Hello ICDESIGN,
ICDESIGN writes:
So if an organism starts out fully formed with the systems it needs to survive already fully developed, that is an act of creation not evolution.
That depends entirely on what you mean by "fully formed". If you mean "in its present condition" (i.e. a fully formed human appearing out of nowhere) then yes, it would be a miraculous act of creation. Of course, the same applies for any creature. A fully-formed lobster, honeybee, chicken, earthworm, E.Coli etc., can not appear out of nowhere fully developed, except through some form of intervention.
Of course, a seriously incomplete individual, e.g. a human with no nervous system would be unable to survive. There are many parts of the human body that are indispensable to a fully developed human. These include obvious ones like the brain, the cardio-vascular systems, the spine etc.
Then there are parts that aren't directly required for survival, but which confer an important evolutionary advantage, such that losing them makes life much more difficult. Your sensory organs such as your eyes, ears, nose, etc. would fall into this category. You can survive without your eyes, at least until you walk straight into an open manhole or something.
In fact, many animals do get by without (or with severely reduced) eyes. Star-nosed moles and blind cavefish are examples of this.
Finally, you've got parts that you could just as easily do without. Your body-hair isn't terribly important in this day and age. The appendix would be a blessing to be rid of. You don't really need those little muscles that wiggle your ears (as amusing as they may be).
The reason I emphasize this distinction between indispensable, semi-dispensable, and completely dispensable parts, is that the distinction will play a role in determining what is a "fully-functioning" individual. I'm pretty sure you consider a man with reduced skin-pigmentation, or without an appendix, to be a "fully-functional" individual, as opposed to someone without a brain or nervous system.
Now, when you contrast the indispensable subsystems of the human body with the more dispensable ones you'll discover something incredible. All of our truly indispensable parts are shared with many other lifeforms, and usually, the more indispensable a given part is, the more it is shared across the tree of life.
Take our nervous system as an example. Not only does it have a lot in common with our close cousins, the apes, but we also share it with other mammals, reptiles, and birds. It's even shared as far as amphibians and fish. The Recurrent Laryngeal Nerve that has been the topic of another thread in which you have taken part, is an example of this. All tetrapods and fish share this indispensable feature of our immune system.
The same thing applies to the musculoskeletal system. Because it is so indispensable, all tetrapods and fish share analogous systems. This implies that the musculoskeletal system has been around for a long long time. It didn't first appear in humans. Nor did it appear in apes, primates, mammals, reptiles or any tetrapod for that matter. The most distantly related animals in which it exists in analogue to the human body are primitive fish.
So our skeletons must have first begun evolving early on in the evolution of fish (possibly starting with a simple notochord)*. Since skeletons were rather newfangled at the time, they would not have been as indispensable as they are now. Probably our first "skeletal" ancestors shared the waters with similar and closely related species that did not need a skeleton.
As time went by, our basal skeleton design slowly added parts as they became useful. Doubtless several were evolutionary dead-ends and never went anywhere. But some managed to become highly successful, and they became the ancestors of all fish and tetrapods today. Most importantly, by the time they had become recognizable as "fish", they would have become so dependent on their skeleton that it had truly become an indispensable part. A fish that lost its skeleton would no longer be "fully-formed".
And here is the message that I'm trying to convey with this rather lengthy post: The ancient ancestors of all fish were still able to go without full skeletons because to them, the skeleton was still a semi-dispensable but useful new tool for their survival. They could add parts to it or new designs willy-nilly, and possibly even lose them again. But once fish discovered a winning formula, they stuck with it and eventually became dependent on their complex musculo-skeletal system to the extent that it became indispensable to them, to tetrapods, to us. We still use a modified fish-skeleton, although of course it has changed a lot in 300 million years.
The theory of evolution accounts for our many indispensable inter-working systems the same way that I just described for fish. By going back to an ancestor where these systems were not indispensable and could be evolved separately.
Respectfully,
-Meldinoor
Edited by Meldinoor, : No reason given.
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