Chris - It’s all down to something called nucleation and that is that the salt in the drink, the little crystals, if you’ve got some of those stuck on your lips or still in your mouth the salt forms a rough surface for the beer bubbles (the carbon dioxide that makes beer fizzy) to form on. It’s much easier to form where there’s a little imperfection. The beer fizzes out and all the carbon dioxide gets released where the salt crystals are and that makes the beer go flat. You can demonstrate this for yourself if you take a bit of beer and pour some salt into the beer it should froth up. That’s the CO2 coming out.

Preston - It works because you have carbon 14 which is a heavier  form of carbon 12 formed in the upper atmosphere with the bombardment of the carbon by cosmic rays and other bits of radiation. We know how much of that is being formed today. Therefore by looking at the ratio of carbon 14 to the carbon 12 in anything that has taken carbon in: any plant or animal that was living in the past you can measure the level of the carbon 14 that’s left. That way you  can infer how long it has been dead since that carbon 14 has decayed.

Chris - Because it stops taking the radioactive form in the minute it dies. Therefore the radioactive carbon in it must decline after death and therefore working out how much is in there tells you how it died: how long ago. Because we know how long the carbon takes to disappear.

Preston - Exactly

Martin - One thing we know is that as farmers spread probably languages spread with them. You can do a family tree of languages and a family tree of genes. There’s a reasonable match but we also know that there was contact between hunter gatherers and farmers and so there would have been an interaction with people with very different languages.  I guess we must just assume that their body languages were sending the right messages.

Chris - And also their tummy telling them they’re hungry so they’d be willing to swap food and things.

Martin - That’s right and I think there are more multilingual communities now than in the English speaking world we imagine there were.