In the 70s, guns were for boys and dolls were for girls. Animals, transport and building-simulation were unisex, and if you really wanted to test the limits of female objectification, you could get a severed head with retractable hair. That was called a Girl's World. Oh what a world.

Our hippy parents did not know they were born. The form for children now is a gender essentialism so extreme that feminist mothers spend their whole lives (ironically) pink with fury. The whole spectrum of pink has gone kaleidoscopic, so that if you were a parent with only girls, you could be forgiven for thinking baby to fuscia was the entire gamut of the toy rainbow. And the world of boys' toys is more than just blue, it is spiky and obnoxious, more likely to flash and to be designed to throw at people; there is an altogether darker, more nightclubby atmosphere to their hardware, and everything is prefixed or suffixed with the word "monster".

This is why even parents who aren't that interested in gender politics still object: it's the narrowness of it all, the very extreme versions of masculinity and femininity that this consumer world represents. In respect of that, Hamleys has just axed its girls' and boys' floors, following focus groups and customer feedback. A more stringent company PR policy I have never encountered: a nice man called Andrew Evenden tells me, "We have made our statement, and that is the only statement I will make." This is what their statement says: "While we welcome comments from all customers and interested parties on improving Hamleys, in this case we regret that the changes to our signage were not due to any campaign."

OK, nobody wake up the politburo, they have this under control: they were not pressured, they decided on their own. From here on in, the third floor will not be called "girls", which will not be written in pink, and likewise, the fifth floor will not be called "boys" just because it contains teeny weeny toy soldiers.

Not that much has changed, if I'm honest: even if the third floor signage is no longer pink, that doesn't make a huge amount of difference when all the toys are pink. It is still weird that "arts and crafts" is in the same category as dolls. I don't think you could organise all the munitions-playware on to one floor without people making certain judgments about who you intended it for, though Hamleys might argue that that was our problem, not theirs.

The gender-stereotyping of the toy industry is not as ham-fisted as you might imagine. In toys for older girls, new sensibilities creep in, like gothic (a "Dracula jewellery box coffin", one box in Hamleys says, as though those four words appear next to one another all the time) and camp (they don't do Ken dolls as boyfriends to Barbie any more; they have a whole wall of "Ken Fashionistas", in which Ken is modelling a fashion item or a male grooming project, like shaving – "barbe magique!" that one is called, in French). It's not all candyfloss. And boys, of course, are considered the key audience for all the films that are any good (Toy Story, Cars). What kid doesn't like telly? A weird kid.

Inescapably, though, there is this idea underpinning the toy industry, as well as strains of modern pedagogy, that male and female children are fundamentally different, that their interests stem from and reveal a difference in their brains and that to object to this is the endpoint of politically correct foolishness, arguing about evidence that's in front of your own eyes.

Neuroscientists talk about "brain sex" now in an openly deterministic way. The sociologist Dr Ellie Lee, of Kent University, notes: "There is a resurgence of this naturalistic, 19th-century idea about men's brains and women's brains being different on a basic level. You see it a lot in discussions that happen around schooling, the idea that you need to school boys differently to girls because all boys want to do is run around in the playground and kick the shit out of each other. Whereas girls like to sit still and do colouring in."

I thought that was an overstatement of the brain-sex position, until I heard Dr Anne Moir, neuropsychologist and author of Brain Sex, at a conference: "OK, so out we pop. The brain is undifferentiated, but we are born with a tilt of interest. Little girls come into the world with a brain that is much more interested and gets much more pleasure from the social context of the world. Little boys come into the world and they take much more pleasure from the physical world, in exploring it, in taking things apart, and there and then you have that dynamic mix: he's exercising his brain in that physical dimension, she's exercising her brain in that social dimension. The big differences are in what gives us pleasure, what motivates us, and that's why men choose some jobs and women choose other jobs."

Lee points out, interestingly, that the plus and minus have been swapped: "People used to ascribe to biology the differences to make the male all that's good and the female all that's bad. Now, it's been reversed, so it's the allegedly female characteristics that we're supposed to value: empathy, emotionality, non-aggression." This fascinating debate, between neuroscientific gender determinism and the sociological rebuttal, took place at the Battle of Ideas festival in London this year (you can see it on YouTube); it's a real and growing academic fissure, magisterially taken on in Cordelia Fine's Delusions of Gender.

To drag this back to the layperson's level, let's call it the parental level, the main argument against the separation of the sexes is that it's rubbish. One minute a kid might furiously identify himself with his sex; children have got to situate themselves as something, and they often don't have much else to go on. It's not as if they have jobs. The next minute he will be dressed as Bo Peep (that is a real example, from this morning; my son said he wanted to be called Little Blue Peep, because Bo Peep sounded too girly. I said maybe it wasn't the Bo that was the problem, so much as that huge makeshift bonnet). The market doesn't have much room for nuance, especially at Christmas. But Hamleys has taken a tiny step back from the brink of gender essentialism, and for that, as well as the late opening hours, I guess we should be grateful.