Genes on:Why we are what we are and why we are who we are.

Charles II of Spain was the last Habsburg ruler of the vast Spanish empire and despite being married twice he was unable to produce an heir, an event which triggered the War of the Spanish Succession and cost more than a million lives. His first wife, Marie Louise of Orleans, complained of the king's impotence and his second, Maria Anna of Neuburg, said he suffered from premature ejaculation.

El Hechizado (the hexed or bewitched as Charles II became known) was the result of several generations of inbreeding. It wasn't accidental inbreeding either. It was done intentionally to enhance what the Habsburgs would've seen as positive attributes and defining characteristics, like pugs or something. Charles II and most of his forebears had huge protruding chins and Charles, being the last in line, had a bigger one than most. If only they'd concentrated on developing a perfect, or at least functional, cock instead of a chin, perhaps war could've been avoided.

This was eugenics in all but name. As his grandparents' children married his grandparents' grandchildren and so on and so on making their family tree look more like a plate of spaghetti than the usual grid, or 'tree', format Charles ended up with a tongue so swollen he could hardly talk and malfunctioning sexual organs to go with a mandibular prominence so infamous it'd be the envy of Jimmy Hill. Recent studies have shown Charles to be more inbred than the child of two siblings.

This was just one of the many fascinating stories in Dr Adam Rutherford's two hour long talk 'A brief history of everyone who ever lived' at Greenwich Skeptics in the Pub on Wednesday. Except it wasn't quite that. At the start of the talk the affable, good natured, informed, educated, and thirsty Dr Rutherford announced he wasn't going to do the advertised talk but a different one. One about Nazis, eugenics, and racism. People cheered. People love talks about Nazis.

Adam is a young (43), good looking (according to my friend Vicki, though I'd concur) geneticist, author, and broadcaster who contributes to The Guardian and Radio 4 and has delivered the Darwin Day lecture for the British Humanist Association and a Douglas Adams Memorial Lecture at the Royal Geographical Society. His books include Creation:The Origin of Life, The Ladybird Book of Genetics for kids, and the upcoming Book of Humans with impressive illustrations by Alice Roberts, another one of those people who seem to be able to turn their hand to just about anything.

He kicked off the talk by telling us that every single one of us is descended from Charlemagne before going on to say that genetics, as a science, is only about one hundred years old and that it's only been in the last ten or fifteen years that it's really been studied as a sophisticated science. People used to think they knew a lot about genetics but the last decade or so has proved that the picture is far more complex than we'd once imagined and revealed there is still a very long way to go before we understand why we are what we are and why we are who we are.

Misunderstanding of genetics is the ultimate manifestation of identity politics but misunderstanding of genetics is very easy. It's a difficult subject. Luckily Dr Rutherford realised this was a pub, not a lecture theatre, and kept the science very much on layman's terms. Pop science like Brian Cox if you like but there's nothing wrong with that and, in fact, very much right with it.

The science of genetics (the word dates back to ancient Greece) really got going with the Augustinian friar Gregor Mendel who inbred pea plants and established clear patterns in the resultant wrinkliness, colour, and height of these specimens. Without naming it he'd prefigured the gene as the unit of inheritance.

People have claimed the ability to roll one's tongue is inherited through the genes as well as the colour of one's eyes, a popular belief is that blue eyes carry a recessive gene and brown eyes a dominant one meaning that eventually, one would assume, blue eyes would die out. Which they clearly haven't. Dr Rutherford said these basic errors in understanding genetics were down to one thing. Genetics are probabilistic not deterministic. It's highly likely that a brown eyed father and a blue eyed mother would have a brown eyed child but it's by no means guaranteed.

DNA tests in North America, provided by companies like 23andMe, claim to be able to identify your 'tribe' (for money) but, really, we all hail from many many tribes. Provided we're not inbred (and most of us will be just a little somewhere along the line) we'll all hail from many different tribes. If you go back just ten generations you should have somewhere close to 1,024 different great great great great great great great great grandparents and, of course, we all go back way more than ten generations.

That's why the doctor can be so sure we're all descended from Charlemagne and how he can have confidence in saying that every pale skinned person in that room has the much in demand Viking ancestry. You go far enough back and everyone is descended from everyone. We're all one big family. Show some love!

Francis Galton was Mendel's co-star in this talk. The Birmingham man did a lot of things in his life. Some of them have stood the test of time. Others not so much. On the plus side he invented the weather map, pioneered biometrics and fingerprinting, and produced the first description of synaesthesia. Less impressively he coined the pernicious phrase 'nature versus nurture' (nurture is part of nature), came up with a frankly bizarre new method of cutting cakes (was that a big problem in Victorian times?), and, most creepily of all, came up with what he considered to be a scientific scale for measuring women's attractiveness. Galton would hang around local parks looking at women and then marking them between one and six based on some preordained factors. Some women were understandably not best pleased with this so Galton invented what he called 'pricker gloves'. With these he simply had to wear these modified gloves and when he saw an attractive woman put his gloved hands in his trouser pockets and fiddle around with some counters he'd secreted down there. Yep, that would look absolutely fine!

It was too good an anecdote to leave out but the reason Galton cropped up in our talk was that he, essentially, invented eugenics. Or at least as a scientific idea (the word, as ever, is Greek). He was quite the advocate of it too. Proposing monetary incentives for those with healthy minds and bodies or, simply, lots of money already.

It wasn't seen as a nefarious idea until the Nazis took the ball and ran with it. If you think of it we all practise a form of eugenics anyway. We generally choose the person we wish to have children with based on their looks, personality, and other, sometimes unclear, factors. I've even proposed the idea that the reason men are attracted to larger breasts is because, subconsciously, they know their offspring won't go hungry!

But forced eugenics? That was a bad idea then, it got worse with the Nazis, and it's still bad now. Back in the day it wasn't just something the right wing were able to get on board with. Vocal advocates of eugenics included Winston Churchill, Theodore Roosevelt, and George Bernard Shaw. Such was the passion even eugenicist Valentine's cards were available.

It wasn't just Nazi Germany that installed eugenic programming as a state policy but also Sweden and the USA. California (perhaps unsurprisingly given that state's predilection for creating fake realities:think Disneyland, LSD, or cyberspace) had the most enthusiastic policy regarding eugenics and, shockingly, the last forced female sterilisation happened there as recently as 2010.

So, it's not just a hot potato and an unfinished story science wise but politically so as well. Thus, the talk didn't tie up neatly in the end but drifted off into a fascinating, and unresolved, Q&A session. Much like our lives themselves. We have a rough idea where we come from but we don't know exactly. We have an even rougher idea of where we're going. Life is like science. There are things we know to be true and there are things we know to be untrue but we can discover things that change everything. We can have lives turned upside down by events that happen in them but with science even our past is a movable feast.

It'd been a great evening that'd given me quite a lot to think about. We'd had a look at some frankly disturbing far right neo-Nazi websites, we'd learnt that celebrated birth control pioneer Marie Stopes was a virulent racist and ableist who wrote love letters and poems to 'Dear' Herr Hitler, and we'd even heard that giraffe's neck lengths had evolved for fighting rather than nutrition ('necking' they amusingly call it, and like the human version of necking sometimes things go further, the winning giraffe celebrates by bumming, raping, his vanquished foe and ejaculating into his anus). We know this but scientists still remain flummoxed to one of the eternal mysteries of our time. Why do men with no ginger hair on their head whatsoever get, in middle age, ginger in their beards?

Thanks to Vicki for coming to this with me, thanks to Professor Chris French for hosting yet another wonderful evening in the Star & Garter, but, mostly, thanks to Dr Adam Rutherford for giving up his entire evening to talk passionately, amusingly, and knowledgeably about such an endlessly interesting subject. I'd recommend buying one of his books.