During his twilight years, American author Mark Twain noted that "life would be infinitely happier if we could only be born at the age of 80 and gradually approach 18."

Twain's quip was only one of many complaints about aging that have been recorded for as long as humans have dreaded the downside of a long life. The ancient Greek poet Homer called old age "loathsome," and William Shakespeare termed it "hideous winter." Oscar Wilde's character Dorian Gray even preserved his youth by aging only in a painting, to hideous effect.

So it's not hard to understand why there have always been hopes and rumors that something soon to be discovered—magic waters, say, or maybe