THE ITCH OF ECSTACY

A QUIRKY AND ORIGINAL TAKE ON THE BIOLOGICAL ROOTS OF SEX

Author: By Chet Raymo

Date: SUNDAY, December 28, 1997

Page: L1

Section: Books

Well, yes, we all do, but we also have our doubts. We can live without sex, and we can't live without eating, but most of us spend more time thinking about sex than about food. The drive is deep within us, a nagging itch that is the source of our ecstasy and despair.

Why the itch? Any biologist can tell you that sex is not necessary for reproduction. A bacterium, for example, reproduces by cloning itself, which has the advantage of conferring a kind of immortality.

Sex -- the mixing of genes -- is not the same thing as reproduction. Many organisms mix genes without reproducing, and other organisms reproduce without mixing genes. But for humans, sex and reproduction are inextricably linked, which means that every offspring is different from either of its parents. This jumbling of genes ensures individuality, so prized by humans. The flip side is the inevitable death of the individual.

Lynn Margulis, a biologist at the University of Massachusetts at Amherst, has a successful track record at teasing out answers to life's riddles. She is most famously known for her idea that the many-compartmented eukaryote cell -- of which all multicelled animals consist -- evolved by a symbiosis, then fusing of simpler organisms. When she proposed this theory several decades ago, it was received skeptically by many of her fellow biologists. Today, it is textbook gospel.

In this new book, Margulis teams up with her son, science writer Dorion Sagan, to tackle the mystery of sex. ``Life always retains clues to its tortuous and weird history,'' they write, and proceed to excavate clues to the origin and purposes of sex. It will come as no surprise to readers of their earlier works that the sex lives of bacteria play a big part in the story.

This is a gorgeous book, illustrated with many full-page, full-color paintings and photographs of flirtations, temptations, seductions, and couplings, rivaling the illustrations in Alex Comfort's infamous ``The Joy of Sex.'' However, let prospective voyeurs be advised: It is mostly bacterial goings-on that you will find in these pages.

With its lurid jacket and blushing interior graphics, the book is a bit of a tease. It will be picked off the bookstore shelf for a prurient glance more often than it will be purchased. That's too bad, because ``What Is Sex?'' is chock-full of lusty science facts and provocative speculations that may someday find their way into the biology and philosophy textbooks.

The book offers a broad vision of sexuality that makes bedside sex manuals pale by comparison. Human sex is actually pretty boring, the authors suggest, and prove their point by giving us graphic descriptions of the love lives of bonobos, bedbugs, and damselflies.

But birds and bees are not the real topics here. Margulis and Sagan are out to do some deep philosophy. They go so far as to look for the meaning of sex in the Second Law of Thermodynamics, which says that the universe is moving toward greater disorder. Life, as they see it, helps create chaos by breaking down ordered sources of energy. Urine, feces, carbon dioxide exhalation, and even our bedroom sweat help the universe make a mess.

As far as I know, this is the first time sexual desire and the Second Law have been made bed partners, so to speak. The effect is exhilarating. Somehow, all of our heavy breathing and heavings and moans of pleasure and groans of frustration are made to seem part of a grand cosmic plan, rather than the apparently absurd biological imperative that so bemused James Thurber.

There are other equally provocative themes. Bacterial sex evolved as a way of DNA repair, say the authors. Hot and bothered by the sun, whose rays ripped apart their genetic material, bacteria on the early earth found ways of borrowing someone else's DNA -- and sex was born. What started by borrowing became embedded in the chemistry of life.

The seasons also played a role in the evolution of sex, say Margulis and Sagan. Sperm and egg cells, with their single sets of chromosomes, correspond to an ancestral mode of life suited to carefree summers or wet seasons. The fused fertilized egg, with its doubled set of chromosomes, evolved as a hardier response to the stress of winter or a dry season. And so today the sex cells of all animals, and most plants and fungi, cycle between what biologists call haploid and diploid stages, with single and double sets of chromosomes.

This is the sort of stuff that one can laugh at or take seriously. I tend to take it seriously because I trust Margulis's intuitions. It is the great virtue of this book that it puts human sexuality into a cosmic context, and anything that stitches our lives into a universal fabric gets my approval. God knows we flounder about looking for a greater meaning; evolutionary biology demonstrates that even our sneezings and orgasms rattle the universe.

Each chapter of this book contains colorful insights, wild guesses, and just-so stories that are anchored in biological fact but allowed to float just out of reach of convincing proof. This may annoy some readers who will find it all a little gushy, but others will love it. Part science, part philosophy, occasionally poetic, ``What Is Sex?'' is a roller-coaster ride through the history of sex on earth, and like a roller coaster ride -- or sex -- it can provoke both excitement and stomach-churning anxiety.

Attentive readers will come away with a deeper knowledge of why we behave in the torturous and weird ways we do, in what Thurber saw as the unending battle of the sexes.

Among behaviors explicated by Margulis and Sagan is the role of female choice in mate selection. In another of Thurber's well-known cartoons, a perplexed little man stands by his marriage bed in mismatched pajamas -- polka-dotted top and striped pants. ``Well, it makes a difference to me!'' says his disapproving wife from the pillows. I've laughed every time I've seen the cartoon. Now I know why.