What good is half a wing?

One of the most common arguments you'll hear against evolution (or, at least, one of the most common arguments I heard growing up amongst creationists) had to do with transitional forms. An eye is a valuable thing, this argument goes. But half an eye? That's just a disability.

Like many of the really common arguments against evolution, this one crumbles the minute you start to apply the slightest bit of fridge logic. Sure, half an eye is less useful than a full eye. (Or, more accurately, a clustering of light-sensitive cells don't have all the functionality of a modern eyeball and optic nerve system.) But, if most of the other creatures have no eyes, and you have a few light-sensitive cells, you've got an advantage. And an advantage is all it takes.

Now apply that to the evolution of birds. One of the cool things about this process is that it appears that feathers evolved before flight. In fact, feathers seems to have evolved rather independently of flight.

You might ask: What's the point of that? How are feathers an advantage if they can't help you fly? Is this just about looking pretty? Maybe. But on his blog, The Loom, Carl Zimmer presents another hypothesis. Feathers and wings, even without flight, might have given their owners a physical advantage over bare-skinned cousins. The birds in this video aren't flying. You can see that their feet don't leave the ground. But the act of flapping those feathers around helps them to walk up inclines that would otherwise be impassable walls. That's enough to escape a predator and live to breed another day. And it's also pretty damn astounding to watch. You'll find more footage at The Loom.

Video Link


  1. Just one look at a flying squirrel (as compared with a bat say) and it s pretty clear there s still an advantage – and because of all of those cat utubes out there I realized with a shock whilst beholding a cat jump from the top of a telephone pole and land running, that its still an advantage even before being as well developed as a flying squirrel (I always wondered why cats are so loose in their skin on the ventral side between the legs).  For some interesting arguments regarding the eye check out

  2. Toss in a few billion years and an awful lot can happen. I once had a classmate who got hung up over entropy. Sure, everything is running down but at the same time we’ve gone from hydrogen and helium to the full periodic table of the elements.
    My only advice is to read the essays of Steven J. Gould. He covered it all.

  3. Any extension in gliding ability gives that creature an advantage.  It can be incremental.  The squirrel born with weird armpit flaps lived longer and reproduced more than his peers.  The proto-archaeapteryx-chicken-lizard with one odd tail-feather could hop 3 cm further to a higher branch, therefore evading a predator, and therefore reproduced to live longer…  I mean, the scenarios are endless why if can be incremental and there isn’t really any meaning to “transition” animals. 

    Maybe WE are transition animals to radiation-resistant cockroach-humans that feed on remnants of supernovae.  I mean, who knows?

  4. That exact ‘What good is half a X?’ question was brought up in Julia Sweeney’s essay  “Letting Go of God”.  

    The subject was what evolutionary good half an eye was. Her answer was along the same lines: It’s still infinitely more of an advantage than having no eye at all. 

  5. Can i run an experiment to verify a billion years of evolution? nope. Can i run an experiment to verify gravity? yep. After years of being a religion-judging atheist, i came to the conclusion that religion and science are actually the same. Both are an admission to “Not Knowing” and both are institutions that provide “stories” about how we got here. It’s pretty easy to swap the words “god” and “evolution” and the underlying narrative usually still works. The narrative itself and the way that narrative becomes truth is much more important than the details of the narrative.
    Having spent oven ten years in a technical university, i’m well aware of power of the scientific method, but I’m also very aware of the fact that if i can’t repeat the experiment myself, then I must question it. Evolution makes much sense to me. I “believe” it and i use it to look at everything in the world. But if i’m to be a true self-aware skeptic, i must admit that it’s nothing like the truth of gravity, which is a daily experience and something we don’t get into fights over.

    1. You show a disturbing lack of ability to search out and read even the most basic technical literature. Religion and science are polar opposites.

    2. “Can i run an experiment to verify a billion years of evolution? nope.”

      But you can run an experiment with ten thousand generations of bacteria and watch evolution take place. And you can examine the genome of hundreds of species and see that the same genes do the same things. And you can examine the fossil record and see that species become more complex over time. And you can selective breed sheep or peas for desired traits, which works as a good analogy for speciation. Religion is nothing like science.
      Your conclusion is wrong.
      If you want a more detailed and eloquent rebuttal, search Youtube for Aronra.

    3. I’m also very aware of the fact that if i can’t repeat the experiment myself, then I must question it

      So until you clone Hitler and get him to try to take over Europe again, you will be on the fence about whether or not WWII happened? Ever heard of indirect evidence?

  6. I understand the potential advantages of feathers and stumps somehow mutating towards flight capabilities (although it does seem odd for the mental software necessary for flight to evolve along with the physical mutations). 

    The thing that gets me, however, is the complexity of the brain given the amount of time it has had to develop. 14 billion years (the estimated age of our universe) is a hell of a long time, but I don’t see how it’s enough time for our brains to evolve to their current state.

    The human brain has a huge number of synapses. Each of the 1011(one hundred billion) neurons has on average 7,000 synaptic connections to other neurons…. An estimate of the brain’s processing power, based on a simple switch model for neuron activity, is around 1014 (100 trillion) neuron updates per second. 

    How did we get one hundred billion neurons each with 7,000 connections to other neurons working cooperatively with each other and our sensory organs in 14 billion years?  This works out to over 7 billion new and functional neurons per year, each with 7,000 connections, integrated into a nervous system that is undergoing massive changes in time. 

    I think any software developer will tell you that introducing 7 billion enhancements per year by way of mutation is an insanely optimistic schedule (especially given that reproduction can take months and years). And mutations, while they may introduce the odd advantage, tend to make things worse, not better. How do we get an average of 7 billion new, fully integrated, functioning neurons each year over the last one hundred billion years?

    1. Each individual neuron isn’t a separate gene, you don’t need to have a discrete random mutation to produce each one. All you need is the ability to produce the first one, then as stem cells are differentiated, the correct genes are expressed to make that cell a nerve cell. You aren’t adding features, just upping the scale of what you already have.

    2. I doubt every single neuron in your head, or in mine, is “fully integrated” and “functioning.”  If a couple get killed from drinking, the whole brain doesn’t collapse like a house of cards or something.

      A software developer might also tell us something about emergence.

      Plus you said, “(although it does seem odd for the mental software necessary for flight to evolve along with the physical mutations)”
      1) How exactly do you think “mental software” works? If you see some guy walking on stilts do you go, “wow, that’s amazing that he has the mental software to walk on stilts?”
      2) I didn’t see any flying in that video, which was kind of the point, wasn’t it?

    3. How did we get one hundred billion neurons each with 7,000 connections to other neurons working cooperatively with each other and our sensory organs in 14 billion years?

      Exponentially. You’ve heard of cells dividing, right?

  7. @chubs considering that every healthy baby ever born manages to build this up from 1 cell in about 9 months, your arguments about impossible complexity aren’t very compelling.

  8. That all said and done, none of those birds have only half a wing. They have a full wing on each side of their bodies that allow certain capabilities. I have two arms but I’m not as strong as an Orangutan. Do I only have two half-arms? And Daniel Paluska is correct. Religious defendants exhibit spiritual self-righteousness and scientific defendants exhibit intellectual self-righteousness. Both sides claim to hold a moral high ground, and sneer at disagreement. Adherents to evolutionary theory are as steeped in dogma that they don’t understand as the next person. They’re just as bad as bible bashers. They’re text book bashers.

    1. Adherents to evolutionary theory are as steeped in dogma that they don’t understand as the next person.

      Huh? Dogma is about ignoring any objections to one’s beliefs. The scientific method only ignores objections that are neither empirically verifiable (either directly or indirectly) nor reproducible. But even this is not dogmatically held – the scientific method is quite open to evaluating empirical evidence that more than empirical evidence must be evaluated in the future.

      So how is being bemused by people who claim that the Moon is made of cheese for no apparent reason intellectually self-righteous?

  9. I fully believe in evolution, except the part that posits that it’s random. If it’s random, then wouldn’t we find a horror of non-life-threatening oddities in the fossil record?  Whether a mutation is passed on is whether or not it is beneficial or not. What of the huge majority that would make no big difference? Small arm horns or a little patch of scales here, a forehead bump, or maybe a tail or two.. Of the entire library of body parts across all species, very little is purposeless, and all is elegant in its own way. I don’t posit a creator, but there would seem to be some sort of biological intelligence at work.

    1. Sadly, half the people who claim to believe in evolution describe it in terms of intelligent design.  A giraffe does not evolve a long neck IN ORDER TO reach the leaves at the top of the tree.  A random mutation creates a long-necked giraffe who gets more food, lives longer and produces more offspring to carry the trait.  10,000 other random giraffe mutations have no effect or are disadvantages. 

      Most mutations are effectively invisible in life, let alone in fossils.  And we have fossils for about 1% of 1% of 1% of 1% of 1% of 1% of all the creatures that ever existed.  If that. And disadvantageous mutations would lean towards spontaneous abortion/stillbirth/infant mortality, which would dramatically decrease the chance of finding fossils.

Comments are closed.