There exist obvious higher-order influences in any planetary system. This is often demonstrated by introducing terraform life onto newly discovered planets. In all such cases, the life in similar zones develops striking similarities of adaptive form. This form signifies much more than shape; it connotes a survival organization and a relationship of such organizations. The human quest for this interdependent order and our niche within it represents a profound necessity. The quest can, however, be perverted into a conservative grip on sameness. This has always proved deadly for the entire system.
Natural selection has been described as an environment selectively screening for those who will have progeny. Where humans are concerned, though, this is an extremely limiting viewpoint. Reproduction by sex tends toward experiment and innovation. It raises many questions, including the ancient one about whether environment is a selective agent after the variation occurs, or whether environment plays a pre-selective role in determining the variations which it screens. Dune did not realty answer those questions: it merely raised new questions which Leto and the Sisterhood may attempt to answer over the next five hundred generations.