Kitsune, that's a fair enough post. I never said that an Oort Cloud wouldn't be discovered someday, or something resembling one, but until now, one has not been observed, only hypothesized.
Also, remember that the reason that the Oort cloud and Kuiper belt were hypothesized is that we know that new inner-solar-system comets are coming from somewhere.
An astronomer explains:
Because of their high mortality rates, periodic comets cannot have been periodic for long but must originally have been comets of very long periods having nearly parabolic orbits. Within the recent past (perhaps the last few thousand years) their orbits have been drastically altered to their present relatively small size by perturbations produced by the planets, especially Jupiter. Those occasional comets that are highly spectacular, and hence cannot have suffered appreciable disintegration, almost invariably have nearly parabolic orbits, and also they have not been seen before in recorded history. --- George Abell, Exploring the Universe
New comets turn up. The hypotheses of Oort and Kuiper try to explain where they come from, but the creationist argument is shot down by the fact that they do.
This was one of the first YEC arguments I came across. Short orbit comets, I was told, can only go fifty times round the Sun before evaporating completely.
So I googled to find out the comet with the shortest known orbit. It's Enke's Comet, and it has a period of 3.3 years. If comets only get fifty trips round the Sun, and if you can use them to date the solar system ... then the solar system was created in 1845, tops.
The alternative explanation is that it only recently became a short-orbit comet, and used to be further out. Unless you believe that the solar system was created eighteen-and-a-half centuries after Christ, you have to believe that explanation.
So whether it came from the Oort cloud, from the Kuiper belt, from the depths of galactic space, or from giant space aliens having a snowball fight, is immaterial to the question of whether you can use such comets to date the solar system. Clearly, you can't.
Given the rate at which evolution occurs, the notion that all present species were produced by evolutionary mechanisms from a common ancestor predicts that the Earth is old (and therefore that the solar system is old, and therefore that the universe is old).
This prediction has been independently confirmed by geologists, physicists, and cosmologists, which is a score for Darwin.
Proof that the universe is only a few thousand years old would falsify this prediction.
I think this is why the vast majority of creationists are YECs. If they can manage to be wrong about the age of the Earth, they don't need to be wrong about anything else. (Of course, they are, but that would suffice.)
Does DNA disprove evolution? [...] If it can't be mapped all the way back to the time when life first began?
But why should it be?
The way to test a theory is to see whether our observations match its predictions.
Now, the concept of evolution does not in any way predict that we should be able to map the genomes of long-extinct species. This is something that we wouldn't be able to do no matter how true or false neo-Darwinism is.
As such it can have no bearing on the correctness of the theory.
One might as well argue that the theory of gravity is wrong because we can't describe the orbits of the bodies in the gravitational field of Aldebaran. To be sure, this is a gravity-related question, and one that we can't answer, but the theory does not in any way imply that we should be able to answer it --- so it is not a test of the theory.
I can make a theory that says all of human emotions are created by the remnants of the fragrance of apples in the air. And to prove my theory through predictions, I predict some people will get upset tomorrow, and some will be happy, and some will laugh.
See, I have made these predictions, so if my theory is correct, this will come true.
I love science!
What does your theory predict if you:
(a) Isolate people from the fragrance of apples by putting them in an environment where they only breathe "scrubbed" air, as in a clean room?
(b) Expose them to extra-large quantities of the esters in question?
(c) Put them in scuba suits breathing an artificial oxygen-helium mix and send them diving?
(d) Observe an anosmic person to see if they have emotions?
Bear in mind that for an idea to count as a theory at all it must be falsifiable. Bear in mind also that a theory is judged by the sum total of its predictions --- obviously one is not allowed to cherry-pick.