Evolution’s Limits – An Appeal to Missing Links

Teach the Doctor Who controversy - you can't prove that he doesn't exist

This is part of a series: Evolution’s Limits



Why am I – an amature creation scientist – featuring an atheist’s meme?  Read on to find out.

I might have figured out a practical way to test for evolution’s limit in a lab, and I want to do the math to find out if it’ll be practical.  I’m also using this project as an excuse to read up on evolution’s limit.

In my previous post, I gave Michael Behe’s definition of evolution’s practical limit – or as he called it, irreducible complexity.  However, before I go further, I need a definition that’s good enough for what I’m doing.  Thus, I’m going through some objections to his argument that life is too complicated to evolve, and if necessary I’ll tweak his definition of “too complicated” to cover some corner cases.

Today’s objection is that while many parts of living things – like flagella – can’t appear by tiny good mutations building up, they could have appeared in a more roundabout way.

Behe used a basic mousetrap as a good example of something that can’t appear by evolution.  It can’t build up bit by bit, with each change making it a better mousetrap than before.  All the parts have to be in place before it works at all.

But what if there was scaffolding?  Tom Schneider gives a good example of this argument.  You can’t build a roman arch bit by bit, or else it’ll fall down.  However, if you build some scaffolding, you can then build it as slow as you want.  Then, after you take away the scaffolding, you have something that – on the surface – looks like it had to have been put together all at once.

What if the same thing happened in living things?  A little of googling turned up this example by Peter Dunkelberg, in which some bacteria learned how to eat pentachlorophenol – a poison used to preserve wood.  It apparently uses three proteins to break the stuff down.  Unfortunately, although he portrays it as an example of this scaffolding in action, the bacteria already had all three proteins at the start.  Two of them were ready to go.

The mutation that gave the critters the power to eat poison forced them to make the protein all the time, instead of only when the bacteria thought it was needed.  It broke a useful system that is just currently more of a liability than a help.  This is hardly a good example of protein or gene “scaffolding” disappearing, and thus it isn’t an example of the thing that Dunkelberg said it was.

It looks like the non-poison-eaters were only one mutation away from this super power, so their ability is not irreducibly complex.

Behe thought of this from the beginning, and here was his response:

“Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one can not definitively rule out the possibility of an indirect, circutous route.  As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously.  And as the number of unexplained, irreducibly complex biological systems increases, our confidence that Darwin’s criterion of failure has been met skyrockets toward the maximum that science allows.”

It’s like the Dr Who controversy of my featured image.  I can’t prove 100% that there’s no possible scaffolding that could’ve let something evolve, when it looks like it couldn’t have; but does that mean that everyone should believe in it anyway?  “Could have, in theory” isn’t proof – it’s speculation.  Or, perhaps, blind faith in evolution.  If you think that evolution works this way, that’s fine.  But if you’re going to use it as evidence against irreducible complexity, the burden of proof is on you to show that it actually happens.

Finally, in my evolution simulator, the scaffolding thing simply doesn’t appear.  Genes don’t disappear when they aren’t needed anymore.  Instead, they break – turning into masses of junk code.  Of course it’s possible in theory that a redundant gene could completely disappear, but it’s overwhelmingly likely that it’ll just turn to junk.  Also, if my simulator is any indication, evolution doesn’t develop version 2 of a gene while the existing one is doing fine.  Instead, it tends to break anything that’s not absolutely critical for survival – including the next version of a gene.  So if this mullerian two-step happens at all in the real world, it should be so rare that it can’t explain most things that look like they couldn’t have evolved.


This is part of a series: Evolution’s Limits



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4 thoughts on “Evolution’s Limits – An Appeal to Missing Links

  1. Good stuff. How much genetic “junk code” has been discovered? or do we even understand genetic code well enough that we would recognize “junk code” if we saw it?


    1. That depends on who you ask, and when.
      As far as I know, the only genome that’s been completely sequenced is the human genome.
      If you asked a lot of scientists 10-15 years ago, they’d say that almost all of the human genome is junk. But then they started finding out what the “junk” did.
      At this point, it looks like if there’s any junk code in the human genome, there’s very little.
      I also don’t think that scientists know enough right now about how genetic code works to tell if code really is junk.
      The only exceptions that I know of are mutations that are known to break an individual protein or switch, like the one that I mentioned in this post.
      And those don’t turn the proteins that they break into utter mush. Instead, they’re almost functional, and are just barely broken.


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