Dr. Tatiana's Sex Advice to All Creation (22 page)

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The variations on these themes are myriad, fascinating, shifting like shards of colored glass in a grand kaleidoscope, often defying prediction. My favorite example is the spraying characid. This little fish lives in murky rivers in Guyana. Surprisingly for a fish, it lays its eggs out of water. When the male and female spawn, they leap out of the water together and stick themselves briefly to a blade of grass or to the underside of a leaf from a plant hanging over the bank. With each leap, the female lays eggs and the male fertilizes them. They do this over and over again until the female has laid perhaps three hundred eggs. Then, for the next three days, the male splashes the eggs with his tail to keep them from drying out. If it's raining, he gives himself the afternoon off. Or, to take an example more similar to your own case, my hyenid friend, look at the Dayak fruit bat, who lives on the Malay Peninsula. In this species, both males and females produce
milk, apparently sharing the responsibility of nursing the young. Is it any stranger for a female to have a phallus than for a fish to lay eggs out of water? Or for a male mammal to produce milk?

 

Gender benders.
The next time anyone wheels out a stereotype and says, “She does this, he does that,” here's your reply:

When you gaze at a couple and wonder
What trait makes him “him” and her “her,”
Beware, for it's easy to blunder
And be false in what you aver.
 
Some creatures change sex before teatime,
Some others find two sexes dull,
And that virile male fish has no free time—
He's got all his kiddies to lull.
 
When it comes to the topic of gender,
Mother Nature's been having some fun.
Take nothing for granted! Remember,
You won't find any rules—not a one!
WHOLLY VIRGIN
No doubt, many of you have been writing to me over the years because you've seen my popular TV program,
Under the Microscope
—
The Deviant Lifestyle Show!
You'll know that the program's had a lot of kinky, if not downright perverted, guests, and of course the audience is used to hearing about weird sexual practices. A few weeks ago, however, we had a really provocative guest. I don't know if you saw the episode, but the most awful fight erupted—there was practically a riot, and I'm sorry to say I almost lost control of the show.
I'm not surprised everyone got so upset. The guest in question doesn't have any weird sexual practices—or indeed, any sex at all. Worse, no one in her family has had sex for more than eighty-five million years. This is an outrage: scientists cannot agree on what sex is for, but they all agree that it is essential, impossible to live without. And yet if our guest can manage without sex—or men—why can't the rest of us? What's sex good for? Is it passé? Are men endangered? Such questions bring us to the heart of perhaps the most fundamental, controversial matter in
biology—what is sex for?—and since most aspects of the topic were hashed out on the show, here's my account of the furor.
We had the biggest turnout yet. All the usual crowd were there—the belligerent ram and his supercilious armadillo friend were both sitting in their regular places in the front row. The pocket mouse was curled up in the small-animal gallery; the homing pigeons were on their customary perch. As always, Moby, that impressive puffer fish from the Congo River, was churning up and down the freshwater fish tank. But a lot of the members of the audience were first-timers. I noticed a bake—if that's the right collective noun—of clams in a corner of the saltwater tank. Several Brazilian lizards, looking rather sickly and depressed, had stationed themselves halfway up the left wall. The back rows were bristling with radical feminists wearing T-shirts that said, “Men, who needs them?” and “Sex is for wimps.” The studio was fizzing with excitement and hostility. The cause of all the agitation? My guest, none other than Miss
Philodina roseola,
the bdelloid rotifer.
From looking at her, you'd never guess Miss
Philodina
is at the heart of one of the most notorious scandals in evolution. Slender and translucent, she looks less like an animal than like a pocket telescope blown out of pale pink Venetian glass. But you don't normally see telescopes eating algae, and before the show Miss
Philodina
had clearly been doing just that. Throughout the entire evening, the remains of a recent feast were greenly visible through her glassy body. (This was my fault: I usually advise translucent guests to skip lunch the day of the show, but this time I forgot.) Her most striking feature, though, is on top of her head, where she has a pair of disks edged with beating cilia, tiny mechanical hairs whose motion gives the illusion of wheels spinning round and round. Of course, she's barely half a millimeter tall, so before anyone could get a look at her, we had to settle her
on a comfortable frond of moss and turn on the microscope so as to project her blown-up image on the screen by my chair. We cut a fine pair, the two of us. I looked my usual glam self in my best scarlet suit. She looked the picture of innocence. And that innocence was the cause of all the trouble …
The show started off much as usual. I welcomed the audience and introduced Miss
Philodina,
giving a few trivial details, such as her favorite spot to hang out (damp moss) and the fact that rotifer means “wheel bearer.” Everyone in the audience applauded on learning that her Latin name means “rosy lover of twirling.” But as soon as I began to talk about the nature of her deviancy, the disturbance began.
Me: Tell us, Miss
Philodina,
when was the last time anyone in your family had sex?
Miss P.: Hmmm. I think it's been about eighty-five million years since anyone in my family has even been on a date.
Me (To audience): And you thought you had problems. (To Miss
Philodina
): No sex, not even a kiss, since before the dinosaurs went extinct. And why not?
Miss P.: My ancestors abolished males. They said they were better off without them.
The studio drowned in jeers and whistles—despite loud cheering from the radical feminists.
Me: So how do you reproduce?
Miss P.: We clone ourselves.
Well, that caused absolute mayhem. The pocket mouse even fainted. But I've seen this reaction before. Many animals, especially
mammals, have a horror of cloning. They seem to think it will produce a flock of monsters or something. So I had to remind everyone that cloning is nothing more than reproducing without sex—something that billions of respectable organisms are doing every day. I paraded my standard examples: strawberries sending out runners and shoots; yeasts and other organisms budding off bits of themselves; sponges, sea anemones, and worms of various kinds falling to pieces and regenerating, whole new animals growing from each piece; all sorts of girls (including bdelloid rotifers) laying asexual eggs. And to the discomfiture of many in the audience, I pointed out that even mammals clone once in a while, when an embryo splits early in development. The resulting individuals are not usually called clones, though. “Twins” is considered more polite. Typical mammalian political correctness.
It's curious. Everyone always forgets there's nothing wrong with cloning from time to time—that cloning mixed with bouts of sex can contribute to a healthy and happy lifestyle. As I explained to the audience, it's only giving up sex altogether that's the problem.
At first glance, however, giving up sex seems advantageous—from a genetic point of view, anyway. Sex may be fun, but cloning is much more efficient. All else being equal, an asexual female who appears in a population should have twice as many offspring as her sexual counterpart. To see why, think of it this way. In a sexual population—the human population, for example—each female must have two children for the population to remain the same size. If females have fewer than two children, the population shrinks; more than two, and the population grows. In an asexual population, however, each female needs to have only one child for the population to remain the same size. More than one, and the population will grow.
But although asexuality often evolves—it pops up in groups from jellyfish to dandelions, from lizards to lichens—it rarely persists for long. On the great tree of life, asexual groups are out on the twiggiest twigs of the twiggiest twigs: lots of buds, no branches. After a brief and glorious flowering, asexuals vanish. Which has led scientists to conclude that exclusive asexuality is an evolutionary dead end, a fast track to extinction. Sex, they insist, is essential. And ancient asexuals—creatures such as the bdelloid rotifers that have lived without sex for millions of years—should not exist. According to all the theories, the bdelloids should have disappeared shortly after giving up sex.
Yet, in scandalous defiance of scientific prediction, there's Miss
Philodina
, thumbing her wheels at us from the frond of moss. How come these rotifers have succeeded where so many others have failed? Or, to get back to the central question, if they can do without sex, why can't the rest of us?
With that preamble, I opened the floor to questions, as usual reminding the smallest members of the audience to step up to the microscope in the aisle. Understandably, the first questions challenged Miss
Philodina'
s claim. What did she mean when she said no one in her family has sex? Did she simply mean that bdelloid rotifers get intimate but avoid genital contact? No, that's not what she meant. But before she could go on, there was a truly embarrassing incident. Two bacteria tried to have sex on live TV
The screen on the wall lit up: someone in the audience had gone to stand under the microscope. Gradually, the image came into focus to show not one but two lozenge-shaped organisms. In actual size, each would've been about a millionth of a meter—tiny even in comparison to Miss
Philodina.
One of them started to squeak: “Good evening, everybody. We're a pair of bacteria of the species
Escherichia coli—E. coli
to our friends. Many scientists keep us as pets, so we often live lives
of luxury and ease in the laboratory. In the wild, we live in the guts of mammals, helping digest food.
“For us bacteria, reproduction is reproduction and sex is sex. Unlike you ‘higher' creatures, we're not so vulgar as to do both at once. For us bacteria, reproduction is asexual: we simply divide into two genetically identical cells. This way, sex—by which I mean the acquisition of extra genes—is something that we reap the benefits of during our lives. If humans could do this, which they can't, it would be like suddenly adding a few genes for longer legs or bluer eyes.”
At this, one of the homing pigeons muttered wryly, “Lucky bacteria. Getting new genes beats a tummy tuck for a midlife crisis. Wish I could get some new genes.”
Before I could turn the discussion back to Miss
Philodina,
the bacteria said, “So, how we do it? We have several ways. We pick up DNA that's loose in the environment. We gather DNA from passing viruses. We even plunder the genes of dead bacteria—the cognoscenti call it necrophilia:”
The thought of necrophilia—even if only bacterial necrophilia—produced gasps of horror from the audience, and someone yelled, “Perverts!”
The bacterium blithely went on: “We also indulge in bestiality, getting genes from bacteria of other species. But above all, when we're in the mood, we have sex with each other. We'll show the rotifer how it's done—I'm going to give my friend here a useful set of antibiotic resistance genes. Look, Miss
Philodina,
watch how we do it!”
As the crowd roared, one of the bacteria started to extend a tube toward the other.
Luckily, at that moment my technician flicked the microscope switch and plunged the screen back into darkness. I tell you, it was a close call. Talking about sex is one thing; as you can imagine,
showing sex would land me in all sorts of hot water with the network and thoroughly upset my commercial sponsors (though
PlayBeast
would've been thrilled). It could've been the end of the show.
The dirty little germs did do me one favor, though. They reminded everyone what sex is—and that it's not the same as reproduction. Sex is any process that mixes genes from different individuals.
To my amazement, Miss
Philodina
took up the cue. Like a pubescent boy, she knows an awful lot about the theory of sex; unlike a pubescent boy, she obviously finds the whole idea disgusting. I guess that's bound to happen if you've got eighty-five million years of celibacy behind you.
“Bacteria,” she said, sighing. “Always exaggerating their sex lives.”
She was right, of course. Despite the impression the speaker tried to give, bacteria are not nature's libertines.
“Most bacteria don't have sex of any sort very often,” she went on, “and
E. coli
are among the most abstemious.” She spun her wheels indignantly. “I wouldn't want anyone to think that we bdelloids are merely a sort of bacteria. Or worse, a sort of virus.”
She was worried that many in the audience might not really know the difference between viruses, bacteria, and all the rest of Mother Nature's children. And that if folks didn't understand the difference, they wouldn't appreciate how truly unique she is.
“Viruses cannot reproduce by themselves. Instead, they invade a cell and hijack its machinery to make more viruses. In fact,” she said with a sniff, “viruses are not even proper organisms. They are little more than bands of rogue genes traveling in a tiny capsule.”
I pointed out that although viruses are mainly famous for causing disease—from polio to AIDS—some of them do merit a
place in the
Kama Sutra.
For example, the reason that humans must make a new flu vaccine each year is that influenza viruses sometimes have sex, getting new genes that help them sidestep the human immune system. All the same, if Miss
Philodina
were a virus—or a bacterium—no one would be making a fuss about her being asexual. The problem is that, just like any mammal or bird, Miss
Philodina
is a eukaryote.
Unlike bacteria, we eukaryotes keep our genes sequestered in a special place—that is, a nucleus. Eukaryotes come in many shapes and sizes—some have only one cell, others, like bdelloid rotifers and humans, have lots of cells. But for all this diversity, eukaryotes are properly puritanical when it comes to sex. If the mood takes them, bacteria and viruses have lots of different ways to mix genes. Eukaryotes have only one. And when scientists talk of sex being essential, it's eukaryotic sex they mean.
In eukaryotic sex, you get half your genes from your mother and half from your father. But which half? That's decided through the lottery known as meiosis. Say you're playing a game with two decks of fifty-two cards. Each card represents a chromosome—a string of genes. The only rule is that each of your offspring gets one complete deck. It doesn't matter whether they get the queen of spades you got from your father and the jack of diamonds you got from your mother. It doesn't even matter if you cut up both aces of spades and stick them back together again as jumbles of the originals. Indeed, genetic cutting and pasting of this sort is an integral part of eukaryotic sex. It is an internal shuffling of each chromosome, and it is called recombination. Thus, at the end of meiosis, each sperm and each egg carries one complete but unique mixture of genes—a complete but shuffled deck. When egg and sperm from two individuals fuse, they therefore produce a new gene combination. Bdelloid rotifers haven't seen a new gene combination in years—eighty—five million years.

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