Nature Podcast

This is a transcript of the 29th January 2015 edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to mailto:podcast@nature.com.

Jingle

Geoff Marsh: This week, doing archaeology amidst civil war.

Savino di Lernia: We have to imagine an archaeology without field work in the future. For this country and this could apply even to other countries.

Kerri Smith: And parts of a human skull found in a hidden cave in Israel.

Israel Hershkovitz: Nobody actually knew that there is a cave there because the entrance to the cave collapsed thousands and thousands years ago.

Geoff Marsh: Plus testing relativity with crazy precision. This is the Nature Podcast for 29th of January 2015. I'm Geoff Marsh.

Kerri Smith: And I'm Kerri Smith.

Jingle

Kerri Smith: A few years ago during some construction work in northern Israel a bulldozer scraped away some earth and revealed a tiny opening to a giant limestone cave. It's a huge cavern with a high ceiling and lot of statuesque orange tinted stalagmites. Amateur cavers soon explored the space but they weren't the first to find Manot cave alluring. Tens of thousands of years ago, humans were already occupying it. Now a team of archaeologists report one particularly good find, a battered, 55,000 year-old piece of skull. It looks remarkably modern. In fact, it may belong to a group of humans who later colonized Europe and might even have interbred with Neanderthals. Anthropologists. Israel Hershkovitz from Tel Aviv University is one of the team. He tells Nature reporter Ewen Callaway about their first visit to the cave. Nature (2015)

Israel Hershkovitz: Nobody actually knew that there is a cave there because the entrance to the cave collapsed thousands and thousands years ago. We first entered to the cave through this small opening that was created by the bulldozer and the immediate survey of the cave told us that the cave was inhabited by prehistoric men for thousands and thousands of years. So it's an amazing, beautiful prehistoric cave.

Ewen Callaway: Tell us about the skull you found.

Israel Hershkovitz: Okay. The skull is very gracile, there is nothing on the skull that makes it different from a modern skull. It is a rounded skull, it's very rounded skull very typical to modern human skull but on top of it the skull, the skull still keeps what you call several archaic traits, you know old traits can be found in much older specimens, so it's a combination.

Ewen Callaway: So your team is arguing that you think that the skull represents a wave of humans, who migrated out of Africa some 60,000 years ago.

Israel Hershkovitz: This is the first evidence that showed that indeed there was a large wave of African migrants coming out of east Africa crossing the Sahara desert, crossing the Nubian Desert coming up along the Mediterranean coast, then inhabiting the eastern Mediterranean region, roughly 55,000 years ago. So it is really a key skull in understanding modern human evolution.

Ewen Callaway: Are you saying that this skull represents the ancestors of the humans who went onto colonize Europe?

Israel Hershkovitz: Yes, the morphology and the shape of the skull clearly show that the Manot skull is very similar to the early upper Palaeolithic skull which implied that the Manot people probably are the forefathers of many of what you call the early upper Palaeolithic population of Europe.

Ewen Callaway: Could the human who possessed this skull, could he or she have encountered Neanderthals?

Israel Hershkovitz: It's a possibility. I mean, what you have to remember if you take the Manot's cave, you can easily see that Manot's cave is less than 50 kilometres from Kebara cave or from Amud cave and we know from the skeletal remains that the people who inhabited those caves, Kebara and Amud were Neanderthals. They were living side by side for thousands and thousands of years. So imagine to yourself, here we actually hold a skull of human being that could interbreed with the Neanderthals.

Ewen Callaway: When humans and Neanderthals interbred you had hybrids, is it possible that this skull could represent one such hybrid?

Israel Hershkovitz: Well, first of all it's a possibility. The problem is how you identity hybrids, how he would look like, a hybrid of Neanderthals and modern humans unless we will succeed in extracting enough DNA from the skull and do the genetic analysis and this would give us the ultimate answer to your question. Otherwise we don't know.

Ewen Callaway: That's exactly what I wanted to ask you next, is there any possibility that scientists, that we'll be able to recover DNA from the skull to answer that question?

Israel Hershkovitz: Well, honestly the chances are not great. I'm very sorry to disappoint you in this respect. The chances are not great. The DNA material is not preserved in the south and Levantine of the climatic condition and so on your chances are much better if you go up to a much colder area but still we don't have to give up because you know technology is improving all the time and we can work with less and less material.

Kerri Smith: That was Israel Hershkovitz talking to Ewen Callaway and there is a high chance there'll be more skull hiding places he says because of Israel's geology.

Israel Hershkovitz: Most of Israel, 90% of Israel is limestone, so basically Israel exactly like a Swiss cheese with millions of folds.

Kerri Smith: So there's a whole lot more to find out about the human conquests of the Middle East.

Geoff Marsh: Stressed out mice and a shakeup of some high school chemistry in the research highlights now with Noah Baker.

Jingle

Noah Baker: White blood cells taken from stressed mice can boost mood in other mice. It's assumed that the nervous system mostly controls mood, but the rest of the body gets involved too. A group at the National Institute of Health stressed mice out by putting in on social situations where they were of lowly rank. Then they transferred some of their white blood cells, lymphocytes to other mice with no white blood cells of their own. These mice ended up with lower stress levels and staved off inflammation. The find could help scientists make fast-acting antidepressants. The paper is in the Journal of Neuroscience. The Journal of Neuroscience 28 January 2015,  35 (4): 1530–1538If you drop sodium into water like your teacher might have done in chemistry class, the sodium can explode. The reaction gives off hydrogen and heat. Chemists believe that the heat ignites the hydrogen and causes the explosion, but that might be a school boy error. A team based in Czech Republic watched the reaction with high-speed cameras and found that the metal is exploding too early for heat to be the cause, instead they think that each sodium atom at the surface loses an electron and now positive ions then repel each other causing the explosion. For more check out Nature Chemistry. The Journal of Neuroscience, 28 January 2015,  35 (4): 1530–1538

Jingle

Geoff Marsh: If you were around in 1880s you might well have been convinced that we lived in something called ether.It would be impossible to decide which of them moves or standstill with respect to the ether.I cannot but regard to the ether which can be the seat as well as the clocks are resting in the ether.

Geoff Marsh: Physicists thought the light waves travel through the ether like sound waves travel through air. In 1887, two physicists called Michelson and Morley put this to the test. They sent out two beams of light, one in line with the earth's rotation and another one at right angles to it. Their thinking was that if there was ether around, the light would go at different speeds in these different directions. To their surprise, the speed of light was the same, no matter how they oriented their experiments. Their finding went onto become one of the most famous negative results in scientific history, known as Lorentz symmetry, the rule is also fundamental to Einstein's theory of special relativity, which says that the speed to light is constant, done deal. The only thing is even with robust laws like this, modern physics can't explain everything, things like dark matter for example have led physicists to question even these most fundamental laws of nature. Thaned Pruttivarasin is among those revamping the Michelson-Morley experiment with ever increasing precision. In his experiment, he has replaced light with electrons. Lizzie Gibney spoke to him starting by asking how he had gone about dragging a 19th century experiment into the 21st century. Nature 517, 592–595 (29 January 2015)

Thaned Pruttivarasin: We used very much technology with trap atoms in our case, a pair of calcium ions. People have been developing this kind of technology in the context of quantum information, quantum computing for the past 20 or 30 years. So we have a really good control over the behaviour of this kind of ions. And that allows us to basically do whatever we want to them.

Elizabeth Gibney: And so in this experiment you're not testing the speed of light, but what about the electrons, are we trying to establish?

Thaned Pruttivarasin: For electrons, the Lorentz symmetry says that no matter what directions these tiny particles travel in, the total kinetic energy shouldn't depend on which direction it's moving, so for example, if the electrons move in towards the left or to upwards then you should measure that same energy. So what we did in the experiment is, we measured the energy between electrons, which is bound in the trapped calcium ions and look for energy shift between electrons oriented in different directions.

Elizabeth Gibney: And go on then put us out of our misery. Was there any difference? Have we broken this rule that has been around for hundred years?

Thaned Pruttivarasin: No, so far as far as you can say about the results of our experiment, the Lorentz symmetry still holds, so far so good (laughs).

Elizabeth Gibney: And is there anything that makes us think that rule shouldn't stand?

Thaned Pruttivarasin: This symmetry is the foundation of what we call the standard model of modern particle physics and we already know that the standard model doesn't explain everything we have seen in nature. For example, it doesn't explain dark matter, dark energy and there are many candidates for this kind of beyond standard model theory and one of the things that people are excited about is String theory and some version of String theory actually predicts or suggests that Lorentz-violation can be violated in a path which actually accessible in this kind of precision measurement.

Elizabeth Gibney: And so how sensitive is your experiment? What kind of levels we're talking about here how fine are we going?

Thaned Pruttivarasin: In terms of number of the tests, Lorentz symmetry in a path in pinned to the 18 so that's probably doesn't mean much if you are not in the business of precision measurement so if you want to compare to what we know in daily life, it's trying to determine, if anyone has added a cup of water into the Caspian sea.

Elizabeth Gibney: Wow so these are really quite stringent tests and what happens next then are you going to try and push it even further?

Thaned Pruttivarasin: So there are quite a few improvement that we can do based on the techniques in this paper and hopefully within a few years we can hope to pick it may be ten thousand times. So that would be the hope but it's just the beginning of this technique applied to this kind of Lorentz symmetry testing. Hopefully, someday we will see some kind of violation.

Geoff Marsh: That was Thaned Pruttivarasin who is affiliated with RIKEN in Japan. He did the study while at the University of California, Berkeley.

Jingle

Geoff Marsh: It's been four years since the Arab spring reached Libya sparking the revolution which toppled the Gaddafi regime but that was only the start. Libya is still plagued by instability and civil war and recent months have seen the violence escalating. Libya is hugely important to archaeologists stretching from the Mediterranean to the Sahara. It represents a hot spot for research into our deep and recent history, boasting nine thousand year old rock art, Islamic tombs and several UNESCO World Heritage sites, but field work in Libya has ground to a halt. With the ongoing civil war making it impossible to work safely and important heritage sites are under constant threat. Italian archaeologists Savino di Lernia from the University of Rome La Sapienza has been working in Libya since 1990. In a comment piece this week, he urges the international community to come to the aid of the Libyan archaeology. He had to make a dramatic escape with his students in 2011. Here he is. Nature 517, 547–549 (29 January 2015)

Savino di Lernia: We were in the south-western Libya and we were doing our field work, we heard about the situation by Arab through the regions that the situation was getting very, very dramatic. So we tried to go away but the roads were closed, were many revolutionary clashes already going on. We were able to get an Italian military aircraft and we directly flew from Sabha to Rome without stopping in Tripoli. The airport in Tripoli was already closed and the situation was very dramatic.

Geoff Marsh: So what would a researcher be risking to be in the field now?

Savino di Lernia: There is now a strong control in the country. The mobility within the country is dangerous. Some of our work in the southwest of Libya, close to the Algerian border and that area is totally out of the central government control. We can't get authorisation by our Ministry of Foreign Affairs; we can't get the authorisation from our universities. At the moment, nobody can even imagine a possibility to go back again in Libya.

Geoff Marsh: What is it about Libya that makes it so special to archaeologists?

Savino di Lernia: It's an incredible place. It's just in the middle of many crucial major connections, it's just on the sea, the Mediterranean sea goes to the Sahara, incredible rich archaeological and historic heritage and UNESCO recognized this, we have five UNESCO World Heritage sites in Libya.

Geoff Marsh: So, what's the worry, can't we just pick up where we left off with archaeology in Libya, once the violence subsides?

Savino di Lernia: First of all, the lack of control by the custodians of the Libyan heritage, the people, the colleagues of the Department of Antiquities, they have great difficulty to do their own work. They can't control the sites, they can't go in the field without planning the risks to being kidnapped or something else. We record a long list of damages and it's so sad to see many beautiful Islamic monuments destroyed in the last few months. It is really something we couldn't imagine four years ago at the beginning of the revolution.

Geoff Marsh: Why are these areas being damaged, it's not just because they're caught in the crossfire, is it sort of ideological?

Savino di Lernia: Some cases, for example, the castle in Sabah, is a town in the desert 200 years old and was hit by rockets just last year. Then we had like in the very important necropolis over Cyrene in the north of Libya, a UNESCO World Heritage Site, there were damages related to the building of houses and again we have ideological damages, many statutes or many images in the country have been destroyed because they do not follow Islamic view of some of the people who want to go ahead with this kind of radical view of Islam. The situation is totally out of control at the moment in Libya in this sense. This is why I'm so concerned about the future for the country and the heritage of the country.

Geoff Marsh: So if it's still too dangerous to go out into the field, what do you propose as your short term solution to keep Libyan archaeology alive?

Savino di Lernia: The most important thing I believe is to let Libyan scientists and colleagues to work again on the archaeological heritage. There is a huge quantity of archaeological materials and context that can be studied in the lab, can be digitalized. So there's much of work that can be done. We have to imagine an archaeology without field work in the future, for this country and possibly not only for Libya, but this could apply even to other countries. We have problems to let Libyans to come in Italy for example for getting visas because the situation, the international situation is becoming more and more difficult we have problems to get fundings in order to do lab analysis on archaeological materials which are stored in Libya and we have problems in moving these archaeological materials from Libya abroad. So if we have to do something, we have to review the way archaeological projects can be funded in Libya, and we have to review the way archaeologists from Libya can really interact with European and other country. They do not apply for nothing at the moment. They are scared by the situations, so it's very important to start again to do something together. Otherwise also this piece of identity related to Libyan archaeology, Libyan cultural heritage could be lost. This is my personal concern.

Geoff Marsh: Do you think that the situation will ever go back to normal in Libya? Do you think that archaeological field work will go back to normal?

Savino di Lernia: To be honest I'm not very optimistic because the country is devastated now by four years of civil war and really nobody can see an end.

Geoff Marsh: That was Savino di Lernia.

Kerri Smith: Now it's news time and US news editor, Matt Crenson joins me on the line from Washington D.C. Welcome Matt. Now Philae, the little probe, the little lander that everyone will remember was dropped off by Rosetta onto the comet 67P is lost, isn't it? Nature 517, 536–537 (29 January 2015)

Matt Crenson: Yes it is. It was lost on arrival in November and although the researchers know roughly where it is, they'd like to be able to pinpoint its location and haven't been able to do that yet.

Kerri Smith: So it's a pretty kind of low-tech reason, its batteries ran out, which you know happens to us all, is anyone going to look for it?

Matt Crenson: Well they can't decide, there's a possibility of making a last attempt to find it. Philae is currently in a spot about 20 meteres wide by 200 metres long they know and it would be possible to take the orbiter Rosetta from its current 20 kilometre orbit down to about 6 kilometres and swoop it over this area to look for Philae but that would use fuel which is in limited supply and it would mean that later on Rosetta couldn't do a similar manoeuvre to take a really beautiful shot of the comet in full sunlight.

Kerri Smith: And are there scientific reasons for looking for the Philae lander or is it mostly just sentimental?

Matt Crenson: No there are actual scientific reasons. It has collected some data and sent it back and understanding those data and what they mean rely on knowing exactly where it's sitting on the comet's surface.

Kerri Smith: And of course isn't it made a bit more difficult by the fact that there is also some great science that Rosetta could continue to do if it wasn't burdened with looking for Philae.

Matt Crenson: Well, mostly the trade-off is this other observation of the comet in full sunlight without shadow from a close range. They get a really great, possibly the best ever look at a comet.

Kerri Smith: And there has of course been quite a lot of science pouring out of the mission so far, which the story goes into. Can you a give us a brief recap?

Matt Crenson: Well, it's gotten a really good look at the comet, so researchers have a good idea of what its surface is like and what's it made of. It's got these little pits on it that seemed to have vented gas as it approaches the Sun and then it's got these round things on it that they're calling it dinosaur eggs and so they've mapped the surface and divided into these sort of sections that they've named after Egyptian gods.

Kerri Smith: I have to say the whole thing reminds me a bit of the film Interstellar where the crew has to make a decision on which exoplanet it's going to go and visit because it doesn't have enough fuel to go to them all.

Matt Crenson: It's a typical problem in space exploration and the thing that you want to send out into outer space, it got to get past earth's gravity and so you always have a limited amount of payload and that includes fuel.

Kerri Smith: Do we know when ESA is going to make a decision on whether to look for Philae or not?

Matt Crenson: We don't exactly. They are turning it over right now and they have to decide soon obviously, but there is no stated time.

Kerri Smith: Okay, hanging in the balance there, poor little Philae. It's really hard not to anthropomorphise that little space lander. Now Matt we're going to move onto second story you've brought for us. Obama gave his State of the Union address last week and of course science got a mention in the form of climate change. Here's what he had to say about it briefly. Nature 517, 535–536 (29 January 2015)Excerpt from Obama's State of the Union AddressOver the past six years, we've done more than ever to combat climate change from the way we produce energy to the way we use it. That's why we've set aside more public land and waters than any administration in history. And that's why I will not let this Congress endanger the health of our children by turning back the clock on our efforts. I am determined to make sure that American leadership drives international action

Kerri Smith: And the news story this week that's by our reporter Jeff Tollefson looks at what Obama has achieved vis-a-vis climate change in the last six years of his office.

Matt Crenson: Yeah, so Obama has had an uphill battle on climate change all along. He came into office promising to do something significant about it and didn't have any success in his first term passing legislation to reduce greenhouse gases emitted by the US. Now he's halfway through his second term, he's only got two years left in office and in the November elections, both Houses of Congress turned Republican, he's got some stiff opposition there and it's unlikely he's going to get any legislation passed.

Kerri Smith: So as you mentioned, you know, the Republican Senate, especially is making it quite difficult for him to get legislation through. What else can he do? What realistically is in his grasp?

Matt Crenson: There's quite a bit he can do in writing regulations and making international agreements. Presidents have pretty broad authority in those areas. So the Environmental Protection Agency is working on some regulations that would affect power plants. One of the biggest sources of carbon dioxide in the US is coal burning power plants and these regulations would clamp down on those emissions and have a pretty significant effect. He's also going to issue some regulations on methane production in oil and gas exploration and those are also pretty significant course methane is much more powerful greenhouse gas than carbon dioxide. And perhaps most notable, he made an agreement with China in November to hit some long-term goals in reducing greenhouse gases. The US has committed to reduce its emissions by about 26% to 28% by the year 2025 and China has agreed to stabilize its emission by 2030.

Kerri Smith: Yeah, so I mean, it's not looking like a bad legacy necessarily. I mean, he's only halfway through his second term but people optimistic about what he might leave behind him in terms of climate?

Matt Crenson: Well it's mixed. I mean, he could certainly do more with cooperation from Congress, but he will be able to make some headway towards meeting the commitments that the US made before the Chinese deal. And you know with some further progress to the commitment to the China deal might be made as well.

Kerri Smith: Just out of interest, from someone who is reasonably naive about the US political system do Presidents get kind of a limited number of these, you know, bonus cards that they can just sort be like right I'm doing that, I'm doing that?

Matt Crenson: They don't in fact and Presidents have of late in the last few decades been using these sorts of executive orders more and more, you know, you hear about gridlock in Washington and this is a way to get around some of that and to get what you want. And so Presidents in both parties have been using these kinds of actions increasingly in recent years.

Kerri Smith: Matt thank you and if you'd like to read those stories in full then as ever, http://www.nature.com/news is the place to be.

Geoff Marsh: We've just released the latest episode of Backchat bringing you the stories behind the stories in science this month. Hear Nature reporters chat about objects lost in space and the experiments that make you think, why didn't I think of that? Find that on iTunes or on the podcast page, http://www.nature.com/nature/podcast or follow us on Twitter @NaturePodcast.

Kerri Smith: We'll be back next week with something that's light and strong and a story that will make the earth move. Thanks for joining us. I'm Kerri Smith.

Geoff Marsh: And I'm Geoff Marsh.

Jingle