Evolutionary biologists are not content merely to explain how variation occurs within limits, however. They aspire to answer a much broader question-which is how complex organisms like birds, and flowers, and human beings came into existence in the first place.
It was very important that it be done in such a way that it be executed with complete conviction. If I had done it both ways, if I was trying to cover myself in case it didn't work, then it would have been to no purpose.