I used to work in anti-infectives research and if you talked to virologists long enough they would all insist that huge numbers of human ailments were caused by

I used to work in anti-infectives research and if you talked to virologists long enough they would all insist that huge numbers of human ailments were caused by as yet undiscovered viruses. I admit that I'm a bit biased toward this myself. But I also have worked with people who are mitochondrial experts and they are convinced that huge amounts of disease are caused by mitochondrial defects. Lots of microbiologists think undiscovered bacteria are to blame. The bottom line is that they are likely all correct. There is a staggeringly large amount of biology that we just don't know anything about. The complexity of it all is almost fractal. Just when we think we've got our heads around something, we peel another layer off the onion to reveal an entire landscape of which we were previously unaware. The best example of this is the recent findings in epigenetics. Before Darwin, Lamarck argued that acquired characteristics could be passed on to offspring. This was widely discredited. I learned about how it was patently false in high school. Now, we are finding that DNA methylation patterns (which work sort of like commenting out blocks of your DNA code) are modified and passed on to offspring. In some studies, if a mother is stressed, her offspring have stress response genes turned on by default at birth. In another, if there is starvation, the animal has starvation survival genes enabled at birth. It's quite remarkable and it means that in addition to our DNA which is fairly static, we have this parallel inheritance pattern that can be shaped and molded by the environment and passed to our offspring. The old "nature vs nurture" debate gets a whole lot more confusing (and might even be the wrong question entirely) with that in play.