Board Thread:Questions and Answers/@comment-28067574-20190903053053

Bratty and Catty reveal that monsters have been trapped underground for millennia, however there are many characters that have seemingly been alive for all that time. Toriel and Asgore’s longevity is explained by the fact that they are boss monsters. We also know that Gerson was present at the war of humans and monsters. He’s definitely not a boss monster, since he’s dead in deltarune, but he is shown to be an old man and he is based on a tortoise, which is a very long living creature. It’s safe to assume that monsters generally live longer than humans.

But then there’s Alphys. We know she’s been alive since Chara was in the underground, because she made Flowey using the first golden flower that bloomed after Toriel left Asgore. But she shows no signs of aging. It seems unlikely that in the millennia that monsters have been underground, all the humans would fall within one average monster’s lifetime. Does this mean she’s a boss monster? We never fight her, and nowhere does it say all boss monsters are goat creatures. 