I believe that understanding of cancer prevalence is overly simplistic and ignores the role of environmental factors (carcinogens, diet, exercise, etc.). Rates of some cancers in various Asian countries (especially breast cancer) is noticeably lower than of Asian populations living in western cultures (I am generalizing because I do not remember which specific country the comparison was done with). There is evidence that exposures to chemicals, diet choice, and exercise plays a role in cancer development, though I will agree that increased lifespan and improvements in diagnosis have a role as well.http://www.nature.com/nrc/journal/v10/n10/abs/nrc2914.htmlhttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC1618773/http://www.usc.edu/hsc/info/pr/hmm/05fall/cultures.htmlhttp://www.breastcancer.org/symptoms/new_research/20070928.jsphttp://sydney.edu.au/science/molecular_bioscience/nrf/documents/symposium_notes_diet_lifestyle_cancer.pdfhttp://www.news-medical.net/health/Breast-Cancer-Epidemiology.aspx
Unfortunately, I don't have access to most of the articles that seem to discuss the topic of DNA redundancy, and items that I do have access to are short on details, but this Princeton article has some interesting information:http://www.princeton.edu/main/news/archive/S27/96/55S87/index.xml?section=science
Specifically, this quote:
"Now we're finding that additional copies of these genetic instructions are important for maintaining stable gene function even in a variable environment, so that genes produce the right output for organisms to develop normally."