Taste buds and evolution

Ok, I know this is going to sound strange as a topic but it's something I've thought about for awhile so here goes taste buds, why have we evolved to have taste buds in certain places, and why are there so called super tasters? Now this is a selfish interest as I am a super taster, it stinks, other than a few party tricks it just makes foods made with certain things enedible, mostly bitter to the point of nausea, now sweet is at the tip of the tongue and bitter at the rear, sour to the sides, and salty/umami in the center, but why? Most bitter foods are toxic to us so you'd think the poison detecter would be farther away from the oops to late down the throat point, and why sweet at the tip? This pattern has evolved to some extent so their must be a reason, have their been nationality/locality studies to see if the structure changes regionally? Our skins melenins are diffrent because of regional enviorment differences, diffrent foods exist in diffrent places yet the taste buds seems to be of Similer design? Why? I don't expect any answers because people can't seem to comment for some reason, but I'm curious, doesn't it make you wonder?