During WWII, Hungarian-born mathematician Abraham Wald undertook a study with the British Air Ministry to use statistical analysis to help protect bombers flying over enemy territory. The data to be crunched included the number and location of bullet holes on returning aircraft, and the goal was to use this information to determine where to best add armor to the plane’s structure.
A nifty little chart was created to show where the maximum number of bullet holes were located on returning aircraft. This chart showed the greatest damage not on the main wing and tail spars, engines, and core fuselage areas, but rather on the aircraft extremities. Based on this, the Air Ministry suggested adding armor to those extremities. Wald suggested they were dead wrong.
As told here by Dan Roam on his blog in May 2006
Wald’s insight: planes hit in the statistically less-damaged areas, weren’t getting home. That’s where armour was needed.
It is possible that something similar applies with “junk DNA” — the 90% of human DNA that is (or was?) thought to have no function. Genetic tinkerings which happen to propel an organism down an evolutionary dead end, leave no trace of themselves. They get shot down. Persistent DNA sequences, however, get back to base in one piece. Either because they do a vital job just fine, or because they can be altered without vital consequences.