Experiments done on humansEdit
Before the Visitors arrived, they experimented on the humans to see if whether or not inter-breeding could work between human and Visitor. Obviously, it worked, and the V's therefore plan to invade Earth and breed with the humans. However, they knew the humans carrying a Visitor baby would have to be given a shot of phosphorous so they and the baby can survive.
Acquiring human DNA, to clone human fleshEdit
Since the Visitors are reptillian and no where near a mirror image to humans, they then took human DNA and made human flesh so it could be placed over their reptillian skin. It worrked but it had a major flaw, it could make a Visitor vulnerable to human emotion.
When Erica was still pregnant with Tyler, she was abducted by the Visitors and experimented on. She was given high amounts of phosphorous, and Tyler's DNA had large empty spaces, which one day would be filled in.
After the Visitors arrived on Earth, Anna learned fromher mother about the human soul, and would therefore go to lenghts to find it and destroy it. The experiments would require hundreds of thousands of humans and every one would result in death. The devise was exact to the ones which were used on the Live Aboard participants, except this devise had six arm claws which would kill the human by removing the water, muscle, bone and tissue.
The Visitors performed experiments to see if whether or not inter-breeding between human and Visitor was possible, however they realized that if had a flaw, that the next generation of V's that would carry human DNA, would therefore be infected by human emotion.
After the events of the suicide bombing on the Sydney mothership, Anna realized the Fifth Column were not only immune to her bliss, but experienced human emotion. She therefore ordered Joshua to perform the experiment by ways of projecting images from human history which to a typical human would make them react strongly to the images and sounds. Any Visitor which has abnormal brain activity would therefore have human emotion. Those who had abnormal brain activity would be killed either by willingly taking a suicide pill or be skinned if they don't take the suicide pill.