Establishing causation for rejuvenation factors requires rigorous animal model experiments and controlled human clinical trials.

“But I think to get to causation, we need these types of experiments, physiological experiments in animal models first to isolate individual factors and then test them on an individual basis with very rigorous methods which we can do and say okay this factor has the capacity to maintain for example brain function in the mouse. And then we have to test it in humans and do it in a in a careful clinically uh controlled trial where people are blinded whether they got the treatment or not and do a big enough study that we can say okay this truly works and then we have a drug.”