Faced with a new mutation in an organism, or a fundamental change in its living conditions, the biologist is frequently in no position whatever to predict its future prospects. He has to wait and see. For instance, the hairy mammoth seems to have been an admirable animal, intelligent and well-accoutered. Now that it is extinct, we try to understand why it failed. I doubt that any biologist thinks he could have predicted that failure. Fitness and survival are by nature estimates of past performance.
George WaldThere was a golden period that I look back upon with great regret, in which the cheapest of experimental animals were medical students. Graduate students were even better. In the old days, if you offered a graduate student a thiamine-deficient diet, he gladly went on it, for that was the only way he could eat. Science is getting to be more and more difficult.
George WaldThe important point is that since the origin of life belongs in the category of at-least-once phenomena, time is on its side. However improbable we regard this event, or any of the steps which it involves, given enough time it will almost certainly happen at least once. And for life as we know it, with its capacity for growth and reproduction, once may be enough.
George Wald