查看文章

The question of whether or not large-scale historical trends in the design of organisms represent progress (i.e., improvement of design) has attracted attention since the beginning of evolutionary thought but has proved extremely resistant to objective analysis. Some of this difficulty reflects the range of time scales and phylogenetic contexts for which the question might be posed, but a more fundamental problem involves the definition of improvement itself. When improvement of design is discussed within the context of current evolutionary thought, it is frequently portrayed as the expected outcome of the sustained operation of natural selection on variation within populations. Such an interpretation of large-scale historical trends in morphology frequently involves some degree of orthoselection and/or adaptive replacement. An alternative interpretation is that many such trends reflect little more than the Markovian …