Is Evolution Reversible

French and the other Romance Languages "evolved" from Latin. Would you expect the French language to slowly change over time so that it sounds more and more like Latin? Of course not, right? The evolution of biological life is no different.

I was trying to use language as an analogy. Languages do accumulate changes in an analogous manner to genomes. These language changes occur at the population level, much like evolution. We also see languages diverging, again very much like biological lineages. There are many parallels which makes the evolution of languages a good analogy (but an analogy only).As I said before, none of the Romance languages are evolving in reverse. None are sounding more and more like Latin. In the same way, genomes do not evolve so that the sequence of DNA becomes more and more like it's ancestors. There is not a DNA memory that forces genomes to move towards a specific DNA sequence in response to an external stimulus. In the same way, there is nothing forcing Italian and French to move towards Latin.Selection occurs at the phenotypic level, not at the genomic level. That is the lesson to learn here. Natural selection affects the results of DNA alteration, but it does not select for specific DNA changes. Also, natural selection is not searching for a specific solution. Natural selection is searching for higher fitness, no matter how it is achieved.

I tend to see things from a genetic perspective. As Dr. Adequate points out, there are over 100 point mutations in each individual in each generation (not to mention the rare indel). There is no way that a species can reverse this accumulation of mutations and return to the genotype of their ancestors. So from a genetic point of view, evolution can not be reversed.However, from a morphological point of view there can be a "reversal". That is, adaptations can go away and then re-evolve. Someone else mentioned the canines of cats, which is a really good example. To continue with that example, it's an arms race. In order to avoid predation the prey species gets larger. In order to kill the larger prey larger canines are selected for. The prey and predator co-evolve. Pretty soon, the cats are highly adapted to killing just one large prey species. If that prey species disappears so do they. This opens a niche for another prey species to evolve a larger morphology, and so it starts again.However, at the genetic level each species of big cat will be different. While the same general morphology may re-evolve the genes do not.