If you put a human in the freezer, the first thing that would happen is that all of our tissues would freeze. About 60 or 70% of the weight of a human being and most mammals is water. Water forms crystals of ice, and those crystals are often jagged and sharp. These sharp ice crystals destroy the cellular structure, burst holes in the cells and make the tissue fall apart. This is the same reason why when you put a strawberry in the freezer and then get it out again it doesn't resemble a strawberry anymore - it just turns into a sort of mess. Some animals that resist this cellular destruction have managed to evolve a natural antifreeze, which works by stopping crystals forming these big jagged shapes. So that's part of it. They form much smaller crystals that have softer edges. There was a very elegant piece of research published about this time last year in the journal "Science", and they were looking at the snow flea, which lives in Canada. The snow flea makes another form of anti-freeze, and when you zoom in on the body of those animals, which can survive down to about minus 10 or something, you see that the tiny crystals of ice which form in their cells look almost like a grain of rice. They don't look sharp and jagged at all, which means that the cells don't get damaged in the same way. These antifreezes also allow them to resist lower temperatures, which means that their blood doesn't actually turn solid until a much lower temperature than it would do normally. So it works a bit like the antifreeze that you would put into your car. The other part of the survival mechanism is that frogs and other amphibians are cold blooded. So unlike us, where we have to stay warm, or we die, those animals absorb a lot of energy from their environment. Doing a little bit of exercise does put their temperature up a bit but they largely rely on absorbing energy from the environment, and that determines their metabolic rate. So how metabolically active they are can go up or down enormously depending upon the temperature. So if you cool a frog down, it just slows down to near stand still metabolically, and doesn't do anything, until you warm it up again, and they're well adapted to being able to survive like that.

We have our body odour to thank for lots of things. One person we interviewed on this programme earlier this year, was John Pickett from Rothamsted Research, who has actually bottled "eau de human", and specifically bottled those components coming off your skin that mosquitoes hate! So there are some people in the population that exude odours that mosquitoes really cannot stand. And some people carry those genes, which enable them to make those chemicals, whereas others don't. By bottling those chemicals you can turn it into the world's best insect repellent, and that's what he's done. So I think that in that respect, body odour is extremely useful and not only mosquitoes but it works against the Scottish Biting Midge as well. People also done research on how attractive women find the smell of sweat from men. They get them to wear a shirt for while and the women sniff them and I think they've shown that you're actually more attracted to people who are less genetically similar to you. This is definitely true in mice and the studies are very robust. We know that if possible, they will try to find a mouse partner who is as genetically different from themselves as possible. If you put two mice together and they're brother and sister, and you don't give them any choice then the female will mate with the male, and have pups with her brother. But if you then introduce a third mouse, which is genetically totally different from the first two mice, then the female can abort her babies and re-mate with the different male. Mice have this very strong and well developed sense of smell, and we know that the smell receptors are on the same chromosome as the structures that control how the immune system works. So we think that mice can use smell as the surrogate marker of how your immune system is working and so you can use that smell to guide you as to how different you are genetically from someone, and therefore go for someone who is as genetically different to you as possible which should make you healthier. The problem is that we humans tend to have very well developed frontal lobes in our brain. Which means we're very social, we think things through very carefully and we're very, very likely to get the argument skewed by things like social pressures, and likes and dislikes and how big someone's wallet is.

Well that's really interesting because one of the most exciting projects that people are involved with on Antarctica at the moment is looking for what's called sub-glacial lakes. They're using radar waves from the surface of the ice to look down. And they think what they've found is a whole series of lakes that are sitting above the rock but below the ice. Of course the really exciting question is, are they ancient life forms in there, and are they unique? And so that's what everybody's hoping to find the near future. As for what's melting the ice, that's a very good question and one that we all want to know the answer to. It is possible that it is what we call geothermal heat from the rocks underneath causing the bottom of the ice sheet to melt. It may be water that's been trapped there for millions of years, and that's what everybody is hoping for.

I reckon it's down to something similar to our kitchen science that we did this evening. That was all about nucleation. What you need is one tiny crystal to kick start the process. But where does this first crystal come from? Well, say he puts the glass bottle of this stuff in the freezer, and the glass where it's not in contact with the liquid, gets that little tiny bit colder because the liquid's not taking away the heat. This means that the glass on one side of the bottle is at a much cooler temperature than the rest of the bottle containing the liquid. Then, when you take the bottle out, because you've had it in the freezer on it's side, and you turn it the right way up, suddenly lots and lots of beer gets in contact with the side that's much colder, which might be enough to kick-start a small crystal forming, which then nucleates it makes it much more energetically favourable for lots of other ice crystals to form and the beer goes slushy.