-- from above --

>Do we have evidence that DNA is added to the Human genome that has not previously existed?

Yes, we do have proof of instances when new genetic material was added to our DNA. When humans migrated out of Africa about 80,000 to 50,000 years ago they interbred with the Neanderthals. Consequently some Neanderthal DNA is now incorporated in DNA of those descents of the mixing. If you, yourself, are not of purely African descent then you will almost certainly have some Neanderthal DNA in your genome. Typcially for European and Asians it is about 2% of their genome originates from Neanderthals. We've established this fact by sequencing and comparing the genomes of pure Africans, Neanderthals and Europeans and Asians.
Now, some of the genes from the Neanderthal have been speculated to give some advantages and some disadvantages in general. But it must be remembered that in evolution, a survival advantage to an individual is often related to the surrounding environment that the individual lives in at the time. So, the beneficial or detrimental effect of a genetic change to a species may change overtime as the environment changes.