Charles Robert Darwin (1809-1882) is of course the man who started the theory-of-evolution ball rolling with his book On the Origin of Species. Although the book did not originate the idea of natural selection or use the term "evolution", it put it all together in a way that caught on big time. Later in life Darwin also did pioneering work on human emotions in The Expression of the Emotions in Man and Animals.
On this day I'd like to draw attention to Darwin's persisting influence, not by gushing praises but by posing a problem. This is not an exercise to which I already know the answer--it's perplexed me for some time now. I'm not a scientist, nor do I have a working knowledge of evolution that goes much beyond Wikipedia, so the answer may be out there. But if I am confused, no doubt there are many others out there who are confused too. So, let's have a joint think, and maybe in the process we can learn a little about evolution. Or at least I will, if you show me what I've been missing!
Wait--isn't evolution just a theory?
Before we get into the thick of it, this nagging question ought to be addressed. Yes it is a theory. Everything is a theory. When I say the sun will rise tomorrow, that is a theory. The question is how well it fits the evidence, and theories that do so exceptionally well eventually earn the status of "fact" or even "law." But in truth they always remain theories. Evolution does fit the evidence quite well--and there is a ginormous mass of it by now. Anomalies remain, but it would take extremely radical and well-documented scientific evidence to seriously challenge it at this point. Even the Catholic church accepts the evolutionary theory, having declared it compatible with Biblical revelation.
Here's the problem as I see it...
So here it is. This is one thing that I have never quite understood. I've asked a number of people to explain it to me, and no one has been able to figure out what I'm talking about. I'm awaiting the day when someone will slap me upside the head with the answer.
Basically, I am blown away by the extremely--and by extremely I do mean extremely--unlikely series of coincidences apparently required for a complex adaptation to get started.
Let me break it down:
The theory of natural selection says adaptations evolve in response to environmental pressures. Those mutations that increase a genetic line's fitness, whether by helping it find mates or avoid predators and diseases, naturally prosper. Those that make the genetic line less fit die out. So far so good.
Now, what about complex adaptations, like bird wings? In their fully functional state there is no doubt that wings help their respective species survive--it would be absurd to say otherwise. But they did not just appear all of a sudden. A wingless mother did not suddenly pop out a little winged freak one day. These things develop gradually, starting with little nubbins that eventually over the course of many mutations develop into wings. Or, to be more precise, bird wings started as something like under-arm webbing much as we see in flying squirrels. They developed into gliding mechanisms, and then the featherless wings of teradactyls. Gradually they became the pinioned glories of today's birds.
My question is this: in those very early stages, long before the adaptation reaches what we might call its fully-flowered state, does it really help the species enough that it would be selected for? Among all the many factors determining life or death, would it make a noticeable difference in the long run? Or would it be lost in the wash?
Consider how rare it is that a mutation proves useful. The vast majority of mutations just cause problems like diseases. A small percentage are harmless enough not to kill off the individuals in their genetic lines. And among these, only a tiny few prove adaptive.
If we assume that the mutation leading to the first step in developing wings does not also carry with it some death-dealing abnormality, it is already a rare thing. Next, we must wonder whether it would hamper its attractiveness to the opposite sex. How would you like to have sex with a mate with floppy under-arm webbing? Eww! I should think most abnormalities would significantly decrease chances of mating. So we have to assume that our nascent wings, by a stroke of luck, occur in a species sexually liberal enough that it doesn't mind a little extra skin flopping around like granny arms. Considering how low the chances are of the adaptation happening at all, it must be a rare thing indeed that it happens in such a charitable sexual climate.
Now factor in the next extremely lucky coincidence: that a second mutation will build positively on the first. For this to happen, the second mutation must be at least as rare as the first: it must be among the few that neither kill off the genetic line nor deter sexual attractiveness. Next, out of all the jillions of effects that this mutation could possible have, from making a tail a little longer to modifying the immune system, it must by chance affect the species in exactly the same way: by adding more under-arm skin. This is lightning striking the same spot twice.
And this has to keep on happening, until there is enough under-arm skin to actually glide on. This gliding power must be efficacious enough that it positively affects survival, and this affect must not get lost in the wash of all the other factors determining survival. Once it reaches that point, where the proto-wings are actually making a difference, then natural selection becomes a little more believable. It builds momentum of a sort, as gliders compete to go farther, faster, and higher. An "arms race" begins which drives evolution, and it becomes almost inevitable that what we call wings will eventually appear. But to get to that point involves an incredible string of coincidences.
Yet wings have not only evolved for birds, but have done so also for insects, and flight has been called one of those adaptations which is virtually inevitable given enough time. There are adaptations much, much less likely than this.
It is so incredible that I wonder if we are not missing some further component in the theory of natural selection. Either we haven't figured it out yet, or I just haven't been educated about it yet. Either way it hardly seems believable in the form as I understand it, the form I have just described.
Those to whom I have posed this problem usually go a bit cross-eyed, and reply that this happens over a very long time. Yes, it certainly does. But if its chance of happening once is just about nil, even over millions of years it is hardly credible that more than a small handful of adaptations should have such miraculous streaks of luck. From where I stand it seems like after this amount of time we should still be on the level of single-cell organisms. And yet, here I stand, an extremely complex result of natural selection.
The question I've posed resembles in some ways Behe's irreducible complexity, but it's not the same. Irreducible complexity says that adaptations which are so complex that they cannot function without all their necessary parts could not have evolved by natural selection. They could not have functioned in the earlier stages, and so they could not have been selected for. By contrast, the argument I've posed says that it is possible, but it would require an extraordinary series of coincidences.
One criticism of irreducible complexity is that earlier stages of adaptation may have served other unrelated functions. For example, in the case of wings, it is possible that the flappy, hangy-down under-arm skin could actually have increased attractiveness. Who are we to judge what's sexy to other species? But while this is possible, it seems to add a still greater coincidence: that the mutation occurs not only in a species that is indifferent to this abnormality, but that it occurs in one positively crazy about it. This adds further unlikelihood upon an already unlikely string of events.
Of course, none of this proves anything about competing theories of how life came about. Challenging one aspect of the evolutionary theory does not prove that creationism must be true, or any other theory out there. It just shows that there has got to be more to natural selection than what I've just outlined. I want to know what that is.
So now I ask: who can slap me upside the head with the answer? I've got my hockey helmet on and I'm waiting. Let 'er rip. Please!
In the news
Darwin Day in the UK - The Guardian
On 'Darwin Day,' many Americans beg to differ - Christian Science Monitor
Opportunities to giveDarwin Day Celebration - promoting public education about science and encouraging celebration of science and humanity
The Charles Darwin Foundation - conservancy in the Galapagos Islands
Galapagos Conservation Trust - another for conservancy