Oftentimes in my science classes I feel like I haven't learned anything. This feeling often sweeps over me when I'm taking a test, which is not a good thing. However, when I'm out of the class room, not preoccupied with getting a halfway decent grade, and just reflecting on the experience as a human being, I realized I've learned lots of things. Like how when nonspecialists try to talk about science, they typically don't have the faintest clue what they're talking about.
Two prime, and interrelated, examples of this are (1) people who think we're going to cure aging and (2) people who think we're going to cure cancer. What's the deal here? Simply, a big part of aging is the death of needed cells. However, a big part of cancer is cells not dying when they're supposed to. Your cells have mechanisms for something called apoptosis, programmed cell death, and when those mechanisms are screwed up, you tend to get cancer. One cell-killing gene, p53, turns out to be screwed up in (if I remember correctly) a fairly solid majority of cancers.
There have been experiments on lab animals where they try to put a stop on mechanisms associated with aging, and the result is the things die even younger, because they get cancer. Keep cells alive to stop aging, cancer risks shoot up. And kill cells to stop cancer, and well, you don't have those cells.
I predict a very long period in human medical history where one of the key issues is figuring out how to balance the two things: cells dying and cells not dying. We may find ways to keep the balancing going longer, but it's going to be a darn long time before we find a way to keep that balance from eventually unraveling.