Fruit flies breed new generations every couple of days. If you run experiments on them for several DECADES, as has been done starting in the early 1900s, then the experiments will involve more generations of fruit flies than there have ever been of humans or anything close to humans on this planet. What this was, was a laboratory test of the theory of evolution in an attempt to create new animal species via mutation, as evolution requires.
These flies were bombarded with everything known to cause mutations: chemicals, radiation, extreme temperatures, blast, noise,, etc. etc. and attempts were made to recombine mutants, and all they ever got was precisely what the breeders told Chuck Darwin would be all he'd ever get, which was sterile individuals, and individuals which returned, boomarang-like, to the norm for a fruit-fly. Basically, all they ever got was fruit flies. No gnats, no wasps, no ants, no roaches, hornets, spiders, or anything else, just fruit flies. With our present knowledge of the information code called DNA/RNA, we now know that this was because the entire process was driven by information, and the only information they ever had to begin with was that for fruit flies.
Again, a decades-long experiment like that would be equivalent to hundreds of thousands of years worth of accumulated genetic change amongst humans or higher animals. The results were so unambiguous that a number of the people involved publicly renounced evolution as a consequence, the most notable case being Goldschmidt who noted that, as a consequence, we was subjected to treatment similar to the two-minute hate sessions in Orwells famous novel. Such is American academia.