Someone please tell this moron that association does not mean causation.
Care to explain please?
While the posted material does not definitively prove causation, it certainly hints at it.
You make mice lacking oxytocin and the mice have less muscle... sounds like there is likely direct causal link between oxytocin and muscle mass.
Now whether injecting oxytocin into the muscle will result in more muscle mass is a very different matter and not what this research had aimed to prove. But the causation bit seems probable