chances are pretty good it's been being done on people for quite some time, but like a lot of things, the public is generally not aware that it's been being done..... so, following the kind of trap logic associated with the proverbial fallen tree in the forrest, as far as the public is generally concerned, it's not been beign done.
The Monarch/MK Ultra program is an example, maybe not the best example since this program had priorities, like the development of a broad scale of mind-control methodology, that were beyound the priorities for tinkering with the human genome, but it definitely has ties to experimenting with human subjects on various other fronts. Research Monarch/MK to find some details about when/where this kind of experimenting was done, who sanctioned it, and who did it; much of what was done in New York - Montauk, and many of the people who did it (the actual hands on experimentation), were imported from the nazi empire during the period when WWII was being closed down. The people who did it as far as overseeing and administering the program, were those people who at the time were known and thought of as the leaders of this country, politicians, banksters, medical minions and other implements of the higher education system. The MK-Monarch program also tied itno other big experimental issues, Eugenics and cloning, to name a few.