That's been known since genes were discovered. Luria and Delbruck got their Nobels for documenting this.
Several errors there. First, some mutations do protect against cancer, we just haven't seen one that offers complete immunity:
Millions of humans carry a genetic mutation that could cause cells to explode
Millions of cells in our bodies undergo programmed death, a crucial process that protects us from diseases by eliminating unwanted, damaged, or dangerous cells and preventing the spread of viruses, bacteria, and even cancer.
Millions of cells in our bodies undergo programmed death, a crucial process that protects us from diseases by eliminating unwanted, damaged, or dangerous cells and preventing the spread of viruses, bacteria, and even cancer.
www.indiatoday.in
Second, every mutation in a population increases information. Again, if you'd like to see the numbers for a simple case, I can show you.
I see a hidden false assumption here. Evolution is not always an increase in information. It is merely a change in allele frequencies in a population. It could reduce information, such as we see in the simplification of mammalian skeletons from reptilian ones or the removal of vitamin C genes as we see in primates.
So a population evolves by filtering out. It may be a matter of replacing existing alleles with new mutations or it could be merely simplifying.
The latter is an important part of new species. Most speciation is allopatric, from small, isolated groups that are ("founder effect") different than the larger populations. This is seen in the evolution of Darwin's finches, dipterans in Hawaii, and many other cases.
Of course, mutation continues in such separated populations, and the new genetic information is often a factor in the speciation of these groups. Would you like some examples?