Board Thread:General Discussion/@comment-27907368-20160604051050/@comment-27907368-20160612052046

I don't think (blatant contradiction in the other theory I had) that beings age Underground. Yeah, time moves forward, but physical aging doesn't occur unless prompted by a human or something else. The Amalgamates may have "fallen down" because Alphys did something to them so that she could test on them.

The only monster that canonically died is Asriel, and that certainly wasn't of old age.

Alternatively, the "Name" that we see at the end of Geno isn't a child, really. They have portrayed their ideal image onto a blank human physical canvas to speak to us. Or, perhaps the protagonist always looked like "Name" does at the end of Geno and the player is blind to it.

One way or another, the dialogue from "Name" makes no indication that they are a child. ^^' Similar to Flowey, they seem old and haggard, "Name" being much more Toriel-esque and sophisticated about it.