The relationship of the domestic dog and wolves is widely recognized and dogs are considered to have evolved from wolves. At some point in the history of domestication a mutation known as a gene duplication occurred in dogs with the
amy2b gene that expresses amylase. Dogs have a variable number of copies and this difference may be due to breed specific genetic drift or regional dietary constraints, but the increase over that found in the wolves has been quantified. Amylase is an enzyme important in starch digestion. Wolves have an
amy2b gene. Dogs have many more copies and thus much increased activity. Where the environment of the wolf does not favor any mutation increasing amylase activity, that of the dog does.
The genome of the dog is not revealing a degradation or de-evolution. A claim of de-evolution is often raised by deniers of the theory of evolution, but it is clear from the use that it isn't a concept understood by those deniers and that genomes are undergoing change and not some loss of purity or reverse evolution. There should probably be a separate thread for a de-evolution discussion. Here I will only say that it is not observed that species are returning to ancestral forms or losing bits of their genome with each generation.
What is observed is that there is change in populations over time that is acted on by the environment and those with more favorable genes tend to reproduce with greater success than those with less protection from the environment.
In this case, dogs, having greater amylase activity, are able to meet the challenge of a dietary environment that living along with humans has provided. Wolves don't need that and the environment doesn't select for that increased activity even if the same mutation occurs in a wolf. They are not eating diets higher in starch so there is no benefit for that mutation to persist.
So, we see dogs and their enzyme profile resulting from the expression of a higher copy number of
amy2b. A change in the gene frequency and increased information that has been studied and the link established.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329415/pdf/age0045-0716.pdf
https://royalsocietypublishing.org/doi/10.1098/rsos.160449
https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0148899&type=printable
https://www.ingentaconnect.com/cont...rt00002?crawler=true&mimetype=application/pdf