This week the team investigates how planets came to be, lighting that brings midges thick and fast, and why flu jabs are even better than you think. They also looking into definitive proof that humans are responsible for global warming and ask "are you a descendant of Ötzi the iceman?"
Plus, in 'Stuff and Non-Science', when you drop food on the floor does it remain clean for 5 seconds?
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, how scientists have sequenced DNA from the iceman to find out who he was.
Kat Arney: This now is the oldest complete DNA sequence of human mitochondria that’s been known to date, and this is from Ötzi who lived around 5,000 years ago. But using new sequencing technology the scientists have been able to compare Ötzi’s mitochondrial DNA with other sequences from modern Europeans who are living now around the place in Europe, and they’ve built an evolutionary family tree for him.
Chris Smith: So are you a relative of Ötzi, the alpine iceman? Kat Arney will be revealing the secrets locked away in his DNA, very shortly, when we'll also be delving even further back in time as scientists get their hands on meteorites from one of the first planets to form in our solar system.
Ben Weiss: We think that this body formed within maybe one and a half to two million years after the origin of the solar system itself. And we have samples from this body. The saltic samples with the vesicles, very similar to what you might see on the flanks of volcanoes in Hawaii today, but these samples are 4.564 billion years old.
Chris Smith: And that material’s helping Ben Weiss to understand the early history of the solar system and how we got here. That’s on the way, as is the answer to another age-old question, which is if I drop something on the floor but pick it up again quickly enough, is it still safe to eat.
Paul Dawson: The test we did was inoculating surfaces with salmonella bacterium and dropping food on those surfaces for five, 30 or 60 seconds and then seeing how much bacteria was transferred, and we found that within five seconds there was significant amounts of bacteria transferred to the food in that short amount of time.
Chris Smith: So that’s a no then, and the full story on the five second rule, or perhaps that should be five second misrule, is coming up shortly on 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 world, and with a selection of the tastiest morsels, here’s our science news hound, Kat Arney. Now Kat, winter’s on the way which means flu is too, but you’ve got some advice on how we should all avoid being laid low.
Kat Arney: Yes, it is that time of year again, mince pies, mulled wine and flu. Now some people, including the elderly and those with chronic diseases like asthma, can benefit from flu jabs, but now two new studies published in the journal PLoS Medicine have shown that actually it may be a case of the more the merrier when it comes to flu jabs. The researchers have found that increasing the number of people in the general population that have been vaccinated can actually cut flu deaths and other health problems, even for people who haven't actually had the jab.
Chris Smith: Because at the moment it's restricted largely to risk groups and people are told to have just one jab, so you’re saying increase the number of people who have the jab and also give them more jabs?
Kat Arney: Exactly, so led by Jeff Kwong from the Institute of Clinical Evaluative Sciences in Toronto, the first paper looked at the population of the Canadian province of Ontario, and they’ve had free flu jabs for all since 2000. And when the researchers looked at data from 1997 to 2004, so that’s covering the time when the jabs were brought in, and they looked at flu deaths, hospitalisations, visits to A&E, visits to the doctor, they found that, as you might expect, that the vaccination programme had really significantly cut these.
And one interesting thing they did find is that actually boosting the immunisation rate in the whole population didn’t really cut that many deaths in very old people, so people over the age of 75. But even though the vaccine’s actually free, it looked like they weren't getting a great take up of it, so they only got around 38 per cent of people going for their flu jab. So actually probably if you can get an even wider coverage of the vaccination of the population, you would do a lot more to protect elderly people from younger people who’ve just got the virus but it's not really causing them problems.
Chris Smith: Do you think that’s partly because some people have this view that if you get a flu jab it causes you to have the flu – which is nonsense, of course. But there is this idea, isn't there, people think you get vaccinated and then you get the flu sometimes.
Kat Arney: Exactly. There is this suspicion of it. I mean obviously a vaccine is something that will protect you against getting the disease, it's not going to give you the disease, but in fact it is very important, and this is where the second paper comes in. This is a study from Carline van den Dool and her team at the University Medical Centre in Utrecht, and they used computer models to look at what’s called herd immunity from flu.
This is trying to build up immunity in the wider population so that, even if not everyone’s covered, you’ve got a good overall immunity to the disease. And they were simulating how flu spreads in nursing homes, and they found that actually by giving the healthcare staff of the nursing home flu jabs, in a nursing home with 30 people in it, this would actually reduce patient infections by about 60 per cent. So that’s probably quite significant and so maybe vaccinating our healthcare workers here could do a lot to prevent the spread of flu this year.
Chris Smith: What about cash though because this all comes down to money, ultimately, and although it sounds awful we have organisations like NICE to work out what’s cost-effective and what isn't. So is this a financially cost-effective thing to do?
Kat Arney: Well, that’s something for NICE and the Government to decide, but obviously this now is some evidence to back up a decision that it really is a good thing to vaccinate your population widely. So obviously NICE makes it decision based on evidence, and here is some good evidence, so maybe they’ll take that into account.
Chris Smith: Well let’s hope so. Have you had your flu jab?
Kat Arney: I'm going to have mine on Monday actually because I do have asthma, so I will be going to get my flu jab.
Chris Smith: Good for you. Well, look, sticking with infectious things, there’s also very interesting data coming out about cholera. Because most people think of this as just something you catch from dodgy water, but they could never explain why you ended up with cholera cases occurring inland well away from the sea where cholera comes from. Now researchers have got a better idea as to what’s going on.
Kat Arney: Absolutely, and this is a fascinating piece of research. It's published in the Journal of Experimental Biology this week. Now cholera is a major killer around the world, it claims millions of lives, and now these researchers from the Hebrew University of Jerusalem have explained that it may be midges that kind of pick up the deadly bacteria and spread it around, and they’ve explained how they’re attracted to inland bodies of water.
Now Amit Lerner and his team have found that female midges, these are the midges that carry the bacteria, seem to prefer certain ponds in which to lay their eggs, but they weren't really sure what was special about these ponds. But then the scientists noticed that these little bugs preferred dark patches of water that reflected little light. And then they did a bit of research into this, and they found that dark water actually reflects more polarised light than brightly lit water.
Now polarised light is light in which the sort of waves have all been lined up in one direction, and you could see this effect if you’d got a pair of polarising sunglasses. So it's a nice theory, you know, maybe midges are attracted to this polarised light, but they had to prove it. And to do this, they did a lovely little experiment where they built a tent, and at dusk they attracted some midges into their little tent and offered them a choice of four trays of water.
Now two were lit with polarised light, one at high intensity, one at low intensity, and the other two were lit with normal light at high or low intensity. And the next day, the researchers went and counted all the eggs that the midges had laid in these trays, and they found that over 60 per cent of the eggs were in the polarised light trays, and most of those were in the high intensity polarised light tray. So this confirms that the midges are definitely attracted to the polarised light.
Chris Smith: But how does it explain how the cholera gets into the midge and then the midge gets the cholera to other bits of water?
Kat Arney: Well, that’s not really what this experiment was about, but it definitely looks like the midges are picking up the bacteria from the cholera in the water and then flying away and laying their eggs in another pond.
This now explains what the midges are actually attracted to. So it actually does suggest quite a good way that you could maybe attract the midges elsewhere by offering decoy pools of water that were lit with polarised light, and it would get rid of the midges away from your water sources and maybe they wouldn’t spread the cholera into those.
Chris Smith: A good idea and, as you say, a major health problem worldwide. Now another problem worldwide is of course we’re all worried about global warming, and there’s evidence this week that what’s going on at the polar icecaps, ie huge amounts of water melting, is definitely down to us.
Kat Arney: Yes, this is research from the University of East Anglia, and the scientists have shown definitively for the first time that the warming climate at the poles is the result of human activity. Because previous scientists have sort of shown that maybe it's down to human activity and maybe it's down to just some natural fluctuations in the temperature.
It's also been quite difficult to detect warming over the poles because there’s a massive hole in the ozone layer over Antarctica, and this is actually causing a problem with the measurements. But now writing in the journal Nature Geoscience, the scientists who were led by Dr Alexi Karpechko, they used a new set of temperature data, along with new computer simulations, and they showed that basically, the warming, it cannot be due to natural variations alone, it doesn’t tie up. And it proves, quite sadly, that we've already caused significant warming, and this has had impacts on wildlife, local populations and the sea level as well.
Chris Smith: Well, if you take their simulation and their model and wind the clock forwards rather than backwards, what does it predict is in store for us going forward from here?
Kat Arney: Well, this is the bad news in that it does predict that things are set to continue and set to get worse. But I guess the good thing that’s come out of this is that this is really definitive evidence that it is human activity that’s caused polar warming. So actually now humans have to suck it up and hopefully do something about it.
Chris Smith: It's hard to say anything positive about that though, isn't it, but moving on now to another icy sort of story. And this one was amazing because I remember when this man was discovered in 1991, Ötzi, the Iceman, was actually disclosed by global warming because the recession of glaciers in the Alps showed his body, which had been buried there for several thousand years, about 5,000 years wasn’t it, and now scientists have done a lot of DNA analysis on him. What have they found?
Kat Arney: Well, yes, this is a lovely story about Ötzi, the Iceman, and the researchers have analysed his mitochondrial DNA. Now this is the DNA that’s found in the energy centres of our cells, the mitochondria, and this kind of DNA is really interesting because we all inherit our mitochondrial DNA from our mothers, not from our fathers, and this is because you get mitochondria passed down in your eggs and not in the sperm cells. And because of this, mitochondrial DNA is really, really useful for telling us about evolution because basically it comes down unadulterated down the maternal line.
So this is how researchers have done all this work showing, for example, that humans came out of Africa, identifying old families of people and where they’ve come from. And this now is the oldest complete DNA sequence of human mitochondria that’s been known to date, and this is from Ötzi who lived around 5,000 years ago.
Now previous research has shown that Ötzi belonged to a genetic lineage called K1, and this is part of the K lineage, and that’s, around 8 per cent of modern Europeans fall into this genetic group. But using new sequencing technology, the scientists have been able to compare Ötzi’s mitochondrial DNA with other sequences from modern Europeans who are living now around the place in Europe, and they’ve built an evolutionary family tree for him.
But, there was a surprise in store because they found that actually Ötzi is out on a limb, on his own, on this evolutionary tree. His mitochondrial DNA doesn’t really match with any of the rest of the K group that are living today. So it suggests that he didn’t really do very well and his family didn’t really do very well in reproducing.
Chris Smith: So he’s a lonely chap. I was just going to say it could be then that it's just that the lineage that he belonged to be just very rare in the population. Because they haven't sampled that many in this paper, have they, a few 100, a 150 or something numbers of mitochondrial samples, and so it might be that the people who exist today that are his descendents make up just less than one in a 150th of the European population?
Kat Arney: Yes, they may be very rare, that is the alternative, so obviously more sequencing needs to be done. But certainly from this analysis it suggests that poor Ötzi was a bit of an evolutionary dead end.
Chris Smith: 5,000 years locked in the ice to discover that you’ve got no relatives – what an awful prospect. Thank you, Kat. That was Dr Kat Arney with a round up of some of this week’s top science news stories. And if you’d like to follow up on any of those items, they’re all on the internet on the Open University’s website at open2.net/nakedscientists.
In just a moment, we'll be finding out how meteorites older than the Earth are helping scientists understand how the planet’s formed.
But first, to what a Second World War famine is revealing about genetics. It turns out that children conceived in the Netherlands at the height of the Dutch hunger winter were predisposed as adults to develop certain conditions like heart disease, obesity and diabetes. Why though? No one knew.
But now a Leiden University researcher, Bas Heijmans and his colleagues have analysed DNA samples from 60 of those people, and they think it's all down to a process called epigenetics. This is where chemical groups, like methyl groups, can be added to DNA where they alter the activity of certain genes. And, interestingly, the famine children have a different pattern of these methyl groups to their unaffected relatives, which might explain why the disease risks are much higher.
Bas Heijmans: The Dutch famine was a very severe famine at the end of the Second World War. So just in the month before the Netherlands was liberated, May 5th, there was a food embargo imposed on the western part of the Netherlands by the German occupiers. And the official food rations were very small, so people had 100 grams of food to eat a day, so it was about 500 kilo calories.
Chris Smith: So that’s about a quarter of what would normally power a healthy adult strapping person like me?
Bas Heijmans: Yes, definitely, I think even less when you go to McDonald’s a lot.
Chris Smith: So what were the impacts of people being severely undernourished like that?
Bas Heijmans: Yes, well what you see now if you study people who suffered this famine, even before they were born, is that they, on average, have a higher weight and have a higher risk of cardiovascular disease.
Chris Smith: So, in other words, effects that happen to your mother whilst you were developing inside her can have a knock-on effect on your health throughout your life?
Bas Heijmans: Precisely, yes. So what we did is we looked at individuals who are now 60 but were conceived during this Dutch famine and compared them to their brothers and sisters who were not exposed to this famine. They grew up in the same family environment, so probably also the same kind of diet, and also they have in part at least the same genes, so they are nicely matched in a sense.
Chris Smith: And how does their health and their risk of disease compare with their brothers and sisters that were conceived outside of that famine window period?
Bas Heijmans: So what we found in our study is that they have a higher weight, and we wanted to know the molecular explanation. And, from animal studies, we know that molecular switches exist that determine whether genes are on or off, and one of the most well-known switches of this form is methylation. So methylation of DNA makes that a gene becomes inactive, and we looked at the methylation of a very specific gene, IGF2. So IGF2 is a gene of which we know that it is involved in growth but, more importantly, it's one of the few genes for which we have a lot of epigenetic data.
Chris Smith: So how does a gene actually get methylated like this in the first place? Is that a chemical change or a tag, to put it like that, that’s added to the gene by other processes in a cell depending upon what’s going on in that cell?
Bas Heijmans: You can see there’s a molecular attack. There are molecules that link methyl groups to the DNA molecule, and it sets about a whole series of events leading to the fact that the DNA will be packed more densely so that the machinery reading the genes cannot reach it any more.
Chris Smith: So it effects how well expressed the gene is?
Bas Heijmans: Yes.
Chris Smith: And so when you looked in these particular individuals at the methylation pattern on their IGF2 gene, what did you find?
Bas Heijmans: Well, what we found is that there was less methylation of this IGF2 gene in the people who were conceived during the famine compared with their brothers and sisters.
Chris Smith: Is there a particular period when a baby is developing inside his mother that’s particularly critical for this to happen? So, in other words, if you look at babies that are at a certain stage of development, when their mum is exposed to a famine, they’re more likely to have this than say a baby at another stage of development?
Bas Heijmans: Yes, that’s definitely the case. We knew from another research that the very first stages of development are actually crucial because that’s the period when all the epigenetic programming occurs. Well, to prove our point, we also looked at people who were not conceived during the famine but were exposed to famine during the very last stages of the pregnancy. While they do have a lower birth weight, you don’t see any epigenetic changes. So, indeed, it's very specific for the very early changes of development.
Chris Smith: So what’s the bottom line here? What does this study add to our understanding of the development of a child and how epigenetics plays a role in future health and disease?
Bas Heijmans: Yes, there are a lot of exposures out there that exist during the first critical phases of development, where you can think of mothers who smoke, of course, and another example maybe that some women get very nauseous during the first few months of pregnancy and throw up a lot, and that may have similar consequences. And the good thing now that we have a marker for problems very early in development – you don’t have to wait 60 years before you see people become obese but right after birth you can test for these epigenetic changes.
Chris Smith: It's amazing to think that something that happens in the first few weeks of a baby’s development can have effects that last a lifetime. That was Bas Heijmans from the University of Leiden, and that work’s published in this week’s edition of the journal PNAS.
And now to early beginnings of a very different sort. This time, the origins of our solar system. Winding the cosmic clock back over 4½ billion years isn't trivial, which means that it's been very tricky for scientists to piece together how it all happened, but now there’s been breakthrough – here’s Ben Weiss.
Ben Weiss: The question is what was the early history of planets and, in particular, when did planets differentiate, and by differentiate I mean when did they acquire this compositionally layered structure that we’re familiar with today in which there’s a core inside of a mantle inside of the crust.
Chris Smith: Well, before we got here, what do we think actually existed? Where do we come from?
Ben Weiss: Yes, well the solar system formed after the collapse of a molecular cloud of gas and dust that eventually formed sort of kilometre-sized, and larger objects, we now refer to as planetesimals. And planetesimals, most of them, are not around any more. They collided and became terrestrial planets and giant planets. The asteroid belt, that we see today, is sort of the remains of these planetesimals that never formed large bodies. And a question has always been is to what extent did these planetesimals experience differentiation? That is experience large scale melting in the formation of cores, mantles and crusts.
Chris Smith: But given that they don’t exist any more, that’s a pretty tricky question to answer, isn't it?
Ben Weiss: That’s right. All that we have left from this early history, in our collection, are meteorites. Since the mid 1800s there’s been a growing number of members of a class of meteorites called the angrites. Now angrites are samples of what we think was an early differentiated planetesimal, some body that experienced melting, that there were probably lava flows on its surface. There’s evidence for the formation of an early core on this body. And it just so happens that our samples from this angrite parent body somehow got to us without any major alteration or shock events, so that they basically retain pristine records of the early history of the solar system.
Chris Smith: When you say early, when were these bodies being produced? In other words, this parent body, this, whatever it was that give rise to these angrites, when would that have been around in relation to the formation of the Earth?
Ben Weiss: So we think that this body formed within maybe 1½ to 2 million years after the origin of the solar system itself, and we have samples from this body. The saltic samples with vesicles, very similar to what you might see on the flanks of volcanoes in Hawaii today, but these samples are 4.564 billion years old.
Chris Smith: So are you saying, then, that this very early body, whatever it was, that formed in the earliest part of the solar system had volcanoes. It effectively was a molten body, and it behaved a bit like a volcano on Earth today?
Ben Weiss: That’s right, and this might seem kind of surprising because when we think of planetesimals, many of us think of the asteroids today, which are remnants of early planetesimals, kind of dead, cold objects. But one of the discoveries that came out of our work and other people’s work in the last few years is that these early bodies were incredibly dynamic and volcanically active.
Chris Smith: So this suggests then that if we wind the clock back right to the beginning of the solar system, something very massively formed, sufficiently massive to then start producing equivalents of volcanoes. It spat out this material. Then what happened to it?
Ben Weiss: We think that maybe that so much melting occurred on some of these larger bodies that more than half of the body, by mass, melted, and as a result of that something that we refer to as a magma ocean formed on the surfaces of many of these bodies.
And now it’s in just such a setting that you can have large scale planetary differentiation. Because in a large body of magma, you can get heavy materials separating out and the metal grains can grow to such a sufficient size that they basically sink all the way to the centre of the body and form ultimately a metallic core. At the same time, the lighter minerals float to the surface and form the crust, and in between you have a mantle.
So what we’re learning from this work and other recent studies is that early bodies differentiated and formed mantles, cores and crusts extremely early. Maybe much earlier than many of us had thought a decade ago.
Chris Smith: It's intriguing to think that the history written into those rocks over 4½ billion years ago is still readable by scientists today. That was Ben Weiss, from MIT, shedding some light on the birth of our own solar system, and you can find that work in this week’s edition of the journal Science.
This is the Naked Scientists: Up All Night with me, Chris Smith, and time now for this week’s Stuff and Non-Science where we massacre myths and bash bad science, and with the highest standards of food hygiene – we hope – here’s Diana O’Carroll.
Diana O’Carroll: This week’s Stuff and Non-Science is all about the five second rule. It's said that if you drop food on the floor but pick it up again within five seconds, it’ll still be bacteria-free. Something tells me it's not true, so with the real story, here’s Dr Paul Dawson. He’s from the Department of Food Science and Human Nutrition at Clemson University in the US.
Paul Dawson: The tests we did were inoculating surfaces with salmonella bacterium and dropping food on those surfaces for five, 30 or 60 seconds, and picking it up and then seeing how much bacteria was transferred, and we found that within five seconds there was significant amounts of bacteria transferred to both, we used boloni, or known as sausage, I believe, in England, and then also bread, and in both cases there were significant transfer of bacteria to the food in that short amount of time.
We were also curious about the effect of surfaces, obviously with different surfaces in a home, and we tested tiles, ceramic tile, which might be the type you either see in a kitchen or maybe in a bathroom – who eats in a bathroom – but also a carpet, also a wood surface, it would be used for flooring, and the interesting thing there was bacteria survived much longer in the carpet, more bacteria than did the tile and the wood, but when we dropped it on the surface, actually less was transferred, and that kind of makes sense because the carpet has a thickness there and the bacteria can spread out and diffuse. But there was really not a significant difference in the amount of bacteria transferred based on the time of contact, at least those times we used.
Diana O’Carroll: Paul Dawson there. His team have also done some research into the evils of double dipping. That’s taking a bite from a chip and dipping it back in the sauce – urgh! Any more myths to debunk? Well send them to me. That’s email@example.com.
Chris Smith: So watch out for food with bits of fluff on it. Thank you Diana. That was Diana O’Carroll with this week’s Stuff and Non-Science.
Well, that’s it for this time. We’re back next week with another round up 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 in the programme by the OU’s website which is open2.net/nakedscientists.
You can also follow the links to get there from the BBC Radio Five Live Up All Night website. Production this week was by Diana O’Carroll from the nakedscientists.com, and I'm Chris Smith. Until next time, goodbye!
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These are the sources used by the team in making the show:
In the news
‘The effect of universal influenza immunization on mortality and health care use’
by JC Kwong, TA Stukel, J Lim, AJ McGeer, REG Upshur, et al.
in PLoS Med 5(10)
‘Reflected polarization guides chironomid females to oviposition sites’
by A Lerner, N Meltser, N Sapir, C Erlick, N Shashar and M Broza, M
in The Journal of Experimental Biology, 3536-3543
‘Attribution of polar warming to human influence’
by Nathan Gillett, Dáithí A Stone, Peter A Stott, Toru Nozawa, Alexey Yu. Karpechko, Gabriele C Hegerl, Michael F Wehner and Philip D Jones
in Nature GeoScience, Oct 30 2008
‘The Complete Mitochondrial Genome Sequence of the Tyrolean Iceman.'
by Luca Ermini, et al
in Current Biology Vol 18, Number 21
‘Persistent epigenetic differences associated with prenatal exposure to famine in humans’, by Bastiaan T Heijmans, Elmar W Tobi, Aryeh D. Stein, Hein Putter, Gerard J Blauw, Ezra S Susser, P Eline Slagboom and LH Lumey in PNAS
‘Magnetism on the Angrite Parent Body and the Early Differentiation of Planetesimals’, by Benjamin P Weiss, James S Berdahl, Linda Elkins-Tanton, Sabine Stanley, Eduardo A Lima and Laurent Carporzen in Science Vol 322, no 5902