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Class Supplement, Nature Podcast Digest, 2012/03/29

2012年5月20日

The original script of this podcast: http://www.nature.com/nature/podcast/v483/n7391/nature-2012-03-29.html
The audio file of this podcast: http://www.nature.com/nature/podcast/archive.html

手のように木の枝をつかむことができると同時に直立歩行もしていた足の骨が発見された。完全な直立二足歩行を示すことで有名なアウストラロピテクスの化石「ルーシー」と同時代の近接地域。樹上生活→地上生活(直立二足歩行)への移行を示し、様々な足の使い方・歩き方をする生き物が同時に存在したことを想像させる。
Bruce M. Latimer: This is a chimpanzee foot. It’s toe, it’s big toe, is very much opposable much like a thumb. So this is a climbing adaptation, compared it to the human and we are the only primate along with our ancestors that have taken the big toe that used to stand out on the side as a grasping big toe, that you now bring it into line with the rest of our foot. Of course, you’ve sacrificed your ability to climb trees, but it does allow you to walk great distances because those little muscles in the sole of your foot serve as shock absorbers. But to really understand the significance of this, what I have to do is to introduce you to fossils that come from Ethiopia, not too far from this site where this came from, that we know quite a bit about. This is the world famous Lucy. The important point is Lucy was living at the same time as this animal, in fact very close to one another.
Charlotte Stoddart: Lucy was discovered in the 1970s. She belongs to the species, Australopithecus afarensis a kind of human-like creature living more than 3 million years ago, and she walked upright in essentially the same manner that modern humans do.
Bruce M. Latimer: This is another individual of her species. Now, this is another big toe. This is domed on the top, which allows you to say that this animal, the Lucy-type of animal, Australopithecus was toeing off and had the same amount of joint mobility that you and I have. We go to the new foot; it was living at the same time as Lucy – no dome. That alone tells you this animal was toe grasping and it was not using its toe the way you and I do, but the Lucy specimen was. So we have a divergent type of bipedality. One, the Lucy animal committed to walking upright on the ground, but not this one. This new specimen is walking upright, when on the ground but doing it in an awkward fashion, not like us, but still maintained its big toe grasping ability and that was one of the big surprises.
Bruce M. Latimer: With the picture of human evolution is becoming more and more complex, the human evolutionary tree is actually an evolutionary bush and our ancestors were experimenting with all kinds of different ways to do things. We have some that came down and they were committed to walking on the ground and they walked very much like you and I, then we have other ones, that apparently when they came to the ground walked but they did in an awkward kind of a way because they could still climb trees. So we now know there are at least two may be more ways to walk around on two feet.

タヒチの海底掘削で見つかった過去のサンゴ礁は、過去の海面上昇の痕跡。現在の10倍以上のスピードで上昇したことが分かる。また、過去の気温上昇の記録と同時であることから、海面上昇の結果(北半球の氷が解けて大西洋に流れ込み南からの温かい海流をふさいで)気温が下がったという仮説は誤りであることが分かった。
Kerri Smith: Just over 14,000 years ago, the earth got a whole lot wetter. It was the end of the last ice age and suddenly the glaciers collapsed, sending a rush of fresh water into the oceans. Researchers studying ancient coral in Tahiti have now pinpointed the date of the flood and determined that it correlates with an unusually warm period around the same time. Geoff Brumfiel called up Alex Thomas at the University of Oxford to learn more.
Alexander L. Thomas: Yes., from the last glacial maximum 21,000 years ago, the sea level was 120 meters lower. They rose up to the present level, but that didn’t occur in a one kind of smooth rise. There was this period where the sea level actually rose quite steadily and then all of a sudden there was a dramatic increase in the rates of sea level rise and what we’ve done in this study is we’ve narrowed down the uncertainties on how long the duration of this rise was and what the magnitude of the melt water pulse was. We are able to say that the rate was at least 40 millimetres per year, which if you compare that to modern sea level rise, currently only about 3 millimetres per year, this is a dramatic increase in sea level rise.
Alexander L. Thomas: Right, yeah. So, our record is essentially independently dated, so we get the age of this sea level rise event, very very accurately and independent to any another kind of dating record. So we were able, in this study, to show that the dramatic increase in temperature in the northern hemisphere at this time is essentially at the same time as this increase in sea level.
Alexander L. Thomas: Getting these records of sea level rise from periods when sea level was lower than today is actually very very challenging because all of the deposits, all of the physiological kind of formations are currently underwater. So, to get access to those, what we need to do is we need to drill down into the seabed. So, we did this with a large international program called the Integrated Ocean Drilling Program. We used a drilling ship, usually used by the geotechnical and the oil exploration industry and we drilled down into the sea floor and recovered almost a kilometre’s worth of coral cores, essentially down into fossil coral reef deposits. Coral reefs essentially only ever grow below sea level. So if we find a kind of a fossil coral reef, in the past, we know that sea level must have been above that point back in time.
Geoff Brumfiel: I should say, I mean, you know, to me just as an outsider, the idea that ice sheet collapse and massive sea level rise happen to sync up with a warming period in the earth’s past. It doesn’t seem that surprising, but this really was up for debate, wasn’t it?
Alexander L. Thomas: Yes, prior to this study, the actual exact timing of the sea level rise events was actually quite controversial and it was thought that the sea level rise coincided with a period of cooling in the northern hemisphere and the idea behind that is that it would perhaps melt a large, kind of massive, ice from the northern hemisphere ice sheets around North America, Greenland and Scandinavia that would put fresh water into the North Atlantic and that the effect of that thought that it would have a cooling effect because it would essentially shut down the transport of warm water from the topics to the high latitudes and that would cause, essentially a regional cooling in the northern hemisphere. So what we’re able to do in this study, we’re essentially falsifying that hypothesis.

ベニスの地盤沈下は止まったとされていたが、実は沈み続けていることが分かった。更に、東方向に傾いている。
Corie Lok: Research in the 1990s indicated that Venice had stopped sinking, but a new study says no. The historic Italian city is in fact still sinking and is even tilting slightly to the east. Scientists analyzed GPS and radar data and found that Venice is sinking at a rate of 1 to 2 millimetres per year. These suggest that shifting tectonic plates and compacting sediments might be responsible. The findings could help the city to prepare for potential flooding due to rising sea levels and seasonal tides.

ギリシャのサントリーニ火山が60年ぶりに活発化の兆し。GPSのデータによれば火口が広がってきており、これは火口の下にあるマグマの膨張を示している。また、地震も頻繁になっている。ただし予測される噴火は小規模。
Let’s tune our attention to another popular European tourist attraction, the Greek islands of Santorini. The volcano that erupted and formed these island thousands of years ago seems to be reawakening after 60 years of silence. Researchers studied GPS data collected from around the volcano over the last six years. They say that the volcano’s crater-like depression has been growing by up to 18 centimetres in diameter each year. What could be causing this – expanding magma some 4 kilometres below the surface. This unrest also coincided with renewed seismic activity. All of this could be a prelude to a small eruption, but a mega eruption is unlikely.

食糧危機問題が深刻なマラウイの対策 (1)人工肥料(高価で環境に悪い)の代わりに、空中の窒素を取り込む木を植えて土を肥やす。 (2)主要作物をサツマイモなど育ちやすいものにする。 食糧問題解決は新たな雇用や学力向上などにより地域発展につながる。
Natasha Gilbert: Yes. Malawi is one of these places in sub Saharan Africa, where they have a longstanding food insecurity problem and the main reason is that the soils are very old and very poor in nutrients and that simply means they can’t produce enough food. So, I went to go and speak to some farmers and hear about some of the agricultural techniques that they’re using to try and boost their crop yields.
Natasha Gilbert: So, some of the techniques that they’re using are organic and environmentally friendly approaches and this is often because inorganic fertilizers are very expensive and obviously we know about the damaging effects that they have on the environment, so you know, some people are seeking alternatives. So it’s quite strange when you walk through the field up there, you see these trees planted in crop fields and these trees are one of the new and important techniques that researchers and aid organizations are looking at and they’re called fertilizer trees.
Gudeta Sileshi: Fertilizer trees are nitrogen fixing trees that grow very quickly and add biomass very fast. They first and foremost add nitrogen, which is the essential nutrient for crop growth and then they of course add organic matter, which is the main source of nutrients and the material that helps the soil to retain water, to maintain its health, the health of the soil.
Natasha Gilbert: So, what happens is these trees have got really nitrogen rich leaves and they get this nitrogen in two ways. So, they’ve got these nitrogen fixing bacteria on their roots which are able to extract the nitrogen from atmosphere and those roots are really long and they can reach deep into the soil, where they can access reserves of nitrogen deep in the soil. So, when these leaves drop, they decompose and the nitrogen goes back into the soil, and it’s then available for crops growing around the area.
Natasha Gilbert: So, another strategy that they’re using is to grow different crops. Traditionally in sub-Saharan Africa, Malawi, they grow maize, just maize which they use to make Nshima ‒ it’s like porridge like meal and maize is their staple crop but it needs a lot of nitrogen and it’s not necessarily the most sensible crop to be growing in nitrogen poor soils. So one lady I spoke to had started to grow sweet potatoes.
interpreter Timothy Kamulingeni: At first this variety orange-fleshed sweet potato, it provides Vitamin A, which is very important in the body and they secondly this variety, orange-fleshed sweet potato, it can replace Nshima. Instead of eating Nshima they can prepare orange-fleshed sweet potato as lunch or as supper.
Natasha Gilbert: Yeah, in some circumstances, these techniques are boosting crop yields but in a lot of cases, they also need chemical fertilizers to really kick start the system and I think taking altogether they can really have a positive impact on the community. Helping them to produce more food will allow them to look for other employment opportunities. So they might be able to get out of the cycle of poverty. Also, it would enable more children to go to school on a full belly which would translate into better grades and all taken together that will give the children and the country a brighter future.

感染力の強い鳥インフルエンザウイルスが実験で作成されたニュースは記憶に新しい。目的は突然変異予測のためだが、実は予測用遺伝子データは驚くほど不足している。 サンプル採取はH5N1が数カ国のみ。他のウイルスのサンプルはほぼ皆無。 全世界に家禽は210億羽いるが、解析済み鳥インフルエンザウイルスサンプルは1000のみ。しかも、家禽の多い国に限ってデータがない。遺伝子以外の調査方法もあるが、遺伝子解析により突然変異の傾向を調べれば次に大流行するウイルスを予測しやすい。’03-’11では、大流行時の調査2件以外遺伝子データはほぼ皆無。原因は資金不足、資料不足、及び大々的調査への無関心。調査範囲が小さくても有効なデータを得る可能性はあるが、場当たり的調査しかしていない現状を変えることが必要。組織的・定期的調査をすれば長期的なコストも抑えられる。
Kerri Smith: Finally this week, remember that mutant flu strain that was created in the lab, more contagious than any natural strains. Well, when one of the main arguments for creating it was that it would aid surveillance and help us look out for similar strains emerging in the wild. But this might have been putting the cart before the horse because a new analysis by Nature finds these surveillance activities badly lacking. Reporter, Declan Butler put the analysis together looking at surveillance efforts focused on the genetics of flu and looking at the main databases used by flu researchers. Declan joins me on the line now. When you looked at how much information was available on different flu strains and sequences around the globe, what did you find?
Declan Butler: We found some really striking trends in the data. The first was just a handful of countries accounted for almost all of the sequences that were collected. Remarkably most countries collected none at all. They only had a few dozen sequences and what you see is most of that data is coming from just a couple of countries like China, the United States as well as places that are doing fairly intensive surveillance for H5N1 such as Egypt, Vietnam, Thailand and Indonesia but then you got to remember that H5N1 is just one pandemic threat and so what that means is in fact the actual surveillance for other types of flu that could equally well cause pandemics, there just isn’t really much regular surveillance happening at all there.
Declan Butler: Well, actually what you find is really quite striking in that many countries that have collected very few sequences have absolutely huge poultry and pig populations and just to give you an overall idea, we look at the data for say, 2010, the world overall had a poultry population of something like 21 billion, but so far, there’s only been 1000 avian flu sequences available for that year for 2010. So I mean, there’s very, very few sequences for the total size. Now you find some countries like Brazil and Morocco, Philippines, who have large poultry populations with no data. You have to be careful with interpreting that kind of data because a country might have very few sequences simply because it has very hygienic farming industry and if you don’t have much avian flu, you’re inevitably not going to have many avian flu sequences.
Declan Butler: No surveillance is a huge area. In that you are actually collecting first of all data on how outbreaks occurred so you detect them so that you cull them, so that you not just stop the spread of flu viruses. There is the, for example, you measure the subtypes. Is it a H5N1, is it a H1N1? So there’s lots of different types of data that is used in surveillance. I think what I’m talking about here is more genetic surveillance and this is how you actually track the evolution of flu viruses and meticulous kind of way you can see how flu viruses are perhaps spreading faster, becoming more adapted to humans and this kind of key data, if you want to actually start understanding to look what are pandemic threats out there.
Kerri Smith: You’ve been looking at data from the past, almost a decade from 2003 to 2011, what’s been the trend in the numbers of sequences available over the past few years?
Declan Butler: Well, here where I find that the data gets really, really interesting. What you see is you see a kind of spectacular increase over the past decade. Then what’s really funny is if you drill down into the data and look at it in different ways that increase completely disappears and the reason is that much of the increase we see is around I think was in the year 2010, there’s like this steep increase in the curve. But when you actually look at the data what you find is that almost all of that increase came from sequences that were actually collected years earlier. We’re actually looking at data that’s older and actually almost all of that taken is drawing actually not to any kind of overall enhanced surveillance effected over the decade but simply two kinds of unusual events. One was that in the mid 2000 , the United States government carried a massive flu survey in wild birds in hundreds of thousands of wild birds and this is because they were worried that H5N1 which was spreading rapidly worldwide at the time, they were worried about that coming to the Americas. And the other reason why we’ve got lot of sequences around 2005-2006 was the big spread into Europe and Africa during that time, when lots of richer countries analyzed lots of sequences from outbreaks on their territories. Take away those two events the actual trend over the past decade is pretty flat. There certainly has been no spectacular increase and the upshot of that is that we’ve really very little data on sequences of recent isolates say from the past three years and now that’s important because if you’re looking at pandemics having data on recent isolates is, you know, really critical.
Declan Butler: Well, there’s a stack of reasons. First of all is there’s been a general lack of funding for sequencing, and also isolates themselves are a bottleneck because they come mainly from broader surveillance programs in countries and there’s very, very little of that broader surveillance happening; that hasn’t been priority.
Kerri Smith: How could we help countries, may be at more risk of fostering these infectious flu strains to collect more and more useful data?
Declan Butler: Well, the thing actually my analysis shows some reasons for optimism and that is one of the things that comes out strongly is that a couple of, you know, small targeted efforts can actually generate enormous amounts of data. For example, back in 2004, the US National Institute for Allergies and Infectious Diseases launched the influenza genome sequencing project to actually sort of isolate sequencing existing isolates and remarkably that project single-handedly now account for almost half of total sequences generated worldwide. The problem at the moment is that all the actual surveillance is very ad-hoc. We do it in response to outbreaks, we do it when we have funding and with sequencing cost falling et cetera, the creation of few dedicated centres could really both improve the amongst sequencing being collected also have them collect it more regularly and people I’ve spoken to say that in fact it probably would end up costing less than the current kind of uncoordinated global system.

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