I agree with Lee
Even Darwin found evidence that when widely separated varieties are bred together it often results in more robust survivable members. Like dogs, when left to themselves either die out or recombine to produce a more wild variety.
If humans spliced traits from every family of life, plant and animal, the result might be fantastically robust. We will have to relax ethical constraints to find out, but once people have the technology to go gene splicing and IVF in their homes, and trade with people online for samples of DNA (fully mapped of course), the demand for it will overwhelm any attempt at regulation.
Life happens. It will find a way.