Peruvian Mummies, Ancient Environments and the Sahara

Researchers at the Fred Hutchinson Cancer Research Centre in the US have found that regular exercie may help to prevent bowel cancer. The researchers recruited 200 healthy men and women, put them on a range of exercise programmes, then studied the cells in their bowels to see how much the cells were growing. If cells in the bowel grow too quickly, then this can be a precursor of bowel cancer. They found that for men who carried out exercise for an hour per day, six days per week, had less cell growth in their bowels than those who did fewer exercise sessions. And even men who just managed four hours per week had some protection. Unfortunately, there appeared to be no protective effect for women who exercised, although other research has shown that regular exercise can reduce the risk of breast cancer. Exercise also helps you to maintain a healthy body weight - after smoking, obesity is the leading preventable cause of cancer in the UK. So as well as helping you fit into your genes, getting moving could also reduce your risk of cancer. More about exercise and cancer here: http://info.cancerresearchuk.org/healthyliving/exerciseandactivity/howdoweknow/.

Bob - This week on Science Update, noise pollution is now a problem in seas as well as cities. But first, Chelsea has a much more pleasant noise to play for us-and you'll probably be surprised by its origin.

Chelsea - If a volcano could play piano, this is what it would sound like. Physicist Domenico Vicinanza of CERN in Switzerland created the music by converting a seismogram from Mount Etna into a score.

Domenico - If the volcano is quiet, the melody of the piano is confined in the middle part of the piano. As soon as the volcano is becoming louder and louder, the melody on the piano starts to scatter up and down, reaching higher and lower notes.

Chelsea - So how will this help? Vicinanza says people are often better at picking out patterns by ear than by eye, so this technique could help scientists find patterns in seismic activity across many volcanoes.

Domenico - Our aim is to use all the recorded data, to transform them into music, and try to understand what happens when the volcano starts to become louder and erupts, and so we can say which is the signature tune, the signature melody which can be taken as a signal of an imminent eruption or imminent earthquake.

Chelsea - He adds that this technique could prove useful in analyzing data in other fields, from stock-market numbers to patterns in language. He also hopes it will be welcomed by musicians as a new way to create nature-inspired tunes.

Bob - Thanks, Chelsea. Well, here's another tune of sorts, but one that's not so welcome.

Bob - It's the sound of a ship-underwater. Scientists think it might interfere with how whales and other sea mammals communicate and find food. Now a team has discovered that ambient underwater noise has increased ten times since the 1960s-at least in the Pacific. But it's not just that the number of ships has gone up. John Hildebrand of Scripps Oceanography says traffic has only doubled since that time.

John - So a very significant part of the increase comes from the fact that the ships themselves must be generating more noise-the ships are bigger, they travel faster, they have greater total tonnage that they're carrying.

Bob - Hildebrand and his colleagues were able to do this analysis because they found declassified Navy reports from the 60s on the ambient noise in the Pacific-part of the Navy's Cold War defense. They were then able to make recordings in the same spot and compare them. Although it's not hard to prove that noise has gone up, he says what is hard to prove is that it's having an effect on the mammals.

John - The insidious thing about this is that the ambient noise has been increasing at probably a fairly steady pace, so there wouldn't be some dramatic event where all of a sudden the marine mammals would be doing something differently. So it's tricky to figure out where the impact has been.

Bob - But he says it may not be as hard as it might seem to convince the shipping industry that noise is a problem-quieter ships would be better for the crew and should be more energy-efficient. He adds that in looking for a solution, scientists may turn again to the Navy, who are, after all, experts in being quiet underwater.

Chelsea - Thanks, Bob. That's all for this week. Next week we'll talk about some ants that do some amazing acrobatics. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists.

Kat - I understand that you're studying the environment of Portugal.

Harriet - Yes, I'm interested in the way ecosystems change over time, and that could be thousands of years or it could be over even shorter periods of time.

Kat - So what's the environment like now in Portugal, and how was it ten thousand years ago?

Harriet - In common with many other Mediterranean landscapes today, the vegetation is very much dominated by shrub land communities, which are extremely well suited to the hot, dry summers and the cool and relatively wet winters. About ten thousand years ago, you would have had a more deciduous type of vegetation with many more trees in the landscape than we would see today.

Kat - So big leafy trees?

Harriet - Yes, deciduous but not so much chestnut because many of those have been imported from the eastern end of the Mediterranean to the western end, but there would have been many more deciduous oaks and other taxa.

Kat - How do you know that this change has taken place? We only see the trees we've got now.

Harriet - There are certain types of environments such as wetlands where we can extract material the dates back over thousands of years. We can use sediment cores and go down a metre at a time where we can retrieve material. We then take it back to the laboratory and analyse small quantities of it and see which pollen has been preserved within the sediment. By looking at the pollen we can identify the different species or more commonly the genera or the families from which the pollen has come. From that we can reconstruct what the vegetation was like.

Dave - Are you just looking at the pollen grains and you can recognise all the different types of pollen grain?

Harriet - Yes. Pollen grains have different types of ornament depending on the species. Some of them look a little bit like mediaeval instruments of torture because they've got large spines sticking off them. These are large in the context of being microscopic of course. They may come from some of the more weedy species such as you might find in the daisy family. By complete contrast, if you look at something like pine pollen, it has air sacs. If you imagine Mickey Mouse's face just for a moment, the face is the basic part of the pollen grain and Mickey's two ears are the air sacs that help to make this particular grain very buoyant and well-dispersed. So different types of pollen have different ornaments that can be relatively easily identified under the microscope and allow you then to identify the grain either to the species or usually to the genus and sometimes only as far as the family level.

Kat - But how do you know how old these things are? Are they fossils?

Harriet - Technically for the last ten thousand years they're not fossils. We might refer to them as sub-fossils, but they are the intact grain that has been preserved in the environment. So they've been washed in or blown in, incorporated in the water column, and then settle out through the water column to be incorporated into the sediment that accumulates at the bottom of the lake.

Kat - But how do you know how old pollen is? It's just incorporated into the mud.

Harriet - Well it is just in the mud and in a sense you can't just date the pollen. What you're dating is the material in which the pollen is found.

Kat - So you're dating the mud.

Harriet - Yes or it could be a peat bog or it might be in a riverine environment where you've got more silty or sometimes gravel conditions. To some extent it depends on how much organic material there is available. If there's a lot of organic material then you can use radio carbon dating and that will then give you some dates.

Dave - Do you see big major events in the pollen record too, such as volcanoes and things?

Harriet - Well you don't tend to see that in the pollen record but you do see it in the sediments. I've got some colleagues who work in Greek lakes and they find layers of ash that have come from some of the Italian volcanoes. If you know what the chemical signature of the ash is, you can then identify which volcano it has come from and by extrapolation from other sources you can work out when it was deposited in the lake.

Kat - So to go back a little bit, you've said that over the past ten thousand years we've seen quite a dramatic change in even just a country like Portugal. What kind of thing has caused that change in climate and are we still seeing the climate changing now?

Harriet - It's a bit of a tricky question to answer because no two people will necessarily give you the same answer with respect to Portugal or other Mediterranean countries. It rather polarises between those who think that the vegetation has changed because people have changed the landscape, and those people who regard it as evidence of climate change. Somewhere about 5-6 thousand years ago there are suggestions that the climate became a bit more arid, and at that time you moved from the deciduous taxa to the more evergreen taxa. But other people argue that that was probably a result of people clearing the landscape for agriculture. The soils degraded and so when there was recovery of any vegetation, it was less likely to be the deciduous taxa that came back in than evergreen taxa. There's some suggestion that there was a slow spread between the eastern Mediterranean towards the western Mediterranean, which might have matched agriculture arriving in the eastern Mediterranean and towards the west and north west to the UK.

Kat - And to extrapolate a little bit to the UK, we know that the climate is changing and it looks like things are getting warmer. Do you think we'll see the sort of trees we have in the UK changing? We have our big oak trees and chestnuts, but could they be doomed?

Harriet - I'm not sure about doomed. There are some suggestions that gardeners ought to be changing the species that they're growing in their gardens. On the radio this morning there was some suggestion that people should start to grow olives and that maybe in a few years time olives will be a crop that you'll find within the UK. I think that it's being grown on an experimental basis down in Devon at the moment. I think it's very likely that the vegetation will change in response to the climate changes that we're seeing.

Kat - So far this evening we've heard a number of different reasons why digging around and finding clues are great for reconstructing the past. Well now we're going to hear from Clive Finlayson at the Gibraltar Museum, about our ancient relatives, the Neanderthals. They were once widespread across Europe, and were thought to have disappeared about 30,000 years ago, but no one really knows why. Now, excavations in a seaside cave overlooking the Mediterranean suggests that they probably clung on to existence for much longer than we previously thought, but ultimately, perhaps the climate got the better of them.

Clive - What we found in a cave called Gorham's Cave, here in Gibraltar, facing the Mediterranean Sea is a series of levels of human occupation, and the Neanderthals that had been occupying this site since 100,000 years ago, continued to do so much more recently than people had expected. There are places where they were making their tools, left their tools, hearths, the food that they were eating, and we've been able to date this very accurately with radio carbon dating to at least 28,000 years ago, but very likely much more recently than that, perhaps as recently as 24,000 years ago.

Chris - How do you know that what you're looking at is definitely Neanderthal, in this region?

Clive - Well, Gibraltar, for a start, has almost a tradition for Neanderthals in the sense that a skull was found here in 1848, and eight years later, one was found, in 1856, in the Neander Valley in Germany, and named Neanderthal, hence the term. So it was, perhaps the first one was actually found in Gibraltar. Another skull was found in 1926, and in all we have eight caves with evidence of Neanderthal occupation, the tools that they made, which archaeologists call Mustherian, are very characteristic. I'm talking of tools made of flint and quartzite, in the shape of stone points to be hafted on to spears, cutting tools, for defleshing and so on. They made these very, very identifiable and very, very specifically characteristic tools. So here in Gibraltar we have evidence of those tools in these layers that we've found, but also close by we also have, from the 19th century, at least two fossils, in two caves, so we are very confident that we've had a long period of Neanderthal occupation, and one that meant their survival until much more recently than we had thought.

Chris - And is that the major implication, or are there others, on the basis of what you found?

Clive - Well, one of the things about the cave is the richness of the fossil material, as well as the archaeological material. The levels of occupation are rich in fossil mammals, birds, reptiles, there's also pollen that we've been able to extract, and of course charcoal from the fires, and that has allowed us to make a reconstruction of the landscape outside the cave. If you go to the cave today, and you look outside, there's a beach, and the Mediterranean Sea, but for much of the period when the Neanderthals were living there, the climate was significantly colder, globally, and the sea level was down by between 80 and 120 metres below the present level. This exposed a huge area of sandy plains, which I could probably best describe as a Mediterranean Serengeti. It was rich in herbivores, and the Neanderthals were eating them, and we know that because we find in the bones evidence of the cutter marks made by their tools. We suspect that their diet was probably quite diverse, there's a lot of bird species have been found there, so it's almost certain that they were eating ducks and partridges, but also marine material; mussels and marine molluscs, quite possibly also fish, and seals, and then the vegetation, which we can infer from the pollen. So this allows us to do a climatic and ecological reconstruction, and what seems to becoming through is that this was one of those, perhaps localised, privileged spots, because of the benign climate that perhaps contributed significantly to this late survival, so I think it goes beyond just the issue of late survival and possible overlap with modern humans; it also suggest reasons why it was that they survived.

Chris - So the cave gives you enormous clues about when these people were there, and up until how recently, but does it tell us anything about where they actually went, and why they may have disappeared?

Clive - Well, apart from the work that we're conducting at the moment, we've been collaborating with colleagues who are looking at deep-sea cores of the Mediterranean, and around 24, or just after 24,000 years ago, there seems to be a very sharp signal of a climatic deterioration. It seems to involve cold conditions, and particularly conditions are maybe arid. So it could be that these last surviving Neanderthals lived in very small populations, they were, after all, the last ones, and any slight environmental change, perhaps a famine over a period of years, caused by drought, may well have tilted them over the edge, never to recover again.

Kat - That was Clive Finlayson from the Gibraltar Museum talking last week to Dr Chris.

String theory is a way of looking at the world to try and work out what we're made of. You may have heard that we're all made of atoms, and atoms in turn are all made of other little bits such as electrons, neutrons and protons. If you break it down even further, things like neutrons and protons and stuff are made up of even tinier particles called quarks and leptons. All these different particles are what makes up stuff. There are different forces that can act on stuff to make things move and stick together. These are gravity, electromagnetic force and the weak and strong nuclear forces. Sounds a bit Jedi to me! These help to stick stuff together. We have a standard model for how you explain stuff, which is that quarks and things stick together and protons and neutrons stick together etc. But you can't really explain how gravity actually works using this kind of model. So some very clever maths bods have been trying to work out a way of explaining how gravity works using the bits that we have. They've come up with string theory, which says that all these tiny bits of stuff are actually like bits of string that wobble around in lots of different ways. It depends how you're seeing that particular waving string as to what you see. So if you see it waving in one sort of way you see a lepton, and if you see it in another way you see an electron. So everything is basically little bits of waving string and this can apparently explain gravity. You can find out more at www.superstringtheory.com. However, no-one has found any evidence that this is the case. All the things it predicts happen at such high energies that no-one has been able to look at them yet.

The myth or story of Atlantis is based upon a gigantic slip of land into the Atlantic or possibly Mediterranean, which contained a civilisation that was privy to lots of information that we no longer have. So yes, there is evidence of slip in the Iron Age in the Mediterranean and particularly around Turkey, but when it comes down to whether we've lost information which mankind would really benefit from today is a bit more difficult to demonstrate unfortunately.

As for the planets, people have interpreted it like that but most of the cave paintings are so bizarre that no-one really knows what they mean. They have animals, which is fair enough, and then they also have lots of demonic creatures. You then have people with duck's heads and so on. So the planet thing is one possibility but it's a rather slim one unfortunately.

If the Earth suddenly didn't have any gravity any more, I guess that the first thing to happen would be its effect on the atmosphere. At the moment, the atmosphere is being compressed by its own weight and squashed down onto the Earth. The first thing that would happen is that the atmosphere would expand very quickly and fly out everywhere. That might blow you up into space. If it wasn't for that, there would be any reason for you to be thrown away from the Earth. You'd just sit there and slowly get pushes around. So you'd have a huge explosion with all the atmosphere disappearing, and this could possibly blow you up into the air.