Shifts in metabolic scaling, production, and efficiency across major evolutionary transitions of life

TLDR

Life’s diversification drove massive increases in size and complexity, with transitions from prokaryotes to unicellular eukaryotes to metazoans bringing major metabolic innovations. Across evolutionary transitions, metabolic rate, population growth rate, and production efficiency scale differently with body size—prokaryotes show superlinear metabolic scaling, protists linear, metazoans sublinear; population growth rate shifts from positive to negative, and production efficiency declines, indicating that early metabolic innovations reshaped constraints and opportunities.

Abstract

The diversification of life involved enormous increases in size and complexity. The evolutionary transitions from prokaryotes to unicellular eukaryotes to metazoans were accompanied by major innovations in metabolic design. Here we show that the scalings of metabolic rate, population growth rate, and production efficiency with body size have changed across the evolutionary transitions. Metabolic rate scales with body mass superlinearly in prokaryotes, linearly in protists, and sublinearly in metazoans, so Kleiber's 3/4 power scaling law does not apply universally across organisms. The scaling of maximum population growth rate shifts from positive in prokaryotes to negative in protists and metazoans, and the efficiency of production declines across these groups. Major changes in metabolic processes during the early evolution of life overcame existing constraints, exploited new opportunities, and imposed new constraints.