By Tobias Carroll For entirely understandable reasons, scientists have spent a lot of time looking into matters of human aging and mortality. What can be more surprising, though, is to see what animals they’ve been researching to gain insight into the matter. Jellyfish, for instance, are a subject of fascination for many researchers — even though the parallels between human and jellyfish biology can be challenging to figure out. The latest animal to pique the interest of scientists is, at least at first, a little closer to humans — if nothing else, they’re also mammals. But the yellow-bellied …