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Old 02-27-2017, 10:21 AM
Machine Elf Machine Elf is offline
Join Date: Feb 2007
Location: Challenger Deep
Posts: 10,553
Originally Posted by adaher View Post
Now the eye, that brings me to another question. How DOES an eye evolve? An eye is very sophisticated, yet it has really only one purpose: to enable one to see. And until one can see, it's not doing anything to aid in survival. So how does that mutation happen? Did a fish just get born with a simple eye one day 4 billion years ago?
This touches on the concept of irreducible complexity - the creationist argument that extant complex biological structures/functions could not have evolved on their own, since evolution (so goes the claim) wouldn't select for any of the expected intermediate structures/functions between "no photosensing at all" and "fully formed vertebrate eyeball". As WhyNot and lazybratsche have shown, there are plenty of intermediate forms (many of which are also extant in other species) that provide useful functionality that can be selected for by evolution. There's that Haldane quote, "The world is not only stranger than we imagine, it is stranger than we can imagine," and it serves as the counterpoint: a person arguing for irreducible complexity demonstrates only that the world is stranger than he can imagine.