 He is arguably the most unpleasant character in all fiction, a petty, unjust, unforgiving control freak, a perverse malevolent, racist housebreaker, the tormentor of childhood nightmares and the destroyer of childhood dreams. It has become customary around this time of year for our culture to celebrate this obscene individual as the cornerstone of our seasonal festivities, as the very epitome of the holiday. This is an evil we teach to our children and it has to stop now. I am obviously talking about that colourful character of common folklore, Santa. Let us start by noting his objectives. Santa's basic priority is the seemingly inoffensive delivery of gifts once a year, but take a look at the intricacies of this operation. Who gets these gifts? Traditionally, it's Western children. There is no trace of sleigh bells in the majority of third-world countries. There are only two explanations for this. Santa is either a corrupt benefactor of Western wealth or Santa is a racist. The third option, he's a corrupt racist. Only boys and girls of the right pigmentation or the right parental bribes get visits from our jolly dispenser of goodwill. Charles Darwin. I'm here to give you some straight talk about sex. Perhaps I could hide your ears and your eyes because you're too young to hear about all this, aren't you? Yes, yes, cover your eyes, cover your eyes. Actually, you know, you can hear this because I'm not really going to be talking about sex. I'm going to be talking about sexual selection, which is one of my two really good ideas. I published it in 1871. My other good idea in 1859 was natural selection. Now, natural selection produces efficient adaptations. So an example of that would be in birds, feathers, down feathers hold in body heat, and flight feathers allow birds to fly. So that would be an example of some very good adaptations produced by natural selection. Sexual selection, however, takes those adaptations that makes them interesting and beautiful so that they're attractive to potential mates. So, for example, in the blue-footed booby, the long blue beaks and the big blue feet, when the males have these characteristics, they have the greatest opportunities for mating with the females. The females really liked the males with big blue beaks, big blue feet. Not only that, but the boobies would, the male boobies would do a little dance. And that's how the males would impress the females. Some scientists have even suggested that the extravagance of the human mind was the result of sexual selection. And natural selection produced the kind of intelligence that let us solve problems, figure things out, find our way through the complexities of social interactions, plan ahead for the future. But it was sexual selection trying to impress potential mates that created art and poetry and music in the complexities of language. Natural selection has made the world, the biological world, efficient. Sexual selection has made it beautiful and interesting. This is Charles Darwin, Tally Ho. This TV show has to be the worst thing I've seen on TV since my mid-uncle was on fifth gear. It might be first year than a camel with a hangover. So it turns out some terrorists have been making a molecule called D2O to make a dirty boil. But accidentally they leak it into a water supply, which some boy drinks and then it cures his cancer. All over the ultrasound now. I checked the other one too just to be safe. This boy's kidneys are immaculate, perfectly normal. So first of all, what is D2O? Well, it's a lot like water, only instead of having hydrogen, which water is H2O, it's got deuterium. Now what's deuterium? Deuterium is a nice type of hydrogen, and hydrogen is basically one proton with an electron spinning around it. And deuterium has that one proton that is needless and also has a neutron in there. And that kind of, as I could say, is making it will heavier. It's normal water. This ice, this from the spring, are so called miracle water. So what percentage of water has to be D2O for the ice cubes to sink? I think we need to go to the lab. Now I have here some D2O. Now why do I have some D2O? Well, in a chemistry lab, we use a solvent for a machine called NMR, an NMR machine. And we basically dissolve our glass samples in deuterate solvent like D2O. And we can find out what our compound is made of or any impurities in there. And you can test for protons, which is the hydrogens of molecules or fluorines or carbons. They're the most likely ones. So I'm showing an experiment that basically says that this heavy water thing is rubbish and concentrations you need of heavy water to shrink. So I'm going to get some D2O and get me some appendorfs and with different concentrations of D2O and water and show what concentration at least you need for it to sink.