Rates, patterns, and effectiveness of evolution in multi-level situations.

Abstract

Evolution is a multi-level process. Actual evidence and theoretical considerations suggest that evolution at single levels and in series of increasingly complex levels decelerates with time. Additional evidence, the expected difference between rapid nonadaptive speciation in small populations and effective adaptation in large ones, and analysis of explosive evolution suggest that effective adaptive evolution occurs primarily in large populations, and that segments of such evolution tend to begin slowly; accelerate, sometimes explosively; and then decelerate. The segments are irregular, and do not occur at regular intervals. The explosive evolution of a general adaptation pre-adapts to and is often followed by an explosive radiation of derivative lineages. This description seems to fit the origin and initial radiation of mammals, and the evolutionary history of man and man''s cultures.