How do you account for the existence of lifeforms that are much older than the 6-10 K range? Was the earth created 10K years ago, or just Man?
Furthermore, you're saying that Man, in his current state, was created first and then degenerated over time. How could such changes occur so quickly? Based on that view, we should have seen significant changes to humans in the last 2000 years or so, but we haven't.
Furthermore, according to the hypothesis you'd think we'd find the most degenerate (primitive) forms in more recent strata and carbon dated more recently as the degeneration continues.
I believe that all life was created in the age range specified. However, dating techniques such C-14 dating are, admittedly, only accurate to about ~50,000 years (some may argue this, but no one tries to use C-14 dating for anything older than 200,000 years), and this is assuming that the ratio of C-14 to C-12 has been constant over the 50,000 year time period. If the atmosphere, pre-flodd, was as the Bible suggests, then it only makes sense that current C-14 dating will be off. I can understand why people believe the dating techniques, taking what can be objectively seen today and extrapolating. However, it is just that, a conjecture an extrapolation. The calculations are not wrong, just misunderstood. Fossils older than 50k are generally dated according to the layer of Earth within which they were found - ironically science dates much of the geologic collumn according to the fossils found there.
How could such changes occur so quickly? Based on that view, we should have seen significant changes to humans in the last 2000 years or so, but we haven't.
You have seen significant changes, according to the Bible man lived almost 1000 in a lifetime, but now seems limited to 120 years postflood, also predicted by the Bible. Also according to evolutionary theory "positive genetic changes" take eons, but we can objectively see everyday that "negative genetic changes" occur quite rapidly - think Down's Syndrome. The reason for the continuation of the "average" man is that we reproduce regularly with a God-given system of sexual recombination. It's worked reasonably well so far, but if you look at human DNA you see a lot more that's useless than useful.