I like reading about the history of science, and one of its more famous chapters is the debate between the Neptunists and the Vulcanists in early 19th century Great Britain. At the risk of oversimplifying, the debate was over whether the earth's features (and life on it) were formed slowly over long periods, or relatively quickly through catastrophes. Secondarily, it was about heat and fire vs. water as forces shaping the Earth (thus the names). Eventually a consensus (an actual consensus, not a declared one) developed that they were both right in some ways and both wrong in others.
What struck me reading about this again over the weekend was that it took decades, and sometimes centuries, for this to sort out. Take the part of this debate over extinction. The initial consensus was that extinction was due to catastrophes, ala the Biblical flood. Then Darwin came along and shifted the consensus away from catastrophes, showing that extinctions occurred in the normal order of species action-reaction to threats and opportunities. And then in the 20th century, revisiting the K-T geologic layer we have come around to dinosaur extinction being catastrophic as a result of a big meteor. Except nowadays there are scientists who think this is too simplistic. Geology, in turn, made it all the way until the 1960's before anyone was even talking about plate tectonics, something that was still being derided in the 1970's but is fundamental to our understanding of numerous aspects of the earth today.
And so it goes in normal scientific inquiry. Scientists expect it to take decades and generations to really shake out new theories and areas of inquiry. Sometimes, as with Newton's laws of motion, we still accept the theory, though even here we have tweaked at the edges (e.g. relativity when things are moving fast) and exempted certain regions (e.g. quantum mechanics and the very small). Other times, we have thrown theories that were cherished for decades completely away (e.g phlogistan). After decades of work, string theory in physics could easily be thrown out completely and looked upon as the 20th century's phlogistan, or it could really be the theory of everything Einstein searched for in vain.
Which is all fine and expected, except when governments are standing by to make trillion-dollar choices, as they are in global warming, a scientific body of inquiry that is barely 20 years old. Go back to any new scientific theory in its first 20-years, and think about the governments of the world betting the entire global economy on scientific understanding of that theory at that point in time. It's pretty scary. We'd probably have a 5-trillion dollar government controlled medical leach industry.