A laboratory at Kyoto University has been maintaining a long-term evolution experiment on fruit flies that started in 1954. Now the flies are adapted to living in pitch black darkness:
To keep the flies away from light, they are reared in vials kept in a large pot painted black on the inside and covered with a blackout cloth. When the vials and food need to be changed, the researchers tend to the flies in the pitch dark, then use a feeble red light to check on their work. Fruit flies can’t see this light because the species lacks those light receptor proteins that absorb red wavelengths.
When [Syuiti] Mori retired, he passed on the precious fly stocks to his colleagues at Kyoto University, who have maintained them continuously to this day. The stock of flies has now spent more than 1,500 generations without light. In human terms, that would be like sequestering generations of our ancestors in the dark for 30,000 years.
It’s an interesting type of experiment, similar to the Long Term Experimental Evolution project that has kept E. coli cultures under a constant environmental regime for more than 64,000 generations. The populations adapt to their environmental conditions, different from the natural situations in which their ancestors evolved.