The DNA never “changed”, the information was already there in those situations you described. Those without that information died or failed to breed leaving the ones with the information to reproduce. Mosquitoes who survived DDT reproduced, those who did not have that specific information did not.
Bacteria resistant to antibiotics survive and reproduce, those that are not, do not. Again, no information gain.
But successive generations can eventually breed information totally out of the gene pool, and that is what I mean by loss of information.
All humans came from an original source, with all of the genes for everything, but successive generations bred the gene out, i.e. no red hair in pure African groupings.
There is no case of information being gained through mutations, except bad information.
As for the whales, show me the genetic information gained. All you have is fossils and fossils do not tell you who their ancestors were.
Is that opinion, or fact? If it's being stated as fact, you'll need documentation of every mutation that ever happened to back it up.
Of course their DNA did change, as has been observed, confirmed and analyzed through DNA testing.
It's not just a matter of latent instructions suddenly becoming active at high altitudes.
It is the fact that people living at those high altitudes have new instructions in their DNA which are not present in the rest of humanity.
Indeed, as I said, the new DNA instructions for Tibetans is different from those for Andeans, demonstrating separate evolutionary paths.
Likewise, some Africans have malaria resistant instructions which also cause cycle-cell anemia.
By definitions, these new DNA instructions are both adaption and evolution, short-term.
None of these changes restrict interbreeding amongst human populations, so there is no speciation involved.
But, were such changes to continue and accumulate over many generations, then slowly, slowly, people of one population would grow increasingly unable, or unwilling, to interbreed with others.
It's how adaption & evolution work.
wbarmy: "There is no case of information being gained through mutations, except bad information."
I have now cited several examples off the top of my head, and a little research could produce many more.
All are examples where DNA "gains information", meaning it developed new instructions for new environments.
Your desire to deny what is obviously true is understandable, but only up to a point.
At some point you have to grasp that DNA does change, does add information and not all that new information is killed off by natural selection.
Some of it benefits a population, and that, dear FRiend, is evolution.