Watch Sarah Silverman: Jesus Is Magic I Give The Jew Girl Toys I German Cars I Watch Tina Fey doing Sarah Palin on Saturday Night Live

Of course men can still be funny. Chris Rock has just finished a sell-out world tour which was consistently amusing. Flight of the Conchords are so funny, they make appliqué jumpers look hot. Chris Morris is working on a sitcom about incompetent al-Qaeda terrorists, and Armando Iannucci and his team have a film version of The Thick of It coming out next year, set in America and starring Tony Soprano. I've no doubt that both will be as funny as funny can be. ÜberLOL.

But while men may still be capable of being funny - and, indeed, continue to be quite good at it - the ground rules of comedy are in flux. And one of the biggest ground rules has just been abolished entirely. For this year it became possible, for the first time in history, to make the following statement: currently, the two funniest people in the world are women.

Both are, inevitably, American. America always seems able to afford these feats of cultural wonderment - rock'n'roll, social networking sites, funny ladies - before we can. Tina Fey and Sarah Silverman are where comedy is at right now.

Tina Fey has been head and shoulders above all other satirists during the US presidential campaign - helped by her startling resemblance to Sarah Palin. Over the past few weeks on Saturday Night Live, Fey has been turning in an escalating series of Palin parodies - perhaps peaking with last Saturday's evisceration of the disastrous Palin/Katie Couric television interview. Skewering Palin's nebulous claim to superlative international diplomacy - based wholly on Alaska's promixity to Russia - Fey/Palin chirruped: “We keep an eye on them [the Russians]. Every morning when Alaskans wake up, they look outside and see if there are any Russians hanging around, and ask them what they are doing there. And if they can't give a good enough reason, it's our responsibility to say ‘Shoo!' and get them out of there.”

Perhaps more devastatingly, nearly a whole minute of the spoof interview consisted of verbatim, increasingly desperate and flailing quotes from Palin on the current $700 billion banking bailout - concluding with Fey grinding to a halt, then brightly saying: “Katie, I'd like to use a lifeline now, please. I'd like to phone a friend.” USA Today has said that Palin's biggest challenge now, in the run-up to the election, is to make Americans forget the “Tina Fey factor”. As the latest twist in a career in which Fey has become the first female chief writer on Saturday Night Live; written, produced and starred in the multi-Emmy-award-winning sitcom 30 Rock and written the $129million-grossing movie Mean Girls, which gave Lindsay Lohan her break-out role, it is unexpected but, in almost every respect, amusing.

Sarah Silverman, meanwhile, is the nearest the comedy world gets to a rock star. Currently on a world tour to promote her DVD Jesus is Magic, and appearing in London on October 19, Silverman is perhaps best known for her satirical song - the deathless, crude and very, very funny I'm F***ing Matt Damon - which made headlines around the world this summer when it hit 17million views on YouTube. For those who haven't seen it, it really is more than just some swearing and a cameo from Matt Damon - there's a joyous, almost reckless silliness to it that only escalated when Silverman's on/off boyfriend, the US chat show host Jimmy Kimmel, produced an “answer” song entitled I'm F***ing Ben Affleck, the video to which included Cameron Diaz, Ben Affleck, Harrison Ford and an all-star We Are The World-style choir. The combined viewing figure for both videos currently stands at more than 25million.

Silverman's appearances at awards ceremonies are invariably the stuff of next day's headlines: after Britney Spears' infamously “fat and confused” performance at last year's MTV awards, Silverman was the next person on stage.

“Wow. She is amazing. She's 25 years old and she has already accomplished everything she's going to accomplish in her life,” Silverman said in her trademark wide-eyed, Rita Rudner-esque manner, before adding: “Have you seen Britney's kids? They are the most adorable little mistakes you'll ever see! They are as cute as the hairless vagina they came out of!” The gasp from the celebrity audience is audible on the YouTube clip.

Silverman's main vehicle, however, is the inventive, anarchic and very funny The Sarah Silverman Program, which she writes, directs and stars in. It is the highest-rating show on Comedy Central.

Neither Fey nor Silverman is being punished for her pioneering success. It is not seen as somehow unfemale for them to be pursuing laughter. It's not like back in the 20th century, when women could be either funny but essentially unf***able - Joan Rivers, Roseanne Barr, Bette Midler, Lily Tomlin, Jo Brand - or f***able but condemned to a lifetime of speaking other people's lines - Lucille Ball, Phyllis Diller, Carole Lombard.

Of course, some would disagree. Last year the usually admirable Christopher Hitchens wrote a rather rheumy-eyed, crumb-spluttering polemic in Vanity Fair entitled “Why Women Aren't Funny”. One of his main, barking assertions in 3,000 words of barking assertion was that women could not be both amusing and attractive. “Most [female comedians] are hefty, or dykey, or Jewish,” he said.

Sadly for Hitchens, his assertion was rather undermined by the fact that Silverman (who is Jewish) managed to make the cover of Maxim, while Fey made the cover of Marie Claire. Maybe it's the global recession, maybe it's the weather, maybe it's all the therapy, but modern men appear quite happy to be laughed into bed.

Hitchens went on owlishly to explain that one of the primary reasons why women can't be funny lies with their wombs, which apparently can roam around the body, getting in the way of jokes. “Those who risk agony and death to bring children into [this world] simply cannot afford to be frivolous,” he harrumphed. “There just aren't that many episiotomy jokes.” Thus proving, if nothing else, that Hitchens has never got blotto on £3.99 cava with a group of NCT mothers on a night off.

Still, Hitchens is scarcely a lone, mad voice in the wilderness. This idea that there are innate female traits - fertility, fragility, some manner of moral superiority - that stop women from being laugh-out-loud funny is still a common one, especially among the older generation.

To do comedy “you need a big hunk of meat between the legs”, commented the late Michael O'Donoghue, the first chief writer on Saturday Night Live. “I do have [a hunk of meat between the legs],” Fey countered in her trademark style, which has been described as “poison-filled jokes in long, perfectly parsed sentences”. “It's just that it's been flayed to a vagina.”

Who needs balls when you have a million eggs and an extra rib, eh? Indeed, in many ways, having established that you don't need balls, who would want them at the moment? For while the greatest thing about being a man is the patriarchy - all those comfortable assumptions! All the guys! All the beers! - the worst thing about being a man is the patriarchy, too.

Let's face it, after aeons of physical, social, political and cultural dominance, men are quite often finding that, y'know ... it's a bit hard to start a conversation any more. They have kind of said pretty much what they want to say.

This is certainly the case in the world of rock and pop, where in the past two years all the hot British artists getting the headlines and breaking America have been women - Amy Winehouse, Lily Allen, Duffy, Leona Lewis, M.I.A and still, God bless them, Girls Aloud. It's hard to imagine a male artist capturing the public imagination in quite the same way.

Similarly, there hasn't been the advent of a young male messiah in the comedy world for some time now. I guess Russell Brand was the last one - but even he got his big break when a rumoured relationship with Kate Moss gave him cultural validity. And, as women assume ever more positions of power, it's logical that a generation of female comedians will need to satirise them. Often it takes a woman to see what tricks another woman is pulling (in Fey's parody of Sarah Palin's shambolic TV interview, she has Palin's inquisitor say, at one point, “Mrs Palin, it seems to me that whenever you're cornered, you just become increasingly adorable.” Palin/Fey responds by wrinkling her nose, making a series of silly “pew, pew, pew!” noises and saying “I dunno - is it?” in a cute little mouse voice). When men makes jokes about powerful women, they can sound so ... bitchy.

At this point in history it was inevitable that women would start to pull ahead of men in humour. For starters, women have a 200,000-year backlog of suppressed gags to get through. I can't wait to hear their material on the Neolithic revolution.

And secondly, women have many more untouched, unclaimed topics to play with, particularly in comedy's most fertile area: the realm of filth. Here, at least, we can find a point of agreement with Christopher Hitchens's Vanity Fair piece. In his thundering finale, Hitchens asserts that what a comedy audience ultimately wants is “filth and plenty of it. Filth in lavish, heaping quantities”. It was his firm conviction, however, that this was women's greatest disability - that women are too prissy, uptight and pleasant to “play dirty” with comedy, and so are condemned to be the unamusing sex.

So, while the most refreshing aspect of Fey's humour is her snappy, exasperated bluestocking pithiness - her backing for Hillary Clinton was “I'm a bitch. Hillary Clinton is a bitch. Bitches get things done” - it is Silverman, gleefully wading into the female viscera, who is a pioneer. She is gaspingly fearless in her topics. Whole episodes of her show have revolved around the vagina and its multifarious malfunctions: vaginal wind; heterosexual Aids, lesbianism, the cry “I stubbed my vagina!”.

When Hitchens asserts that Oscar Wilde was the only person “to ever make a decent joke about the death of an infant”, he had clearly never seen the scene in The Sarah Silverman Program in which Silverman uses the story of her abortion, at the age of 18, as an inspirational pep-talk. “Let me tell you a little story about courage,” she starts. The inspirational pep-talk is to a nervous ten-year-old about to enter a children's beauty pageant.

Silverman's killer weapon, however, is that while she never saw a taboo she didn't want to bust - she also has a winning line in satirical racism, and her material on homophobia reveals many supposedly “pro-gay” comics to be mortifyingly patronising - she delivers it all with an air of, well ... feminine charm. Girlish winsomeness. Joy. Imagine Audrey Hepburn doing stand-up, or Gigi writing and starring in a sitcom about malfunctioning vaginas.

Silverman is both Wife of Bath bawd and Amelie-esque ingénue. Along with Fey's ability to bring down an opponent that even Barack Obama couldn't manage, it is, perhaps, the kind of trick that only a woman could pull off.

Sarah Silverman performs at the London Hammersmith Apollo on Sunday, 19 October. Tickets: £42 and £35, available from 0844 576 5488, www.livenation.co.uk .

Sarah Silverman: Jesus Is Magic”is released on DVD by Warner Music Entertainment on Monday 13 October.

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