"No, I'm arguing that because that ability arose in the 20th century, it is unable to explain the speciation that occurred prior to the 20th century." -Physicist
OK, this is progress. Now you are implying that the only problem with my example completely refuting for all time the Theory of Evolution is: timing.
Can we now agree that Intelligent Design has been demonstrated and will refute Evolution (and send it packing its bags for the land of scientifically discredited theories) if your timing concern is dealt with adequately?
No, and this has been answered before. Why is it that you never digest the answers you're given and go on repeating things that have been shown to be false? Are you not interested in the truth?
The fact that genetic engineering now occuurs does not mean that it did in the past.
Even if there were agents capable of performing genetic engineering in the past (a completely hypothetical statement) that would not mean the they were in fact responsible for evolutionary change.
It would not invalidate natural selection. Only an inability to think logically allows one to think so. Both natural selection and genetic engineering can exist. Your argument is based on the premise that they can't, which is absurd.