The level of convergence in biology has been found to be amazing in recent decades. Strikingly similar designs run all through the biological world. Such similarities do not bode well for evolution because (i) they are supposed to be independently created by chance events, (ii) often they must have arisen in different initial conditions, (iii) often they are found in different environments and (iv) the design space is large. How can we understand these strikingly similar masterpieces?
Well it really isn’t so difficult after all. You see, if our eye evolved once, then why not twice? Evolution is a story of serendipity, so why not add a bit more? Accepting the evolution of life requires a credulous mind. Once evolution is accepted as fact, all kind of events can be accommodated.
Consider how evolutionist Simon Conway Morris explains convergence at the Map of Life website that documents convergences. Incredibly, for Morris, not only is convergence not a problem for evolution, it actually is yet another proof text. The message from biology’s massive convergence is “First, that evolution is true.” And how do these convergences help support such an amazing conclusion? Morris explains that biology’s very complex structures, such as the bacterial flagellar motor, “evolved independently at least twice.”
In other words, if you think complexity argues against evolution, just look—convergence reveals independent versions, which of course must have evolved. Such independent evolution proves such structures can’t be too complex. So rather than a question mark, convergence actually serves to remove a different question mark: complexity.
I guess the complexity of the eye is even more deceptive given how many times it converged:
The Map of Life documents many more examples of convergence for you to explore, and in fact in the case of the camera-eye alone there is much more to be said. The camera-eye has actually evolved at least seven times, most extraordinarily in a group of jellyfish known as the box-jellies (or cubozoans). Although these jellyfish have a nervous system, they don’t have a brain, and furthermore they belong to a phylum known as cnidarians, widely agreed to be amongst the most primitive of animals.
The more people learn about evolution, the more amazed they are. Religion drives science, and it matters.
The more people learn about evolution, the more amazed they are.
ReplyDeleteThe devil* is in the details.
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*Speaking metaphorically.
One again we get Cornelius unable to rebut the actual evidence for convergence that Morris presented. So it's back to his usual hand-waving and feet-stomping
ReplyDelete"I just don't believe it, it's SOOOOOOO improbable, therefore GAWDDIDIT!"
Cornelius is nothing if not predictable.
PZ Myers critiques some of the ideas of Simon Conway Morris here:
ReplyDeleteConvergence, schmonvergence
Where he offers the following (my emphasis):
Common descent tangles the interpretation of convergence hopelessly. I recommend an article in this week's Nature by Shubin, Tabin, and Carroll that argues for an important concept of deep homology. We do see similar structures, such as limbs in insects and invertebrates, that are not at all homologous on a morphological level, but when we examine their molecular genetics, we find similar substrates for both. This is the central idea of deep homology, that we have shared primitives, a set of regulatory networks, that see reuse over and over again in evolution. So while limbs arose independently in insects and vertebrates, when we look more deeply, we find that both use the distal-less developmental pathway. We see convergence because there are common functional demands that channel the solutions of selection, but there are also shared molecular constraints that limit the range of likely solutions.
Cornelius Hunter: A million different paintings are possible, the traveler would never expect to see such similarity in independent masterpieces.
ReplyDeleteOrganisms are not artwork. They are subject to selection. So a dolphin is superficially shaped like a fish, but a closer look reveals their separate ancestry.
Thornton:
ReplyDeleteYou are dismissive of the probability argument, but is not a probability calculation essential to understanding whether something can evolve?
Evolution posits random variation as the first step in an evolutionary transition. It seems to me that science needs to know the probability of that first step occurring such that it provides a change that natural selection can act on.
Depending on how many changes are required for a given morphological change, science also needs to know if, given the known rate of mutations, evolution can come up with the required changes in the time available.
I recall on previous post, someone said in effect that probability calculations are irrelevant; all the other evidence confirms the fact of evolution.
Without an understanding of the probabilities involved, the theory of evolution is a grossly under informed theory.
Doublee: You are dismissive of the probability argument, but is not a probability calculation essential to understanding whether something can evolve?
ReplyDeleteDarwin didn't have a workable theory of genetics, but still marshalled a great deal of evidence in support of his theory. For instance, domestic pigeon evolution shows that the natural variations is sufficient to explain broad morphological changes, and addresses your concerns about probability.
Doublee: Evolution posits random variation as the first step in an evolutionary transition.
Variation is a lot more complex than just simple mutation.
Doublee: Without an understanding of the probabilities involved, the theory of evolution is a grossly under informed theory.
You would have to carefully relate the calculations to the known facts of biology. Did you have something specific in mind? Or are you just arguing about the gaps?
Norm, said "Common descent tangles the interpretation of convergence hopelessly...This is the central idea of deep homology, that we have shared primitives, a set of regulatory networks, that see reuse over and over again in evolution. So while limbs arose independently in insects and vertebrates, when we look more deeply, we find that both use the distal-less developmental pathway"
ReplyDelete---
Why couldn't the "deep homology" that is seen be the result of convergence also?
Nothing in evolutionary theory prohibits that either.
Neal:
ReplyDeleteWhy couldn't the "deep homology" that is seen be the result of convergence also?
Because, according to the argument (if I understand it), deep homology is the result of a shared set of regulatory networks that evolved once in the common ancestor and were thus passed down to all descendants. Because all descendants share this common toolkit, we sometimes see convergent evolutionary "solutions".
Doublee said...
ReplyDeleteThornton:
You are dismissive of the probability argument, but is not a probability calculation essential to understanding whether something can evolve?
No, knowing the exact probability is not essential. First off, for all intents and purposes it's impossible to calculate an accurate probability because there are too many unknowns lost to time and history. Second, no matter what the number is (between 0=impossible and 1= certainty) it won't change the fact that there is copious positive evidence that life on the planet did indeed evolve.
No one can calculate the probability that My.Everest would be the exact height at the exact time with the exact topography that we see now, but that doesn't mean we should reject mountain building via plate tectonics and claim Mt. Everest was intelligently designed.
The whole 'it's too improbable' is a cheap rhetorical ploy on the part of Creationists/IDiots. It carries no weight as an argument in the scientific world.
Norm, couldn't evolutionary theory just as easily say that the "common toolkit" itself was a result of independent evolution multiple times? Other than just assuming it, what is the evidence that the "common toolkit" was a result of common descent?
ReplyDeleteDoes this "toolkit" cause echolocation in bats and whales?
It seems like just another arbitrary and subjective story.
Neal,
ReplyDeleteIf the toolkit is exactly the same in every known animal, wouldn't it be most parsimonious (assuming common descent is true) to attribute that to a feature of the universal common ancestor? What do you think is more likely, that exactly the same regulatory pathways evolved independently multiple times, or that such pathways were present in the common ancestor and are highly constrained due to their vital role in development?
Anyways, have a read of this post by Steve Matheson on deep homology if you have a moment, it's not long and is quite interesting:
Deep homology and design: why Notch?
Cornelius,
ReplyDeleteFirst, I'm flattered. And I thought my comments were falling on death ears.
Second, note several important differences in my comment.
Scott: Imagine some alien species ran across out planet. They may predict we would carry personal digital entertainment devices, such as iPod and iPhones, if our technological ability had reached a particular point in their own historical progress.
Here, the prediction assumes the alien species is similar enough to us that they too made a similar technological progression. Technology had become so ubiquitous that it had made it's way into personal communication devices as well. Without such similarity, these aliens wouldn't have made this prediction as it would not correlate with their historical progression.
In other words, the prediction, if found true, would occur for a reason: the alien species was very similar to us.
However, in your analogy, we're the ones visiting some inhabited planet. Who's to say we would even find art museums? Certainly, anything remotely similar to our modern day art museums didn't exist 10,000 years ago, let alone the particular painting styles of Picasso or Van Gogh.
So, first, it's unclear why this observation holds no mystery, yet particular painting style does. Apparently, we should expect to find art museums, but similar painting styles would be unexpected? If a species is similar enough to create "great museums" similar to our own, then it's unclear why they would not be similar enough to develop similar painting styles. However, if everything on the planet was vastly different, with the exception of the discovery of paintings very similar to our own, then this would become a observation that needed an explanation.
We could say the same if the planets inhabitants only saw in black and white, but had painted in color, were based on some other form of life, such as silicon, had compound eyes, etc. The discovery is contextual based on a number of other factors.
Again, It's unclear why you're singling out this particular observation among many.
Second…
CH: Such similarities do not bode well for evolution because (i) they are supposed to be independently created by chance events,
You've omitted natural selection, as usual.
CH: (ii) often they must have arisen in different initial conditions,
The conditions has important differences rather than being complexity different, as they might be on some other planet.
CH: (iii) often they are found in different environments
The environments in which eyes are found are usually beneficial or were beneficial for their common ancestors. For example, variations of Mexican tetra, which live in deep underwater caves, are essentially blind. They have eyes, but they are eventually covered with skin and degenerate completely.
Apparently, that's just what the designer wanted.
CH: (iv) the design space is large.
The design space is constrained by the similarity in conditions, common ancestors, etc.