Undeniable (9 page)

Look around. So much of what goes on in our society is motivated by the process of sexual selection, and there are many subtle and not-so-subtle things that affect that process: There's mascara. Expensive watches. Amazing shoes. Sports cars, perfume, skirts, ties, jeans, boots, and on and on. Now, compare us to everybody else. By everybody else I mean dogs and cats and lions and tigers and bears … and squids and whales. All the other animals around, and all the plants, have seasons to their mating. We humans don't seem to. When it comes to our babies, birthdays are pretty well distributed around the calendar. Why is this? Why our species-wide sexual overdrive?

One of the leading theories is that it's an artifact. It's a result of being good enough in the process of evolution. The battle of the sexes is so strong perhaps because all of us ended up with big brains (compared to other animals—and my old boss). These brains make us aware of our place in the scheme of things and that somehow leads to doubt and altruism and loyalty and the ability to so easily do the wrong thing. To keep us from not getting around to mating, our sexual selective processes are turned on 24-7. Wherever it comes from, it works. This is to say, although we are continually stymied by broken hearts, loyalty, disloyalty, professional concerns, familial criticism, and other distractions, the human species reproduces at a prodigious rate. In ten thousand years the number of people on Earth has exploded, from a few million to more than seven billion. Apparently, sexual selection left us with our need to engage turned up to eleven.

And so I, a victim of evolution, did manage to go to the prom. It was opportunistic; I admit it. My date spent a lot of time with the older guys, guys from a class or two ahead of ours. When it was prom time, they were all in college and not available. I asked her out, and she agreed to come with. Apparently, neither one of us could help ourselves. I saw her at our reunion recently and she is still, as it is expressed in modern parlance, all that. I guess it's seared in the proteins that create memories in my sex-driven brain.

 

9

THE TALE OF THE RED QUEEN

In the previous chapter I discussed when sex evolved, and explored how sex evolved, but you may notice that we (or I) didn't really address the “why.” Why does anybody—I mean why does any organism—have sex? The amount of energy we put into it is crazy. We spend billions on lipstick and hair product. About every third advertisement in any medium is for a car—one with plenty of sex appeal. We get our pants pressed, our nails done, and we work hard to smell nice—all to attract a mate, one that will enable us to have sex and offspring. Why do we go to all the trouble of attracting a mate? Why not just get this literally vital task done on our own? Why not just let our lips be lips and drive around in gray, featureless blob cars?

It's not as if sex is the only way to reproduce. We humans could, for example, just split ourselves in half, DNA, bones, muscles, brains and all, like any self-unaware, or perhaps self-respecting, bacterium. The separate pieces form new membranes and boundaries as they separate. A replica of the DNA from the parent is built on each side—I mean, inside each of the two individuals that emerge from the original. If it's hard to imagine a person splitting in half that way, try picturing a genetically identical baby budding directly off of a mother or a father. There's no reason why it couldn't work in the big picture, yet here we are instead surrounded by all of those made-up lips, polished nails, fancy fragrances, gym memberships, sporty cars, and the like.

And those are just the obvious examples from our human experience. Much more important, from a planetary perspective, are the billions of other species here on Earth that use energy from the Sun and the soil to build flower petals, pistils, and stamens—to build bioluminescent appendages—to grow fruit on their limbs just so some jerk like me will yank it free, cart it off, and spit the seeds out someplace, where they might find friendly soil and a place to grow some offspring fruit of their own. Why bother?

Salmon swim and swim. They spend most of their lives eating other fish with the goal of finding a fish-mate that they can swim upstream with, lay a pebble bed, fertilize with milky sperm, and die. Why bother? You can try not to make jokes about it: A pregnant elephant takes up a lot of room, but getting an elephant pregnant looks like a good bit of difficulty. Why bother?

Let me start by saying as of this writing, no one is absolutely sure why organisms like you, me, armadillos, and trees have sex. Broadly speaking, sex produces offspring with a new mix of genes, a mix inherently different from the parents. It may provide more chances for innovations, which might lead to a more successful successive generation. The new mix of genes might weed out genetic errors.

But we do have an outstanding theory about why sex is useful, a theory that places sexual reproduction within the larger picture of the theory of evolution. It is survival of the fittest, survival of those that fit in the world, specifically the ecosystem that is best. It's competition. And one's chief competitors are seldom other troublesome large animals: Humans really have very little trouble keeping up with and living around lions and tigers and bears. Instead, our most troublesome bad guys are germs and parasites. These are what can kill us or disable us to the point where we cannot produce or care for offspring.

We're not the only organisms with this germ and parasite issue. If you lick your lips, you might ingest right around 1 million viruses that specifically attack bacteria. By long tradition, they're called bacteriophages, or just phages for short. (
Phage
is from the Greek word for eating. Phages eat the insides out of bacteria.) In other words, even bacteria, these relatively uncomplicated single-celled organisms, have great difficulties with phage viruses, whose sole function in life, or along the border of life, is to hijack a bacterium's metabolism and use it to make copies of themselves.

A striking feature of phages is how specific they are. That is to say, a specific phage only attacks a specific type of bacterium. The surface of the phage identifies and sticks to a specific protein on the specific bacterium. The main defense a bacterium has against a phage attack is to somehow modify or reconfigure the protein pattern on its outer membrane. Now, individuals cannot change themselves, as such. Instead, their descendants, their offspring, can have modifications as their DNA is replicated. Random changes may or may not help them resist a phage. Keep in mind that we're talking about bacteria. They may not change very quickly, from one generation to the next. But they reproduce like crazy, doubling over just the course of a few hours for most species, so bacteria produce almost uncountable numbers of descendants. In those lots are bound to be new configurations of imperfectly copied genes, some of which will have the ability to resist or just not be identified by phages that could have killed their ancestors.

It is this fast replication of bacteria, viruses, and other not-too-complicated parasites that can cause us big organisms trouble. The germs are out there reproducing and chancing upon ideal protein-pattern-attachment genes, which are well suited to infecting us. Meanwhile, big organisms like you, me, and redwood trees cannot reproduce over the course of a few hours. It takes redwood trees centuries. It takes us months and months, then years more to get ready to do it again. So to stay in the evolutionary game, we, and especially our ancestors, have (had) to come up with a different scheme, or we would never have been able to keep up with all the phagelike viruses out there all set to take our cell metabolism and turn it against us. Put more accurately, our distant ancestors did indeed come up with a different scheme; otherwise you and I wouldn't be here to ponder the question(s).

The key to fighting germs and parasites seems to be sex. At one level, this may bring you down. All the lipstick, high heels, hair products, salary seeking, sports cars, and weightlifting seem to be a result of germs. But then, so are art, and music, and good cooking. By having sex, organisms like dandelions, sea jellies, perch, parakeets, and termites can stay ahead in the game of life just enough to have offspring that succeed in producing more offspring in a subsequent season.

By relatively recent tradition, this is called the Theory of the Red Queen. The charming sobriquet comes from the fictional Alice of Lewis Carroll's books
Alice's Adventures in Wonderland
and
Through the Looking-Glass
. In this story, Alice has an encounter with the Red Queen. (By many accounts, Mr. Carroll smoked some form of marijuana from time to time, and perhaps enjoyed a glass of wine or two.) Somehow the Red Queen is a sort of hybrid chess piece/person, who slides along, on something akin to a Chess Board of Life. So when one is with the Red Queen, her whole world is moving … somehow. So, Alice is constrained to run like crazy to have a conversation. This is the Red Queen's day at the office or day at court. Alice remarks, “Where I come from, if you run all day, you end up somewhere else.” The Red Queen, as she raises her royal-chess-piece-person eyebrows, remarks, “Why, that seems like a very slow sort of country. Here it takes all the running you can do to keep in the same place.”

Apparently, the process of evolution that you and I, and every other living thing on Earth, are caught up in is like the land or country of the Red Queen. In evolution, we have to run constantly; we have to continually come up with new combinations of genes to keep our genes in the game. To be successful as a living thing, you have to have offspring, who have offspring, who have offspring. Rest assured, your family did, or you wouldn't be here. As troubling as it may seem, your parents had sex—at least once. If you have brothers and sisters, more than once … One shudders to think of it.

Like any scientific theory, we can use the Theory of the Red Queen to make predictions of phenomena we see in nature. When I participated in a debate with the creationist Ken Ham, I used the example of the small fish called topminnows. These fish are remarkable. When times are tough and the pickings of opposite sex fish are slim, these particular topminnows (
Poeciliopsis monacha
) can produce eggs that develop into fish, without the egg having been fertilized with another fish's sperm. This is known as asexual reproduction. Of course, boy topminnows and girl topminnows also get together to reproduce sexually by having regular fish sex.

The topminnows in question live in Mexico, in rivers. When it rains and rains, there are plenty of pools in which the fish can make their homes. When the weather dries up, the pools get separated by tracts of dry land. These fish are attacked by a parasitic flatworm, which in English we call the black spot flatworm. In the isolated populations of fish, the ones that were forced to reproduce just by themselves were subject to more black spots than the same species of fish that had enough prospective mates around to enable them to reproduce sexually. Wait, there's more. There was also a gradient to this disparity: The populations that had a higher percentage of asexual reproducing individuals also had a higher percentage of black spot flatworms.

There's more, more: The researchers, Bob Vrijenhoek at the Monterey Bay Aquarium Research Institute and his colleagues, found a population in a certain isolated pool, where the sexually reproducing fish had more parasites than the asexual fellows or females. They discovered that the sexual fish had inbred; they had had sex with their brothers and sisters more than outsiders. So the random mutations introduced by the asexual reproducers were outpacing the sexual ones, which was surprising. Since there is no shortage of these fish and no shortage of such pools, Vrijenhoek introduced some outsider sexually reproducing topminnows into that pool's particular mix. A season later things were back, as one who acknowledges the influence of the Red Queen would expect. The asexuals were more infected than the sexuals.

It's a wild world out here where we live. But these fish are a remarkable example of a scientific theory making predictions that come true. In this species, we could compare directly the effect of a single type of parasite on a single type of fish. They're wonderful special fish, the topminnows, because they reproduce in two different ways, and we can observe them from one season to the next. We do not have to wait decades or centuries, as we would if trying to study humans or giant sequoias doing this.

This is one of the reasons I get such joy from studying evolution. This kind of science is amazing and sexy.

 

10

DOGS ARE ALL DOGS

People love dogs. This is, I hope, the least surprising sentence you will read in this book. I myself have had long discussions with my dog friends, and by that I mean my friends who are dogs. I will admit that these discourses were largely one-sided. When dog people get together, they often ask each other what or which kind of dog does each person has. They're talking about breeds of dogs: Collie, corgi, Labrador Retriever, pit bull, or poodle. Generally, I love 'em all, because dogs are all dogs. They are a great walking, barking definition of what a species is. Evolutionary relationships are defined not by looks but by what's inside. If a male and a female can hook up and produce offspring, then by the simplest and most meaningful definition they belong to the same species.

Put another way, I love all of you dog lovers, but I have to spoil your fun a little with a fundamental truth. There is, in an important evolutionary sense, no such thing as a specific breed of dog. If a Great Dane has sex with a dachshund, you get a dog. If a Standard Poodle has sex with a Jack Russell terrier, you get a dog. If a mutt has sex with a so-called purebred, you get a dog. You don't get anything else. All dogs are descendants of common ancestors. So, when we all enjoy the kennel club's show, which is divided or organized by breed, we are participating in a ritual that is, at an important level, arbitrary. There are gradations, or there is a spectrum of dog types or breeds. The word
purebred
is something we can define by counting generations back in dog-sex land. But it is not an indication of species or anything special, really.