Fig. 1
Coupled evolution of life and atmospheric oxygen. Major evolutionary and developmental events that have been linked to “pulses” in the atmospheric oxygen (O2) concentration based on the GEOCARBSULPH model (Berner 2007; Berner 2009). a Note that since the origin of life within 500 million years of Earth’s formation (LUCA, Last Universal Common Ancestor), oxygenic photosynthesis was responsible for the rapid increase in atmospheric O2 levels during the Proterozoic Eon of the Pre-Cambrian period (~ 0–10% in < 1 billion years) preceded by endosymbiosis, emergence of cellular respiration with adenosine triphosphate the universal energy source and cephalization, a characteristic feature of the ancestral bilateria, leading to the first appearance of a central nervous system (Holland et al. 2013). Pre-Є, Pre-Cambrian; Є, Cambrian; O, Ordovician; S, Silurian; D, Devonian; C, Carboniferous; P, Permian; Tr, Triassic; J, Jurassic; K, Cretaceous; T, Tertiary. b Stochastic changes in atmospheric O2 levels during the Phanerozoic eon peaked during the Carboniferous/Permian periods resulting in gigantism subsequent to augmented O2 diffusive capacity and heralded major evolutionary advances that included a 3.5-fold increase in hominin brain volume over ~ 2.75 million years (Seymour et al. 2016). Also note the three major extinction events (red bands) associated with dramatic falls in atmospheric O2 levels. c Parabolic projection of the decline in future atmospheric O2 levels using a stochastic model (Livina et al. 2015) applied to original data obtained from recording stations in the Scripps Programme (Keeling 1988). Note that the model predicts that in ~ 3,600 years, atmospheric O2 levels will be so low that hypoxia will be encountered even at sea-level, equivalent to being exposed to a terrestrial altitude of ~ 5,340 m which represents the highest elevation know to sustain lifelong human habitation with complete (O2) depletion predicted within ~ 4.4 millennia (Martin et al. 2017)