Back when our great-great-grandparents a-squillion-times-removed left Africa's Rift Valley, they were black – which was a good idea, because it's kinda sunny in Africa and darker pigmentation was the only way not to die from skin cancer. But when people eventually wound up in Northern Europe, where it rained whenever it wasn't just depressingly overcast and grey, the dark pigmentation wasn't all that important anymore, so if an occasional mutant was born with a genetic defect that produced lighter skin, he or she could survive long enough to reproduce that genetic defect – and in fact had the edge on the darker-skinned people because lighter skin could absorb the lower levels of sunshine to make Vitamin D better, so white people wound up prevailing in Europe and inventing racial discrimination.
Okay, so I'm postulating that those original black ex-Africans in Europe didn't find the paler mutants all that hot, which meant that the pale folk wound up having to settle for each other when it came to rubbing their mutated genes together and making mutated kids.
The dancing bit? Well, in the normal course of events back in the Rift Valley Social Club, anyone who had a genetic defect that made them a crap dancer wouldn't have got a chance to pass on their crap dancing gene, coz they'd have just been wallflowered instead of deflowered, and left unmated-with. Like, no way was a black person gonna get it on with another black person who couldn't shake it out on the floor and hopefully later down on it, so that was that.
But in Europe, because there were increasing numbers of pale wallflowers still considered too unattractive to be invited to dance by the black people, they'd sneak outside together and console each other as deeply as possible. In other words, you didn't have to be a good dancer to get laid. And that meant that any crap dancing genes could also be passed on along with the pale skin gene – but, and here's the clincher: only in liaisons between pale skinned people!
So eventually Europe had decreasing numbers of Vitamin D deficient black people whose bones had become too brittle to risk dancing (or even banging each other, hence their gradual disappearance from Europe in general), and more and more white people who had Vitamin D enhanced bones but couldn't move their feet to save their lives and therefore had to develop pale imitations of dancing like minuets and pavanes so they could hit on each other and breed more bad dancers.
There you have it. Why white people can't dance. Coz we're mutants.
But fortunately for the human race, and kinda inconveniently for all those sub-human segregationists and racial bigots, the fact remains that all of our most important genes are still the original black ones.
"It's got nothing to do with
your weird skin colour, Dork –
my folks are just freaked out
coz you're a crap dancer
without any kind of future."