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Superior Oblique
Superior Oblique  
I've been reading about the idea of "irreducible complexity" in evolution- that all known biological traits can be logically traced back to simpler evolutionary precursors, but that if a trait was discovered which cannot be logically traced back to an evolutionary precursor, then it would be "irreducibly complex" and thus disprove evolution. Obviously, nothing irreducibly complex has been, or is likely to be, discovered. There is one biological trait in particular has been confusing me, though. Connected to the human eye is a muscle called the superior oblique (see picture below) which literally hooks through a pulley-like structure in order to allow the eye to rotate. I'm having a hard time conceiving of how this complex system evolved from a simpler precursor. I've tried Googling "evolution of the superior oblique" and so forth, but I'm not finding anything readily available. Can you assist?

Answer
Dear Wade,

This might be one of those "unanswerable" questions, simply because we can't go back in time and see how the eye muscles evolved.  However, I can say that we now know that relatively small genetic changes can result in major phenotypic changes.  If there were muscles attaching the eye to the early vertebrate skull, and a mutation occurred such that one of those muscles accidentally attached in a slightly different way, allowing the eye to rotate, this could certainly be considered adaptive.  An eye that rotates allows the bearer to see its surroundings--including predators and/or prey--more effectively.  And such a trait, if it increased the chances of survival and reproduction of the bearer (or bearers, if multiple individuals inherited this trait from a parent), then it would be naturally selected.

I don't see the superior oblique eye muscle as being much different from the other eye muscles, in terms of being selectively advantageous.

Not much of an answer, I guess.  But the combination of chance mutation and natural selection can explain a great deal of what appears to be "intelligent design" in nature.

Cheers,

Dana

Evolution

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Dana Krempels

Expertise

I can answer questions about evolutionary mechanisms and theory, including genetic drift, mutation, natural selection, etc. I also can clear up misconceptions about evolution as it's sometimes talked about by those not well-versed in the subject (e.g., some politicians and many religious fundamentalists).

Experience

I have a Ph.D. in Biology, and presently teach Evolution and Biodiversity, Genetics, Botany, and Zoology at the University of Miami.

Organizations
House Rabbit Society Beta Beta Beta Biological Honor Society

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Exotic DVM Magazine (veterinary journal)

Education/Credentials
B.S. in Biology B.A. in English Ph.D. in Biology

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