The link is not the end all of this debate, that happened over 100 years ago.
Ok, but what the link shows is an adaptable species, the result of evolution. Evolution requires genetic variability in a population. This variability is produced at meiosis. When the environment chafes, which it always does, and in this case that change was precipitated by the researchers, evolution predicts that individuals within the population will adapt to varying degrees, based on their genetic variability.
Some individuals will have the genetic makeup that leads to success in the current environment, some will not be as good. Evolution DOES speak to adaptability within the lifetime of an individual. But this adaptability is a result of the genetic variability within the population.
If the environmental changes are long-term, or even directional, then the genetic variability at the population level will shift towards fitness in the new environment. If the changes are short-term, shifting back and forth, then the gene pool will remain relatively unchanged over several generations.
The results of this experiment are remarkably exactly what evolution theory predicts.