I have not, but scientists have been doing just that in numerous ways and have so proven it. What alternative do you have anyway? That God creates some new genes for each person? I'd agree to that one.
BTW - the question is not why I believe the above, the question is whether it has been scientifically proven or not. The discussion arose on whether science proves anything. I would say that you have not denied the examples so you must agree that they have been proven. Oh and BTW - the above has been OBSERVED and TESTED in dozens if not hundreds of different ways.
Oh I won't argue that certain results can be shown to have occured, and that those results can be reliably reproduced, but what you appear to refuse to understand is that no matter how many times you reproduce a particular result, the underlying theory has STILL not been proven. The confidence in the theory will increase each time a conforming result is observed. And the expected chance of an anomalous result decreases with each iteration. But proof of a theory is an asymptotic goal.
For any theory, select examples get tested and are found to conform to the expected results. From this sample, the results are generalized to the rest of the world. Because testing every possible combination is simply not possible, science accepts a very small statistical probability that the theory will not apply in all cases. What matters is how useful a theory is to model a specific aspect of the world.
The best one can say of any theory is only that it hasn't been disproven yet.