The paper investigates the timing and sequence of events during eukaryogenesis, the origin of eukaryotic cells. The authors use a relaxed molecular clock methodology to date gene duplication events related to key eukaryotic features, particularly those of archaeal and bacterial descent. Their findings suggest that the archaeal host cell was already complex, possessing an elaborated cytoskeleton, endomembrane, and a nucleus/protonucleus, before mitochondrial endosymbiosis occurred. This timeline rejects "mitochondrion-early" models and supports a "complexified-archaeon, late-mitochondrion" sequence, placing the origin of the eukaryotic cell assembly between the Mesoarchaean and the late Palaeoproterozoic eras. The text also details the evolution of specific cellular components, like the cytoskeleton, endomembrane system, and nucleus, based on the calculated ages of their gene duplications.

References:

• Kay, C.J., Spang, A., Szöllősi, G.J. et al. Dated gene duplications elucidate the evolutionary assembly of eukaryotes. Nature (2025). doi.org