Rational Philosophy

Why sex makes sense.

Yesterday I posted a piece on new or renewed questions about why organisms reproduce sexually (as opposed to asexually). In short, no current theory can explain why organisms have evolved to reproduce sexually. Theories have been proposed — such as the desirabilty of high gene mutation rates to aid adaptation and resistance to parasites — but these theories haven’t been borne out through scientific analysis.

VS.

As I tried to clear my mind for meditation this morning on my subway ride to work, it occurred to me that perhaps we are asking the wrong question. Instead of asking why evolution led to such a broad and successful range of sexual reproducers, would it make sense instead to ask “why not”?

I’ll try to explain what I mean.

Darwin’s theory of natural selection is often misparaphrased as “survival of the fittest.” (I almost did it myself, before I researched the origin of that phrase; Herbert Spencer coined it after he adopted, adapted and misused Darwin’s theory for his own purposes). If we look around us we see that the world is far from filled with absolutes. Instead, the various paths that life and evolution have taken have led to an enormous and bewildering array of living things. The number of types and subtypes of plants, animals, insects, etc., is dizzying.

Bdelloid Rotifers do very nicely without sex, but that doesn’t mean that we all need to. We’re not competing with Bdelloid Rotifers, we’re all just doing what we do until something comes along to stop us.

To couch this in more scientific terms, theories of gene mutation don’t need to explain why sexual reproduction is better than asexual reproduction as an evolutionary fork in the road. They just need to explain how it is that sexual reproduction is a viable evolutionary fork.

Mathematically, a new species will only fail to survive if the threats to its survival outweigh its ability to adapt and thrive. When the number of threats is low, the species doesn’t need to be a super-survivor, it just needs to be good enough.

The same is true within human society. We can’t all be superstars, supremely attractive, incredibly smart, strong, mature, creative, resourceful. But that doesn’t mean we can’t survive and lead a fruitful life, reproduce, create a genetic legacy. Just one clear look at the world around us demonstrates the futility in seeking to understand why, from an evolutionary perspective, a particular trait has survived. Why not? What was the force that would have stopped it from being perpetuated?

And given the amount of time most people spend thinking about sex and participating in it or wanting to participate, there would have to a fairly major turn of events to stop us continuing down this particular alley.

For a rational, science-based explanation of life’s meaning and purpose, please refer to my book: LIFE! Why We Exist… And What We Must Do To Survive.

Reports from a team of Cambridge scientists last week presented a theory explaining how an asexual organism (a tiny invertebrate pond-dweller, the bdelloid rotifer) has been able to survive 80 million years without sexual reproduction.

In a related article scientists from the University of Sussex show that the rate of mutation in a range of sexual organisms is lower than it would need to be if sexual reproduction occurs to guard against the harmful effects of mutation.

All of which seems quite new and interesting to those of us who haven’t been keeping up with the theories of evolutionary biology. But apparently the elusive evolutionary benefits of sexual reproduction over asexual reproduction have been much hunted and seldom in clear view for quite some time.

I also read the first two parts of a fascinating essay by Errol Morris “Which Came First, The Chicken or The Egg.” Although it’s about photographs from the Crimean war, the Morris piece reminded me, as did the two science reports, that evidence and hypothesis make a far less solid foundation for our understanding of the world than it sometimes seems. Morris’s article also makes a powerful case for the importance of careful, methodical, skeptical inquiry. It may be a long time before we know as much about the wending path of evolution as we once thought we did. And for this reason what we think we know can’t tell us as much as we might hope.

But if we look through the other end of the telescope things become a little less dizzying. We can ask the question: Do we need to know the details of each stage and step of evolution to know that organisms evolve? If organisms evolve, what can this tell us about the purpose of evolution?

For the past few mornings when I’ve walked into my office and pressed the light switch, the lights have flickered on and then off. Only after repeatedly pressing the switch off and on again have they remained “on.” Through my experience I know enough about electrical circuits to deduce that there is a loose connection somewhere.

I don’t know very much about electricity. As far as I understand it, there’s a flow of electrical current (electrons). I couldn’t design a generator. I would be able to replace a light switch, but that’s about it. My point is that I don’t need to know about electricity to turn on a light. When I press the light switch, the lights generally come on.

The concept of evolution says that living organisms tend to improve their ability to survive by becoming better adapted for survival over time. Using the parallel of the light bulb, understanding that this happens doesn’t require us to know exactly how it happens.

I’m immediately struck by the thought of extinction. (Yesterday I was reading Mo Willems story about Edwina — the dinosaur who didn’t know she was extinct — to my son; highly recommended.) Species that become extinct at first seem to be counter-examples of evolution. But when we think again, we realize that they instead provide evidence that a species won’t survive if it is not well adapted to its environment.

Another possible counter-example: Genetic weaknesses. Genetic weakness that can be produced by in-breeding (either by cultural or social practice or by design). But this again supports the general concept that evolution works more effectively when such circumstances don’t interfere.

Generally then, we can say that as time passes organisms tend to become incrementally better adapted to their environment. This is actually a much narrower conceptual risk than to accept the specific details of the evolutionary process itself.

But I believe we can even take another step away from the whole question and ask whether the principles of space and time provide a philosophical basis for the concept of evolution. (An approach I pursue in my book LIFE! Why We Exist… And What We Must Do to Survive.)

The principles of space and time show us that things will continue to exist in space if their form remains stable over time. If we think about fundamental particles and the way the stuff of the universe has persisted we can understand that stable particles and stable conglomerations of matter predominate. The same is true of living organisms. The more stable and persistent organisms, the ones that evolve, survive, and adapt, tend to predominate over time. Extreme circumstances can produce counter-examples, but then statistics will take over again and evolution will tend to win out over time.

While it’s helpful to be skeptical, methodical, and careful, and remember that we know a lot less than we’d like to think we do; we also perhaps know a lot more than we sometimes care to imagine.