Board Thread:General Discussion/@comment-26006155-20190617222636/@comment-26006155-20190704114135

We also know that a long time passed between when Gaster died in Undertale's timeline, and when Asgore picked Alphys as his replacement.

If we're not supposed to compare The Date Chara Arrived At New Home to the MTT Memorial fountain, one of the few dated items we find in the game, then what are we supposed to compare it too? Find me an alternative.

Again, the issue is whether Gaster could have used Chara as a test subject to study Determination. She's the one known human in the underground at that time, and no souls have been collected yet.

If Chara never visited Gaster's lab before Gaster died, how did Gaster learn about Determination?

If we go with your suggestion that Gaster already knew how to make a DE Extractor, and never needed to actually build the machine, it actually helps my case. It's proof that Gaster had a source of knowledge about Determination other than Chara, and that he's had exposure to humans before she arrived.