How would Charles Darwin feel if he were alive today, a radio show asked this week? Much like the rest of us I imagine - pretty depressed.

Oh, I suppose he could enjoy a smug “told you so” over the Vatican's admission on Tuesday that the theory of evolution may, erm, be on the right track after all. And he could have a laugh by clicking on www.creationism.org and discovering that there are still people who believe that Noah really did squeeze all those animals on to the Ark because, and this is a quote, “one could fit, for example, a dozen brachiosaurus eggs in the trunk of a car, with room to spare!”

But there'd be bad stuff too. On the Origin of Species wouldn't be much of a seller down at WH Smith because there's no tie-in fitness DVD and he doesn't have a story to tell about his time in rehab. It's doubtful he'd get his own series with the BBC because they've already got one beardie talking about Nature and that's Bill Oddie.

And I reckon he'd be consulting his lawyers right now about the weird, commemorative £2 coin that the Royal Mint has just brought out in his honour. Have you seen it? It features a picture of Darwin gazing into the eyes of an ape with an expression that seems to say: “Your place or mine?”

But I'd guess the thing that would most depress Darwin in 2009 would be that he'd start to wonder whether he'd got his theories all wrong. I certainly would. It is hard, for instance, to swallow the idea of natural selection when you gaze upon the über-rich creature that is Jocelyn Wildenstein. This is a woman who spent a reported £2.7million on cosmetic surgery and once said: “I lost my peripheral vision after my last cheek implant but I weighed it up carefully and realised I only used it for driving, so it was a decision I could live with.”

In centuries past it was easier to believe in concepts such as the survival of the fittest. If you had good-quality food to eat and a decent gene pool you flourished and lived, and if you didn't, you withered and died. Simple. The ascending breeds were recognisable from having plenty of fat on their bones and a glass of fine port in their hand, denoting wads of money and a place high up the chain. The weakling underclass, too, were easy to spot because they were the ones with sunken eyes, stumpy teeth and xylophone ribcages who died at 25 because they had to last an entire winter on three turnips.

But not any more. Oh no. If we look again through the demented prism of the 21st century, we'll see that the reverse applies. It's not about survival of the fittest now but the triumph of the thinnest. Today, the second that people - especially famous, Western, female ones - acquire wealth, the first thing they do is stop eating, or, alternatively, gorge themselves on chocolate and regurgitate it all into their lavatories. Then they flaunt their skeletal frames in OK! and Heat magazine, usually with an oversized Birkin bag, looking just like the starving peasants of yore, for which they are roundly admired and envied.

Living through an entire winter on cabbage soup is not a sign of bereftness any more but of abundance: “I'm so successful I can afford the time to starve myself!” The more money you have the fewer offspring you tend to produce, lest you pollute the planet and are unable to afford that extra skiing holiday.

Meanwhile, it's the very poor who have become fat, piling on calories with cheap BOGOF pizzas and fizzy cola and being followed round by TV documentary crews so that we can all sit back and gawp at the lardbuckets.

Some believe, controversially, that this progeny breeds far more successfully and rampantly than any other in order to cash in on something known as “child benefit”. But that's really a specialist subject and one that is best left to Wife Swap.

I wonder what Darwin would think today if he was shown a picture of Victoria Beckham - an unhappy-looking specimen who seems so malnourished that if she collapsed in the savannah the hyenas would barely think it worth the bother - and told that this is what millions of females aspire to. Or Jodie Marsh, who has swapped her breasts for 32GG spacehoppers and endured five hours of surgery to acquire a set of perfectly symmetrical, toilet-porcelain veneers on her teeth - “giving a smile”, according to a leading dentist, “that bears little resemblance to what is human and natural”.

Something has gone wrong with evolution. It seems to be going backwards. Devolving, if you like. Thomas Hardy's plump, desirable, fecund wench is today's mocked, self-loathing yo-yo dieter, who is patronised by Trinny and Susannah and tempted to either get liposuction or wear Spanx pants.

Now that there are vaccines, medicines and life-support machines to help us to combat disease, the fight to survive, in the developed world at least, has become a bit too easy-peasy. So we have switched our fight from prevailing physically to prevailing socially. Having your toes straightened to fit into designer shoes or a couple of ribs removed to facilitate a waspish waist may weaken the body and make you not such a dab hand in the wild but, hey, think of the social victory.

In fact, the nearest we get to witnessing the survival of the fittest today is in watching The X Factor, Big Brother and Britain's Got Talent. This is where the too freakish, the too old and the too ugly get weeded out and killed off in the early stages so that the path is clear for the talented and physically attractive to win.

Come to think of it, Darwin might have made a good panellist on a naturalist version of The X Factor. He'd have been just as brutal as Simon Cowell. “On that performance, and being totally realistic, you'll never survive out there,” you can imagine him saying, to boos from the audience. “Your body's too heavy, your beak is just weird and you can't even fly. I'm sorry, Dodo, but it's a 'no' from me.”

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