and in the case of fossett, i had grown up reading all these books saying, well, there could not be a complex society in the amazon. it had to be a very poor, prim tuf tribe, it was just too inhumane an environment to sustain a large civilization. so the question he was after, that object of his obsession, was also equally fascinating. >> and, malcolm, a lot of -- i mean, your stories are much more about actual experiments. i mean, do you feel, do you wish that -- they seem to be less open-ended than the stories david tells. do you, how do you work that? i mean, how do you work through the sort of uncertainty in a lot of the science in your books? how do you make that sort of work as a story? >> uh, that's a good question. um, you, i mean, you -- the -- what you try and do is find a principle or an idea in science and then illustrate it with a story. keeping in mind that the science -- there's always a level of uncertainty in science, and so you are kind of choosing a particular past, both interesting and thought-provoking path to take. and you necessarily have to kind of simplify thi