Why do apples taste good?

iceage writes:
Some have theorized that avocado's had originally adapted to a symbiotic relationship with now extinct large mammals such the giant ground sloth. These giant mammals could swallow and pass the massive pits and disperse the seeds far and wide. However, since the seeds were large, bird eating the fruit were largely destructive, so Avocado evolved chemicals that were harmless to sloths but toxic to birds.How could a sloth spread a seed far and wide?Also if the avocado had "adapted to symbiotic relationship with now extinct large mammals", then the adaptation is no longer useful right? Then why doesn't it evolve back? Or does it still have a use?

wow you are right. The giant sloth was about the size of a modern elephant and probably weighed about 5 tons. Next time I better do research before I say anything.