The slow rise of complex life as revealed through biomarker genetics.

Organic molecules preserved in ancient rocks can function as 'biomarkers', providing a unique window into the evolution of life. While biomarkers demonstrate intriguing patterns through the Neoproterozoic, it can be difficult to constrain particular biomarkers to specific organisms. The goal of the present paper is to demonstrate the utility of biomarkers when we focus less on which organisms produce them, and more on how their underlying genetic pathways evolved. Using this approach, it becomes clear that there are discrepancies between the biomarker, fossil, and molecular records. However, these discrepancies probably represent long time periods between the diversification of eukaryotic groups through the Neoproterozoic and their eventual rise to ecological significance. This 'long fuse' hypothesis contrasts with the adaptive radiations often associated with the development of complex life.