DECLINING VOLATILITY, A MACROEVOLUTIONARY PROPERTY OF DISPARATE SYSTEMS: FROM FOSSILS, TO STOCKS, TO THE STARS

There may be structural principles pertaining to the general behavior of systems that lead to similarities in a variety of different contexts. Classic examples include fractals, surface area to volume constraints, entropy, and mathematical rules of growth and form. Documenting such overarching principles may represent a rejoinder to the Neodarwinian synthesis that emphasizes adaptation and competition. Instead, these principles could indicate the importance of constraint and structure on form and evolution. Here we document congruent behavior in very different systems. We focus on the notion that universally there has been a tendency for more volatile entities to disappear from systems such that the net volatility of these systems tends to decline. We consider origination and extinction rates in the marine animal fossil record, the performance of stocks in the stock market, and the character of stars and stellar systems. We show that volatility declines in the marine fossil record even as overall diversity has increased: volatility is highest in the Cambrian, but even if Cambrian values are excluded Ordovician to Holocene volatility declines from 0.6 to 0.25. Volatility declines because of the long-term evolutionary risk of high volatility. High origination rates are correlated with high extinction rates, and high volatility increases the chance that the diversity of a taxon will fall to zero, which represents extinction, the evolutionary point of no return. We document similar patterns in the behavior of the stock market and star systems, and consider the broader significance of this. Similarities arise between the different areas because with stars, stocks, and taxa, we are dealing with historical entities. The more volatile such entities are, the more likely they are to reach a zero point from which there can be no possibility of return. The predilection for variable entities to reach a zero point is seemingly exaggerated during times of heightened variability, for instance, mass extinctions and stock market crashes, and for stars early in the history of the universe. We also discuss this in the context of themes in the work of Stephen Jay Gould: evolutionary trends, the decline of the .400 hitter, and evolutionary constraint.