Scales: There’s so much going on then. I don’t think yet we’ve really kind of, certainly, got anywhere near to the bottom of understanding the differences between why boys and girls perform differently at school and where that comes from. It’s certainly a big debate, and I think this does give us a little bit more information about the sort of things that are going on.
Chris Smith: Well, it’s reassuring to know that it’s not just this country where boys and girls are different.
Now let’s look at this story which I spotted this, this week, and I thought wow, that really is fantastic. So scientists have now got to the bottom of where turtles come from?
Helen Scales: Well, they may well have done. This is really exciting news from the reptile world, and it is the announcement of the discovery of the world’s oldest turtle. Well at least the oldest one we’ve found so far. And it’s an ancient creature that really could help us solve a great mystery: how did the turtles evolve their shells?
Now it’s thought to be the ancestor of all living turtles that we see today. And that’s turtles, tortoises and terrapins. And it’s a story that’s in the journal, Nature, this week, and it’s really turned the world of turtle science upside down and left it rolling around on its shell, wiggling its legs in the air, because it suggests that, contrary to what we really thought before was that turtles evolved on land, it now seems they may have actually started off in an aquatic environment around 220 million years ago.
Chris Smith: So is the turtle shell a sort of modified skeleton? Is that their skeleton round the outside? So where we have ribs on the inside, and we’re hung around our skeleton, their skeleton has them hanging inside it?
Helen Scales: Well, that’s been the big question all this time. Is it that? Is it a case of, more or less, that their ribs grew out and got wider and flatter, and fused together to make this shell, or are they actually bony plates that grow out of the skin and then fuse together to sort of form it from that way? That’s been the two, the two sides of the argument that really people have been arguing over.
And it seems from this new evidence that it actually is, it’s the skeleton argument that might be winning out, because what they found in this very old specimen was that there was no evidence at all for these bony plates in its skin. It doesn’t have any of those. But it does have some parts of its ribs do seem to be growing out and fusing together, most importantly, only on one side of it. Because this creature they found is called Odontochelys semitestacea. Can you guess what that might mean? It’s Latin. And it translates as a toothy turtle with half a shell. Like some of the other earlier fossils that have been dug up, it only has a hard shell on its underside. And that’s called the plastron. It’s a bit like a breast plate. And it doesn’t actually have a complete shell on its back yet.
Chris Smith: So do they think that the breast plate then extended around the side and around the back?
Helen Scales: That could be it. And certainly this kind of idea is supported by observations of modern day turtles if you look at them when they’re developing as embryos. And, in fact, the underside forms first and then the other side forms afterwards. And, if you think about it, it should link to the idea of these things evolving in water. Because, as you can imagine, if you start swimming around in the water column, you’re exposing your soft undersides, and if you could protect that from predators coming up and nipping at you from underneath, that would be really great. So that is sort of one little piece of evidence as well that this would certainly make sense, if this is what has happened.
Chris Smith: Terrific! So scientists turn turtle the idea of where we thought turtles came from. Now sticking with the sea, where icebergs come from and what limits their size, what have scientists found about that this week?
Helen Scales: We’ve come a step closer towards understanding how icebergs form, and in particular, most importantly, how they might respond to climate change. Because we have, in both the Arctic and in the Antarctic, we have ice sheets or glaciers on land, and they spread out over the sea forming very thick layers of floating ice, and those are called ice shelves. And then, eventually, these break apart to form icebergs, and that’s a process known as calving. So it’s nothing to do with cows, but it’s called calving, so they shear off into icebergs. And up until now, climate models haven’t really considered just how that happens. Because actually it’s a real key to climate change in the sense that if there are ice shelves that are still intact at the edge of the continents, they limit the rate at which the ice comes off the land.
Chris Smith: So if you get lots of icebergs, and there’s nothing holding the rest of the ice on land, so then you get more of a mass exodus from the land and that speeds things up?
Helen Scales: Essentially, that’s what it is. It seems to be. It’s almost like the ice shelves, while they’re still intact, are buttresses and they’re holding everything back.
Chris Smith: So what have the scientists found this week?
Helen Scales: Well, this was a study in the journal, Science, and it was from a team of researchers led by Richard Alley from Penn State University in the States. And what they did was they gathered together existing and then some new field observations of icebergs forming. Essentially, where they are, how fast they form, and what they look like. By analysing all that data and looking at it, they found that the main factor controlling how fast calving of icebergs take place is the rate at which the ice shelf is moving away from the continent. And then they also showed that the narrower the ice shelf is, they actually tend to calve off into icebergs more slowly.
So that may seem a bit simplistic but, essentially, this is something that we never really understood before. No one really looked at the sort of things that influence iceberg formations, this really is, ha-ha, the tip of the icebergs, sorry, that a lot more needs to be done. But really this is the beginning of an understanding that will hopefully really build better models that will build a picture of what will happen as the oceans warm up and as ice melts more and adds more to that rising sea level.
Chris Smith: Right. I want to say fantastic discovery, but it’s a bit of a sombre thought isn’t it? And to finish up this week, how are robot lizards helping scientists to understand a bit more about their real-life counterparts?
Helen Scales: This has to be a fantastic story for the week. Robot lizards! Who would have thought of it? What an idea. These are researchers from the University of California at Davis. Terry Ord and Judy Stamps had this fantastic idea. Because they wanted to find out how Anolis lizards that live in Puerto Rico make themselves conspicuous in a noisy forest. And that’s not a noise that you can necessarily hear but noises that you can see.
So, as you can imagine, as the forest vegetation blows around in the wind, it’s much harder to pick out the movement of a little lizard. And why that’s important is that these lizards, male lizards, gesture to each other to kind of defend their territories, and what it seems they do is that they do press ups to catch the attention of a distant enemy and warn them off.
Chris Smith: And what’s this got to do with the robots?
Helen Scales: Right, well, what they wanted to do was find out if this is an alert behaviour. They’ve seen lizards do this, push up behaviour. They also then go on to do things like bob their heads around and then unfold a colourful dew flap, which is a sort of flappy bit of skin. It’s wonderful. They sort of open it up like a concertina, and it’s a big flash of red.
So what they first of all did was they went to the forests of Puerto Rico, and they had a look, and they watched the males to see what they were doing. And it seemed to them that when there was more wind and also when there was less light, when it was darker, the males did this press up behaviour. They pushed their bodies up and down.
And so what they did was they made these little robots that were based around a dead lizard that they’d found, and they sort of modelled it in latex and put a little mechanism inside so that it can actually do exactly what the real lizards do.
Chris Smith: So a sort of robo-corpse?
Helen Scales: It is a bit. And so they basically put these robots back into the forest and got them to perform different sequences of signals. And then they watched what the other real lizards, how they responded to this, and they didn’t just …
Chris Smith: And what did they do?
Helen Scales: They didn’t just stand there going what the hell is this? They actually obviously believed that it was a real lizard. And what they were interested in, the scientists were interested in how they responded, did they pay them attention, and you can tell that simply by which way they’re looking. And they found that when light conditions were poor in the forest that the bobbing up and down behaviour definitely increased the rate at which other lizards got their attention. And also when the real lizards were further away, this bobbing up and down was more effective at catching their attention.
So what it really points out is that, yes, it is an alert signal. It is something that they do more often when conditions are difficult. So it’s shown that they can detect when’s a good time to do this and when to keep quiet and sit down and not really make yourself so conspicuous.
Chris Smith: A 101 things to do with a dead lizard! Thank you, Helen. That was Helen Scales with a roundup of some of this week’s top science news stories. If you’d like to follow up on any of those items, the details are on the Open University’s website at open2.net/nakedscientists.
In just a moment, new insights into how bones form and why some people are prone to osteoporosis. But first, is this the biggest geyser in the galaxy? Candice Hansen.
Candice Hansen: I work on a spacecraft called Cassini. And Cassini has been in orbit around Saturn since 2004. And Saturn has this peculiar little moon called Enceladus. It’s not terribly big, nothing terribly remarkable, but in 2005 we discovered a huge plume of water vapour coming from the south pole. And this, of course, was a big surprise.
Chris Smith: So this is a sort of geyser on a massive scale. But put some sizes on it for us, how big is this plume of water or vapour?
Candice Hansen: Oh, it’s actually bigger than the moon itself. The moon is 500 kilometres in diameter, and this plume of water vapour goes out thousands of kilometres.
Chris Smith: So what do you think that gas is made of?
Candice Hansen: We have data, where we watched a star go behind the plume. And we watched how the nature of the starlight changed the spectrum. And from the features in the spectrum, we could identify that this is water vapour.
Chris Smith: Is this because all different compounds and all different elements absorb different wavelengths of light?
Candice Hansen: Yeah, that’s right.
Chris Smith: So as you see the plume go in front of the star then certain wavelengths will be missing from the star which were there before and that tells you what must be in the plume?
Candice Hansen: That’s exactly right. It’s about a little over 90 per cent water. There’s also CO2, there’s methane, there’s nitrogen, and those are all at the couple of per cent level.
Chris Smith: So you’ve got this huge geyser that’s spurting enormous amounts of water but other things there, too, out of the surface of this tiny moon – does it come and go in fits and starts or should I say fits and spurts?
Candice Hansen: Spurts, I would say. It looks like there is some variability, but it looks like it has been going the whole time that our spacecraft has been there. This moon spurting this water out into its environment is the source of one of Saturn’s rings. It’s a very tenuous ring called the E-Ring.
Chris Smith: Given that you now know what the composition of that spurt is, what does that tell you about what must be under the surface of this moon? If there’s a lot of water in the spurt, presumably there’s a lot of water on Enceladus?
Candice Hansen: The temperatures are almost minus 200 degrees Celsius. And so we’ve always known that it’s composed of water. We’ve always assumed it was ice. And once we found this plume, we started looking at the possibility that there could be liquid water. And, in fact, our new results are one more clue, if you will, that there’s water, liquid water, not just warm ice.
Chris Smith: And given that the ambient temperature, as you’ve said, is minus 200 degrees, how does something turn into water at those sorts of temperatures?
Candice Hansen: Oh, that’s the mystery. So where’s that energy coming from? We have, our spacecraft is there, it’s got a complement of instruments, and using the instruments that we have, we can only see what’s on the surface and what’s coming out. This particular observation that we just did actually gives us one more clue that there is liquid underneath the surface, and the clue is that we can now say that the gas is coming out at supersonic speeds.
Chris Smith: And what’s driving that impressive speed of gas eruption? Do you think that this is a gravity phenomenon? Because some people have suggested that the orbits of some of these moons are a bit eccentric, they’re elliptical, so the moon itself gets squashed and squeezed and stretched as it goes around the planet, and that stretching and squashing and squeezing makes some heat by friction, and that’s what’s superheating some of this water.
Candice Hansen: Yes, and I would call that tidal energy. And that was another one of the things that we were testing, actually, with this observation. There are fractures, or what we would technically we would say fissures, across the south pole of Enceladus, and that’s where the water vapour and the ice grains are coming from. And so this model predicted that these fractures or fissures would open and close depending on where Enceladus is in its orbit, because it’s not a circular orbit. And our results actually are not consistent with that predicted timing.
Now that doesn’t mean that the model is wrong. In fact, the authors of that model are back to the drawing boards adding in some more sort of what you might have thought were second-order effects and, at this point, it looks like once they add in that additional physics that, in fact, our data and their model will agree a lot better.
Chris Smith: So what remains to be answered? What are you going to look at next to try and get to the bottom of some of these mysteries?
Candice Hansen: The next observation that our instrument will be doing - and this I have to say is not until May of 2010, so I do have to be patient - we will have an observation of the Sun going behind the plume, rather than a star. And so from that we can look at a different wavelength range, and we’ll be able to look more at the other gases that are coming from the plume.
Chris Smith: Candice Hansen describing her latest findings from Saturn’s moon, Enceladus. She’s at Caltech in the US, and that work’s published in this week’s edition of the journal, Nature.
Now, from moons behaving badly and letting off steam to bones behaving badly and getting osteoporosis. This is a bone-thinning disease that’s caused by loss of bone tissue, and it affects about half of all women and about one man in every five. Mostly, it’s people over the age of 50 who get it. But in order to understand what causes it, we first need to find out how bone density, which is how much bone material the person actually has, is controlled.
This has been a mystery for a long time but now scientist Gerard Karsenty has tracked down the chemical that controls bone growth, and there are several surprises. For a start, it’s the same chemical that the brain produces, serotonin, that makes us feel good, and it comes from the intestines.
Gerard Karsenty: The gut is controlling bone because it makes this molecule that everybody associates with mood and appetite like serotonin because it is made in the brain. But only five per cent of serotonin is made in the brain, 95 per cent is made in the gut. And what we have shown is that it is an extremely powerful inhibitor of the formation of bone. It is so powerful that if you, in fact, inhibit the sensitivity of serotonin in mice that are menopaused they do not develop osteoporosis.
Chris Smith: So just talk us through the process here. So how does the gut produce this signal and how does that signal then go and tell the bone what to do?
Gerard Karsenty: So there are folds in the duodenum in this part of the stomach, and they have the machinery to make serotonin. And then the serotonin goes in the blood, and from the gut, through the blood, it goes to the bone and binds on a specific receptor and inhibits the proliferation of this sensor. When you have too much serotonin in blood, you have less cells making bone and so you make less bone. When you have less serotonin in the blood, you have more cells making bone and you have more bone. And the importance of this work is that it is not done in animals only but it is true also in humans.
Chris Smith: So obviously, osteoporosis being the important thing that it is, understanding how bones form is very important, but how does this map on to what we see happening to people’s bones over the course of their life? Because when we’re first born we continually add to our skeleton until we’re, what, 20 years-old or so and then your skeleton begins to get thinner again, so is that down to this same signalling system?
Gerard Karsenty: So this signalling system is certainly one cause why we lose bone, for instance, in woman after menopause, because after menopause the concentration of serotonin in blood tends to increase. But beyond the physiology what you can imagine that if we could come up with a drug that decreases the synthesis of serotonin, there will be a treatment of osteoporosis just by increasing the formation of bone.
Chris Smith: And looking at it from the other angle, which is that people who are depressed have too little serotonin in their brains, they take drugs, serotonin reuptake inhibitors, antidepressants like Prozac, do those drugs also affect their bones then?
Gerard Karsenty: So it is well known that these drugs affect bone and that patients that take Prozac on the long term chronically can develop osteoporosis. We do not know yet if this is due to the effect of Prozac on the synthesis of serotonin in the stomach or in the brain, but certainly Prozac can cause osteoporosis and it was known.
Chris Smith: And given that you’ve now mapped out this metabolic pathway by which the signal from the gut can affect the behaviour of bone cells that grow new bone, this presumably means that you’ve now got new targets, chemical targets that you can make drugs aimed at that could manipulate this and offset diseases like osteoporosis?
Gerard Karsenty: So that’s the idea, that in fact in doing so the enzyme responsible for making serotonin in these cells could be a drug target, and that this drug, by increasing bone formation, would overcome the disease in post-menopausal women, and this is one of the directions in which, towards which we are working.
Chris Smith: Does the serotonin do anything else, apart from affecting bones?
Gerard Karsenty: So it’s a very good question and the answer, again, comes from the patients. The patient that exists that has this very rare disease with low serotonin in blood, their only symptoms is that they have a high bone mass and that they do not develop osteoporosis, but they have no other symptoms. It doesn’t appear to have an effect deleterious in any other organ.
Chris Smith: Which is good news, because it means we might be able to prevent osteoporosis by blocking that serotonin signal and there would be relatively few side effects. That was Gerard Karsenty. He’s at Columbia University and he’s published that work in this week’s edition of the journal, Cell.
This is The Naked Scientists: Up All Night with me, Chris Smith, and it’s time now for this week’s Stuff & Non-Science where we’re massacring myths and bashing bad science. And hopefully not provoking a riot, here’s Diana O’Carroll.
Diana O’Carroll: This week on Stuff & Non-Science is the case of the riotous crowd. There’s been an assumption for some time that a crowd of people is prone to sudden and spontaneous action. Take a group of football fans from an away team. Would you be scared of them? Well, here’s David Canter to put things straight.
David Canter: Yes, the myths of a crowd being some great animal-like entity that really operates at a very emotional level probably has its origins in the French Revolution, when the masses did gang together and did indeed overthrow all the figures of authority. And studies over many years have shown that crowds are not naturally volatile. In fact, quite the opposite, you can have an individual who is trying to stir up a crowd, and because all the other individuals in the crowd don’t accept what that person is trying to do, they will actually quieten him down and tell him to shut up.
So really crowds are made up of individuals who make their own decisions, but from time to time they become aware of that unity and just the sheer energy that they can generate, and this could mean that if they then feel that they are being attacked or there is something very unfair going on, they will use the power of all being together to then carry out actions that they probably would be very reluctant to do if they were on their own.
Diana O’Carroll: And it’s the knowledge about the individual in the crowd that police now use for crowd control tactics. That was David Canter from the University of Liverpool where he’s Professor in Investigative Psychology. If you have a science myth worth debunking, then send it to me, firstname.lastname@example.org.
Chris Smith: But don’t all rush! Thank you, Diana. That was Diana O’Carroll with this week’s Stuff & Non-Science.
Well, that’s it for this time. We’re back next week with another roundup of the latest findings from the world of science. The Naked Scientists: Up All Night is produced in association with the Open University, and you can follow up on any of the items you’ve heard in this week’s program via the OU website, that’s at open2.net/nakedscientists, or you can follow the links from the BBC Radio Five Live Up All Night web pages to get there too.
Production this week was by Diana O’Carroll from the nakedscientist.com, and I’m Chris Smith. Until next time, goodbye!
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In the news
'A Simple Law for Ice-Shelf Calving’
by Richard B. Alley, et al
'Global Sex Differences in Test Score Variability'
by Stephen Machin and Tuomas Pekkarinen
'Alert signals enhance animal communication in "noisy" environments'
by Terry J. Ord and Judy A. Stamps
'An ancestral turtle from the Late Triassic of southwestern China'
by Chun Li, et al
Gerard Karsenty, “Lrp5 Controls Bone Formation by Inhibiting Serotonin Synthesis in the Duodenum', by Yadav et al in Cell
Candice Hansen, 'Water vapour jets inside the plume of gas leaving Enceladus’, by C. J. Hansen, et al in Nature
Professor David Canter for 'Stuff and Non-Science'