The Naked Scientists explore archaeologists' revelation that people have been riding on, eating and drinking the milk of horses for over 5,000 years; why the Amazon forest might become a carbon criminal; how marine organisms produce laughing gas; how a mutated gene has been linked to pancreatic cancer; how observations from space provide information on how the ground recovers after an earthquake.

Plus in 'Stuff and Non-Science', are old glass windows thicker at the bottom because glass is a liquid?

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Chris Smith: Coming up this week, just how long have people been betting on horses? Well okay maybe not betting, but certainly saddling them up.

Helen Scales: Archaeologists revealed that people have been riding around on horses, as well as eating them and drinking their milk, for at least five and half thousand years, and that’s the oldest evidence we found yet for the domestication of horses.

Chris Smith: Helen Scales, on the history of horses, and also on the way, why the Amazon rainforest might cease to be an ally in the battle against global warming and, instead, become something of a carbon criminal.

Oliver Phillips: Prior to 2005, for at least 20 years, and that’s about how far back the measurements go, on average each year the system was a sink, and that’s about 500 million tons of carbon. Then in 2005, according to our calculations, a billion tons of carbon was emitted from the system. That means that the impact of the drought itself was worth about one and a half billion tons of carbon.

Chris Smith: That’s ecologist Oliver Phillips from Leeds University. He’s found evidence that as the Amazon gets drier in the future, which we think it will, then it could begin to contribute to climate change in a very big way. That’s coming up.

Plus, in this week’s ‘Stuff and Non-Science’, we’ll be taking a look at the myths framing ancient glass and why are old panes thicker at the bottom? Hello, I’m Chris Smith, and this is Breaking Science which is produced in association with the Open University.

To kick us off this week with news of how marine organisms are making laughing gas, why most people have a global conscience these days, and the history of horse-riding, here’s Helen Scales. But first up though, Helen, scientists are on the trail of a gene that’s linked to pancreatic cancer?

Helen Scales: Yes, that’s right. This could be another breakthrough in understanding what causes this particular cancer; that’s the cancer of the pancreas. Well, Siân Jones and colleagues from Sol Goldman Pancreatic Cancer Research Centre in Baltimore, in the US, sequenced the DNA from the tumour of a patient with pancreatic cancer, and their study published in the journal, Science, describes how they identified a number of genes in the DNA of that tumour that were not present in a reference human genome of someone who we know doesn’t have pancreatic cancer.

Chris Smith: Do you mean as in the genes are completely absent, they don’t exist, or that they don’t exist in a certain form in the cancer patient?

Helen Scales: You’re right; they do exist but not this mutated form of it. We all have these genes because they’re actually very important in our own DNA repair. This is a gene called PALB2, and when the mutation happens, it’s actually to do with an extra stop codon which basically has come on to stop the genes being translated into a protein and so the protein’s almost cut a bit short really, and so it doesn’t work so properly.

Chris Smith: Just in pancreatic cancer or do other tumours show the same behaviour?

Helen Scales: No, we’ve also seen this earlier. An earlier study showed that PALB is associated with breast cancer. So certainly there’s some implication of what PALB is doing in the body and when it’s mutated, when it goes wrong, then it seems that it can lead to these sorts of problems.

Chris Smith: Was this an isolated case because I know you said they just looked at one patient, so have they verified that the same mutation crops up in other patients or is this a one-off?

Helen Scales: No, what they did was they then went and looked at 96 pancreatic cancer patients, and they actually looked for this gene in their DNA, and out of those 96 they actually found three people with a mutation in the PALB2 gene, actually slightly different mutations but basically all to do with adding in stop codons. So, yes, three people out of 96 doesn’t sound like very much but it does mean that it is a way that a genetic change like this is leading to cancers including, as we say, pancreatic cancer. So this is, hopefully, pointing a way forward to understanding a little bit more about what causes it and perhaps eventually ways we might fight it.

Chris Smith: Certainly good news indeed! Now let’s wind the clock right back to one of the first things that really helped mankind to get mobile, and that was horses. An interesting bit of archaeology’s come out this week.

Helen Scales: Absolutely, yes. Archaeologists revealed that people have been riding around on horses, as well as eating them and drinking their milk, for at least five and half thousand years, and that’s the oldest evidence we’ve found yet for the domestication of horses.

Chris Smith: So who’s done it and what did they find?

Helen Scales: Well, this is Alan Outram from the University of Exeter here in the UK, and he led a team of researchers, who picked through the archaeological remains of horses left behind thousands of years ago by the Botai people, and they lived in vast areas of grassland called the Kirghiz Steppe in Northern Kazakhstan, and their study is published in the journal, Science. And they took several approaches to actually finding out whether or not these Botai people used domestic or wild horses.

So, first of all, they collected horse bones from the area, and in particular the metapodium or cannon, and that’s the bone between the knee and the fetlock joint of horses, and because of their important load-bearing role in the leg, it seems these bones actually changed shape when horses were domesticated, and Outram and his team found that the Botai horses had cannon bones that resembled bronze-age domestic horses rather than wild horses from the same region.

And they say don’t look a gift horse in the mouth but this team examined the horses’ teeth, and the bridle bit that goes in the gap between the horse’s front teeth and back teeth, and over time it can lead to a distinctive pattern in the wear on the enamel, and that’s exactly what Outram and his colleagues found in these ancient horse remains.

Chris Smith: And the final thing that you said was they were even eating these horses, which sounds a bit unfair.

Helen Scales: Well, I suppose we’re just used to thinking of horses as pets and as things to ride, not to eat, but people did eat horsemeat and…

Chris Smith: They still do in France.

Helen Scales: And they still do in France, absolutely. I don’t think I ever have. Have you eaten horse, knowingly?

Chris Smith: Not knowingly, but probably. I’ve eaten in France a few times.

Helen Scales: Probably. Ever been to France, absolutely! But we had seemed to have been doing it for at least, as I say, five and half thousand years. And we know this because Outram and his team also looked at shards of pottery that the Botai people left behind and in particular traces of chemicals in fatty acids that they’ve extracted from those pottery shards, and they’ve done isotope analysis.

They’ve looked first at different forms of carbon. It can distinguish between the remains of animals that ruminate, those are things like cows and goats and sheep, and non-ruminants like horses. And the carbon isotopes extracted from this Botai pottery did indeed show that the fatty acids came from non-ruminant animals, and that was most probably horses.

They also did a fingerprint analysis of another element, this time deuterium, and that was able to distinguish between horse meat and horse milk in these pottery shards, and it was indeed milk traces also found in these pottery shards.

Chris Smith: It’s intriguing stuff. So this population of people, they are the earliest archaeological evidence of us having ridden horses, but that’s not to say that there aren’t older ones; we just haven’t discovered them yet.

Helen Scales: That’s always the case with archaeology, but this is the earliest evidence, and it’s really interesting because this is a place a long, long way from the Fertile Crescent, the part of the Middle East where we think a lot of agriculture began and other types of domestication of cows and so on.

Chris Smith: Well talking of farming animals and keeping animals and beasts of burden and things. I don’t know if horses are linked to the greenhouse effect, cattle certainly are, and now it looks like we can blame burps, not just from cattle, but from aquatic animals too for the greenhouse effect. Tell us about this.

Helen Scales: Yes. Animals that live in rivers, lakes and in the seas emit burps or farts, if you like, of nitrous oxide which is a potent greenhouse gas, and a new study has shown for the first time this is what’s going on.

Chris Smith: So it’s a laughing gas, nitrous oxide, isn’t it?

Helen Scales: It is, absolutely. I’ve never tried it. Does it actually make you laugh?

Chris Smith: It made my wife laugh when she had too much of it having a baby but…

Helen Scales: That’s good. If you can laugh when you’re having a baby, then it must…

Chris Smith: Sounds like she was being bad for the environment too though.

Helen Scales: Well, maybe, yes.

Chris Smith: So tell us about these animals. Why are they producing it?

Helen Scales: Right, well this is, it’s coming from their guts of these various creatures, and it’s actually the bacteria inside their guts that are beginning to break down nitrates which are taken in from the environment. And this was a study in the journal, PNAS, led by Peter Steef and colleagues from Aarhus University in Denmark, and they went out and collected 21 different types of animals from lakes and rivers and from coastal areas in Denmark and in Germany, and that included various invertebrates like various molluscs and insect larvae, including something called Chironomus plumosus, which is a midge.

What Steef and his team did, they brought these animals into the lab, and they measured the gas that was coming out of them, and that's both from intact animals, still alive, and from their dissected guts, and they discovered that nitrous oxide is indeed produced by a variety of species, in particular ones that filter their food from the water, or scoop and scrape it up from muddy sediments, and they’re called deposit feeders.

Chris Smith: Now you mentioned earlier that what they’re doing is metabolising nitrates that are in the water. So does that mean there’s a strong association between putting fertiliser on fields and then these animals putting this out as nitrous oxide in the air?

Helen Scales: Yes, this is what’s particularly worrying about this is we know that the amount of nitrate in rivers and seas is going up, and that’s mostly, like you say, due to fertiliser. We put nitrates on the land, so we can grow bigger crops faster, but they do wash out in rainwater into these water systems. And in this particular case, having more nitrate could end up leading to more nitrous oxide being emitted by these creatures.

Chris Smith: And the bottom line is less fertiliser on fields means less nitrous oxide coming out of these bacteria, is it?

Helen Scales: That should be the case, and it’s certainly points the way towards another reason why we really have to look at what we’re putting on the land and how that’s affecting our ecosystems and eventually maybe the global climate.

Chris Smith: Absolutely. And from global warming to globalisation! Turns out that us all being in contact with the whole world is, not surprisingly, helping with scientific research and communication and problem-solving.

Helen Scales: Yes, there’s no doubt at all that we live today in an interconnected globalised world, but is it a good thing or a bad thing? Well a new study suggests that globalisation could lead to people co-operating more at a global level. Well Nancy Buchan from the University of South Carolina in the US led an international team of researchers who’ve been looking into the issue in a study published in the journal, PNAS.

Chris Smith: So what have they done?

Helen Scales: What they did was they took a load of volunteers, over a thousand people from lots of different countries including Argentina, Iran, Italy, Russia, South Africa and the US, and basically they gave each volunteer ten hypothetical tokens each worth an equivalent of about fifty US cents, and they asked them to allocate the tokens between a personal, a local or a world account. And the question they faced was essentially do you want to keep all the money for yourself with no return, or do you put it into a local account that will give you a moderate return, but it will also benefit other local volunteers involved in the study, or do you put it into a world account, and that sees a smaller return but it will benefit other people in other countries. And the volunteers weren’t told how many other tokens people involved in the study were putting into the world account but the more they did the more each volunteer would gain.

Chris Smith: And when they do this, was everyone altruistic and did they put all their money in the world account, or were they greedy people who just put it in their “I’ll keep that all to myself thanks” account?

Helen Scales: There was a mixture, very interestingly. There was a great range in what people did. And the interesting thing that came out of this study was that the researchers also measured something called Individual-level Globalisation Index, or IGI, and that essentially is a sort of scoring of how connected someone is to a global network. It involves asking questions like do you use a mobile phone to ring people in a different country, things like that, and what they found was that people with higher IGI scores were those ones who were allocating more of their tokens to the world accounts.

Chris Smith: So you didn’t see all the capitalists keeping the money for themselves and saying, no forget the poor, and you didn’t see all the poor people thinking no we’ll keep all this to ourselves because we need it more than anybody else - it was actually a fair spread?

Helen Scales: It was a mixture, I think. You know, very much a spread within each country and between countries. I mean it’s a very clever way of doing the study, and it’s very involved actually how they do these questions, but it does indicate your willingness to co-operate, and that could reflect very importantly in real world scenarios not just in pretend paper money.

Chris Smith: But are they nicer when they’re playing Monopoly - I very much doubt it. Thank you very much, Helen Scales from the Naked Scientist, taking a look at some of this week’s top science news stories. And if you’d like to follow up on any of those items, the details and the references are all on the Open University’s website, and that’s at open2.net/breakingscience.

In just a moment, how to spot an earthquake from space and then watch as the ground recovers itself. But first to the carbon sponge that’s the Amazon Rainforest.

The Amazon is a massive consumer of carbon dioxide. It currently locks away something like a 100 billion tons of carbon, and the whole forest covers an area of about six million square kilometres, so it’s truly huge.

But now researchers have found compelling evidence that climate change could in fact turn it from our carbon companion into a carbon criminal, and that’s because a drought in 2005, which was triggered by abnormally warm water in the North Atlantic, then went on to turn the Amazon from a carbon sink into a carbon source. Oliver Phillips…

Oliver Phillips: The problem we’d like to solve is ultimately what’s the carbon balance of the Amazon, this vast system, the biggest tropical forest in the world? It’s processing an enormous amount of carbon each year. There was a big drought in 2005 which affected a big part of the Amazon. The question that we address to is then how much impact did that have on the carbon balance, in the context of the fact that the previous two or three decades the system had actually been a sink of carbon, so it had been absorbing rather more from the atmosphere than it had been letting out.

Chris Smith: Do you think that that drought can give us some kind of insights into what might be in store for us in the future then?

Oliver Phillips: Well it could do. One of the interesting things about the 2005 drought was it was actually driven, we think, by warming in the north tropical Atlantic, and that also was the same year, if people remember, 2005, was the year of Hurricane Katrina and, in fact, it was by far the most violent hurricane season on record in the Atlantic.

Chris Smith: And how did you work out or study the impact of that drought on the Amazon in 2005 to try and get a handle on what might be in store for us?

Oliver Phillips: The important thing to say on the paper we’re talking about there were actually 68 co-authors. So it’s such a huge area; it’s six million square kilometres. We rather naively set out to find out what’s happening in the system by measuring lots of small plots in different places and actually eight different countries across the Amazon. And every so often, every few years, you go back and measure each tree and see how it’s grown, or if it’s died as they occasionally do.

You need to work out what species you have, because depending on what actual species the tree is it’ll store more or less carbon within it. And then knowing the diameter and the species you can work out, to a reasonable degree of accuracy, how much carbon’s in the system.

Chris Smith: Well can you put some numbers on it for us then because the Amazon is, as you say, huge and therefore the amount of impact it can have on world climate, potentially, could be huge so how much carbon are we looking at here?

Oliver Phillips: Well the system stores probably, we think, more than a 100 billion tons of carbon. So to put that into perspective, that’s getting on for 14 times the global annual emissions from burning fossil fuel. So there’s a big number there.

What we find is that prior to 2005 for at least 20 years, and that’s about how far back the measurements go, on average each year the system was a sink, and that’s about 0.5 billion tons. Then in 2005, according to our calculations, the best estimate, a billion tons of carbon was emitted from the system. So you have a baseline that was a sink of half a billion, in 2005 there was a source. That means that the impact of the drought itself was worth about one and a half billion tons of carbon.

Chris Smith: But what about the knock-on effect, because it’s one thing to look at the drought as it happened and say in that particular year there was a big release, but it takes a while for the trees that die to then surrender the carbon dioxide, or to surrender the carbon they’ve got locked up inside them, back into the atmosphere so the legacy of 2005 will go on for a lot longer won’t it?

Oliver Phillips: Exactly, so that one and a half billion tons is the total impact that the drought had on the forest. And, as you say, the atmosphere itself won’t see all of that in the first year because trees take a, once they’ve died, they take time to decompose, and it’s only when they decompose that the carbon’s returned as carbon dioxide to the atmosphere. So, if you like, that one and a half billion ton hit is smeared over several years, probably 2005 and mostly four or five years since then.

Chris Smith: These are pretty big numbers so, and you sort of hinted at this earlier, which is that this gives us some kind of insights into what could be in store for us if we carry on business as usual, and the models that people are predicting for what will happen to Earth’s climate in future do play out. So where do you think this sees us heading?

Oliver Phillips: Well they are big numbers. The Amazon is in some centres we expect to be quite resilient, so we can almost expect the system to have recovered because there hasn’t been a big drought since. But I think the interesting thing about the study is not so much the number that we put on 2005, as saying here’s the sensitivity of the forest, and given that climate models, most of them, do predict an increased drought risk in the Amazon, by knowing the sensitivity we can project what that climate change is likely to do to the system.

Chris Smith: A sober thought for the world’s largest rainforest. That was Oliver Phillips from the University of Leeds. He’s published that work this week in the journal, Science.

Now from mending the weather to fixing the Earth’s crust, and scientists have observed how the ground recovers after an earthquake. But they haven’t done it from Earth’s surface. They’ve actually done it from space using a European Space Agency satellite to collect very precise radar measurements.

The area they’ve been focusing on is a fault that runs beneath the Iranian city of Bam and which was responsible for triggering the 2003 earthquake that killed over 26,000 people. The problem with faults like this one is that they remain invisible until they cause a catastrophe, and so scientists are very eager to understand how the ground changes around faults like this so that we can become better at spotting them in future. Here’s Eric Fielding…

Eric Fielding: We’ve discovered a healing event that happened after an earthquake in Iran where the earthquake caused damage to the upper layers of the Earth’s surface and then in the three and a half years after the earthquake those layers started to heal from the damage that was done during the earthquake.

We know that the fault rupture started at a depth of around seven kilometres beneath the Earth’s surface and the earthquake rupture propagated from south to north, unfortunately, putting the energy into the city of Bam, and some of that energy reached the surface. So then, as soon as we received the seismic waves on the earthquake, we realised that this was a large earthquake and put in a request with ESA to have them collect images on the European Space Agency satellite called Envisat.

Chris Smith: How are you actually making the measurements?

Eric Fielding: We use radar data by using a processing technology called interferometry, which is basically a fancy word of subtracting one radar image from the other, because the satellite has a 35-day orbit, and we had to wait 12 days to get the first image after the earthquake, and then we continued the radar monitoring every 35 days for the three and a half years afterwards to see what happened after the earthquake.

Chris Smith: And what sort of resolution can you see? How much can you pick up in terms of the detail of these movements from space?

Eric Fielding: Well the total deformation that we measured with this technique is about three centimetres over the whole time interval, so we’re picking up a relatively small motion that you wouldn’t really see if you were out there behind your house. It’s a very sensitive technique, and we can see motions as small as a few millimetres.

Chris Smith: So, as you watched the grounds change over time, how did it change, if you could just talk us through the timeline of what actually happened on the ground and bring us up to the present day where we are now?

Eric Fielding: Well the biggest signal that we measured from the radar data is the ground surface moving downward, almost like a ditch, about 200 metres wide and ten kilometres long. The area went down after the earthquake, rapidly at first and then slowly decelerating. It’s still going down somewhat now but at a much lower rate.

Chris Smith: And why did it go down at all?

Eric Fielding: This is caused by this healing process where during the earthquake, as the energy from the earthquake rupture came up to the surface and spread out into this wide damage zone in the surface layers of the Earth, it caused those rocks there to expand somewhat. Then after the earthquake those rocks are contracting to go back to a new configuration that’s compatible with the slip at depth.

Most of the earthquakes occur on large faults that we can see. You know, the San Andreas Fault is a famous one here in California that is very visible even from some distance way. Other faults are buried like this one that happened to be underneath the city of Bam and unfortunately ruptured in 2003.

Chris Smith: Despite the fact that it has ruptured and triggered an earthquake, is it still buried? You still can’t see the actual site of the fault from space?

Eric Fielding: Well we can see the site of the fault from space by using the radar interferometry technique. So in fact, after the earthquake happened, I sent some of our radar images to a colleague of mine in Iran. He went to the field and was able to locate small cracks at the surface. But the amount of motion on those cracks was only a maximum of around 25 centimetres, and we know from the radar data that the total slip on the fault at depth is maybe two metres.

Chris Smith: And what does this actually add to our understanding of earthquakes? I mean they’re a major phenomenon, they kill lots of people. Well earthquakes don’t, buildings do. What does this add to our understanding of how earthquakes occur, how we might be able to predict where they’re going to occur and what happens after them?

Eric Fielding: This tells us about how some of these faults have surface layers that absorb the fault motion over some wide zone. Because it’s absorbed over a wide zone, it’s a very subtle sign at the surface. These small cracks that we observed after the earthquake will likely be erased by erosion within 50 years or less, so we need to have other ways of finding these faults to evaluate the risk of earthquakes in places where there might be these types of blind earthquake faults.

Chris Smith: And does this study give you clues as to where they might be and how to spot them?

Eric Fielding: Well I think it tells us how this process works. It’s a matter of now taking that information and applying it to, looking for other types of places that would include this type of surface material that would be likely to absorb earthquakes. The fault beneath Bam, we think, hasn’t ruptured in at least 2,000 years. We need to look in other parts of Iran where there may be some subtle motion that we can pick up with radar imagery or other techniques such as a global positioning system or other ground measurements.

Chris Smith: So we could find more hidden fault lines in the future. That was Eric Fielding from NASA’s Jet Propulsion Laboratory in California. He’s published that work this week in the journal, Nature.

You’re listening to Breaking Science with me, Chris Smith, and it’s time now for this week’s ‘Stuff and Non-Science’, where we massacre myths and having a smashing time shattering a myth about glass, here’s Diana O’Carroll.

Diana O’Carroll: This week on ‘Stuff and Non-Science’, we’re taking a look through antique glass. Some people say that century-old windows are thicker at the bottom because glass is a liquid and has flowed down over time. But is this true, Stephen Byrne?

Stephen Byrne: In brief, it’s a myth. I mean people often say this and what they mean is that within a window there are individual pieces of glass which are thicker at the bottom. But then the assumption is that they were all uniform before, and I don’t think this is correct.

First of all, you can think about how glass was historically made, and a lot of sheet glass was made by the so-called Crown method which is where, at the end of a rod, you attach a globe of molten glass and spin it faster and faster until this globe of glass is flattened, and it’s thinner at the outside of the sheet and thicker at the inside. But what it doesn’t explain is when you go into a church and look at old windows, why so often, and people are quite right to say this, there are little bits of glass which are thicker at the bottom than they are at the top. And the reason for that is a reason to do with the way in which stained glass windows are actually made. If they’re well made, that’s how they’ve been put together.

Now, when you’re putting together a window, if you’ve got a piece of glass that’s thicker on one end and thinner at the other, you obviously put the thicker piece of glass at the base, into the lead, because then it’s more stable; it’s got a bigger base. And, secondly, it gives you better protection against the weather. If the glass is thicker at the bottom, there is very little space for cement which means there isn’t any space for the rain to corrode cement and go in.

Diana O’Carroll: Stephen Byrne of Williams & Byrne Glass Studios in Shropshire with a very practical solution for making stained glass that will last. More ‘Stuff and Non-Science’ next week, but if you’d like to suggest some more, then email me and that’s diana@thenakedscientists.com.

Chris Smith: And it turns out that glass isn’t the super-cooled liquid that people often think it is. It doesn’t actually flow like a stodgy fluid at all. Thank you, Diana. That was Diana O’Carroll with this week’s Stuff and Non-Science.

That’s it for this time. We’ll be back next week with another round-up of global science news.

Breaking Science is produced in association with the Open University and that means you can follow up on any of the items that are included in the programme by the Open University’s website which is at open2.net/breakingscience. You can also find the way there from the BBC Radio Five Live Up All Night web pages.

The production this week, it was by Diana O’Carroll from thenakedscientists.com, and I’m Chris Smith. Until next time, goodbye.

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Background

These are the sources used by the Naked Scientists in making the show:

In the news

'The Earliest Horse Harnessing and Milking'
by Alan K. Outram, et al
in Science

'Exomic Sequencing Identifies PALB2 as a Pancreatic Cancer Susceptibility Gene'
by Siân Jones, et al
in Science

'Nitrous Oxide Emission by Aquatic Macrofauna'
by Peter Stief, Morten Poulsen, et al
in PNAS

'Globalization and Human Cooperation'
by Nancy Buchan, et al
in PNAS

Interviews

Oliver Phillips on 'Drought Sensitivity of the Amazon Rainforest' by Oliver L. Phillips, Luiz E. O. C. Aragão, Simon L. Lewis et al in Science

Eric Fielding on 'Shallow fault-zone dilatancy recovery after the 2003 Bam earthquake in Iran' by Eric J. Fielding, Paul R. Lundgren, Roland Bürgmann & Gareth J. Funning

Stephen Byrne for 'Stuff and Non-Science'