By Steve Jones
Professor of genetics, University College London
If the 21st Century belongs to women, could men become extinct? It's the question raised in this week's BBC Two drama documentary If... women ruled the world?
Superhero or zero? Professor Jones says men are indispensable
Professor Steve Jones explains why, in spite of the rumours, men are biologically hard to get rid of.
One of the biggest questions in biology is: what is the point of men?
Why do women let them get away with it? All they do is force the unfortunate female to copy their own, male, genes.
And why are there so many of that selfish tribe?
Imagine a city with 10,000 women and just 10 men
Each one, each time he has sex, makes enough sperm to fertilise every woman in Europe. Surely a few lucky lotharios would be enough and we could do away with the rest in the interests of economy.
In fact the question of males raises not one, but many biological issues: the origin of sex, of distinct sexes, of why there are only two sexes rather than dozens.
And how is that pastime maintained, given that it is so expensive? A woman, it seems, could much increase the rate at which she copies her own genes if she avoided having them diluted by those of a man.
Yes, men are a complicated lot, and there's a lot we do not know. As we look through the living world, one thing is clear: it is very hard to get rid of them.
If... women ruled the world
Wednesday, 31 March 2004, at 2100 BST on BBC Two
There are plenty of creatures out there that have done the job (including a California lizard in which every animal is a female but, strangely, half pretend to be male by trying to mate with its sister).
Plants - think banana or potato - have dumped males again and again. However, almost none of those lineages have evolved very far.
On the great tree of life, they are at the tips of the branches, each at a dead end. Males act to reshuffle the genetic cards, handing a new mixture of DNA to the next generation, rather than exactly the same mix as that in their mother.
In the great casino of life, they are essential, for any creature that always gambles with the same hand, however good, is bound to lose in the end.
In mammals like ourselves there are also boring technical reasons why some genes have to pass through a father to work properly (which is one reason why cloning is so hard).
But why equal numbers of the sexes? Like so much in life it is a matter of investment strategy.
Imagine a city with 10,000 women and just 10 men.
Every man would have lots of mates perhaps a hundred or more but however energetic the men were, many of the women would remain without a partner.
The cells that make sperm are preserved from decay while those who bear them age and die
Being a man would be very, very, advantageous, and the gene for maleness would get commoner in the next generation.
In time, the city might, perhaps, end up with more men than women - and then the shoe would be on the other foot for many of those males would fail to reproduce.
In the end, things would settle down at 50-50, which is where it more or less is, at least in the west.
In China and India, though, lots of girl babies are killed off as they are seen as valueless. That effect has led to a great excess of young men (more than 120 to every 100 women in some places).
Now, it seems, some parents actually prefer to have girl babies as they are guaranteed to find a partner when they grow up.
Why are babies born young?
The laws of nature are less forgiving than those of television, and in spite of the rumours men are going to be around for a long time yet.
In fact there is another reason why we are going to be hard to get rid of.
Men are at the heart of another central question of biology: Why are babies born young? How can two old and decayed pieces of protoplasm (mothers and fathers, as we call them) get together and, with remarkably little effort, generate a new, rejuvenated, one?
It has to do with sex: for the cells that make sperm are preserved from decay while those who bear them age and die.
Without men, babies might be born as old as their mothers. Imagine what a great television drama that would make!
Professor Jones has written a book on the issue called: Y: The Descent of Men.
Professor Steve Jones took part in the BBC television programme If... women ruled the world.
The programme was broadcast in the UK on BBC Two on Wednesday, 31 March, 2004 at 2100 BST.