What slightly worries me about regeneration, is that simpler animals can do it, but higher animals can't. So at some stage, we must have mutated to lose the ability. But regeneration seems so massively evolutionarily selective, that it's inexplicable why such a mutant outcompeted those who could regenerate -- unless losing regeneration conferred some other even more gigantic benefit, perhaps in increased resistance to cancer or in reduced birth defects. I'd want to see several generations of these mice live and die happily before I was convinced this was a Good Thing.

Peter