And here we thought it was all about sex.

The infamously fickle Y chromosome, that essence of masculinity that we XXers from Venus blame for everything — from war to the messy toilet seat — is full of surprises.

Turns out that the Y chromosome has three times more genes than scientists had expected, but, at 78 active genes, that’s still puny compared to the X chromosome that, with about 1,000 genes, determines femininity.

But enough about X or XX. All we do is complain about this being a man’s world despite there being more women on the planet.

Today is your day, Y. Take a bow.

That’s about all the Y can do, too. It can’t, as other chromosomes do in their genetic dating game, go all out and swap matching pieces of DNA with its X partner, or the world would be all males, and then, poof!, they’d be gone. For the sake of reproduction, the swapping, called recombination, occurs only at the tips of the Y and X. If it goes beyond that, then the male genetic structure would take over the X chromosome, and there would be no more girls.

Over the millennia, the Y has lost hundreds of genes precisely to save the X from extinction. I don’t mean to speak for all the XXers, but this one thanks Y for the sacrifice. Denied the full swapping ritual with the X chromosome has cost the Y hundreds of genes that eventually mutated and became useless because they could not swap and create new, healthier combinations.

But the Y is an enterprising sort, we learn from researchers at the Whitehead Institute for Biomedical Research in Cambridge, Mass., and the Washington University School of Medicine in St. Louis. After six years of research, scientists have decoded the whole Y chromosome. It may still look like men are from Mars, but at least we now know what the martians are made of and why they do the crazy things they do.

The big news is that the Y is not all about sex. It recombines with itself as a way to strengthen its DNA and keep the male chromosome from extinction. Making a sharp bend in the middle of a palindrome (an area of the chromosome that carries the same, exact DNA sequences, but they run in opposite directions) the two sides of the Y recombine, and this leads to genetic conversions that keep hope alive.

Survival of the fittest, and all of that.

Whitehead Institute biologist David C. Page says the research shows that genetic differences between men and women are greater than once thought. Differences in behavior or cognitive skills may not be hormonal, as once believed, but genetic. And the irony is, Page notes, that the Y chromosome isn’t so super-sex-charged, after all. It survives through asexual behavior.

And a healthy dose of narcissism — don’t you think? — to save itself in a gene-eat-gene world.

This might explain the findings in a recent Newsweek poll of men’s self-image. Men, the poll shows, are quite happy with themselves. They’re optimistic and not too worried about their health, their looks or their gals being unfaithful.

In fact, 90 percent of men polled said they were happy with their physical appearance. The one thing they worried about most was losing financial security.

Like I said, it’s not all about sex. Amazing.

Myriam Marquez is an editorial page columnist for the Orlando Sentinel. HEr e-mail address is mmarquez@orlandosentinel.com.