Umm, flies switching food supplies is not significant change.
More like the fly turning into something completely different, like a spider or something radically different.
You know, a real CHANGE, not changing diet.
Try reading again. They're not just switching food supplies, they've switched numbers of chromosomes, etc.
More like the fly turning into something completely different, like a spider or something radically different.
We've observed larger changes genetically and in the fossil record, but it's silly to expect us to observe something in the lab that takes lots of time. That doesn't mean we can't prove that it happened.