"Scientists in the past decade have discovered that remnants of ancient germ line infections called human endogenous retroviruses make up a substantial part of the human genome. Once thought to be merely "junk" DNA and inactive, many of these elements, in fact, perform functions in human cells.

Now, a new study...suggests for the first time that a burst of transpositional activity occurred at the same time humans and chimps are believed to have diverged from a common ancestor — 6 million years ago. "

The key word is "burst". Junk DNA activating and evolving humans. What was the trigger?

"Results of a new University of Michigan study suggest that junk DNA - dismissed by many scientists as mere strings of meaningless genetic code - could have a darker side.

... in cultured human cancer cells, segments of junk DNA called LINE-1 elements can delete DNA when they jump to a new location - possibly knocking out genes or creating devastating mutations in the process."

More "junk" DNA causing mutations.