Why Is There Sex?

Pardon me for boasting, but on the way home from the gym this morning I seem to have solved a long-standing problem in evolutionary theory. I don’t think I’ve read this idea anywhere — it just sort of popped up.

The problem is, why does sexual reproduction exist? Evolution is ruthlessly economical. Any behavior that doesn’t “pay off” in terms of reproductive fitness will sooner or later get weeded out. Sexual reproduction is expensive in behavioral terms — all the trouble of finding a mate, fighting off rivals, and so forth. What’s the payoff?

A theory that I have read is that the payoff is protection from microbes. The microbes in your immediate environment, which includes the millions of tiny critters living on your skin right at this moment, breed much faster than you and I do, so they can evolve faster. There’s a kind of arms race going on. Any advantage they gain (in making you sick, which will increase their numbers radically) has to be fought off by your immune system. Sexual reproduction, according to this theory, jumbles up the genes of the next generation, which essentially confuses the microbes. They have to start over, trying to figure out how to make the next generation sick.

I’m sure that’s a fine theory. I’m not a cell geneticist, so I’m not equipped to evaluate it. But here’s a different idea.

When we talk about evolutionary fitness, we’re not really talking about the fitness of a big, strong animal. We’re talking about the fitness of the genes that encode information with which to build a big, strong animal. It’s the fitness of the genes that is crucial in evolution.

In asexual reproduction, the mother passes all of her genes on to her daughter, and so on, unto the nth generation. Because evolution is ruthlessly economical, it will tend to trim away redundant genes. An asexual creature would quite likely have, for instance, only one gene to produce an essential digestive enzyme, because if there was ever a second gene that did that, when the second gene fell apart or got mis-copied, it could never be reconstructed.

Genes do occasionally mutate. Not often, but it happens. And there are, in your genetic makeup and mine, thousands of genes that are essential for the organism to remain alive. You have genes that constructed your heart, your lungs, your skin, and so on. If you had only one copy of each of these genes, any mutation (in the portion of your own developing body that produced egg cells) would be fatal to your offspring. You would never produce any viable children.

But when you have two copies of these important genes, one from your father and one from your mother, a defect in one of the copies is not necessarily fatal to you or to your offspring. If you only have one copy of the gene that makes that essential digestive enzyme, you may never even know it — and half of your children won’t inherit it. True, fatal mutations can still occur. But the redundancy of the genetic information lowers the rate of fatalities due to mutation.

This is all Biology 101. But the essential point is this: From the point of view of your genes (anthropomorphizing a bit here — genes obviously have no point of view), sexual reproduction protects all of them against the occasional fatal “traitor” gene. The healthy genes work together, producing a sexually reproducing species, in order to protect themselves from those occasional traitors.


The Big Picture

Physicists have pretty well established that the way the universe works depends on the values of a small bunch of numerical constants. The strength of gravity, for instance. If gravity were slightly stronger, stars would all collapse into neutron stars, so there would be no planets with life. If it were slightly weaker, stars would never have formed at all; the entire universe would be just a cloud of drifting gas.

That’s just the example that’s easiest to understand. There are other similar numbers. When you look at the big picture, it does appear that our universe has been fine-tuned at the factory to allow our sort of life to emerge.

This is not an argument for the existence of a god, however. If our universe did have a Grand Designer, there are several possibilities, most of which don’t involve anything that would resemble traditional conceptions of “God.” The Grand Designer might have died billions of years ago, for instance. Or might have drifted off to work on some other project, and might have no concern at all with the fate of this one.

Nonetheless, physicists are confronted with a puzzle: Why are things the way they are? One suggestion holds that there’s an infinite supply of universes. At the beginning of each universe, the values of these physical constants are established in a random manner. Most universes, then, would be devoid of anything resembling life. Our own universe might be part of a tiny minority — but only in that tiny minority will intelligent beings evolve who can look around and say, “Wow! Look how perfectly these numbers are set up!” This is called the weak anthropic principle. Read more

Life Is a Brewery

I’m re-reading a couple of science books I read a few years ago — The Violinist’s Thumb by Sam Kean and Microcosm by Carl Zimmer. Both are about cell biology, and while they’re addressed to the intelligent layman, they’re not gee-whiz pop science books. They really do present a fairly clear picture of what happens inside cells, and how we’ve learned about it all. Kean is far too fond of anthropomorphizing; his descriptions of DNA and other molecules give them very human intentions, and that’s bogus. In reality, the molecules are just bumping around at random, but the process happens so quickly that the results (one molecule fitting into another so as to catalyze a reaction) operate as if they were intentional.

Cells don’t reproduce sexually. They sometimes swap genetic material with one another, but that’s not quite the same thing. Cells reproduce by dividing in two. And no new cells are ever assembled from raw molecular ingredients — that hasn’t happened for billions of years, and may in fact have happened only once. All of the cells in all of the animals and plants that are alive today have arisen through the splitting of previously existing cells. And from the point of view of a cell (if we can speak of such a thing), in splitting it has budded off a daughter cell. A daughter cell isn’t a new-born: It’s still the same cell as before.

This fact has a dizzying consequence: That very first cell that somehow assembled itself 3.8 billion years ago is still alive. It’s you. It’s me. It’s all of life on Earth. With the possible exception of viruses, but I’ve read a theory that viruses evolved from the breakdown of more complete cells. They aren’t a separate creation, they’re just efficient parasites. Be that as it may, it’s humbling to realize that every single cell in your body is 3.8 billion years old. For the last 550 million years or so it was continuously an egg cell; each time an embryo differentiated, the cell that became you was one that remained an egg cell. Before that, you were just swimming around, being a cell.

That’s mind-blowing enough, but once we peer inside cells to discover what makes them tick. what we find is a vast array of chemical reactions, a constantly bubbling stew of molecules bumping against one another and catalyzing reactions. All behavior — all human behavior and all of the other behavior of every living thing on the planet — is ultimately a chemical process that occurs when molecules interact. We can’t even say that behavior is the result of chemical reactions. Behavior IS chemical reactions. Unimaginably complex chemical reactions, to be sure, but there’s nothing else going on. It’s all proteins and methyl groups and whatnot bumping into one another. That’s how you get Shakespeare; it’s also how you get a common garden slug. In fact, many of the same chemical processes that happened in Shakespeare also happen in a slug.

Of course, molecules pass in and out of cells all the time. A cell that couldn’t pass molecules in and out through its membrane would soon be dead. No cell is an island. Once you realize this, if you twist the zoom control all the way out and look at life on Earth as a whole, what you discover is that life on Earth is all one ongoing chemical reaction. It has been going on for 3.8 billion years, constantly stirred by energy from the sun. If we say, “That’s a redwood tree,” or, “That’s a sonnet by Shakespeare,” what we’re doing is giving a name to some small part of this single enormous chemical reaction.

This is humbling, but it’s also freeing. You and I are nothing but burbling masses of chemicals. The molecules are going to do whatever they’re going to do. Nobody is in control, so there’s no blame. Just relax and burble along.


Surprisingly often, scientific researchers make what (eventually, perhaps after decades) turn out to be bad assumptions. They simplify a vexing problem in order to investigate it with the available tools, and then assume that what they’ve learned describes what happens in the real world, forgetting that they began by making a simplifying assumption.

Right now I’m reading Microcosm, a wonderful layman’s science book about the bacterium E. coli. You may not know much about E. coli, but they know quite a lot about you, at least in a vague, utilitarian way, because billions of them are living in your intestines right now.

E. coli has been quite extensively studied in the laboratory. It’s right up there with mice and fruit flies as one of the favorite organisms used in research. But research can’t be done in your intestines. On p. 51, the author (Carl Zimmer) says this:

“Out of the 4,288 genes scientists have identified in E. coli … only 303 appear to be essential for its growth in a laboratory. That does not mean the other 3,985 genes are all useless. Many help E. coli survive in the crowded ecosystem of the human gut, where a thousand species of microbes compete for food.”

But I’m not here today to meditate on intestinal parasites (though that’s a topic worth meditating on). I’m a lot more interested in what happens inside of E. coli. The little critter is a jam-packed protein circus! Large molecules are whizzing around carrying out amazingly intricate Read more

Win or Lose

Back in the early ’80s, I used to play pool with a guy named Dave Williamson. We would drive down to a nearby pool hall and play 8-ball while eating lunch. Dave was Keyboard’s advertising director, and a very competitive guy. In order to understand this story, you have to know a little about the rules of 8-ball.

There are two ways to win a game of 8-ball: You can sink all of your balls, followed by the 8, or your opponent can foul. If you foul, you lose immediately. Sinking the 8 ball too early is a foul … but here’s the nasty bit: Once you’ve sunk all of your balls and you’re shooting for the 8, if the cue ball strikes one of your opponent’s remaining balls before it hits the 8, you’ve fouled, and you lose.

If your opponent gets too far ahead — if he’s shooting for the 8 while you still have four or five of your balls on the table — you have a tactical opportunity. You can Read more

Lingua Franca

So you’re describing the human species to a xenosociologist named Erbq, who comes from a planet somewhere near Aldebaran. You tell him (actually, Erbq is a him/2, but let’s not get into that) that we humans use tools and communicate using spoken words, which signify objects, actions, and relations. Also, we have a glandular system that releases chemicals into the bloodstream to stimulate quick action — emotions, in other words.

From this data, Erbq might reasonably conclude that humans will express their emotions by making sculpture and paintings. (I suppose we’d better tell him we have color-sensitive eyes too. That’s important information.) He might also be able to predict that in order to depict our social relations, we will tell stories, write poetry, and enact dramas, either onstage or in a film/video medium of some sort. All of this seems pretty natural, given the raw material of the human organism.

But would Erbq be able to predict the existence of music?

Music is a very odd art form. It’s almost entirely abstract, and yet it communicates. Music is a language whose words and sentences are, technically, meaningless. But somehow, the listener Read more

Morality Unraveled

If you ever wonder why we are the way we are, I recommend reading Robert Wright’s fascinating book The Moral Animal. Wright lucidly explains the insights of the emerging science of evolutionary psychology.

It’s more than a little disheartening to see one’s grand pretensions laid bare, but it’s also freeing. The foundations of human morality seem very clearly to lie in the adaptive trait of reciprocal altruism — you scratch my back and I’ll scratch yours. Like our cousins the chimpanzees, we form alliances by doing one another small favors.

There’s more to the book than that. Wright discusses both status hierarchies and cheating in considerable detail, along with the values related to mate selection.

After re-reading The Moral Animal, I’m afraid I may need to rethink my fondness for the ideals of socialism. As I define it, socialism springs from the insight that we’re all in this together. It’s a small planet, and if we can’t figure out how to live with one another, we’re doomed. But while this insight is inarguable, it also Read more

Social Cohesion

Evolution has equipped the human species with a fairly strong herd instinct. We all want to be part of a close-knit group. The craving may be stronger in some people and weaker in others, stronger at certain points in life and weaker at others, but it’s seldom entirely absent.

It’s not hard to see why. In the environment in which our ancestors lived, being part of a group meant both more physical safety and more access to potential mates. Those who went their own way faced greater dangers, and had less chance of passing their genes to the next generation. So genes that promote social behavior would inevitably have flourished.

From what I’ve seen, fitting in with a group is far more important for most people in the modern world than thinking for themselves. For a great many people, this is a sensible strategy: They’re Read more

The Illusion of Free Will

We like to think that we have something called “free will.” But do we? I don’t think the term can even be defined in a way that makes sense.

The subject came up in conversation today, so I figured I’d better lay out my thoughts in an orderly way. Not that I expect to change many minds. This is a subject that arouses deep feelings.

That’s an interesting fact in itself. I suspect that many people confuse free will with personal responsibility. The idea being, if you aren’t free to choose whether to do or not do certain things (perhaps praiseworthy things, perhaps despicable things), then there’s no point in holding you accountable. There is no way to exercise any moral judgment. Everyone gets to engage in any sort of naughty behavior that their impulses may suggest, because, “Hey, I couldn’t help it.”

Well, okay, you couldn’t help it. But we’re still going to lock you up for a while. First, so that maybe next time you’ll think twice before you Read more

Digging It

Archaeology is how we come to understand who we are. The traces that remain of the distant past are being obliterated across the globe — submerged behind new dams, bulldozed to make way for freeways and high-rises — and that’s a horrifying tragedy. When it’s gone, it’s gone.

Other sites that would have yielded up priceless knowledge were looted in the 19th century, before the rise of modern archaeology. The human race is heedless. Who was it who said, “What we learn from history is that we learn nothing from history”?

And of course the soft bits rot. With a pitifully few exceptions, we have not a shred of evidence about what people wore 10,000 years ago. We know what kinds of meat they ate, because they left the bones scattered around. But we don’t know what they may have carved from wood — toys for their children, perhaps? — because the wood is gone. We don’t have their dances, their songs, their stories. All we have, for the most part, are Read more