Why lithium? The Missing Ocean Mineral conjecture: a possible Ediacaran origin for neural lithium function.

We propose the Missing Ocean Mineral (MOM) conjecture that lithium, through competition
with magnesium at the catalytic sites of regulatory enzymes, originally functioned as a
stochastic environmental interrupt — a low-frequency signal that allowed early eukaryotic
cells to pause high-priority processes and permit periodic maintenance. Acute depletion of
ocean lithium following the Marinoan glaciation (~635 Mya) disrupted this ambient
regulation and would have imposed selection pressure for internal lithium retention and
control. The metazoan lineages that survived this crisis could have evolved mechanisms to
retain, regulate, and release lithium on demand; converting an unreliable environmental signal
into a controllable intracellular one. This innovation may in turn have prompted the evolution
of the metazoan neuron: a cell type whose defining capacity for controlled state-switching
would have derived from the internalisation of an ancestral lithium-based interrupt.